Digitized by the Internet Archive 
 
 in 2010 with funding from 
 
 Boston Library Consortium IVIember Libraries 
 
 http://www.archive.org/details/notesongeologyin191220gord 
 
Notes on the Geology 
 
 IN THE 
 
 Vicinity of Bennington, Vt. 
 
 G. E. Gordon 
 
 UHW. Of KlliSS. ffiW^ 
 
 From the Ninth Report, Vermont State Geologist, 1914. 
 
Notes on the Geology 
 
 IN THE 
 
 Vicinity of Bennington, Vt. 
 
 G. E. Gordon 
 
 
 LO 
 
 CO 
 
 ■• — From the Ninth Report, Vermont State Geologist, 1914. 
 
 
LEGEND 
 
NOTES ON THE GEOLOGY IN THE VICINITY OF 
 BENNINGTON, VERMONT. 
 
 C. E. Gordon. 
 
 TABLE OF CONTENTS. 
 
 Introduction. 
 
 Location. 
 
 Topography. 
 
 Drainage. 
 
 General Geology. 
 
 General Relations of Geology and Topography. 
 
 Table of Rock Formations and Component Members. 
 
 The Gneiss and Associated Quartzite. 
 
 The Valley Quartzite South of Bennington. 
 
 The Valley Quartzite and Interbedded Limestones and Quartzite North 
 
 of Bennington. 
 The Limestone Formation in and South of Bennington. 
 Limestone and Schist Northwest of Bennington. 
 Limestone and Schist of Mt. Anthony. 
 
 The Limestone and Schist in North Pownal and Pownal Villages. 
 The Schist of Mann Hill. 
 The Schist and Limestone of Mason Hill. 
 General Relations. 
 The Pleistocene. 
 
 INTRODUCTION. 
 
 In the summer of 1912 the writer spent two and one-half 
 weeks in the study of the geology in the vicinity of Bennington, 
 Vt. Though the work speedily involved a detailed inspection 
 from outcrop to outcrop, it was purposely carried out as a recon- 
 naissance. It was expected that another season's work would 
 bring out the broader structural relations among the different 
 formations and lead to more positive conclusions with which to 
 return to the task of mapping the Bennington region. 
 
 It has proved inadvisable to carry out the original plan. In 
 view of the brief period spent in the field and the intricate nature 
 of the problem only such notes as were collected and such sugges- 
 tions as they seem to afford can be offered in this report. 
 
 Attention was chiefly given to the hard rock formations. So 
 far as observed, the surface deposits offer no special features 
 of interest. 
 
338 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 A map is offered herewith to show the outcrops which were 
 examined. The boundaries of the different formations are drawn 
 in on the basis of these observations. Certain probable structural 
 relations are involved which are also exhibited on the map and 
 discussed in the report. 
 
 LOCATION. 
 
 The area discussed in this paper is situated in the extreme 
 southwestern part of Vermont and forms approximately the 
 western third of the Bennington quadrangle. The southern 
 boundary of the Bennington sheet is on the west less than one- 
 half a mile, and on the east somewhat more than a mile from the 
 Massachusetts line. The western part of the map includes a strip 
 of the Hoosick quadrangle, varying in width from a mile and a 
 half to two miles, which separates the western margin of the 
 Bennington sheet frorh the New York State boundary. 
 
 The Bennington quadrangle lies between parallels 42° 45' 
 and 43° north latitude and meridians 7Z° and 72)° 30' west 
 longitude. The particular parts of the quadrangles discussed in 
 this paper embrace the townships of Pownal and Bennington, 
 the major part of Shaftsbury and small strips on the west of 
 Stamford, Woodford and Glastenbury. 
 
 TOPOGRAPHY. 
 
 The area includes the southern portion of the great limestone 
 "valley of Vermont." Within the Bennington quadrangle the 
 valley is hemmed in on the east by the steep western slope of the 
 Green Mountain Plateau, which extends as a rugged wilderness 
 through the towns of Stamford, Woodford and Glastenbury. 
 East of Bennington the plateau is cut by the northeast-southwest 
 valley of Walloomsac Brook. North of this stream are the espe- 
 cially rugged masses of Bald and Glastenbury mountains. 
 
 The plateau has a high average elevation. "The Dome" in 
 the eastern part of the town of Pownal is 2,750 feet high, while 
 other knobs farther east in Stamford reach an elevation of 3,000 
 feet or more. Bald Mountain northeast of Bennington is 2,865 
 feet high ; other peaks in Glastenbury Range from this altitude to 
 3,764 feet in Glastenbury Mountain. 
 
 From the western edge of the Green Mountain Plateau the 
 descent to the valley is very steep throughout most of the area. 
 This abrupt topographic break is a striking feature of the land- 
 scape. 
 
 East of Bennington the western margin of the plateau has 
 been offset to the west a distance of two miles. This east-west 
 break is marked by the course of Walloomsac Brook. Both north 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 33y 
 
 and south of this fault the western margin of the plateau has 
 practically the same general trend to the north-northeast. 
 
 By this same offset the valley is shifted to the east at Ben- 
 nington. South of Bennington the valley extends in a somewhat 
 southerly direction, gradually narrowing up, and ending abruptly 
 at the northern end of Mason Hill in the town of Pownal. 
 
 The valley which comes down from the north through the 
 towns of Manchester, Sunderland, Arlington and Shaftsbury is 
 bounded on the west by a high range which terminates west of 
 Shaftsbury Center in West Mountain with an elevation of 2,000 
 feet. The valley widens out as it enters the quadrangle, its west- 
 ern margin bending west around the southern end of West Moun- 
 tain. Northwest and west of Bennington is a wide-open valley 
 area which extends west beyond the limits of the map. 
 
 The valley south of Bennington is bounded on the west by 
 the Mount Anthony ridge. This ridge begins two miles west of 
 Bennington. Its eastern margin follows a southerly course as 
 far as Pownal Center. Here the ridge bends to the southeast, 
 cutting off the valley of Bennington, and bringing up abruptly 
 in Mason Hill against the Green Mountain Range. Mount An- 
 thony, southwest of Bennington, is 2,345 feet high. The elevation 
 falls off southward to 986 feet at Pownal Center and rises again 
 through 1,500 feet in Mann Hill to 1,660 feet in Mason Hill. 
 The North Adams-Bennington electric railway rises from the 
 549 feet contour at Pownal village to an altitude of 986 feet at 
 Pownal Center, a vertical distance of 437 feet in. about three miles, 
 through the lowest pass in this mass which cuts off the valley of 
 Bennington at the south. 
 
 Although there are numerous altitudes in the valley south of 
 Bennington higher than this pass, the essential ridge-like char- 
 acter of the whole stretch from Mount Anthony to Mason Hill is 
 reasonably apparent, its former relatively higher altitude at 
 Pownal Center being obscured by the erosion of the mass between 
 Pownal Center and the bed of the Hoosick. The Mount Anthony 
 portion of the ridge is at the northern end of a southwardly pitch- 
 ing syncline. This fact perhaps in connection with the favor 
 shown by the forces of erosion may account for its present rela- 
 tively higher altitude. 
 
 An inspection of the map will show that in correspondence 
 with the eastward extension of the valley west of Bennington 
 the northern end of the Mount Anthony ridge lies farther east 
 than does the boundary of the valley as formed by West Moun- 
 tain in Shaftsbury. And the southeastward bend of the Mount 
 Anthony ridge through Mann and Mason hills finds a parallel in 
 the great eastward sweep of the valley region of Williams- 
 town and North Adams around the southern end of Clarksburg 
 Mountain to the Hoosick Range. 
 
340 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 DRAINAGE. 
 
 In southern Vermont and northern Massachusetts the Green 
 Mountain Range is the divide between the drainage of the Hudson 
 and the Connecticut rivers. 
 
 Hoosick River, which rises on the western slope of the Green 
 Mountains in Massachusetts, flows north to North Adams, then 
 westward past WilHamstown, and then crosses in a northwesterly- 
 direction the extreme southwestern corner of the state of Ver- 
 mont. Five miles northwest of Hoosick Falls it turns west to 
 join the Hudson. 
 
 Near Hoosick Junction, N-. Y., the Hoosick receives the waters 
 of Walloomsac River which drains the larger part of the area 
 discussed in this paper. The Walloomsac gathers its headwaters 
 in the Green Mountain Range, five miles east of Bennington, from 
 two large brooks, one of which forks and drains the southern 
 slope of Glastenbury Mountain, while the other forks in a similar 
 manner and drains the northern slopes of Stamford Mountain in 
 its northern extension in the town of Woodford. The sources of 
 these terminal, tributary streams come close to the headwaters of 
 the tributaries of the Deerfield River. 
 
 North of Bennington, Furnace Brook and Paran Creek head 
 on a low divide which parts the drainage of the Walloomsac from 
 that of the Batten Kill. They flow south to join the Walloomsac. 
 South of Bennington, South Stream and Jewett Brook flow north 
 from Pownal, the former receiving the drainage of the western 
 slope of Stamford Mountain, and the latter that of the eastern 
 slope of Mount Anthony. South Stream and Jewett Brook join 
 near Bennington and flow into the Walloomsac in the eastern part 
 of the town. 
 
 The western slope of the Mount Anthony ridge drains to the 
 Hoosick. 
 
 In general, the Walloomsac has an east-west direction across 
 the gneiss, quartzite, limestone and schist. Probably its course 
 was primarily determined by certain important structural features 
 of the region. 
 
 GENERAL GEOLOGY. 
 
 The core of the Green Mountain Range is made up of gneiss 
 of pre-Cambrian age. 
 
 Time did not allow a careful examination of the gneisses 
 within the area. It was extremely difficult to accomplish much 
 on the mountains of the range. The country is still mostly a 
 heavily-wooded wilderness crossed by only two roads and a few 
 overgrown trails. Glastenbury Mountain, which is the most in- 
 accessible, is especially disappointing in outcrops. Seemingly any 
 separation of the elements of its pre-Cambrian core would prove 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 341 
 
 very difficult under present conditions. Nevertheless, the writer 
 had hoped to make some study of these rocks. 
 
 It would seem that an important line of investigation sup- 
 plementary to the researches of various workers in the pre- 
 Cambrian rocks of the Green Mountain belt is still open.^ The 
 difficulty in drawing always a sharp line between the Cambrian 
 and the pre-Cambrian was expressed by Professor Pumpelly.^ 
 
 Professor Wolff argued for the presence in the Cambrian 
 ("Vermont Formation") of the Hoosick Range of coarse gneisses, 
 finer-grained banded gneisses, shghtly micaceous gneiss, meta- 
 morphic gneiss conglomerate and ordinary quartzite conglomerate, 
 these rocks or phases passing into one another along the strike.^ 
 Later Van Hise* made the white gneiss of Hoosick Mountain pre- 
 Cambrian and maintained that there is no transition between the 
 pre-Cambrian igneous and the Cambrian sedimentary. 
 
 Keith° describes as a result of recent studies in Vermont a 
 great thickness of schist, dolomite, graywacke, quartzite and con- 
 glomerate overlain unconformably by the Cambrian quartzite 
 which transgresses the whole of the lower series. This series is 
 classed as Algonkian. 
 
 Resting against the gneiss all along the western front of the 
 range within the area is a lofty brow of quartzite which slopes 
 steeply, often precipitously, to the valley on the west. This quartz- 
 ite is a conspicuous feature for many miles northward in Ver- 
 mont along the western margin of the Green Mountain Range. 
 
 The Woodford-Stamford gneissic core of the Green Moun- 
 tain Range extends down for a short distance into Massachusetts 
 and terminates in Clarksburg Mountain directly northwest of 
 North Adams. The quartzite formation extends from the town 
 of Pownal southward on the western face of the range and east- 
 ward around the southern slope of Clarksburg Mountain. It 
 lies unconformably on the pre-Cambrian (Stamford) gneiss. 
 
 In the quartzite formation "east of Bennington," and also 
 on the western slope of Clarksburg Mountain, Dr. C. D. Walcott" 
 discovered fossils (Olenellus) which definitely proved the quartz- 
 ite to be of Lower Cambrian age. 
 
 On the east of Clarksburg and Stamford mountains, north 
 from North Adams, the quartzite extends some distance north of 
 the village of Stamford through Hartwellville towards Woodford. 
 Its further northern extension was not followed. 
 
 1 C. p. Berkey, Structural and Stratigraphic Features of the Basal 
 Gneisses of the Highlands, Bull. N. Y. State Mus. 107, 1907. 
 
 A. Keith, A pre-Cambrian Unconformity in Vermont, Bull. Geol. Soc. 
 Amer., Vol. 25, p. 39. 
 
 2 Mon. U. S. G. S., XXIII, p. 25. 
 
 3 Idem, pp. 35-118. 
 
 *Bull. U. S. G. S., No. 360, p. 588. 
 ^ Log. cit. 
 
 '5 The Taconic System of Emmens, Amer. Jour. Sci., Series 3, Vol. XXXV, 
 1888, pp. 235-236. 
 
342 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 In the southern part of the area, as shown on the map of 
 this report, the quartzite on the western slope of the range hes 
 against the schist of Mason Hill, and north of Mason Hill against 
 limestone and schist, and then for the rest of the distance south 
 of Bennington against the quartzite formation of the valley. 
 Southeast of Bennington the floor along the eastern edge of the 
 valley is quartzite. It extends south of the fault along Walloom- 
 sac Brook, between the range and the limestone which borders 
 it on the west, and wedges out to the south against the edge of 
 the plateau. The western margin of the range cuts somewhat 
 diagonally northeastward across the general trend of the forma- 
 tions of the valley, south of Bennington. 
 
 The valley quartzite south of Bennington is bordered by a 
 broad limestone band which extends south from Bennington and 
 which narrows up and ends somewhat abruptly at the south 
 against Mason Hill. The limestone gives place at the west and 
 south to the schist of the Mount Anthony ridge. At numerous 
 places along the eastern slope of this ridge, north of Pownal 
 Center, the limestone is seen to dip westward beneath the schist. 
 It appears again dipping east along the northwestern slope of 
 Mount Anthony. It forms the high hill just east of the village 
 of North Pownal. It lies on the schist on' the west side of the 
 Hoosick, two and a half miles south of North Pownal, and out- 
 crops again on the southwestern slope of Mason Hill along the 
 Williamstown-Pownal road about two miles southeast of Pownal. 
 
 East-northeast of Bennington, as described in the topog- 
 raphy, the plateau has suffered an offset to the west so that east 
 of Bennington, south of Walloomsac Brook, the quartzite of the 
 valley forms a recess eastward, while north of the stream is the 
 steep southern slope of Bald Mountain and the western quartzite 
 slope of the range lies two miles farther west. Northeast of 
 Bennington from the Walloomsac northward to Buck's Cobble 
 the quartzite was traced as a well-defined band about two miles 
 wide along the east side of the big valley and east and north of 
 Buck's Cobble it was followed somewhat indistinctly as far north 
 as Maple Hill. 
 
 The same sharp topographic break which marks the ascent 
 from the valley quartzite to that which fronts the range south of 
 Bennington also distinguishes the relations of Glastenbury Moun- 
 tain to the valley on the west. North from Buck's Cobble the 
 quartzite is replaced by sharply-folded interbedded limestones 
 and quartzite. West from the margin of the valley quartzite and 
 the westernmost scarps of the hills of interbedded limestones and 
 quartzites, so far as it is possible to learn about this heavily drift- 
 covered region, the valley is underlain by limestone which extends 
 to the eastern foot of West Mountain and around its southern end 
 and south through South Shaftsbury and North Bennington to 
 the northern end of Mount Anthony. West of North Benning- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 343 
 
 ton the limestone is mixed somewhat with the schist, but in gen- 
 eral bounds the schist formation at the west much as shown on 
 the map. 
 
 The quartzite, limestone and schist which have been men- 
 tioned form the eastern members of the great Taconic belt of 
 rocks which extends from northern Vermont southward along 
 and near the boundary of New England and New York. 
 
 As early as 1872 it had been established through the inves- 
 tigations of the Rev. Augustus Wing that the Hmestones (Eolian) 
 lying west of the Green Mountain Range contained strata, as 
 shown by fossils, ranging from the Upper Potsdam or Lower 
 Calciferous to the Trenton.^ From Wing's investigations the 
 term "Calciferous-Chazy-Trenton" was apphed to the limestone 
 in general as it outcropped in and west and north of Rutland. 
 
 Later studies in the limestones of Dutchess County, New 
 York, by Professors Dana and D wight showed the presence there 
 of the Georgian, Potsdam, Calciferous and Trenton in rocks hav- 
 ing field relations similar to those in northern Vermont and to be 
 regarded as essentially the southwestward continuation of the 
 Stockbridge and Eolian limestone formations of Massachusetts 
 and Vermont.^ 
 
 In 1887, Dr. Walcott carried his studies into the region 
 around Bennington and southward into Massachusetts, and found 
 fossils in the limestone which he assigned to the Chazy-Trenton.'"^ 
 
 By these and other researches the age of much of the lime- 
 stone of the Taconic region was shown to be of Ordovician age. 
 
 In 1890, Professor Wolfif studied the area around Rutland, 
 Vt.* He found the limestone (Eolian) of the main Rutland 
 valley to lie conformably along the west side of the valley on the 
 quartzite of Pine Hill. Pine Hill is a ridge just west of Rutland 
 which divides the main limestone valley of Rutland from a 
 smaller limestone valley in Center Rutland. Wolfif found the 
 quartzite forming the eastern slope of Pine Hill to bend to the 
 eastward north of Rutland and join the quartzite of the main 
 range. At Pine Hill the quartzite passes upward into limestone 
 through beds of "calcareous quartzite." Cambrian fossils were 
 found in the limestone above the contact with the quartzite. 
 Associated with the quartzite of Pine Hill was a series similar 
 or identical with that associated with the quartzite east of the 
 valley, in each case older than the limestone. The limestone of 
 the Center Rutland valley, just west of Pine Hill, as shown by 
 fossils is of Ordovician age. The general significance of these 
 relations will be appreciated. Part of the Eolian limestone near 
 Rutland was thus indicated to be of probably Lower Cambrian 
 age. 
 
 1 Amer. Jour. Sci., Series 3, Vol. IV, 1872 ; Vol. XIII, 1877. 
 
 2 Papers by W. B. Dwight, Amer. Jour. Sci., 1879-1889. 
 
 3 Amer. Jour. Sci., Series 3, Vol. XXXV, 1888, p. 238. 
 *BulI. Geol. Soc. Amer., 1891, pp. 331-337. 
 
244 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 The schists which he to the west of the hmestone of the 
 Vermont valley, extending north from West Mountain in Shafts- 
 bury through East Poultney and beyond, were colored Cambrian 
 by Walcott^ in a map accompanying his discussion of The Taconic 
 System of Emmons, while the Mount Anthony ridge and the 
 schists to the west of it and around Hoosick Falls, together with 
 certain schist outliers in the limestone of the valley between 
 Shaftsbury and Rutland, were shown as belonging to the Hudson 
 terrane. 
 
 In Pownal, at what appears from the description and the 
 map to be on the southwestern side of the Mason Hill mass, 
 Walcott discovered fossils which he described as Trenton, and 
 again on the east side of Mount Anthony, about three miles south 
 of Bennington Center, in the limestone beneath the schist, he 
 found parts of crinoids allied to a form found in the Trenton 
 limestone of New York. Near Hoosick Falls, in limestone about 
 200 feet below the "shales," he found fossils of the genera 
 Maclurea and Murchisonia and assigned the limestone to the 
 Chazy-Trenton. On the basis of these discoveries, the schist of 
 Mount Anthony and the region about Hoosick Falls was placed 
 in the Hudson terrane and considered to be of Ordovician age. 
 
 The terrigenous sediments, described above as colored on 
 Walcott's map as Georgian, were so designated on the basis of 
 fossils of Lower (then called Middle) Cambrian age, contained 
 in thin interbedded limestones. These fossils were "distributed 
 at various horizons throughout the 14,000 feet or more of strata 
 referred to this terrane." These slaty, or phyllitic rocks Walcott 
 regarded as the off-shore equivalent of the quartzite of the Green 
 Mountain Range. Two belts of the Cambrian slates are shown 
 with a belt of the Hudson terrane faulted in between them. 
 
 Probably most of the eastern portion of Walcott's eastern 
 Georgian belt, including West Mountain, is of Ordovician age. 
 
 GENERAL RELATIONS OF GEOLOGY AND 
 TOPOGRAPHY. 
 
 The whole region is mountainous in structure. Viewing it 
 as a whole, we find that the mountain folds have been truncated, 
 exposing the older rocks along the anticlinal axes, while in the 
 synclinoria the younger strata were folded down and thereby pre- 
 served. In the valleys certain strata, which primarily belonged to 
 faulted upthrust blocks, have been dropped back by normal ad- 
 justment faulting and are now exposed by erosion in abnormal 
 relation to adjacent strata. 
 
 Professor Davis- early described the region as a Avorn-down 
 mountain area peneplaned by sub-aerial agencies. The higher 
 
 1 Amer. Jour. Sci., Series 3, Vol. XXXV, 1888. 
 siMon. Nat. Geogr. Soc, Vol. 1, 1895, pp. 279-284. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 345 
 
 eminences were interpreted as monadnocks. Professor Dale^ 
 later questioned the peneplaned character of the Taconic physi- 
 ography on the ground that the peneplain theory would require 
 for the region, as shown by its history, an elevation of from 1,500 
 to 2,000 feet at the beginning of the Tertiary and that subsequent 
 time was seemingly not long enough to carve to its present con- 
 dition a dissected peneplain, if, as seemed likely, such sculpture 
 involved the removal of at least half of the Taconic topographic 
 belt since its post-Ordovician elevation. 
 
 Recently Professor BarrelP has come forward with the view 
 that much of the Piedmont belt of southern New England and 
 New Jersey, which is generally regarded as part of a great pene- 
 planed region, could be explained as the result of marine plana- 
 tion at right angles to the lines of drainage. In western Massa- 
 chusetts and Connecticut and extending into New York and 
 southward, he has described a more or less clearly recognizable 
 series of wave-cut terraces at different levels, showing the former 
 presence of the sea, at the time of its maximum transgression, a 
 long distance inland from the margin of the present coastal plain. 
 He correlates the terraces with definite formations of the present 
 coastal plain and recognizes in the planes of disconformity among 
 the deposits of the present plain the record of the uplifts that 
 successively elevated the different terraces, assuming, of course, 
 that the oscillitary movement reached the coastal plain. 
 
 Condensed Table of Hard Rock Formations. 
 
 Age. 
 
 Cambro- 
 Ordovician. 
 
 Basal Cambrian. 
 
 Pre-Cambrian. 
 
 Formation. 
 
 Schist. 
 
 Limestone. 
 
 'Vermont Formation." 
 Unconformity. 
 
 Members. 
 
 Shales. 
 
 Slates. 
 
 Grits, Phyllites. 
 
 Calcareous Schists. 
 
 Sericite Schist. 
 
 Marbles. 
 
 Compact and granular 
 crystalline limestones. 
 
 Limestones and calcareous 
 quartzites with inter- 
 bedded quartzite. 
 
 Quartzite. 
 
 Quartzitic schist. 
 
 Schistose quartzite. 
 Dense compact quartzite. 
 "Granular quartz rock." 
 Conglomerate. 
 
 Gneiss of Stamford Moun- 
 tain and Harmon Hill. 
 
 1 Bull. U. S. G. Sur. No. 272, p. 33. 
 
 2 Bull. Geol. Soc. Amer., Vol. 24, pp. 688-690. 
 
346 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 At the time of its farthest advance the sea is believed to have 
 reached the south side of the Adirondacks and the southeastern 
 side of the Green Mountains in Massachusetts, there cutting the 
 oldest, or "Becket terrace" in middle Cretaceous time. Later ter- 
 races range from this epoch into the Pleistocene. 
 
 The absence of unconsolidated marine deposits far inland 
 from the margin of the present coastal plain is held not to in- 
 validate the claims of this later view of the Piedmont region, 
 since such deposits might well have been almost completely if 
 not quite removed by erosion. 
 
 The approximate elevation of the inner margin of the oldest, 
 or Becket terrace, is now 2,400 feet, but the region is known to 
 have undergone progressive warping. 
 
 THE GNEISS AND ASSOCIATED QUARTZITE. 
 
 GENERAL DESCRIPTIOiV. 
 
 The gneiss was examined on the western slope of "The 
 Dome" and on the western and northern slopes and summit of 
 Harmon Hill. The western boundary of the gneiss, where 
 shown, is drawn in somewhat arbitrarily. The boundary was not 
 touched on Bald or Glastenbury mountains. 
 
 On the southwestern side of "The Dome" the quartzite rests 
 unconformably on the gneiss. West-southwest of this eminence, 
 lower down the slope and about on the 1,700-foot contour, in a 
 valley recess southeast of the pond, the gneiss is exposed in a 
 wet-weather gulley. The rock is in place, but the strike and dip 
 of the foliation could not be satisfactorily determined. North- 
 ward from this outcrop along the steep slope east of the pond, 
 gneiss talus boulders were common with some admixture of 
 quartzite northward. 
 
 At a point due east from the pond, well up the very steep 
 slope at this point, limestone and interbedded calcareous quartzite, 
 quite like that which will presently be described as commonly 
 occurring apparently at no great distance above the quartzite of 
 the valley south and north of Bennington, forms the slope with 
 strike N. 17° E. and dip 25° easterly. This limestone at a short 
 distance to the northeastward passes upward into black, shiny, 
 graphitic-looking schist, or phyllite, which forms the summit of 
 the sharp spur that sticks out northeastward from the range in 
 the direction of Barber's Pond. Descending this spur towards its 
 apex, the phyllite, which seems to be conformable, gives place to 
 limestone and interbedded quartzitic layers like those described 
 above. The phyllite is less gritty than the schist of Mason and 
 Mann hills, and differs somewhat from any which I have else- 
 where observed in the area. I have not elsewhere found it asso- 
 ciated with these particular limestone beds as shown in this spur. 
 The relations are peculiar and difficult of explanation. The phyl- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 347 
 
 lite apparently lies in a syncline of limestone closed northwest- 
 ward and pitching towards the range. Northwest of the log 
 cabin the limestone beds stand at high angle. 
 
 I have drawn a fault, from the outcrop of gneiss mentioned 
 above, north-northeastward where this spur abuts against the 
 range to show the prevailing tendency of the older rocks to appear 
 against the younger by reverse faulting. To what extent the 
 older rocks moved upward will be discussed later on. This spur 
 is mentioned in connection with the gneiss as it helps to develop 
 the writer's interpretation of the structural relations along the 
 western margin of the range. 
 
 Northeast of this spur is another sharp recess, on the eastern 
 edge of which ascends the road that crosses the range to Stam- 
 ford. Along this road just before it makes the abrupt turn up 
 the steeper slope of the mountain limestone outcrops in the road. 
 Definite readings could not be made. The limestone is not 
 succeeded by any outcrop along the road for a long distance. 
 Near the summit thin-bedded quartzite with irregular, rusty part- 
 ing surfaces outcrops in the road and woods with low westerly 
 dip. 
 
 North of the mountain road to Stamford the western slope 
 of the range is quartzite above the lower drift-covered portion. 
 It was observed at places, in the woods, dipping gently westward 
 and in some places lying nearly flat. Near the summit the thin- 
 bedded quartzite was observed passing upward into gritty schist 
 which, in some places showed great similarity to certain lower 
 members of the schist formation overlying the limestone in Mount 
 Anthony. 
 
 The valley occupied by the pond northwest of the gneiss 
 outcrop, which was described above, is apparently underlain by 
 limestone, but south of this recess the quartzite of the range 
 extends a half mile or more west of the outcrops of gneiss and 
 along Reservoir Brook abuts against the schist of Mason Hill. 
 The quartzite stands as a fairly high scarp above the brook about 
 one mile north of the Williamstown reservoir. At this place it 
 is a thick-bedded, compact white rock. Higher up the brook it 
 becomes more thinly-bedded and the scarp in consequence dimin- 
 ishes in abruptness to the northward. Where the scarp is com- 
 posed of the compact heavy quartzite, we have exposed lower 
 beds of that formation. The dip is flat, or slightly easterly. The 
 general relations are shown in figure 27. 
 
 Along the mountain road east of Reservoir Brook and 
 between the brook and road are frequent low-lying ledges of the 
 thin-bedded quartzite, having a notably flattish position. The 
 quartzite is often rather a quartzite-schist with well-developed 
 micaceous bands. Ledges are often "flaggy" and under the 
 hammer break into irregular chips with rusty parting planes. 
 Along the brook east of the mountain road, at the base of the 
 
348 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 Steeper slope on the west of the southward extension of "The 
 Dome," it changes to a fine-grained quartz-pebble conglom- 
 erate. Along the mountain road just before it leaves the 
 woods at the north, just east of the source of Reservoir Brook, 
 the thin-bedded quartzite is badly crumbled and frequently carries 
 veinlets of quartz. East of these outcrops is the thin-bedded, 
 flaggy quartzite which prevails over most of this flat hill lying 
 southwest of "The Dome." 
 
 Along the higher portion of the western slope of the range 
 the quartzite, as far as the physical difficulties made it possible, 
 was traced from Roaring Branch to the southern end of Harmon 
 Hill. On the western slope of this hill the gneiss comes down 
 close to the base and stands in ledges from 30 to 40 feet above 
 the quartzite. The contact is clearly a faulted one. Here the 
 upthrust brought the gneiss against the quartzite, as now exposed. 
 The quartzite dips slightly to the westward and passes by gradual 
 slope into the valley west of the hill. 
 
 The actual contact of gneiss and quartzite was not observed, 
 but ledges of the two formations are less than 100 feet apart. 
 The quartzite strikes nearly north, or slightly west of north, while 
 the strike of the foliation of gneiss is east of north. The rela- 
 tions here described are best observed in the pasture about one- 
 half mile northeast of Woodward's Corner. 
 
 The fault between the gneiss and quartzite I have repre- 
 sented as dying away southward in the quartzite, its place being 
 taken by another break farther west which faulted the quartzite 
 of the range against that of the valley. 
 
 From its outcrops near the quartzite along the fault, the 
 gneiss continues up the slope to the summit of the hill. A read- 
 ing at the summit gave the strike of the foliation as N. 60° E. 
 and the dip 80° NW. 
 
 The relatively ancient character of the foliation of the gneiss 
 is impressive. It seemingly antedates the deposition of the 
 quartzite, as shown by the discordance in strike and dip, and 
 belongs to a pre-Cambrian mountain-building time. The gneiss 
 had acquired practically its present fohated condition before the 
 deposition of the quartzite. 
 
 East of Bennington, in the valley along the Woodford road 
 which skirts the northern end of Harmon Hill, the quartzite out- 
 crops in frequent ledges. Less than a mile east of the trestle 
 bridge across the Walloomsac the road has been blasted through 
 a heavy ledge of quartzite which rises abruptly from the bed of 
 the brook. This ledge is nearly along the northward projection 
 of the quartzite just west of the fault at Harmon Hill. It also 
 probably lies south of the cross fault, which is represented on 
 the map as cutting off the Bald Mountain mass at the south. 
 
 Numerous ledges of the quartzite outcrop along the road to 
 the eastward. This formation was traced from the fork in the 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 349 
 
 road, along Walloomsac Brook to the junction of Bickford 
 Hollow and Bolles brooks, and also beyond the forks along City 
 Stream for three-fourths of a mile. Along the upper reaches 
 of the Walloomsac the quartzite is the rusty, flaggy rock which 
 has been described. 
 
 A mile from the fork, along the Woodford road, the gneiss of 
 Harmon Hill outcrops in the road, showing the foliation strike 
 as N. 50° E. and the dip 70° E. The quartzite was not traced 
 farther east. 
 
 It seems likely that a great irregular fault cuts off the gneiss 
 of Harmon Hill at the northern end, and that this formation rests 
 with faulted contact against the quartzite in the valley north of 
 the hill. 
 
 PETROGEAPHY OF THE HARMOJ^ HILL GNEISS. 
 
 The gneiss as it appears along the Woodford road is a rather 
 fine-grained biotite gneiss without pronounced foliation. The 
 biotite appears in fine flakes uniformly distributed in the rock 
 both across and with the foliation. The thin section shows a 
 granitoid texture with prominent anhydrous of feldspar and 
 quartz of allotriomorphic type with biotite of igneous habit and 
 distribution, usually enclosed in the feldspars. The feldspars 
 are somewhat decomposed and are partly clouded with kaolinite 
 and other decomposition products. 
 
 The gneiss at times carries coarser bands of quartz and feld- 
 spar which roughly alternate with micaceous bands of a texture 
 similar to the finer-grained gneiss described above. Where 
 freshest the feldspars appear to be chiefly plagioclase. Zircon 
 occurs as an accessory. There appear to be no pronounced strain 
 effects. While there is usually a decided wavy extinction of the 
 quartz, the twinning lamellae of the feldspars are not broken per- 
 ceptibly and show uniform width along their entire lengths. 
 
 The rock at the top of the hill is essentially the same as that 
 along the Woodford road, although it is more prominently 
 gneissic. It has the same general texture in thin section and the 
 same mineralogy, with the addition of some microcline. 
 
 The rock near the contact with the quartzite along the west- 
 ern slope of the hill clearly shows the effect of shearing. In the 
 hand specimen it appears crushed and when hit by the hammer 
 breaks along smoothed surfaces. In thin section the quartz ap- 
 pear shattered. The fragments have recrystallized and healed 
 without extensive migration. Where before were large quartz 
 crystals are now patchworks of small grains with independent 
 extinction. The plagioclase shows badly bent and pinched out 
 lamellae and the biotites are broken into numerous fragments 
 and dustings. 
 
350 
 
 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 INTERPRETATION. 
 
 So far as I have observed, there is Httle evidence of folding 
 in the gneiss and not much of shearing, except in the zone of 
 faulting. 
 
 From the gentle dip of the quartzite and its frequent almost 
 flat position we may suppose that this formation, as a general 
 rule was not violently folded. At places accommodation was 
 effected in the gneiss by shearing, but over large areas, so far as 
 observed, even shearing is inconspicuous. The quartzite was 
 folded somewhat in the general movement of elevation and in 
 some places buckled into small folds, as, for example, along lines 
 on which the gneiss was shoved up on the quartzite, the break 
 often dying away along the line into a fold in the quartzite. 
 
 The breaks were primarily initiated by the crystalline gneissic 
 substratum refusing to fold. The tendency to rupture was doubt- 
 less augmented by the covering of heavy quartzite which was 
 also reluctant to fold. 
 
 The release of the highly crystalline substratum was ap- 
 parently effected by numerous breaks along the strike. At some 
 places, for some reason, the rupture occurred earlier than at 
 others and at some places farther west, so to speak, than at others, 
 the effect being a sort of echelon of faults along the western 
 margin of the range. 
 
 Figure 26. — Generalized section to show reversed fault between the gneiss 
 and quartzite on the west of Harmon Hill. 
 
 The fault on the west of Harmon Hill, figure 26, is repre- 
 sented as dying away southward in the quartzite. Its place is 
 taken by another break farther west by which the quartzite rests 
 against younger quartzite at the west. The latter fault is rep- 
 resented as dying away northward in the quartzite west of Har- 
 mon Hill. Southward it is drawn near the base of the slope as 
 far south as the latitude of Barber's Pond. It then probably 
 merges with a break that bounds the valley quartzite south of 
 Bennington on the west or passes directly into the fault shown 
 along the western slope of "The Dome." 
 
 The fault on the west of "The Dome" dies away southward, 
 its place being taken by another break farther west by which the 
 quartzite was thrown against the schist of Mason Hill along 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 351 
 
 Reservoir Brook. My interpretation of the probable relations at 
 Mason Hill are shown in figure 27. The famous "Sand Springs," 
 
 
 
 ,....-' ''^^<^:^ 
 
 
 
 '' ' ■ ^-^'^^^^'^y^^ "^ "^ "^ "^ '' •/ 
 
 
 
 '€"u''''l^^'/'y''y/^y:- 
 
 
 
 - - v^^^^tA^J'i>/_^-;v!;<^ y ^ ■/ J J ^ J ■' ^ 
 
 rv 
 
 r_: 
 
 ^^^^^^^^^^^V/fr^'^^ " ^ ^GTie-fss". ^ ^ ./ " 
 
 Sc7i >si' 
 
 
 7^==^^Pff^ :'>y/ ' :: ' : -^■' "-/- -- ^-i 
 
 Figure 27. — Generalized section to show the interpretation of the relations 
 
 at Mason Hill. 
 
 a resort two miles northwest of Williamstown, lies along or close 
 to the southward extension of the Mason Hill fault along Reser- 
 voir Brook. This spring issues from clear white sand and in win- 
 ter and summer, as well as in dry and wet seasons, gives an average 
 flow of 400 gallons a minute. The temperature of the water in 
 winter and summer is about 76° Fah. Its freedom from organic 
 contamination and its remarkable mineral content have given the 
 water a wide reputation for medicinal purposes, both for drink- 
 ing and bathing. The water is now extensively used for the 
 manufacture of "soft drinks," and the excess flow is utilized for 
 a swimming pool. The following analysis was made by Leverett 
 H. Mears, Professor of Chemistry at WiUiams College. 
 
 Parts per 100,000. 
 
 Lithium chloride 0.0353 
 
 Sodium chloride 0768 
 
 Acid calcium carbonate 3.2249 
 
 Acid magnesium carbonate 2.6479 
 
 Calcium sulphate 7262 
 
 Aluminium sesquioxide 0325 
 
 Iron sesquioxide 0075 
 
 Silica 7026 
 
 Sodium carbonate 4641 
 
 7.9178 
 
 The spring issues from the drift, but its constancy, tempera- 
 ture and mineral content suggest a deep-seated source and argue 
 for the great depth of the fault along which it comes. 
 
 The fault shown on the map as bordering the quartzite of the 
 range on the west of the low hill just southwest of Harmon Hill is 
 marked by a rugged talus slope across the edge of the quartzite 
 beds just within the edge of the woods southwest of Woodward 
 Corner and Harmon Hill. This scarp and talus was distinctly 
 followed southward for two miles. 
 
 There would have been a tendency to break across the strike 
 on the north of this hill, but it seems more likely that the fault 
 
352 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 on the west dies away northward owing to compensation by the 
 fault at the east on the west of Harmon Hill. 
 
 Southwest of "The Dome," however, there may be a cross 
 fracture for here the quartzite passes northward into limestone. 
 This limestone may, however, be of Cambrian age as discussed 
 beyond. 
 
 The "valley quartzite" is represented as probably wedging 
 out to the southward against the range. The quartzite of the 
 range cuts somewhat diagonally across the general trend of the 
 formations in the valley. 
 
 The presence of the quartzite formation high up on the 
 slopes of the range and its eastward extension along Walloomsac 
 Brook in themselves strongly argue for the former extension 
 of this formation over the range toward Woodford. The quartz- 
 ite, as noted in the discussion of the general geology, extends 
 northward from the southern end of Clarksburg Mountain for a 
 long distance toward Woodford on the east of Stamford Moun- 
 tain. The presence of the quartzite formation along the head- 
 waters of the Walloomsac and in City Stream may be explained 
 by down-faulting. 
 
 THE VALLEY QUARTZITE SOUTH OF BENNINGTON. 
 
 By this term may be understood the quartzite formation as 
 it outcrops in the valley west of the prominent gneiss or quartzite 
 scarps and slopes of the range. 
 
 East of Bennington outcrops are concealed by modified drift 
 as far east as the foot of Harmon Hill and the outcrop along the 
 Woodford road a mile east of the bridge across the Walloomsac. 
 
 South of Walloomsac Brook the only outcrop observed 
 between the range and South Stream was two and a half miles 
 south of the brook, so effectually are outcrops concealed by the 
 heavy surface deposits over this area. Near the south road to 
 Sucker Pond, about half way between the foot of the range and 
 the old lumber mill along South Stream, where this road makes 
 its sharp bend southward, are outcrops of quartzite. 
 
 Drift conceals this formation between these outcrops and 
 South Stream. In the bed of the latter, near the bridge, a fourth 
 of a. mile north of the old lumber mill, the quartzite gives a strike 
 of N. 42° E. and a dip of 17° SE. From the bed of the stream 
 the topography eastward rises by gentle slope to the foot of the 
 range. Near the old lumber mill the limestone is interbedded 
 with calcareous quartzite at the dam and in and west of the road 
 just above the stream. Similar beds outcrop along the stream 
 at the gentle rapids five or six hundred yards south of the dam. 
 All the beds along the stream have a notably flattish position. 
 
 The valley quartzite and its associated interbedded series 
 were not traced farther south, but probably continue under the 
 drift for a distance of three or more miles southward to the foot 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 353 
 
 of the range, seemingly wedging out where the Hmestone extends 
 down into the recess southeast of Barber's Pond. 
 
 Northward along the road that follows South Stream to 
 Bennington, about three-fourths of a mile north of the old lumber 
 mill, the interbedded calcareous quartzite and Hmestone outcrop 
 in the bed of the stream and on each bank. The beds vary from 
 two to four to six inches in thickness and dip gently eastward ; 
 a stratum of limestone beds alternating with a stratum of cal- 
 careous quartzite. The road to Bennington forks just north of 
 these outcrops. At the fork a ledge of quartzite was blasted to 
 make way for the road. The quartzite in this ledge is sheared 
 vertically, apparently at right angles to the bedding, which, how- 
 ever, is obliterated, and along the shearing planes are numerous 
 crystals of pyrite which have stained the sheared surfaces a rusty 
 brown. The five feet of vertical exposure here is all dense steel- 
 blue quartzite. Two or three outcrops of the quartzite were 
 noted farther north along the east road from this fork. 
 
 The data are meager for forming definite conclusions, but 
 from the sheared quartzite just described and the general flat 
 position of the beds, I imagine the valley quartzite to have buckled 
 very little, but on the contrary, to have faulted against the rocks 
 farther west. In the course of adjustments following reverse 
 faulting it would probably have dropped back again by normal 
 faulting along earlier thrust planes so that its present position 
 w^ould be misleading as to its real history. The valley quartzite 
 east of Bennington would have folded with that of the range until 
 the great breaks along its eastern and northern margin occurred 
 when it would have slumped somewhat. The amount of displace- 
 ment of the valley quartzite along its western margin would have 
 been less than that which occurred in the quartzite and gneiss 
 of the range on the principle that the reverse faulting would tend 
 to die away westward. 
 
 THE VALLEY QUARTZITE AND INTERBEDDED LIME- 
 STONES AND QUARTZITE NORTH OF 
 BENNINGTON. 
 
 Northwest of Bennington on the south bank of the Wal- 
 loomsac, at the edge of the golf links of the Mount Anthony Golf 
 Club, near the covered bridge, quartzite is interstratified with 
 limestone, the whole forming a gentle arch. At this place there 
 is no shearing and the outcrop is considered to lie east of the 
 probable western boundary of the valley quartzite in its occurrence 
 north of Bennington. 
 
 A mile and a half north of the outcrops at the golf links 
 along the road to South Shaftsbury, the quartzite outcrops in the 
 road. North of this outcrop two roads leave the South Shafts- 
 bury road, one going west, the other east. On the latter, close to 
 
354 
 
 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 the main road and south and north of it, ascending the slope to 
 the eastward, are numerous ledges of the quartzite lying nearly- 
 flat, or dipping gently eastward. This road is locally known as 
 the "Stony Hill road." 
 
 An almost continuous outcrop of the quartzite was traced 
 northward through the woods along the edge of the hill, one- 
 fourth of a mile east of the South Shaftsbury road, for nearly a 
 mile. Westward the quartzite descends by gentle slope to the 
 South Shaftsbury road, but the slope is across the edges of the 
 quartzite beds. Eastward the formation passes under drift. 
 
 North of the next crossroad, the quartzite forms a high 
 hill just northwest of Wait's Corner. Well up the rather steep 
 eastern slope of this hill are great patches of white granular 
 quartzite dipping easterly. The southern end of this hill is a 
 berry pasture. North of the pasture are thick woods with some 
 clearings. Through this wood the quartzite was followed nearly 
 to the next crossroad running from South Shaftsbury to the 
 Madison school. The northernmost outcrop of the quartzite, as 
 thus followed from Bennington northward was noted near Buck's 
 Corner. North of the South Shaftsbury crossroad begins the 
 southern limestone slope of Buck's Cobble. The limestone con- 
 tinues northward through Harrington Cobble and across the next 
 road and then passes under a gentle west slope, lying between 
 Harrington Cobble and the crossroad which skirts Trumbull 
 Mountain on the south. 
 
 East of the north-south road on the east of Buck's Cobble, 
 everything is concealed by drift as far north as Maple Hill. 
 The quartzite forms the eastern slope of Maple Hill and out- 
 crops a mile eastward at the apex of the loop formed by the 
 road that runs to the base of the range, east of Maple Hill. At 
 the latter place, within a space of 50 feet, the structure exhibited 
 in figure 28 was shown. The quartzite is thin-bedded and lies 
 
 Figure 28. — Structure in limestone and quartzite east of Maple Hill. 
 
 quite flat. At the west it bends downward and passes beneath 
 limestone which is folded down at a rather sharp angle. 
 
 North of Maple Hill, south of the loop road, in the thick 
 woods on the north side of a deep gully, the quartzite in vertical 
 section shows the structure exhibited in figure 29. The folding 
 of the quartzite here, as contrasted with its flat position farther 
 south, is in line with the relations exhibited in the "Cobbles" west 
 of Maple Hill, which will be described presently. 
 
 Along the road leading to the old abandoned hamlet of Fay- 
 ville (see Equinox sheet; not shown on the map of this report) 
 
PLATE LXIX. 
 
 A. BUCK'S COBBLE, A VIEW LOOKING NORTH. 
 
 B. FOLD IN INTERBEDDED QUARTZITE ON TRUMBULL MT. ON THE 
 CREST OP AN OVERTURNED ANTICLINE. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 355 
 
 quartzite outcrops in the bed of the brook. It is a heavy, com- 
 pact rock in beds from 2 to 5 feet thick and strikes N. 25° W. 
 with a dip about 12° S. W. 
 
 It will thus be seen that a band of quartzite 2 miles wide 
 extends north from Bennington as far as the crossroad from 
 South Shaftsbury to the Madison School. So far as observed, 
 there is no limestone overlying or interbedded with the quartzite, 
 within this distance, except at the south near Bennington. Along 
 the road leading northeast from the covered bridge at the Mount 
 Anthony Golf Club links, a half mile north of the railroad, lime- 
 stone outcrops in the road and in the fields east of it are numerous 
 ledges. A reading gave the strike as N. 13° W. and a dip 9° west- 
 erly. Because of their apparent superjacent conformity to the 
 quartzite and because of the resemblance to other limestone, which 
 the writer has elsewhere observed in the Taconic belt, lying a little 
 way above the quartzite, the rock was closely searched for Lower 
 Cambrian fossils, but without success. How extensive this lime- 
 stone is north and east of these outcrops it was not possible to 
 tell on account of the drift. Southward from them there are no 
 outcrops in Bennington north of Main St., so far as observed. 
 These ledges probably represent an outlier resting on the quartz- 
 ite and conformable with it. 
 
 The sudden transition from quartzite, east of Buck's Corner 
 on the South Shaftsbury crossroad to the limestone of Buck's 
 Cobble on the north of it suggests a cross fault between them. 
 The high scarp on the west of the Cobble suggests a strike fault 
 here, which extends north on the left of Harrington Cobble, 
 beyond which it apparently shortly dies out. Harrington Cobble 
 has much the same structural outlines as Buck's Cobble (see 
 Plate LXIX, A) but its western slope is less precipitous and 
 merges gradually into the eastern slope of Hale Mountain at the 
 west. The western slope of Hale Mountain is, however, deci- 
 dedly steep and scarp-like. The limestone on the east slope of 
 Buck's and Harrington Cobbles dips eastward at a rather high 
 angle. On Hale Mountain a reading on the eastern slope at the 
 southern end gave strike N. 19° E., dip 40° E., and on the north- 
 ern slope, strike N. 46° E., dip 23° E. 
 
 Figure 29.— Quartzite north of Maple Hill. 
 
 As contrasted with the hills at the north, now to be de- 
 scribed, the hmestones of Buck's and Harrington Cobbles and of 
 
356 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 Hale Mountain, so far as observed, show no associated quartzite. 
 
 At Maple Hill, the limestone which forms the summit and 
 western slopes exhibits in cross section a close folding and slight 
 overturning which are features in line with the folding of the 
 quartzite (as shown in figure 29) at the northeastern end of the 
 hill. Near the base of the western slope the rock is a slightly 
 banded, rusty, medium-grained "buckwheat" marble. It dips 
 eastward at a high angle. 
 
 The hill just west across the road from Maple Hill is lime- 
 stone. On the eastern slope the beds dip eastward. In this 
 hill there is no associated quartzite. Its western slope is steep 
 and suggests a break as also does the slope on the west of Maple 
 Hill. (See Plate LXIX, B). 
 
 The next hill to the west shows quartzite on the eastern slope 
 dipping eastward, but at the summit the dip is westward, in- 
 dicating overturning. My notes indicate that it is interbedded 
 with limestone and calcareous quartzite. 
 
 The next hill on the west is Trumbull Mountain. At the 
 south end of this hill, which rises very steeply from the road 
 which skirts it on the south, the quartzite forms the eastern slope, 
 dipping east. Near the top of the hill, but 300 or 400 yards east 
 from the summit of the western slope, quartzite shows a struc- 
 ture seen in Plate LXX, A, which is a view looking north. It 
 will be observed that the bed of quartzite dips east on the right 
 of the photograph and west on the left. Associated limestone 
 beds outcrop near by at the south on the southern pitch of the hill, 
 also dipping slightly west. A little farther west they stand 
 nearly vertical and on the western slope dip to the east, forming 
 an overturned anticline. 
 
 Similar relations were shown in the hill east of Shaftsbury 
 one mile north. (See Equinox sheet). Quartzite which forms the 
 eastern slope of this hill outcrops at the western base of the next 
 hill to the east with strike N. 25° E. and dip of 24° easterly. 
 
 Figure 30. — Structure seen in hill near . Shaftsbury, interbedded limestone 
 
 and quartzite. 
 
 A wide swampy track borders the steep western scarp of 
 Trumbull Mountain. West of the northward extension of this 
 swamp, east-southeast of Shaftsbury (see Equinox sheet), is 
 another high hill, showing interbedded limestone and quartzite, 
 standing at high angles on the summit. At one place the struc- 
 ture was similar to the accompanying figure 30. On the top of 
 
PLATE LXX. 
 
 A. LOOKING NORTH FROM HARRINGTON COBBLE. TRUMBULL 
 MOUNTAIN ON THE LEFT. . MAPLE HILL ON THE RIGHT. 
 
 MINOR COMPRESSED FOLDS IN LIMESTONE OVERTURNED TO 
 THE WEST, ONE-HALF MILE NORTH OF HARRINGTON COBBLE. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 357 
 
 the hill the limestone was folded down in a minor syndinal. The 
 structure was interpreted as that of an anticline, but with one or 
 more infoldings along its crest. 
 
 South of the transverse series of hills beginning with Maple 
 Hill on the east and ending with Trumbull Mountain, between 
 them and Harrington Cobble and Hale Mountain at the south, is 
 a gentle westward slope of low rehef. Plate LXX, A, is a view 
 looking north from the summit of Harrington Cobble across this 
 slope. The scarp-like character of the western slopes of the hills 
 in the distance is brought out in the photograph. The lOO-foot con- 
 tours of the map of this report do not bring out these hills as' 
 sharply as do the 20-foot contours of the United States topographic 
 sheet. In the foreground of the plate is the gentle, northern 
 drift-covered slope of Harrington Cobble. The northern slope 
 of Hale Mountain is more abrupt. In the southern portion of 
 the gentle western slope, north of the crossroad on the north of 
 Harrington Cobble, are numerous ledges of limestone. In the 
 brook that crosses this portion of the slope the limestone dips 
 gently westward. Plate LXX, B, gives a view of a portion of a 
 limestone ledge 500 or 600 yards south of the brook. This ledge 
 was interpreted as connecting under the drift with Harrington 
 Cobble and as genetically a part of it, thus revealing the close- 
 overturned folding that caused the Cobble. 
 
 The general flat position of the quartzite in the broad band 
 north of Bennington indicates that it was not folded much. It 
 buckled a httle. In its southern portion a downward fold caught 
 and preserved the hmestone outlier north of Bennington. At 
 the northern end an upward bulge formed the long high hill of 
 quartzite south of Buck's Cobble. 
 
 All the different hills that have been described in the eastern 
 part of Shaftsbury are of similar genetic type, including the hill 
 of quartzite south of Buck's Cobble. They form long camel- 
 hump arches along the strike with anticlinal structure and all are 
 overturned. Probably all have suffered some overthrusting or 
 developed a strong tendency in that direction. It may be that 
 Buck's and Harrington Cobbles and Hale Mountain had a quartz- 
 ite member of the interbedded series at one time covering them, 
 but not being so violently folded as the hills farther north, there 
 was no infolding of the quartzite along their crests. It is also 
 possible that the limestone of these Cobbles belongs to a higher 
 horizon than the interbedded limestones and quartzites farther 
 north and that the latter did not reach the surface in Buck's and 
 Harrington Cobbles. The former view, however, seems more 
 likely because the limestone outlier north of Bennington would 
 seem to suggest that the quartzite was succeeded by a certain 
 thickness of limestone before the deposition of the interbedded 
 series and the occurrence of the quartzite at the surface at the 
 south points to diminishing reversed faulting northward so that 
 
358 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 Buck's and Harrington Cobbles with Hale Mountain take an in- 
 termediate position with respect to the quartzite south of them 
 and the interbedded series at the north. The exact relation of 
 the broad quartzite band to the adjacent limestone on the west 
 could not be positively determined, but I believe it is a faulted 
 one. An intersecting cross fault south of Buck's Cobble dies 
 away eastward. North of this break folding was more violent, 
 the tendency towards which is recorded in the quartzite at the 
 high hill just south of Buck's Cobble. The tendency to folding 
 increased northward and inversely as the tendency to upthrust of 
 the lower beds diminished. 
 
 If there is a reversed fault on the west of the broad band 
 of quartzite it becomes a question how far north it should be 
 drawn. The interbedded series appear to be at no great distance 
 above the basal quartzite, whether we reason from the surface 
 succession northward from Bennington or eastward from the 
 range through Maple Hill, and I have drawn a probable break 
 northward to the limit of the map to show the probable close age 
 relation of all the rocks of this broad band on the east of the 
 valley north of Bennington with intervening probable strike faults 
 between this major break and the foot of the range. 
 
 In view of the heavy drift covering in the central and west- 
 ern part of Shaftsbury the probable stratigraphical relations of 
 the east and west portions of the valley in this town are hard 
 to work out. If there is a reversed fault all along the western 
 edge of the quartzite and the series of "Cobbles" north of it, it 
 would mean that the interbedded series underwent some folding 
 before the break occurred and were caught at whatever stage of 
 folding they had attained when the heavy quartzite basal member 
 broke. 
 
 South of Bennington the interbedded series lies flat for the 
 most part. The high hill just west of the brook that joins South 
 Stream three-fourths of a mile northwest of the old lumber mill 
 shows interbedded calcareous quartzite and limestone like those 
 in the hills of Shaftsbury and obeys a similar arching tendency 
 along the strike. A reading on the steep eastern slope of this hill 
 gave the strike as N. 35° E. and the dip 80° E. At the northern 
 end of the hill a reading gave strike N. 33° E. and dip 70° W. 
 
 Placing this hill with the valley quartzite formation the 
 western boundary of the latter should perhaps be drawn through 
 or on the west of this hill and southward so as to include the 
 spur sticking out northwest from the range towards Barber's 
 Pond. The limestone of the base of this spur in its lithology 
 recalls the limestone of the outlier north of Bennington and 
 underlies the interbedded upper series of the spur. 
 
 Possibly the western margin should be drawn even farther 
 west to include certain outcrops south of Meyer's house on the 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 359 
 
 extreme northeastern slope of Mason Hill which are lithologically 
 similar to the limestones just mentioned. 
 
 The calcareous quartzites of the interbedded series so 
 strongly resemble the quartzite that one must always carefully 
 examine them to be sure. They weather to look like the quartzite 
 although frequently showing a pitted surface. These siliceous 
 limestones, as they may be equally well designated, effervesce 
 rather strongly with cold dilute acid and under the microscope 
 show an approximately equivalent amount of calcite and quartz 
 distributed in grains over the section in such manner as to in- 
 dicate detrital origin for both and free admixture during deposi- 
 tion. The siliceous elements of the thin section show some 
 microcline and other feldspar but are predominately quartz. 
 
 THE LIMESTONE FORMATION IN AND SOUTH OF 
 BENNINGTON. 
 
 On Hillside street in Bennington, near the house of J. T. 
 Remington, the limestone as blasted in the road shows the struc- 
 ture as exhibited in figure 31. The section indicates close fold- 
 ing, overturning and reversed faulting. 
 
 Figure 31. — Limestone on Hillside Street, Bennington, near J. T. Remington's. 
 
 Just south of Main street under the west bank of the 
 cemetery the limestone dips easterly at 54° and strikes N. 31° E. 
 One mile south of Main street, along the road leaving the latter 
 west of Jewett Brook, near "Camp corner," in the quarry beside 
 the road, the limestone dips 60-65° easterly, the strike in the 
 quarry varying in a distance of 50 feet from N. 45° W. to N. 
 7° W. One-half mile directly south of this quarry, on the north- 
 ern slope of the hill, the limestone lies quite flat. This outcrop 
 is on the extreme northwestern slope of the hill which a mile to 
 the southeast shows interbedded limestone and calcareous quartz- 
 ite as described above, dipping 80° E. on the eastern slope and 
 70° W. on the northern slope. 
 
 In Bennington on Main street near the mill pond the lime- 
 stone dips eastward at a low angle and shows shearing structure 
 dipping eastward at a high angle. 
 
 South of Bennington, between South street and Dunham 
 avenue and the Pownal road, the limestone is dove-colored, carry- 
 ing many wavy bands of a chamois color, reminding the writer 
 very strongly of certain portions of the calciferous of Dutchess 
 
360 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 County, N. Y. The rock has every appearance of having under- 
 gone shearing whch has developed an eastward dip so that it 
 proved very difficult to distinguish between shearing and bedding. 
 Near the Pownal road the dove and buff seem to be clearly inter- 
 bedded, dipping east so that the shearing is with the bedding, but 
 200 yards to the southwest the dip is 19° W. with the strike of 
 N. 27° W. Weathered surfaces were searched for fossils with- 
 out success. It was not possible from the surface exposures 
 to determine to what extent the shearing and dip approximately 
 coincided. 
 
 In Bennington, three-fourths of a mile west of South street, 
 in the Lebanon Springs R. R. cut the limestone dips east with 
 shearing joints across the bedding. 
 
 In the field north of Dunham avenue, between it and the next 
 road north, a greatly brecciated limestone appears in numerous 
 small and large ledges over an area several acres in extent. 
 Plate LXXI shows the vertical face of one of these ledges. The 
 brecciation is often coarser than that shown in the plate, but is 
 also rather fine, the two passing into one another. The frag- 
 ments range from the size of a marble to that of a man's head. 
 The brecciation is clearly apparent on the lichen-covered surface 
 outcrops but is most conspicuous on comparatively fresh surfaces. 
 
 Just west of the Pownal road, a few hundred yards north- 
 west of these brecciated outcrops, the limestone strikes N. 81° W. 
 and dips 24° southerly. 
 
 Both east and west of the Pownal road, south of Robinson's 
 crossroads, and one mile north-northeast of Carpenter Hill, the 
 limestone generally dips westward. One reading one-half mile 
 south of the crossroads gave the strike N. 30° W. and dipped 
 48° westerly. At this place there is confusion ; .another reading 
 gave a dip clearly to the southeast. The limestone is frequently 
 brecciated, breaking into many irregular pieces under the hammer. 
 Westward up the hill the dip is eastward. 
 
 Along the mountain road, running west of Carpenter Hill, 
 about a mile and a fourth from Robinson's crossroad, and just 
 beneath the eastern edge of the Mount Anthony schist, which 
 rises very steeply here, the structure shown is exhibited in the 
 composite section of figure 32. One-fourth of a mile northeast 
 of this outcrop, just west of the road, the limestone shows pro- 
 nounced shearing. It is the gray or dove-colored rock seen so 
 frequently farther north, to the east of the Pownal road, and 
 carries the same chamois-colored wavy patches and streaks. 
 
 Just south of the ledge, whose structure is shown in figure 
 32, the limestone of Carpenter Hill gives place to schist. On the 
 summit of this hill the eastern margin of the schist is one-half 
 mile farther east than along the mountain road. In both places 
 the schist dips to the west. 
 
PLATE LXXI. 
 
 A LEDGE OP COARSELY BRECCIATED LIMESTONE WEST OF 
 DUNHAM AVENUE IN BENNINGTON. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 361 
 
 Existing maps show the limestone passing over the moun- 
 tain west of Carpenter Hill to join the limestone in the valley of 
 the Hoosick. My observations find the schist intervening and con- 
 tradict this connection across the mountain. 
 
 The limestone east of Carpenter Hill and southward, west 
 of the Pownal road along the foot of the mountain to Pownal 
 Center, so far as observed, dips westward beneath the schist. 
 Where Jewett Brook crosses the road, and in the electric rail- 
 way cut just east, the dip is apparently eastward. 
 
 PiGUEE 32. — 10'-12' Limestone and schist on east side of Mount Antliony, near 
 Carpenter Hill. Composite section. 
 
 Only a few non-committal outcrops occur southeastward on 
 the hills as far south as the road going east from Pownal Center. 
 On the northeastern slope of the hill lying in the angle between this 
 road and the one going south from "Irish corner" the limestone 
 and schist are mixed in great confusion, outcrops of one passing 
 within short distances into those of the other, the whole side hill 
 presenting the aspect of limestone overthrust or overfolded and 
 resting on the schist. 
 
 Around Barber Pond and northward for a distance of three 
 miles or more the drift conceals the limestone, leaving the struc- 
 ture over this broad area wholly in the dark. 
 
 It is a problem how to interpret the structure of the lime- 
 stone south of Bennington, but the observations which have been 
 noted show close folding, overturning, overthrusting, extreme 
 and violent brecciation and shearing. I believe the limestones 
 south of Bennington to be mainly older than those which -pass 
 beneath the schist of Mount Anthony. Studies which the writer 
 has elsewhere made in the Taconic rocks have shown great blocks 
 of limestone to move upward as a mass by reverse faulting 
 against younger strata, at the same time suffering extreme fold- 
 ing and minor breaks within the block. 
 
 I would hesitate to assert that this is what has happened 
 south of Bennington, but in view of the tendency to reverse fault- 
 ing and the structural features observed in the field such a history 
 does not appear improbable. 
 
362 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 LIMESTONE AND SCHIST NORTHWEST OF 
 BENNINGTON. 
 
 Limestone outcrops in the road and along the Walloomsac 
 in Papermill Village and in Paran Creek along the trolley road 
 toward North Bennington. Outcrops in Papermill Village show 
 some minor folding westward. In the quarry east of the lumber 
 mill on Paran Creek and a few hundred yards south of it the 
 strike is N. 80° E. and the dip 11° S. SE. The fiat position of 
 the limestone in the bed and eastern bank of the creek, south of 
 North Bennington, is very conspicuous. 
 
 North of the village the limestone outcrops in patches here 
 and there. One of these is at Mattison corner and others occur 
 a mile to the north in the fields southeast of Horton corner. 
 Along the eastern slope of the hill at the latter locality the dip is 
 west-northwest at one place and at another apparently northeast, 
 forming a part of a low doming arch. 
 
 Abundant outcrops occur in the fields west and northwest 
 of Morton's corner near "Cold Spring." A reading of the dip 
 gave 14° NW. North of Clark's corner another reading gave 
 the apparent dip southeast at a high angle, but at this place the 
 rock was greatly sheared and distinction between dip and shearing 
 was not easily made. A patch of the limestone north of "Cold 
 Spring" showed many gray patches resembling fossils on the 
 weathered surface. Nothing positively distinct was found and 
 the rock was too tough to break. 
 
 The limestone formation over much of the area north of 
 Bennington shows the same gray rock which streaks and patches 
 of bufif as described for so much of the area south of Bennington, 
 and likewise showed evidence of much shearing. 
 
 On the west slope of the hill at Taper's corner, one and a half 
 miles south of Shaftsbury Center, the limestone dips to the north. 
 In the Rutland R. R. cut a mile northeast of South Shaftsbury 
 the dip is to the south. Southeast of South Shaftsbury the dip 
 is south or southeast. 
 
 On the southeastern slope of West Mountain the schist comes 
 down to within a half mile of the Shaftsbury road. The south- 
 ernmost outcrops of limestone just north of the road running 
 west of Shaftsbury Center dip to the south. Along the base of 
 the eastern slope of the mountain one-half mile farther north the 
 dip could not be made out. 
 
 There is seen to be considerable apparent variation in the 
 strike and dip of the limestone formation north of North Ben- 
 nington. In some cases the dip may have been that of shearing 
 structure, but in general the limestone appears to lie in gentle 
 undulating folds and to have suffered shearing which has pro- 
 duced an apparent eastward dip in many cases. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 363 
 
 North of the road at the base of the southern slope of _ West 
 Mountain the schist formation succeeds the limestone dipping to 
 the east-southeast. 
 
 In North Bennington village, one-half mile northwest of 
 the post office, near the railroad track, slate or phyllite outcrops 
 dipping west with eastward cleavage. A few hundred _ yards 
 west are outcrops of limestone. Westward in the direction of 
 Sodom the limestone gives place to slates. 
 
 The eastern and southern slopes of the low hill southwest 
 of Bennington are underlain by limestone dipping to the south- 
 east. This limestone is farther west than the slate in North 
 Bennington village. On the western slope of the hill the lime- 
 stone is succeeded by papery slates which are the southward con- 
 tinuation of the outcrops at Sodom. 
 
 On the south slope of the hill the limestone comes down close 
 to Henry Bridge and continues across the Walloomsac. A half- 
 mile southwest of the bridge the papery slates outcrop in the 
 brook on the west side of the road dipping to the southwest with 
 strike N. 55° W. The limestone occurs a few yards east on the 
 east side of the road. On the east slope of the hill to the south- 
 west of these outcrops the limestone rests on the slate. 
 
 The high hill southeast of the "ore pit" is capped by slates 
 and flanked by limestone on the east. 
 
 The schist was thus traced along an irregular line beginning 
 two miles west of the northern end of Mount Anthony, as shown 
 on the map, as far north as Sodom. Another trip was planned 
 to trace the boundary north from Sodom. There are reasons for 
 thinking that the Vermont Report has the boundary substantially 
 correct in representing the limestone as entirely cut off in the 
 west by the slate just east of the state boundary. 
 
 The apparent dip of the schist up the south slope and at the 
 summit of West Mountain is eastward. The rock at the summit 
 is a sericite schist which does not differ essentially from that of 
 Mann Hill both in the hand specimen and in thin section. 
 
 The country immediately southeast, east and northeast of 
 North Bennington and northward through South Shaftsbury and 
 Shaftsbury Center is so largely drift covered that outcrops are 
 few and to a great extent non-committal. Limestone outcrops on 
 the west slope, southeast of South Shaftsbury, below the slope 
 that truncates the beds of the quartzite, with strike N. 40° E. 
 and dip of 18° E. The limestone outcrops at a few places in 
 the Rutland R. R. cut north of South Shaftsbury. 
 
 The outcrops on the whole through this drift-covered area 
 suggest that the limestone is not greatly folded, as is also the case 
 around North Bennington. 
 
 The western portion of this broad valley area northwest of 
 Bennington is much sheared and the field observations indicate 
 that the limestone has been pushed against and over the schist 
 
364 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 at the west. The map shows that this hmestone area has suffered 
 at offset to the west corresponding with that in the valley quartz- 
 ite north of Bennington and also with that of the Bald Mountain 
 mass. 
 
 Throughout this broad area no marbles were found corre- 
 sponding with those that pass beneath Mount Anthony and the 
 formation was considered to belong to an older terrane than the 
 Mount Anthony limestone. 
 
 It was hardly possible to make out the structural relations 
 on the south and east of West Mountain. The schist of West 
 Mountain is regarded as younger than the limestone and so also is 
 that which the valley limestone rests against or upon at the west. 
 
 It is not possible to assert how far west the great fault that 
 bounds Bald Mountain on the south extends in the limestone 
 northwest of Bennington and so it is represented as dying away 
 west of Bennington. 
 
 LIMESTONE AND SCHIST OF MT. ANTHONY SOUTH- 
 WEST AND WEST OF BENNINGTON. 
 
 Beginning at a point about three miles south of Bennington 
 Center near the base of the eastern slope of Mt. Anthony and 
 proceeding northward along the slope, the limestone was found 
 dipping westward into the mountain beneath the schist. The 
 formation is sometimes thinly bedded, but consists mainly of beds 
 of white or clouded marble ranging from two to three or more 
 feet in thickness. The dip is as low as 5° in some places and 
 always at a low or moderate angle. Towards the northern end 
 of the mountain the dip changes to the southwest and at the north- 
 ern end to due south. Southwest of Dunham's corner the lime- 
 stone shows much confusion of strike and dip, the latter changing 
 from easterly dip through a vertical position to the characteristic 
 southwest dip. The schist near here is two or three hundred 
 feet below its normal contour. A small normal fault has dropped 
 the schist and disturbed the limestone. 
 
 In quarry excavations just southeast of the Edward H. 
 Everett mansion the strike of the limestone was N. 29° W. with 
 dip 28° S. W. Along the wood road following up the brook west 
 of the mansion the slaty schist appears showing eastward dip- 
 ping cleavage. The limestone outcrops a few yards north on 
 nearly the same contour. Farther up the mountain in the woods 
 at an old quarry the schist rests conformably on blue limestone 
 which strikes N. 80° W. and dips 47° southerly. 
 
 Along the edge of the woods northwest of the Everett man- 
 sion the limestone varies in strike between due east and west and 
 N. 48° W. Along the northwestern slope a short distance up 
 from the base the rock is a thick-bedded marble. Along the 
 northern slope just below the woods these heavy beds dip south- 
 
PLATE LXXIT. 
 
 BLUE CRYSTALLINE LIMESTONE BENEATH MT. ANTHONY 
 SCHIST AT COLGATE'S QUARRY. THE ROCK IS USED FOR ROAD 
 METAL. 
 
 -^gSoa^j^" • '^.^'■s-a;. 
 
 B. CONFORMABLE SCHIST AND LIMESTONE JUST SOUTH OF OUT- 
 CROP IN PLATE VI. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 365 
 
 ward and this same dip appears along the Pownal road from 
 Bennington Center just west of the brecciated ledges which were 
 described above and also along the road running east and west 
 through Bennington Center. 
 
 A private road ascends the northwest slope of Mount An- 
 thony on the estate of James C. Colgate. Along this road the 
 limestone gives place to the schist which strikes N. 50° E. and 
 dips 20° easterly. In some slaty beds in this schist some distance 
 up the road a crushed crinoid stem was found. 
 
 Along the road to North Pownal, which branches from the 
 Bennington-Hoosick road on the west side of Mount Anthony, 
 the dip of the limestone is southerly. In a quarry used for road 
 metal, about a mile south of the Bennington-Hoosick road, a blue 
 limestone with the same southerly dip conformably underlies the 
 schist (see Plates LXXII, A, and LXXII, B). The conditions are 
 similar to those in the quarry in the woods west of the Everett 
 mansion. 
 
 In Bennington Center, three-fourths of a mile northwest 
 of the monument, the limestone was observed with the same 
 southerly dip. 
 
 Along the North Pownal road, from the quarry south of Col- 
 gate, only the schist formation outcrops to within a mile of 
 North Pownal village. The western slope of Mount Anthony is 
 schist and this was followed over the ridge to Carpenter Hill. If, 
 as seems likely, there is a fault on the northwest of Mount An- 
 thony it dies away southward. 
 
 Mount Anthony is a synclinal pitching southward and capped 
 by the schist formation which is conformably underlain by blue 
 crystalline limestone and heavy-bedded marble which outcrop on 
 the northwest, north, northeast and a part of the east slopes 
 of the mountain. 
 
 THE LIMESTONE AND SCHIST IN NORTH POWNAL 
 AND POWNAL VILLAGES. 
 
 Northeast and east of North Pownal village is a large inlier 
 of Hmestone, as shown on the map. It extends east of North 
 Pownal as far as the road running south from Arnold's (school 
 house) corner along which it is mixed with the slate as far as 
 the next corner south. This inlier is surrounded by the slate or 
 schist on the west, north and east and at the south extends along 
 the valley of the Hoosick as far as Pownal. South of Pownal 
 it seems to be cut off by the schist from the limestone northwest 
 of WilHamstown. 
 
 At the northern end of this inlier, east of the road from 
 Bennington Center to North Pownal, the limestone forms a con- 
 spicuous hill. A reading here gave the strike N. 35° E. and the 
 dip 23° SE. Across the road at the "Wash Tubs" (see plate 
 
366 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 LXXIII) the limestone arches gently as shown in figure 33. At 
 this place the stream has cut into the gently arching limestone and 
 made a series of large pot-holes locally known as the "Wash 
 Tubs." 
 
 In the old quarry at Whipple's corner in North Pownal 
 village the limestone is rather massive. In the north wall a small 
 overturned fold was observed, the axial plane lying flat. In the 
 south wall the dip appeared to be gently westward, but dynamic 
 movement has largely effaced distinct bedding. 
 
 East of Main street in the village the limestone forms a high 
 scarp to a point one-half mile south of the railway station. At 
 the quarry at North Pownal station the limestone shows folding 
 on large and small scales with severe jamming. In the railroad 
 bank just under the highway, southwest of the quarry, is the slate 
 which is greatly jammed and crushed. Just across the river 
 opposite the quarry the slate or phyllite forms a knoll between 
 the river and the road near the Dean place. Here the slate shows 
 severe crumpling which dips eastward. 
 
 Figure 33. — Limestone structure at Wash Tubs. 
 
 Southward along the west bank of the stream a thick drift 
 covering conceals the rock near the river, but schist outcrops up 
 the slope of the hill to the west. A mile south from the Greylock 
 Mills, on the west side of the stream, a knoll of limestone lies 
 close to the river clearly resting on or against the slates. South 
 of this outcrop past the abandoned Service farmhouse all is slate 
 nearly to Daniel Gardner's house. 
 
 Along the road south from the Service house, just after it 
 makes its turn west of Gardner's house, the slate outcrops in the 
 road and the brook with limestone in close proximity. The actual 
 contact was not seen but the two are less than eight feet apart. 
 Limestone outcrops south of the road and elsewhere partly sur- 
 rounding the slate, indicating that the limestone has been pushed 
 over on the slate. 
 
 At the bridge in Pownal limestone outcrops in the bed of 
 the river. 
 
 Along the road west of the Hoosick, south of Pownal, the 
 drift hides the underlying rock, but near the quadrangle boundary, 
 a half mile east of the road, near the railroad bridge, the schist 
 outcrops in numerous ledges dipping west into the hill. West- 
 ward the schist passes beneath the drift of an immense drumlin. 
 It forms the west bank of the river south of the railroad bridge, 
 but east of the river is succeeded by Hmestone. 
 
PLATE LXXIIl. 
 
 THE WASH TUBS, NORTH POWNAL. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 367 
 
 In thin section this schist shows a felt work of sericite with 
 quartz and some magnetite as accessory and numerous flakes of 
 chlorite rather uniformly distributed in the section. In corre- 
 spondence with the presence of the latter the hand specimen 
 shows a greenish color, although the parting planes show the 
 same silvery luster exhibited by the schist of Mann Hill. 
 
 On the map, between the railroad bridge and Pownal, the 
 schist of Mason Hill is made continuous with that west of the 
 river. The schist was traced along the Pownal road east of the 
 Hoosick to and through the village of Pownal to a point about one 
 mile south of North Pownal station, where it is succeeded by the 
 high scarp of limestone along the road. At this point the bound- 
 ary turns northeastward and passes west of the brook to the 
 mixed outcrops of schist and limestone that have been described. 
 
 All along the Pownal road at the base of the westerly slope 
 of Mason and Mann hills, the dip of the schist is eastward, 
 while west of the river, so far as observed, it is normally west- 
 ward. 
 
 The eastern margin of the limestone hill east of North 
 Pownal shows pronounced shearing, especially about one mile 
 north of Wright Bridge corner, just west of the brook. It is 
 here a gray rock with chamois-colored stringers and patches like 
 that so common north and south of Bennington. Although the 
 limestone in the quarries in North Pownal is somewhat different, 
 in the surface outcrops near by, it weathers in a similar way. I 
 have not found in this inlier any heavy beds of marble like those on 
 the east and north slopes of Mount Anthony. 
 
 I look upon this limestone at North Pownal as a faulted inlier 
 which is thrust against or on the slates at the west and which 
 pinches out southward in Pownal village. 
 
 SCHIST OF MANN HILL. 
 
 Through the fields and along the road from North Pownal 
 northeastward to Carpenter Hill and eastward to Pownal Center 
 are numerous outcrops of the schist dipping east. Along the 
 eastern margin of the Mount Anthony ridge north of Pownal 
 Center the dip is westward into the hill. There is, therefore, 
 Avithin a mile going south, a change in dip from west to east. All 
 the schist south of the road from Pownal Center to North Pownal 
 and along the road, as described above, from Pownal to North 
 Pownal, and on the west slope and summit of Mann Hill dips east. 
 On the east slope of Mann Hill the schist also dips east and passes 
 beneath the hmestone which is mixed with the schist in great 
 confusion south of "Irish corner" as described above. 
 
 The schist of Mann Hill has been overturned, and the lime- 
 stone east of it has been either thrust or overturned on it. 
 
368 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 The rock at the summit of Mann Hill is a silvery sericite 
 schist. In thin section it shows a felt work of sericite with quartz 
 and without apparent accessories. 
 
 THE SCHIST AND LIMESTONE OF MASON HILL. 
 
 The summit and western slope of Mason Hill are underlain 
 by schist similar to that of Mann Hill. Along the road over the 
 summit it is noticeably crumpled. 
 
 The modified drift is piled high against the southwestern 
 slope of Mason Hill above the Hoosick River. Limestone out- 
 crops from beneath the drift along the Williamstown-Pownal 
 road a hundred yards southeast of the railroad bridge. 
 
 A road ascends the hill one-fourth of a mile south of this 
 outcrop. Four or five hundred yards north of this road just 
 above the gravel pits limestone lies on the sericite schist as shown 
 in figure 34. The limestone continues up the hill northward 
 
 
 
 if y^ 
 
 
 
 ^^^ _ S...K.,,^ 
 
 1^' ™ 
 
 
 y^ Slope of Mason Hill 
 
 
 / 
 
 e. 
 
 Figure 
 
 34.- 
 
 — Limestone and schist. 
 
 along the slope and is succeeded by the schist, both dipping east- 
 erly. Here again the limestone rests on the schist. 
 
 East of the road over Mason Hill the schist outcrops under 
 the west bank of Reservoir Brook and just across the brook less 
 than 50 feet away rises the high scarp of compact, white quartzite. 
 The schist along Reservoir Brook is greatly shattered. This 
 broken schist was also found east of Meyer's house along the road 
 and at this place lies close to the northward extension of the 
 fault along Reservoir Brook. 
 
 Along the Pownal road towards Williamstown the limestone 
 outcrops along the east side of the road with southeasterly dip 
 and strike N. 18° E., and southward joins the limestone area of 
 Williamstown. 
 
 The Hoosick between the Massachusetts line and North 
 Pownal has apparently availed itself of a great line of rupture. 
 Along this break the limestone has come to the surface, as now 
 exposed, except in the interval between Pownal and the railroad 
 bridge two miles southeast of the village along which the schist 
 of Mason Hill apparently joins that west of the river. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 369 
 
 GENERAL RELATIONS. 
 
 It is difficult to represent on the map the probable intricate 
 structural relations of the rocks of the area. The writer hoped 
 by another season's work to get some" light on the relative ages 
 of the rocks which in so many cases apparently lie in faulted 
 positions against each other. 
 
 It is possible that the major flexures which ultimately were 
 to find expression in the Green Mountain elevation began early 
 in the Cambrian period and that folding went on slowly enough 
 to allow for continuous deposition from Lower Cambrian to 
 Ordovician. The writer has elsewhere suggested that faulting 
 and erosion may possibly account for the apparent absence of 
 portions of the Cambrian. 
 
 The thick masses of sediments which accumulated in the 
 great troughs of the older rocks underwent profound folding as 
 the basement crystalline floor slowly closed in on them. They 
 were often greatly jammed, overturned and sheared. It would 
 seem that after a time the pre-Cambrian floor reached the limit 
 of strain and broke into blocks which were thrust upward into 
 the younger rocks, but not in all cases reaching the surface, as 
 now exposed. The folded younger rocks were caught at what- 
 ever stage of folding they had reached when the gneissic floor 
 broke. 
 
 Later adjustment faulting would have probably caused some 
 slumps along the planes of earlier reverse faulting. 
 
 Similar relations obtain in other portions of the Taconic belt ; 
 as at Rutland, Vermont, and in Dutchess County, N. Y. at Stiss- 
 ing Mountain, near Stissing Junction, at East and Schaghticoke 
 mountains near Dover Plains, at Corbin Hill near Pawling, in the 
 Fishkill Mountains and also at "Pine Island" near Patterson, in 
 Putnam County. 
 
 The great abyssmal swell of the pre-Cambrian floor caused it 
 to break at numerous places, often pushing the gneiss up into 
 much younger strata, the gneiss often carrying the quartzite with 
 it. Movements of lesser violence would have caused similar 
 breaks between younger rocks which would not be so apparent 
 as where the movement was violent enough to carry the pre- 
 Cambrian against the Ordovician limestone and schist. 
 
 THE PLEISTOCENE. 
 
 Only incidental attention was given to the surface deposits. 
 
 Typical kame moraine topography prevails over the area 
 around Barber Pond and two miles north of it. (See Plate 
 LXXIV, A). Barber Pond is very shallow and is surrounded and 
 formed by kames. A tongue of ice probably projected down the 
 valley from Bennington and the drainage from this tongue was 
 impounded in a shallow basin formed by Mann and Mason hills 
 
370 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 on the south and the ice on the north. In this basin the kames 
 were built. They are the marginal moraine deposits of the ice in 
 the valley. 
 
 Northeast of Barber Pond a long serpentine ridge rises 
 gradually from the flat ground just west of Brown's corner and 
 extends one-fourth mile up the hill in a northeasterly direction 
 towards the range. It has the form of a typical esker and was 
 probably formed when the ice rested on the lower slope at the 
 foot of the range. (See Plate LXXIV, B). 
 
 There is evidence of border drainage along the eastern edge 
 of the valley southeast of Bennington. 
 
 East of Bennington the Walloomsac has cut through a thick 
 bench of gravel and sand which the stream built out towards the 
 ice margin as it receded from the range. This delta terrace ex- 
 tends for two miles southward west of Harmon Hill. At the 
 time it was forming the drainage of the Walloomsac may for a 
 time have passed as a marginal stream along the eastern edge 
 of the ice and around its southern end to find exit at the pass at 
 Pownal Center. 
 
 On the southern flank of Mason Hill the modified drift, 
 which is piled high above the river, consists of thick deposits of 
 well-sorted sands and gravels and probably represents deposits 
 from glacial streams into a lake at the south during a halt of the 
 ice in its retreat northwest along the Hoosick Valley. 
 
 North of Bennington the typical knob and basin topography 
 is lacking. One or two kames were noted on the southern end of 
 West Mountain. 
 
STUDIES IN THE GEOLOGY OF 
 WESTERN VERMONT 
 
 CLARENCE E. GORDON, Ph. D. 
 
 Professor of Geology, Massachusetts Agricultural College 
 
 X^X^'-T.^^ 
 
 From the Twelfth Report, Vermont State Geologist 
 
REPORT OF THE VERMONT STATE GEOLOGIST. JIS 
 
 tracks at Chester Depot and is equipped with Raymond crush- 
 ing machinery, etc. 
 
 In spite of the general car shortage, Vermont talc companies 
 report no difficulty in moving their products. 
 
 The American Soapstone Finish Company, Chester Depot. — 
 C. P. Dodge, sole owner ; E. E. Holt, superintendent. 
 
 This company mines a low grade talc from the Carleton 
 Quarry, in Chester, and makes it into a variety of substances : 
 plaster board, soapstone finish, dusting powder for tires, etc. It 
 also sells its product to the roofing and paper trade. 
 
 SOAPSTONE. 
 
 As already stated, the soapstone industry in Vermont has 
 been at a standstill for several years, although this substance is 
 by no means exhausted. 
 
 Recently the Steatite Electric Products Corporation, of York- 
 town Heights, N. Y., has been formed for the manufacture of 
 a new electric flatiron, the core of which will be made of soap- 
 stone. It is understood that this corporation has leased the old 
 Union Soapstone Company's properties and will supply itself 
 with soapstone from them. 
 
STUDIES IN THE GEOLOGY OF WESTERN VERMONT. 
 
 Clarence E. Gordon, 
 Massachusetts Agricultural College. 
 
 TABLE OF CONTENTS. 
 
 Introduction. 
 Physiography. 
 
 The Green Mountain plateau and its ranges. 
 
 The Vermont valley. 
 
 The Taconic range and its foothills 
 
 The Champlain lowland. 
 Review of the geological terranes of western Vermont and their dis- 
 tribution. 
 
 Pre-Cambrian. 
 
 Lower Cambrian. 
 
 Middle Cambrian. 
 
 Upper Cambrian. 
 
 Beekmantown ( Calcif erous ) . 
 
 Chazy. 
 
 Black River. 
 
 Trenton. 
 
 Utica. 
 
 Later Ordovician ("Hudson"). 
 General Structural Considerations. 
 
 Description and discussion of field studies by the writer in western 
 Vermont. 
 
 Orwell Township. 
 
 Benson Township. 
 
 Sudbury Township. 
 
 Brandon Township. 
 
 Danby, Mount Tabor, Wallingford, Tinmouth, Clarendon, Rutland, 
 Proctor and Pittsford. 
 
 Shaftsbury, Arlington, Sunderland, Manchester, Dorset, Rupert and 
 Pawlet. 
 
 Pownal, Stamford, Bennington, Woodford, Shaftsbury and Glasten- 
 bury. 
 
 Whiting and Shoreham. 
 
 Leicester, Salisbury, Middlebury, Cornwall, Bridport, Weybridge, 
 Addison, New Haven, Waltham and Vergennes. 
 
 Burlington. 
 
 St. Albans Bay. 
 
 South Hero and Grand Isle. 
 General summary. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 115 
 
 INTRODUCTION. 
 
 General. The writer's studies among the rocks of the 
 Taconic region were begun in the summer of 1906 in Dutchess 
 County, N. Y.^ and were continued intermittently for several 
 seasons, first in the Hudson valley around Poughkeepsie and later 
 eastward into the Dover-Pawling valley and the hills that bound 
 it east and west. The area at the east proved so complex that 
 it appeared advisable to examine other portions of the Taconic 
 belt before suggesting any interpretations of the geological 
 structure. 
 
 In the summer of 1912 an examination was begun of the 
 southwestern portion of the State of Vermont, in Bennington 
 County. Although only about three weeks were spent in this 
 region a number of interesting observations were made, and 
 because it did not appear practicable to continue the work with 
 the idea of mapping a quadrangle, the results obtained were 
 published in the Report of the Vermont State Geologist in the 
 form of notes on the geology in the vicinity of Bennington.^ The 
 work around Bennington, although hardly more than started, 
 opened up many problems and served as a stimulus to further 
 studies in western Vermont which it is the object of this paper 
 to describe. These later studies were undertaken with the kind 
 consent of the State Geologist. 
 
 The field studies on which this paper is based were made 
 in part in the summer of 1918 during a three weeks' trip on foot 
 through the Vermont valley and portions of the Champlain low- 
 land, from Bennington at the south as far north as Vergennes, 
 with occasional trips into the mountains which hem in the valley 
 on each side and bound the Champlain lowland on the east. Very 
 brief examination was also made during the same season of the 
 formations around Burlington and along the lake shore at Mal- 
 letts and St. Albans bays. This trip was cut short by an attack 
 of influenza. During parts of the next two summers more de- 
 tailed studies were made in the towns of Pittsford, Chittenden, 
 Brandon, Leicester, Whiting, Shoreham, Sudbury, Orwell, Ben- 
 son and Hubbardton. In addition the writer was able in the 
 season of 1920 to inspect with care portions of the formations on 
 Grand Isle, both alone and in company with the State Geologist, 
 and to review some of the relations in the vicinity of Bennington. 
 In the season of 1918 it was hoped to make a more thorough 
 study of the rocks within the slate belt and also in the Green 
 Mountain plateau than circumstances permitted. 
 
 In all the work it was the practice to inspect as many out- 
 crops as possible, but especially in connection with the studies in 
 Brandon, Sudbury and Orwell, which was a region selected in 
 
 ^ Geology of the Poughkeepsie Quadrangle, N. T. State Mus. Bull. 148, 
 1911. 
 
 2 Ninth Report of the State Geologist, pp. 337-370. 
 
116 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 which to make a wide surface section from the Green Mountains 
 to Lake Champlain. The real purpose in mind of getting a first- 
 hand knowledge of some of the important field relations shown 
 by certain formations and their members under various aspects 
 of deformation and erosion at widely separated places made it 
 advisable to give a discursive but critical examination to a rather 
 extensive region. 
 
 Brief historical statement. To most people the rocks of 
 Vermont are known because of the great quarries of marble and 
 slate which have been opened in them and from the excellent de- 
 scriptions which have been given of these valuable assets of the 
 State. To geological students the part played by Vermont rocks 
 in the annals of American geology has become known and ap- 
 preciated through the work of many geologists, among whom may 
 especially be named that keen, patient and tireless investigator, 
 Rev. Augustus Wing. Vermont rocks also played a part in the 
 controversy which grew out of the diverse interpretations made 
 by different students in efforts to unravel the difficult stratigraphy 
 and structure of the Taconic region. The great controversy has 
 passed into history and most of the reverberations of its acrimony 
 have died away; but many differences of opinion have persisted 
 and probably always will. These and the controversy itself have 
 served useful ends in directing attention to a region of much in- 
 terest and importance in the geology of eastern North America. 
 
 In the end probably all will have to subscribe to what Elkanah 
 Billings wrote as long ago as 1872, that, on account of the ex- 
 tremely complicated structure of the rocks, no man living (and 
 one might add, or those who are to come) would ever see a perfect 
 map of the Taconic region. Nevertheless, towards that end the 
 workers of future generations will continue to go forward. 
 
 General plan of the paper. The paper is divided into two 
 somewhat distinct and yet closely correlated parts : 
 
 1. (a) The description of the principal physiographic divisions 
 
 of western Vermont ; 
 (b) An account, accompanied by brief descriptions, of the 
 characters, distribution and other features of the 
 various formations with which the paper deals. 
 
 2. (a) The description and discussion of a number of observa- 
 
 tions made by the writer in various parts of western 
 Vermont, particularly with reference to the secondary 
 deformations of the different rocks; 
 (b) Conclusions reached or interpretations suggested by the 
 writer. 
 
 A part of the program is avowedly an ambitious one. It 
 should be stated that any interpretations which are offered are 
 advanced with a full appreciation of the difficult geology involved 
 and of the achievements and contributions of others who have 
 labored to solve the problems of the region. 
 
PLATE XXI. 
 C A N A D/^ 
 
 2. Ba^ttEN kiuc 
 
 3. METY/^weE H. 
 +. CASTLETOhf R. 
 ■S. OTXER CF(EEK 
 6. WiNOOSKi R. 
 'X LAf»\OiiLi.E R. 
 8. M ISSlSQUoi R, 
 
 i. Snake mt-. 
 10. Buck mt. 
 
 Jfl. P»ME MILL 
 
 1Z. DANBr- CLAFreVfoohr 
 
 RIOGE 
 i3. DORSET i-iT. 
 
 PHYSIOGRAPHIC 
 Dl VISIONS 
 
 OF 
 
 WESTERN VERMONT 
 
 eENERALIZED 
 
 NOTE! EASTEFfM A,M) NORTHWESTERN 
 
 1ARC1NS OF GREEN TIT. PLATEAU 
 
 And northeastern r>iAF?GiM of 
 
 CHAMPLAIN L0»V1.AN0,LEFT INDEFINITE, 
 
 MASSAC HUS ETXS 
 
118 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 PHYSIOGRAPHY. 
 
 General. Mention has been made of certain physiographic 
 features of Vermont which for the general reader require a some- 
 what further brief description. The natural relief features and 
 to some extent the political boundaries of a region are landmarks 
 which form the framework on which one hangs, in the form of 
 maps and otherwise, the description and account of the geological 
 features. A map is therefore offered to show the principal 
 physiographic divisions of western Vermont. This map may be 
 useful in conveying some idea of the present lay of the land. It 
 has, however, many limitations in following any but the most 
 recent geological processes. If the present land forms and surface 
 conditions are too narrowly followed they may become a source 
 of embarrassment in interpreting the true geological history. 
 
 For the purposes of the paper four physiographic divisions 
 are recognized. The discussion of the geology is inevitably de- 
 veloped about these divisions. As explained above, personal 
 observations have not been made with equal thoroughness over 
 all four divisions. 
 
 1. The Green Mountain Plateau and Its Ranges. 
 
 2. The Vermont Valley. 
 
 3. The Taconic Range and Its Foothills. 
 
 4. The Champlain Lowland. 
 
 GREEN MOUNTAIN PLATEAU AND ITS RANGES. 
 
 This prominent physiographic division from which Vermont 
 has derived its name, is a broad upland which extends as a wide 
 region lengthwise across the State from north to south. It crosses 
 Massachusetts and its counterpart forms the highlands of west- 
 ern Connecticut, southeastern New York and New Jersey and 
 may be traced to Pennsylvania and beyond. Northward it passes 
 into the Province of Quebec. The western portion of this divi- 
 sion which extends from New Jersey northward into Canada 
 was designated by Dana^ as the "protaxis" of the Appalachian 
 chain, which extends from Alabama to Canada. 
 
 In their present development the Green Mountains form an 
 elevated plateau throughout their extent. In Vermont the plateau 
 is already deeply trenched by some rivers, particularly in its north- 
 ern part, and more or less incised by tributary and other streams. 
 On the whole its rugged outlines give it a youthful aspect, which 
 may be attributed in part to the resistant character of its rocks. 
 
 Generally speaking, the surface is broadly undulating and 
 averages roughly about 2,000 feet above sea-level. There are 
 numerous rather broad areas about 500 feet higher, and numerous 
 peaks and ridges rising to and above 3,000 feet. Mt. Mansfield, 
 the highest elevation, is 4,406 feet high. The sharper elevations 
 
 1 Manual, Fourth Edition, p. 24. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 119 
 
 which may be thought of as the more distinctly ridge-hke elements 
 of the plateau, in the northern part of the State form two rather 
 distinct ranges which merge into one in the southern half. 
 
 The highest peaks of the State are all only a few miles distant 
 from the western edge and succeed one another along a line that 
 suggests a prominent general structural axis which rather closely 
 parallels the western margin of the plateau. This margin is 
 marked for long reaches by a prominent scarp or by a series of 
 cliffs. It begins in Pownal in Bennington County and follows 
 a north-northeast direction to the northeastern part of Manchester 
 township and thence has a general northerly direction to about 
 the latitude of Pittsford. Then it bends slightly to west of 
 north and is sharply distinct as far north as Monkton. North 
 of Monkton it appears more broken in character, but a general 
 return to a north by east course can be discerned. The margin 
 as thus described has embayments at places from Pownal north- 
 ward. The structural and physiographic axes often have sug- 
 gestive coincidence, afthough there are variations whose import 
 is not clear. 
 
 While generally well settled and intersected by roads, some 
 of which cross the plateau into the valley at the west, there is a 
 wide strip along the western portion, from the Massachusetts 
 boundary northward two-thirds the way across the State, which 
 has only a few roads and is still mostly a wilderness. 
 
 THE VEEMONT VALLEY. 
 
 Directly west of the Green Mountain plateau, and extend- 
 ing from Pownal to Brandon, lies the "Valley of Vermont." The 
 topographic break between the two divisions is generally abrupt. 
 The western margin of the plateau upland is usually bold, often 
 precipitous. The streams which come down from it to the valley 
 have not strongly impressed their drainage upon the plateau. 
 
 In its present topographic stage of development this division 
 is only a relative lowland between the Green Mountains on the 
 east and the rugged Taconic range on the west. In its southern 
 part the lowest contours are 540 feet along the Walloomsac 
 River near Bennington, and 620 feet along the Batten Kill at 
 Arlington. Along the course of Otter Creek from Danby north- 
 ward the contours descend from 660 feet to 340 feet near Bran- 
 don, where the Vermont valley merges with the Champlain 
 lowland. 
 
 The floor of the valley is in fact almost throughout a moderate 
 upland which is obscured by the higher lands which hem it in. It 
 is mostly uneven and studded with hills. The average relief is 
 probably above 800 feet. The valley form is not, as one unac- 
 quainted with it might infer, such as would have been produced by 
 a single master river running through it. 
 
120 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 North and south of Bennington, around the head streams of 
 the Walloomsac River, this division is about six miles wide. To 
 the west along the river it passes by a broad gap into the Hudson 
 valley lowland. At Bennington the Vermont valley is offset two 
 miles to the east and in Pownal is completely intercepted by the 
 Mount Anthony-Mason Hill ridge. Towards the north in Sun- 
 derland it narrows to a width of two miles. It widens again near 
 Manchester around the head streams of the Batten Kill and the 
 Mettawee. North of Manchester it is interrupted by Dorset 
 Mountain and here is about one-fourth of a mile wide. North of 
 Dorset Mountain the major valley is broken into minor ones by 
 prominent intermediate ridges. Otter Creek occupies the eastern 
 minor valley, which from WalHngford to Rutland is over three 
 miles wide. As the topographic map shows the creek changes 
 direction at Rutland from north to west, crossing the structural 
 axes of the rock formations ; but at Center Rutland the stream 
 regains a general northerly direction and flows through a narrow 
 valley to Proctor. Thence it passes into the open valley of Pitts- 
 ford which leads into Brandon. In Brandon the major valley 
 has a more uniform surface and widens out northward to form 
 the Champlain lowland. 
 
 The Vermont valley has its physiographic, and to a consider- 
 able extent also its geological, counterpart in the Berkshire valley 
 of western Massachusetts along the upper reaches of the Hoosic 
 and Housatonic rivers. There is a recognizable apparent simi- 
 larity in general configuration between the two, and in the modifi- 
 cations occasioned by hills, ridges and outlying masses of the other 
 physiographic divisions. 
 
 The Berkshire valley continues into Connecticut, but at 
 Canaan the Housatonic leaves a wide valley for a narrow one 
 across the upland, which in Connecticut, however, has a lower 
 average elevation than in Massachusetts and Vermont. In north- 
 western Connecticut and southeastern New York irregularities 
 appear consequent upon the geological structure and relations 
 there present. 
 
 THE TACONIC EANGE AlfD ITS FOOTHILLS. 
 
 The Taconic range bounds the Vermont valley on the west 
 throughout its length, except for erosion gaps, the widest of 
 which is west of Bennington. In Vermont this division is the 
 continuation of a similar range that lies along the border between 
 Massachusetts and New York. It extends in Vermont from 
 Shaftsbury in the southwestern part of the State to Orwell and 
 Sudbury. North of Pownal practically all the range is in Ver- 
 mont and all the higher summits are in this State. Viewed as a 
 broad unit the range overlaps the New York- Vermont boundary 
 in its southern half. North of Rupert the western margin hugs 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 121 
 
 the State line as far as Poultney, whence it passes due north to 
 Orwell and Sudbury. 
 
 In its course across Vermont the relation of the range to the 
 Vermont valley is marked by at least two prominent structural 
 irregularities. Southwest of Bennington, in correspondence with 
 offset in the Vermont valley already mentioned, Mt. Anthony 
 lies farther -east than does West Mountain in Shaftsbury, and in 
 the town of Dorset the mass -of Dorset Mountain rises abruptly in 
 the valley midway in its course from Bennington to Brandon. 
 
 The higher elevations of this division range from about 2,500 
 feet to about 3,500 feet above sea-level. Equinox Mountain 
 reaches 3,816 feet and Dorset Peak is 3,804 feet high. Most of 
 the higher summits lie along the eastern border of the range. 
 West and north the surface falls off in elevation into the foothill 
 region ; but many scarps and precipices marking probable fault 
 lines greatly disturb the surface regularity and contribute notably 
 to the present topographic outlines. Although symmetry of con- 
 tours is therefore lacking in the present stages of topographic 
 development if one were to generahze very broadly the northern 
 and western slopes of the division, the erosion features of the 
 elevation would fall off gradually westward and northward by 
 slopes of similar gradient to the relative lowlands of the Hudson 
 and Champlain valleys. 
 
 This division is cut across and otherwise by streams whose 
 branches heading rather deeply into it have dissected it into a 
 series of peaks and ridges. In its outlines the division offers 
 some contrasts with western edge of the Green Mountain plateau ; 
 but stream incision has not been pronounced in either wall of 
 the valley and the topographic outlines of its two slopes wear 
 much the same expression for long distances. 
 
 The valleys which cut through the range mark the extension 
 of the lower Hudson valley levels into the intermediate upland of 
 the Vermont valley. There are certain notable differences among 
 these valleys which may be mentioned here. The valley of the 
 Walloomsac River is wide and is really a broad extension of the 
 Vermont valley westward. That of the Batten Kill is narrower 
 and hemmed in by steeper slopes. The valley formed by the 
 Mettawee and the West Branch of the Batten Kill is fairly wide 
 and the bottom lands are well developed. The valley of Castle- 
 ton River is rather narrow and its northern are steeper than its 
 southern slopes, as nearly all its branches within the range come 
 in from the south. 
 
 THE CHAMPLAIN LOWLAND. 
 
 The distinctness of this physiographic division as a whole is 
 sharper when viewed from a distance in broad sweeps rather 
 than from a close examination of the topography of its surface, 
 which, like that of the Vermont valley is studded, in some places 
 
122 REPORT OP THE VERMONT STATE GEOLOGIST. ^ 
 
 more than in others, with hills. It may first be described in its 
 larger outlines. 
 
 Lake Champlain lies along its western border, and rising from 
 the western side of the lake, with their bases dipping into it at 
 places or separated from the lake shore by a narrow strip of 
 hilly land, stand the rugged Adirondacks. In its southwestern 
 portion it is bounded by the northwestern foothills of the Taconic 
 range. The boundary at the southwest swings eastward around 
 the Orwell hills and then encloses a narrow embayment extend- 
 ing up the valley of the Lemon Fair River between the Orwell 
 and Sudbury hills. It then passes around the northern end of 
 the Sudbury hills to Brandon and thence northerly along the west- 
 ern base of the Green Mountain plateau, with the topographic 
 break sharply outlined between the lowland and tlje plateau as 
 far north as Monkton. North of Monkton the Green Mountain 
 plateau surface is more broken along the edge; but the higher 
 average relief is well enough preserved to give an outline to the 
 Champlain valley in its extension northeastward to the Canada 
 line. At the north the Champlain lowland merges with the St. 
 Lawrence valley. At the south along the narrow region of the 
 lake it joins with the Hudson valley. 
 
 The lowest surface in this division is that of Lake Champlain, 
 which for high and low water conditions averages about 100 feet 
 above sea-level. But the lake occupies a depression, the actual 
 depth of whose rock bottom will probably never be known, as it 
 could hardly have escaped being modified by glacial deposits. 
 Soundings have shown that the waters now fill a basin of vary- 
 ing depth and bring out in the channel-Hke character of its west- 
 ern portion the indication of former stream erosion. The max- 
 imum depth reached is about 400 feet near Essex, N. Y., but the 
 present bottom ranges from that depth to comparatively shallow 
 water. The bottom of the lake in many places thus stands in 
 marked contrast with even the lowest portion of the present ex- 
 posed surface of this lowland. The lake has many low islands 
 of varying dimensions throughout its extent. 
 
 Between Lake Champlain on the west and the Green Moun- 
 tains on the east for a distance of about 40 miles from the 
 northern end of the Taconic range to BurHngton, converging 
 somewhat towards BurHngton, and again north of Georgia through 
 St. Albans and Highgate to the Canada line, a large portion of 
 the surface ranges from about 100 feet at the lake to 350 feet 
 inland, with the rest of it from 350 to over 400 feet. Along parts 
 of the Otter Creek valley and along the lake for a width of about 
 six miles, in the areas just described, the contours are relatively 
 
PLATE XXIII. 
 
 t 
 
 
 
 
 
 
 \^ 
 
 \ 
 
 - ' ^:^ \; - 
 
 o^'^^^i;: 
 
 
 ^1 B^^^S'i-- 
 
 /; A>y^"V/ -i^S' nPA ^rr- ^4,._ 
 
 Township Map of Vermont. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 123 
 
 widely spaced and run long distances without closing. There is 
 distinguishable a low range of hills extending north from Orwell, 
 which is so reduced over most of its surface as hardly to deserve 
 the name, but which is noticeable by reason of the lower land 
 along the lake and from the excavation of Otter Creek on the 
 east. This range reaches its greatest altitude in Snake Mountain 
 (1,271 feet) and terminates in Buck Mountain (927 feet) south 
 of Vergennes. Mt. Philo in Charlotte is 968 feet high. In 
 Bristol and Monkton there are prominent hills including Hogback 
 (1,220 feet), and several conspicuous hills occur west and north 
 of Lake Dunmore. St. Albans Hill (910 feet) and Aldis Hill 
 (840 feet) are the conspicuous elevations north of Georgia. The 
 Orwell-Buck Mountain ridge at the south merges topographic- 
 ally with the western foothills of the Taconic range. 
 
 In late Pleistocene time much of the Champlain lowland was 
 covered probably by the waters of the sea which probably ex- 
 tended into the Vermont valley as far south as Rutland. The 
 present surface, both on the islands of the lake and on the main- 
 land, gives clear evidence of the former submergence of a wide 
 portion of this lowland by an inland water body. 
 
 North of the Winooski River to the latitude of Georgia the 
 surface has a more uniform and a uniformly higher elevation, 
 ranging from 300 to 350 feet. The contours are more narrowly 
 spaced and close within short distances, giving a more cut-up 
 topography. 
 
 Four streams, Otter Creek, and the Winooski, Lamoille and 
 Missisquoi rivers, cross the lowland to enter Lake Champlain. 
 
 REVIEW OF THE GEOLOGICAL TERRANES AND 
 
 FORMATIONS OF WESTERN VERMONT AND 
 
 THEIR DISTRIBUTION. 
 
 General remarks. A short acquaintance with the rocks of 
 western Vermont in their field relations will soon convince one 
 that they have had a long and varied history, that their present 
 geography is very different from that which existed at various 
 times in the past, and that many of them are now remote from 
 the positions which they once occupied. 
 
 The general geology of areas contiguous to Vermont and 
 extending for some distance north and south of the State shows 
 that while the Vermont rocks have had in some ways an inde- 
 pendent history they are in a broad way genetically related in 
 age and perhaps quite as much so in certain general structural 
 characters to rock formations over an extensive region. 
 
 It is more or less widely recognized that many similarities 
 in the age and structural relations of the rocks over this wide 
 region permit a certain amount of generalization with regard to 
 broad crustal movements concerned in their deposition. Account 
 has been taken of great tectonic displacements which are known 
 
124 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 to have occured, in explaining the absence of certain strata, or 
 better perhaps certain faunas, over the entire region and the ap- 
 parent limitations of others ; but these phenomena have also been 
 explained, at least in part, on the basis of minor crustal move- 
 ments which have operated to cut off faunal provinces from each 
 other and to restrict the areas of continental seas. 
 
 As investigations have extended our information concerning 
 details of stratigraphy we have had positive confirmation of the 
 wide extension of certain ancient seas within the region. On the 
 other hand extensive study has failed to reveal any conclusive 
 evidence of the former presence of certain seas, which are gen- 
 erally assumed to have been wholly absent, or the wider exten- 
 sion of others, whose faunas are present in places, and whose 
 ancient boundaries are set on the basis of known outcrops. 
 
 From the nature of the complex geological relations now 
 present the explanations of these absent intervals cannot be based 
 upon positively identified depositional unconformities between 
 younger and older rocks than those which are absent. It is, of 
 course, necessary to recognize the possible existence of erosion 
 intervals of varying degrees of duration among sedimentary 
 formations, due to periods of restlessness of the internal forces 
 which disturb the crust, but one must also consider the evidence 
 that the crust may apparently remain relatively quiet for immense 
 intervals of time, and particularly, for the region of western 
 Vermont and related areas, it is necessary to take account of the 
 evidence of profound crustal displacements and metamorphism, 
 and of erosion at various periods of the region's history. 
 
 It has not been clear just how far it would be well to go for 
 the profit of the general reader as well as for the more precise 
 information of the geological student in reviewing the characters, 
 variations and distribution of the different terranes and forma- 
 tions of the region under discussion. It is clear that some idea of 
 these different rocks and the confusion that prevails among them 
 in the field should be given as an aid to the discussion that will 
 follow. 
 
 A categorical statement of such matters is likely to leave an 
 impression of simplicity; but care will be taken in the sequel to 
 point out the many difficulties that lie in the way of positive de- 
 terminations of field relations and that conclusions are based on 
 what seems most probable, with the evidence at hand, among 
 several possibilities that are presented. 
 
 The following descriptions are purposely given with con- 
 siderable fullness, but structural considerations are largely post- 
 poned for later treatment. 
 
 PRE-CAMBRIAN. 
 
 According to many observers the pre-Cambrian basement, or 
 old sea floor, on which the Lower Cambrian rocks of this general 
 region were deposited, is decisively exposed at various places 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 125 
 
 in the Green Mountain plateau. The rocks which have been 
 described as pre-Cambrian consist of gneisses, which are notably 
 chiefly of probably igneous origin, and otiier rocks such as schists, 
 quartzites, graywackes and crystalline limestones. 
 
 The discrimination of the pre-Cambrian is most satisfactory 
 in those places at which a heavy basal quartzite, or a conglomerate, 
 appears to rest unconformably upon, or to be separated by a 
 thin, schistose layer from a rock whose structural features are 
 in pronounced discordance with those of the younger rock, and 
 are apparently of much more ancient date. In Massachusetts and 
 New York similar relations have been described and seem to 
 leave no doubt of the exposure at the present surface of a pre- 
 Cambrian core in the Green Mountains. That certain old gneisses 
 antedated the Cambrian and formed its floor of deposition is sub- 
 stantially borne out by numerous localities where the advancing 
 Cambrian sea caught and preserved portions of the regolith of 
 the land which it was overlapping. The more or less decayed 
 material seems to have been only partially sorted at times and 
 seems to have taken on in greater or less degree the bedded 
 structure of the Cambrian while grading at depth into less altered 
 rock which retained more or less of the structure of the parent 
 gneiss. Such relations seem especially significant with respect 
 to the question of depositional unconformity in a region that 
 gives evidence of more than one orogenic movement and of pro- 
 found overthrusting ; for it is conceivable that contacts of pure 
 quartzite, or even conglomerate, could in such a region be the 
 results of other processes than marine overlap. It will be noted 
 later also that there are numerous places in western Vermont 
 where Ordovician limestones apparently rest by unconformity on 
 rock that appears to be Cambrian without any traces of a basal 
 transgressive sand or other rock intervening. 
 
 The separation of the Vermont pre-Cambrian into systems 
 such as have been recognized elsewhere is a task which has yet 
 to be worked out for the Green Mountain plateau generally. In 
 various parts of the plateau Whittle, Keith and others have de- 
 scribed as probably pre-Cambrian various metamorphic rocks 
 such as quartzite, schists and crystalline limestones which have 
 been called Algonkian, Huronian and so forth. Similar rocks 
 have been described for Massachusetts, New York and Quebec. 
 The discrimination of older rocks from altered Paleozoic has not 
 always been made with a sharpness that is conclusive. 
 
 While there is, generally speaking, an abrupt passage from 
 the less metamorphosed rocks of western Vermont to those of 
 the plateau this fact by itself is discounted somewhat by the un- 
 doubted upthrust or overthrust relation of the plateau to the rocks 
 at the west of it. It is somewhat significant, although exhaustive 
 search has yet to be made, that in northwestern Vermont no pre- 
 
126 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Cambrian basement contacts have yet been discovered to the 
 Paleozoic rocks. 
 
 In spite of metamorphism and apparent absence of fossils, 
 investigations have already extended the range of Paleozoic seas 
 over this region, although it remains to show that in some cases 
 these were the same seas that laid down the rocks of what is now 
 western Vermont. 
 
 In western Massachusetts Professor Emerson early suggested 
 a separation of the pre-Cambrian, and in early descriptions of 
 certain rocks he used the term Algonkian. Coming in later years 
 apparently to a more conservative view he called the pre-Cambrian 
 rocks of western Massachusetts, Archaean, and the Green Moun- 
 tain plateau a "broad Archaean-Silurian upland." 
 
 The basal Cambrian quartzite has been found some distance 
 eastward from the western outcrops of the gneisses in Vermont, 
 Massachusetts and elsewhere where it has been preserved by 
 down-folding or down-faulting as erosion outliers. The quartzite 
 or its probable equivalent extends for miles as a fringe along the 
 western margin of the plateau. Throughout the ages-long history 
 of these rocks we may beHeve it has in some way been protected 
 from erosion. It is plausible that conditions were not favorable 
 for the preservation of vast areas of Cambrian beds, and possibly 
 also later ones, elsewhere in what is now the plateau. 
 
 West of the Green Mountains presumably the pre-Cambrian 
 extends at unknown depth beneath the rocks now present at the 
 surface. 
 
 CAMBRIAN. 
 Lower Cambrian. 
 
 The Lower Cambrian has been described as represented in 
 Vermont by the following-named formations : 
 
 1. "Vermont Formation." 
 
 2. Dolomite and a quartzite-dolomite interbedded series. 
 
 3. "Red Sandrock." 
 
 4. "Georgia Slates" ("Georgia Group"). 
 
 5. "Roofing Slates" (with associated rocks). 
 
 Parts of all these formations were presumably contempora- 
 neous and lithological differences were presumably due to different 
 conditions of deposition. Certain members of the Vermont 
 Formation can be reasonably shown to be basal and conformable 
 to the dolomite. The interbedded series in some places lies on 
 the dolomite and this seems to be the normal succession. There 
 has been so much disturbance of the region that the present rela- 
 tions are sometimes obscure. In some places the interbedded 
 series apparently lies on quartzite of the Vermont Formation. 
 The Red Sandrock has been described as conformably subjacent 
 to the Georgia Slates in northwestern Vermont. As indicated 
 above the base of the Vermont Formation and its pre-Cambrian 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 127 
 
 contact has been fairly conclusively demonstrated ; but the deposi- 
 tional bases of the Red Sandrock and the Roofing Slates are 
 unknown. 
 
 Each formation presents horizontal differences which are 
 better shown in some than in others. In all cases the intrarela- 
 tionships and the relations of the formations to each other and 
 to associated rocks are much confused and disguised by deforma- 
 tions which the rocks have suffered. 
 
 The Vermont Formation. The Vermont Formation has the 
 following-named members at various places throughout its extent 
 at the present surface : 
 
 a. Various basal gneisses or schists, probably altered deriva- 
 tives in most cases of pre-Cambrian gneisses and other rocks, 
 sometimes rather sharply delaminated from the parent rock, but 
 often imperfectly transitional between gneiss and quartzite, con- 
 glomerate, or arkose. 
 
 b. Arkoses. 
 
 c. Conglomerate. 
 
 d. Granular quartz rock. 
 
 e. Massive brownish quartzites. 
 
 f. Schistose quartzites and schists. 
 
 The first-named have been described by different observers. 
 Conglomerate is not uncommon, sometimes arkosic. White, 
 granular quartzites are very common and pass into massive, 
 brownish rocks, which in turn grade into schistose quartzites. 
 The massive quartzites with conspicuous, white, granular mem- 
 bers are of great apparent thickness and prominence in scarps 
 along the western front of the Green Mountain plateau and by 
 faulting are also widely distributed along the Vermont valley. 
 
 By thrusting, members of this formation may have been car- 
 ried westward into the Taconic division, but this question will 
 be discussed beyond. 
 
 Fossils in the quartzite (and the limestones) together with 
 the field relations fix the age of these various rocks certainly in 
 some cases and probably in the others, as Lower Cambrian, 
 
 Dolomite and the interhedded series. This formation con- 
 tains : 
 
 a. At some places at least, at the base, a limestone of mod- 
 erate thickness ; at other places at the base a dolomitic limestone 
 of uncertain thickness. 
 
 b. Above (a) a succession of dolomitic limestones inter- 
 bedded with calcareous quartzites, rather pure, massive quartzites 
 and schistose quartzites. 
 
 In the interhedded series the quartzitic members seem to be 
 more abundant near the base. The more purely siliceous mem- 
 bers range in thickness from about 2 inches to one bed at least 
 10 feet thick, possibly 20 feet, unless folded. The dolomitic 
 members range from a few inches to about 3 feet in thickness. 
 
128 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 The interbedded series is extensively developed along the 
 Vermont valley from Bennington northward and was traced by 
 the writer as far north as East Middlebury. It is best shown 
 among the hills along the eastern portion of the valley and forms 
 the visible part of most of the camel-hump arches that make up 
 the valley floor. The outcrops of the members of this series are 
 conspicuous features and the quartzites have undoubtedly been 
 important factors in preservation from erosion. The series is 
 often clearly present, beneath the surface in places intermediate 
 between the hills just mentioned. The westward extension of 
 these rocks and their relations to other terranes will be discussed 
 at other places. 
 
 The intimate association of this series with quartzite of the 
 Vermont Formation is clear at many places along the Vermont 
 valley. At Bennington the succession from quartzite of the 
 Vermont Formation through dolomitic limestone to interbedded 
 limestones and quartzites is particularly clear (see fig. 21). The 
 two formations have plainly been deformed together in a large 
 way, although the interbedded rocks appear to have suffered some 
 independent deformation both with regard to folding and faulting. 
 
 The present distribution of the series tells nothing about its 
 original horizontal extent. 
 
 Red Sandrock. This name has been and is now applied to 
 a formation that shows much variation in composition and in 
 color, and which in some localities is chiefly dolomite. The forma- 
 tion is practically restricted in its outcrops to the west central 
 and northwestern parts of the State. It is prominent at the 
 present surface around Monkton, at Snake Mountain in Wey- 
 bridge and Addison, at Buck Mountain in Waltham, and thence 
 northward through Charlotte, Shelburne, Burlington and beyond. 
 At the south in Addison County, and also along the shore of Lake 
 Champlain in Shelburne and BurHngton, much of this rock is a 
 quartzite and often has a dark, brick-red color. In Chittenden 
 and Franklin counties it is described as prevailingly dolomitic. 
 In Georgia, as early described by Walcott, it consists of a series 
 of bluish gray, steel gray, gray massive, and reddish pink dolo- 
 mitic limestones and gray, massive, arenaceous limestone, variously 
 banded, colored, or mottled, and passes upward into the Georgia 
 Slates. 
 
 At the Canadian line, according to Logan, it consists of white 
 and red dolomites and sandy layers, with some strata mottled red 
 and white and a few brick-red. Some beds were said to be very 
 siliceous. All weather yellowish or reddish brown. The Red 
 Sandrock series extends across the Canada line for about five 
 miles. 
 
 The quartzitic members are all more or less calcareous and 
 the dolomitic beds are all somewhat siliceous. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. ^29 
 
 The base of this formation is not known. The formation 
 has been described by some observers as merging with the quartz- 
 ite of the Vermont Formation near Monkton. 
 
 Lower Cambrian fossils have been found at various places 
 and within different phases of this formation. 
 
 Along the lake shore at and near Burlington, members of 
 this formation can be seen to rest by thrust on younger (Ordovi- 
 cian) rocks. 
 
 Except for certain marked features of color the Red Sand- 
 rock series bears much resemblance in general sequence to the 
 quartzite and its overlying dolomite and interbedded series that 
 have been described. 
 
 Georgia Slates {"Georgia Group/' "Georgia Slate Group''). 
 The members of this group were first described from the town 
 of Georgia by C. D. Walcott and were represented as conform- 
 ably succeeding the Red Sandrock series. The group is typically 
 developed in the towns of Georgia, St. Albans, Swanton and High- 
 gate in Franklin County. 
 
 Walcott distinguished a series somewhat as follows, begin- 
 ning at the base : 
 
 a. Argillacio-micaceous and arenaceous shales, with many 
 Lower Cambrian fossils ("Georgia Shales"), 200 feet. 
 
 b. Argillaceous shales with occasional layers of hard gray 
 limestone, ^4 inch to 2 inches thick, 3,500 feet. 
 
 c. Light gray quartzite, 50 feet. 
 
 d. Gray limestone in massive layers, with intercalated bands 
 of argillaceous shale, 1,700 feet. 
 
 e. Argillaceous shales similar to (a) conformable at base 
 with (d) and cut oflf at the top by a fault, 3,500-4,500 feet. 
 
 The total thus gave the extraordinary maximum thickness 
 of 9,950 feet. The correlation was mostly with Lower Cambrian. 
 In 1891 Walcott described (d) of the above as appearing to be 
 a great lenticle of limestone and the fossils as approaching the 
 Upper Cambrian (in the absence of Olenellus). 
 
 Ulrich has "hazarded" the opinion that the upper 3,500 feet 
 of the shale of the section described by Walcott may be of "Cana- 
 dian" age (basal Ordovician). He also questions the age, in the 
 stratum of limestone and shale to which Walcott assigned a 
 thickness of 1,700 feet, of a limestone which gives fossils that 
 may be of Middle Cambrian age. 
 
 The thickness assigned the series and other features may 
 have to be revised by future study of the deformations of the 
 region. 
 
 Roofing Slates (and associated rocks). From the northern 
 end of the Taconic region southward along its western slopes, 
 forming in Vermont a strip 8 to 11 miles wide north of Fairhaven 
 and a strip from 2 to 3 miles wide south of Fairhaven to West 
 Rupert, and extending from the north and east into eastern New 
 
130 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 York to form a broad band in that State, is a belt of rocks known 
 over much of its length of 70 miles or more as the "roofing slate 
 belt." Over a distance of 40 to 50 miles the rock of this belt is 
 extensively quarried for roofing slate. 
 
 At the northern end of the Taconic range in Sudbury, arena- 
 ceous slates and phyllites which have been described as Cambrian 
 occur in close association with masses of heavy quartzite and 
 again in proximity to other phyllitic rocks which have been de- 
 scribed as of probably Ordovician age. South of Hubbardton 
 near the western boundary of the State and across the line in 
 New York have been described large areas of slate of probably 
 Lower Cambrian age, as determined by fossils in associated lime- 
 stones, interspersed in no regular way with slates and other rocks 
 which have been described as of Ordovician age on the basis of 
 graptolites found in the slates, and apparently sometimes from 
 associated limestones and other field relations. Lower Cambrian 
 fossils are reported widely distributed among the rocks of the 
 slate belt and numerous localities yielding graptolites have been 
 found. 
 
 The structural relations of the rock masses yielding these 
 different fossils are still mooted problems. 
 
 In 1888 Walcott published a preliminary map of this region. 
 In 1891 he correlated the Cambrian slates of this belt with those 
 of Georgia, Vt. In 1899 T. N. Dale published a revision of 
 Walcott's map and added many additional fossil localities to those 
 which had been reported by Walcott. 
 
 As described by Dale the members of the slate belt are as 
 follows : 
 
 Cambrian. 
 
 a. Olive grit (a graywacke), more or less massive, some- 
 times with small quartzite beds. Has associated with it, in 
 places, a bed of quartzite 12 to 55 feet thick. 
 
 b. Roofing slates, grayish green, purple, or mixed green and 
 purple, alternating with beds of calcareous quartzite (5 feet) and 
 limestone breccia up to 40 feet thick. 
 
 c. Dark gray grit, or sandstone, with shaly patches. 
 
 d. Black shales or slates with thin beds of limestone breccia. 
 
 e. Quartzite usually with spots of limonite, with some varia- 
 tions and sometimes associated with a quartz conglomerate. 
 
 Ordovician. 
 
 a. Gray or black shales and thin-bedded limestones; pos- 
 sibly intermittent ("Calciferous"). 
 
 b. Black or gray shales and slates, sometimes banded from 
 bedding ("Hudson Shales"). 
 
 c. Greenish or black, more or less quartzose, shales and 
 slates, weathering white or whitish ("Hudson White Beds"), 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 131 
 
 d. Gray grit (graywacke) interbedded with black shales or 
 slates ("Hudson Grits"). 
 
 e. Green or dull reddish or purplish phyllite with very thin 
 beds of quartzite, more frequent towards the east ("Hudson Thin 
 Quartzite"). 
 
 f. Red and green roofing slate or shale ("Hudson Red and 
 Green Slate"). 
 
 Limestone is also described as occurring mostly west of the 
 slate belt. It is called "Trenton," and is thought of as perhaps 
 representing Trenton, Chazy and Calciferous (Beekmantown). 
 "Berkshire Schist" (sericite, chlorite and quartz schists), con- 
 taining beds of greenish quartzite up to 10 feet and over in thick- 
 ness, is further described as occurring east of the slate belt, and 
 is regarded as probably representing all the above-named ter- 
 rigenous rocks called Ordovician, and as including Lorraine and 
 Utica horizons. 
 
 Middle Cambrian. 
 
 Over most of western Vermont, so far as records obtained 
 from present outcrops go, there is above the Lower Cambrian a 
 great absent interval. That later Cambrian, and particularly Mid- 
 dle Cambrian, may have once been more fully represented is in- 
 dicated by the discovery of a Middle Cambrian fauna within a 
 rock which was designated as an "intraformational conglomerate." 
 
 This so-called intraformational conglomerate was described 
 by G. E. Edson as formed of dark-colored, fine-grained limestone ; 
 bluish or dove-colored limestone ; arenaceous shale, in which in 
 some instances are found nodules of pure limestone and enclosed 
 water-worn pieces of bluish-colored slate; sandstone resembling 
 quartzite; arenaceous Hmestone in which the enclosed grains of 
 sand are dark thus giving the rock a mottled appearance ; and a 
 light-colored limestone. The rocks (fragments) forming this con- 
 glomerate vary in size from small pieces to bowlders weighing 
 many tons. 
 
 According to Edson this formation first appears at the present 
 surface near the north line of Georgia. Here its "brecciated" 
 condition does not appear at its best and the rock has the appear- 
 ance of a massive, dark-colored, arenaceous limestone. The out- 
 crop is described as continuing without a break to the north line 
 of Georgia, but there disappears. It reappears northward in St. 
 Albans. At this place the "brecciated" condition is usually well 
 shown and the rock is in places associated with a shale. It ap- 
 pears intermittently northward to the St. Albans line and passes 
 into the town of Swanton, in which town it is represented by the 
 shale with which it is associated farther south. Northward the 
 conglomerate appears again and passes into Highgate, to the bank 
 of the Missisquoi River. • 
 
132 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 The State Geologist submitted specimens of the fossils found 
 in this conglomerate to Dr. Walcott, who had in his possession 
 some which he had collected from the same region. From a pre- 
 liminary examination Walcott thought the fossils Middle Cam- 
 brian. They showed a considerable range, but Paradoxidcs was 
 described as occurring in the matrix which would make this rock 
 actual Middle Cambrian and an "interformational conglomerate." 
 
 As further described by Edson a L. acuntinata was found in 
 a shale lying close to the conglomerate. In Swanton shale is 
 found on both sides of the conglomerate and also "interstratified" 
 with it. On the western side shale passes under the conglomerate 
 and dips to the east. The same fossils are described as found in 
 the various limestones and sandstones as are found in the shale 
 and the matrix of the conglomerate. From the descriptions it 
 appears that the structural relations to other formations are prob- 
 lematical. One may hazard the opinion that the structural rela- 
 tions of the rocks to each other are also complicated and pos- 
 sibly abnormal in some cases. The possibility of the so-called 
 conglomerate being an autoclastic needs to be considered. 
 
 Upper Cambrian. 
 
 On the New York side of Lake Champlain an Upper Cam- 
 brian sandstone is widely present and has been described as rest- 
 ing by depositional unconformity on pre-Cambrian rocks. Ex- 
 posures occur around Port Henry, Essex, Port Kent, and Keese- 
 ville. This sandstone forms a wide fringe along the northern 
 side of the Adirondack mass of ancient pre-Cambrian rocks. 
 Professor Kemp has described small outliers back from the lake, 
 west of Port Henry. On the west side of the lake faulting is 
 common in this sandstone and in some places erosion has been 
 heavy. This rock has long been known as the Potsdam from its 
 type locality at Potsdam, St. Lawrence County, N. Y. 
 
 In his descriptions of the exposures around Port Henry, 
 Ruedemann has indicated that what is regarded as the base of 
 this formation in this region shows anomalous features in com- 
 parison with localities in Clinton County, N. Y., and on the north- 
 ern side of the Adirondacks, especially in the slight development 
 of a conglomerate and in the absence of red, hematitic arkoses, 
 and reaches the conclusion that near Port Henry the Potsdam 
 format-ion does not attain the great thickness which it has farther 
 north and that the lower Potsdam, and perhaps the upper, were 
 not as fully developed as in Clinton County. 
 
 East of Lake Champlain the outcrops of known Cambrian 
 that have certainly and definitely been determined by fossils, ex- 
 cept the "intraformational conglomerate" described above and 
 occasional small exposures to be mentioned beyond, belong to 
 the lower part of this system, including the rocks along the lake 
 shore which as has already been mentioned, can be seen to rest 
 by overthrust on greatly disturbed younger (Ordovician) rocks. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 133 
 
 In his early studies in the town of Highgate, Walcott de- 
 scribed a hmestone conglomerate in the shale T apparently repre- 
 senting the rock discussed above under Middle Cambrian and 
 later described by Edson; containing fragments of limestone van,^- 
 ing in size from pebbles to masses 6 feet in diameter. At that 
 time Dr. Walcott thought the fossils to have an Upper Cambrian 
 aspect. In his later examination of specimens submitted to him 
 by the State Geologist and in a re-examination of his own material 
 he gave the forms a wide range, although inclined to concede a 
 Middle Cambrian age for the matrix of the conglomerate, if 
 Paradoxides occurred in it (see above, page 129 j. 
 
 A somewhat siliceous and magnesian limestone, associated 
 with a thick-bedded, barren, dolomitic series that stratigraphically 
 lies above it, is known in southeastern Xew York State, and in 
 its exposures near Poughkeepsie in Dutchess County, in the Wap- 
 pinger CBarnegat; limestone, was first described by W. E. 
 Dwight and later further discussed and described by the writer. 
 Fossils were found by both observers, consisting of brachiopods, 
 (Lingulepsis pinnaformis, and others according to Dwight; and 
 of trilobites, (Ptychoparia, of species found by Walcott at Sara- 
 toga;. These fossils were considered to mark the rock as of 
 "Potsdam" age. The region w^as mapped by the writer and the 
 fossiliferous rock just described was found to pitch southward, 
 in what was called the western strip of the Wap>pinger belt, 
 beneath the thick-bedded, barren dolomite which was regarded as 
 perhaps forming in part the upper portion of the Cambrian of the 
 region and as older than other strata of "Calciferous" TBeekman- 
 town) age lying above the Potsdam along the so-called "central 
 strip" of the Wappinger belt as shown near Rochdale, a hamlet 
 just northeast of Poughkeep>sie. 
 
 The fossiliferous limestone in Dutchess County, assigned to 
 the "Potsdam" by Dwight and Gordon, Walcott correlated with a 
 rock, carrying similar fossils, which he had described as occurring 
 at Saratoga. He has called the horizon the 'Totsdam-Hoyt Lime- 
 stone," and is inclined to place it in the Upper Cambrian. There 
 is some resemblance lithologically between the rocks of the two 
 localities thus correlated, particularly betsveen certain gray, arena- 
 ceous beds carr}dng blackish streaks and patches. 
 
 Messrs. Brainerd and Seely in a paper entitled "The Cal- 
 ciferous Formation in the Champlain Valley," wrote with much 
 positiveness of an Upper Cambrian T Potsdam; horizon, repre- 
 sented by a sandstone and a magnesian limestone directly beneath 
 other beds which they called Eeekmantown. The line between 
 the "Potsdam" and the Beekmantown was drawn just above 
 certain strata in which brachiopods related to Lingula were 
 found. 
 
134 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 In the writer's studies in Vermont, in the towns of Shoreham, 
 Orwell and Benson, following in some places in the steps of 
 Brainerd and Seely, these so-called "Potsdam" rocks were ex- 
 amined and their lithological similarities in some places with the 
 Dutchess County strata, familiar to the writer, were noted. But 
 what was more striking was the aspect of similar deformation in 
 both cases. The characters of the Vermont rocks just mentioned 
 will be further discussed beyond. 
 
 Mr. Wing argued for the presence of the Potsdam beneath 
 the Calciferous in Addison County, in his descriptions of the 
 sections near Shoreham, and gave practically the same account 
 of the rocks as that furnished later by Brainerd and Seely. Mr. 
 Wing also apparently, like a great many other observers of his 
 time, regarded certain rocks that are now more generally looked 
 upon as Lower Cambrian as belonging to the Potsdam. 
 
 In December, 1889, Walcott announced the discovery during 
 the preceding summer of a small outcrop of Potsdam sandstone 
 at Phillipsburg, Canada, on the east side of Lake Champlain, 
 along the shore of Missisquoi Bay, and just north of the Vermont 
 border. . It was described as carrying characteristic fossils and 
 as lying subjacent to limestone of the Beekmantown terrane. At 
 the same time he mentioned the discovery during the same season 
 in the lighter-colored members of limestone at Point Levis, 
 Quebec, of numerous fossils of Upper Cambrian or "Potsdam" 
 age. 
 
 In 1889 Ells described among several distinct zones of con- 
 glomerate present in the vicinity of Quebec, one at Point Levis 
 interstratified in the fossiliferous shales of the Levis Formation 
 and which contained a mixed fauna. Some of the pebbles held 
 an abundance of "Potsdam" forms, while the paste of the con- 
 glomerate contained fossils characteristic of the Beekmantown 
 formation. He further described a series consisting of red and 
 green shales, green and gray sandstones, and beds of limestone 
 which represents what was formerly called the "Sillery and 
 Lauzon" of the "Quebec Group" of Logan. He considered the 
 series to be of Upper Cambrian age. 
 
 On the Montreal Sheet, Eastern Townships map. Province of 
 Quebec, to accompany Part J, Vol. VII, new series, Geol. Sur. of 
 Canada, a large area, beginning about 15 miles north of the Ver- 
 mont boundary and extending from Brigham Junction north- 
 northeast to the boundary of the map, is shown as probable Upper 
 Cambrian. The rocks are red and green shales with sandstones 
 and grits, and belong to the upper part of the Sillery of the Quebec 
 Group. 
 
 In western Quebec and eastern Ontario the Potsdam sand- 
 stone appears to pass without a break into the overlying Beek- 
 mantown. The lithological dissimilarity between the Potsdam of 
 western Quebec and the supposed Upper Cambrian of the eastern 
 
REPORT OF THE VERMONT STATE GEOLOGIST, 135 
 
 townships is very striking and is supposed to have been due to 
 different conditions of deposition. The lower part of the Sillery 
 is said to be undoubtedly Cambrian and to carry characteristic 
 fossils {Agnostus, etc.). 
 
 Some of the rocks bordering the Sutton Mountain anticline in 
 Quebec have also been thought to be Upper Cambrian; but the' 
 basal portion of these rocks was thought to be the equivalent of 
 the Georgia series of Vermont and thought to lie on "Huronian." 
 
 It is now known that the conglomerate beds in the Levis 
 Formation carry in their pebbles Lower Cambrian, Upper Cam- 
 brian (or Lower Ordovician) and Beekmantown fossils. 
 
 Ulrich has created and defined a new period and system 
 under the name '''Ozarkian," based on sections in Missouri, Ar- 
 kansas and the southern Appalachians, which is made to inter- 
 vene between the true "Upper Cambrian" and the basal Ordovician 
 (Canadian). In this system he places the New York formations 
 known as the Hoyt Limestone, the Potsdam Sandstone, the Little 
 Falls Dolomite, and certain "passage beds" first described by 
 Cushing from Jefferson County, N. Y., and called the "Theresa 
 Formation." 
 
 Schuchert adopted the term Ozarkian (1909), but used it in 
 a different sense from that of Ulrich and made it synonymous 
 with Upper Cambrian, or "Cambric" in a restricted sense. 
 
 Schuchert has referred certain conglomerates of the "Quebec 
 Series," whose fossils have been described by Walcott, to the 
 "Ozarkian," as he employed the term. The formation from 
 which the conglomerate pebbles came is not known in the St. 
 Lawrence valley. 
 
 Schuchert would also put Brainerd and Seely's divisions A 
 and B of their so-called Beekmantown, and apparently their so- 
 called Potsdam also, as described for Shoreham, in the "Ozark- 
 ian," as Ulrich would also, but with a different general significa- 
 tion for the term. 
 
 It is not fully settled whether any true Potsdam, and how 
 much that may properly be called Upper Cambrian, can be dis- 
 tinguished with certainty in western Vermont. 
 
 OEDOVICIAIf. 
 
 Beekmantown (Calciferous), 
 
 The Vermont report shows this formation, as traced on a 
 lithological basis, as rather limited exposures in the western 
 parts of Addison County and in the northwestern part of Rutland 
 County. The thickness is described as about 300 feet. The 
 large areas of limestone lying to the east in Addison County and 
 northern Rutland County were called by the special name of the 
 "Eolian Limestone." 
 
 Mr. Wing first described Calciferous fossils from this "Eolian 
 Limestone" and is reported to have found them in the Otter Creek 
 
136 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 Valley at New Haven, Middlebury, Salisbury, Leicester and Bran- 
 don, on the east side of the stream, and in Weybridge, western 
 Cornwall and Shoreham, on the west side of the creek. Mr. 
 Wing also thought the Calciferous to occur half way between 
 Rutland and West Rutland, and also farther south. 
 
 Brainerd and Seely studied this formation particularly in 
 the Champlain valley and with great industry examined "every 
 important exposure on the Vermont side of Lake Champlain 
 from PhilHpsburg, Canada, to Benson, Vermont, and most of 
 those on the New York side." From the sequence exhibited at 
 Shoreham they estimated the entire thickness as about 1,800 feet. 
 The formation was described as showing a variety of rock and 
 in some beds an abundant fauna. Partly on the basis of lithology 
 and partly by fossils the Beekmantown was separated into divi- 
 sions known as A, B, C. D, and E, and described somewhat as 
 follows (descriptions abbreviated) : 
 
 1. Dark, iron-gray, magnesian limestone, more or less 
 siliceous, often almost a sandstone, in beds usually 1 to 2 feet 
 thick. Div. A, 310 feet. 
 
 2. Dove-colored limestone, intermingled with light gray 
 dolomite, in massive beds. Div. B, 295 feet. ' 
 
 3. Gray, thin-bedded, fine-grained, calciferous sandstone ; 
 followed by thick beds of magnesian limestone; then sandstone, 
 sometimes pure, but usually calciferous or dolomitic; magnesian 
 limestone containing masses of chert. Div. C, total 350 feet. 
 
 4. Blue limestone in beds 1 to 2 feet thick ; drab and brown 
 magnesian limestone ; sandy limestone in thin beds ; blue lime- 
 stone in thin beds separated from each other by thin, tough, slaty 
 layers, often with conglomeratic appearance in the presence of 
 small, angular pebbles. Div. D, total 375 feet. 
 
 5. Fine-grained, magnesian limestone in beds 1 to 2 feet 
 thick, weathering drab, yellowish or brown. Div. E, 470 feet. 
 
 From PhilHpsburg, Quebec, a series extends into Vermont 
 for four or five miles in which Brainerd and Seely found beds 
 lithologically similar to all the above-described divisions, although 
 division E seemed "poorly represented" at the north. The Phil- 
 lipsburg series was classed by Logan in his "Quebec Group," 
 under his divisions A and B. 
 
 Beekmantown strata are described for many somewhat scat- 
 tered localities along the lake shore and among the islands. The 
 series as a whole, and the different divisions, are variously rep- 
 resented at the present surface in the different exposures of this 
 formation. At Shoreham the apparent thickness is great and 
 the formation is well represented in Orwell township and in ad- 
 jacent portions of New York State. 
 
 An assemblage of remarkable fossils was early discovered 
 at Fort Cassin. The collections which were made here by Pro- 
 fessors H. M. Seely and George H. Perkins were described 
 
REPORT OP THE VERMONT STATE GEOLOGIST. I37 
 
 chiefly by Whitfield and became known as the "Fort Cassin 
 Fauna." Through the stratigraphic work of Brainerd at Ball's 
 Bay, according to Seely, this fauna was finally assigned to the 
 upper part of division D. Representatives of the fauna were 
 also found at a few other places, as at Stave and Providence 
 islands (near Grand Isle), at Valcour Island (Van Ingen and 
 Ruedemann), and at Phillipsburg (Billings) ; but nowhere in 
 the abundance and fine condition of preservation as at Fort 
 Cassin. 
 
 The Beekmantown shows a small exposure on Grand Isle 
 and is present at the southern end of Isle La Motte and in both 
 places has been mapped by Professor Perkins. Brainerd and 
 Seely, and later Gushing and Ruedemann, identified the several 
 divisions described for Shoreham on the west side of the lake 
 by means of similar lithologic characters. 
 
 The Vermont report shows a wide band of calciferous rock 
 (called "Eolian") extending from Milton southward through 
 Charlotte and Hinesburgh into Monkton. The rock is predom- 
 inantly calcareous, but usually somewhat siliceous. Its precise 
 age has proved difficult to assign. Professor Perkins classifies it 
 tentatively with the Beekmantown, although suggesting that part 
 of it may be Cambrian. In Colchester, Mr. Dan B. Griffin, as- 
 sistant to the Survey, has found fossils {"Pleurotomaria" and 
 "Cryptosoon") and the State Geologist is inclined to think that 
 this band is largely if not wholly Beekmantown. 
 
 The localities in Salisbury, Leicester and Brandon at which 
 Wing reported Beekmantown (Calciferous) fossils were described 
 by him as occurring west of the marble belt, and as belonging to 
 the upper part of the Beekmantown terrane ("'Ophileta beds"). 
 Following the stratigraphy of that time, the quartzite lying along 
 the eastern border of the valley being regarded as Potsdam, the 
 limestone which lies directly west of it, "half way from Rutland 
 to the West Rutland valley," was supposed to be Upper Cal- 
 ciferous ("Ophileta beds"), but no fossils were found. 
 
 The extent of the Beekmantown formation in Addison 
 County, and along both sides of the lake, its northern extension 
 into western Quebec, its representation southward in eastern New 
 York State, and even farther south, so impressed Seely that he 
 wrote: "and when all the geological facts are in, will it not be 
 found that the valley quarries of limestone and masses of marble, 
 those early known as Stockbridge and later as Rutland, are 
 largely comprehended in the Beekmantown ?" 
 
 The calciferous rock lying to the east of the marble belt in 
 Sahsbury, Leicester and Brandon, and southward through the 
 Vermont valley, and which borders the Lower Cambrian quartzite 
 of the plateau on the west and is associated with the quartzite of 
 the valley, has been described as a part of the Lower Cambrian 
 series. See above. On the map to accompany his paper on 
 
138 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 "The Commercial Marbles of Vermont," Dale calls this somewhat 
 regular belt of dolomitic rocks "Cambrian Dolomite." He draws 
 a distinction only between this formation and the marble, although 
 he includes some dolomite with the latter. In the legend he calls 
 the whole limestone formation of the valley "Cambro-Ordo- 
 vician." In the text he writes : "The marble has been shown by 
 Wing and others to include beds of Chazy age and probably some 
 of Trenton age above them and possibly some Beekmantown 
 below them. There is, however, a question whether any or how 
 much of the dolomite is of Beekmantown age. As this formation 
 along Lake Champlain is largely dolomitic it would naturally be 
 sought among the dolomite beds of the Vermont valley." 
 
 In the present state of knowledge the assignment of any 
 portions of the limestone of the Vermont valley to the Beekman- 
 town is conjectural and provisional. 
 
 Dale has described a number of localities in the slate belt 
 which exhibit certain dark-gray, calcareous or very quartzose, 
 finely-bedded shales or black shales with thin limestone beds. 
 These rocks are described as inconspicuous and easily overlooked. 
 They are of inconsiderable thickness, and are further characterized 
 by extremely fine bedding and a graptolite fauna. These features 
 serve to distinguish them from adjacent rocks. While some of 
 the fossils have a range outside the Calciferous (Beekmantown), 
 several of them are regarded as probably of Calciferous age. It 
 is uncertain whether the horizon is everywhere present or only 
 intermittent. 
 
 In eastern Quebec is so-called Calciferous (Levis Forma- 
 tion) which is very different lithologically from the Beekmantown 
 described from western Quebec, Ontario, Vermont, and eastern 
 New York. It consists of black, gray and green shales, and beds 
 of dolomites, sandstones and conglomerates, the latter carrying 
 Cambrian fossils (Walcott). As explained on the map to ac- 
 company Part J, Vol. VII, new series, Montreal Sheet, Eastern 
 Townships, the Levis is supposed to be the age equivalent of the 
 western Quebec Beekmantown and the differences in lithology as 
 due to different conditions of deposition. The Levis shales carry 
 a very different fauna from the western Beekmantown. The 
 fossils are graptolites which were correlated by Lapworth with 
 Arenig (basal Ordovician) of England. This correlation is said 
 to ally the Levis fauna with a different faunal realm from that 
 of the Beekmantown of the lake region, the latter being the east- 
 ern extension of a "Pacific realm" fauna which was prevented 
 from interminghng with the eastern European fauna represented 
 by the Levis by a land barrier which separated the "Levis trough" 
 on the east from a more western "Chazy trough" on the other 
 side of the Green Mountain axis. 
 
 As explained in the discussion of the Upper Cambrian, 
 Schuchert, and Ulrich by implication, place the lower portion of 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 139 
 
 Brainerd and Seely's Beekmantown in the "Ozarkian," which 
 Schuchert makes Upper Cambrian and which Ulrich regards as 
 a separate system, belonging to the basal Ordovician. 
 
 It has been suggested that the upper part of Brainerd and 
 Seely's Beekmantown is probably more closely allied with the 
 Chazy. 
 
 Chazy. 
 
 In the Vermont report the Chazy was grouped with Birds- 
 eye (Lowville) and Black River, which together were shown 
 forming a strip about five miles wide narrowing north and south, 
 along the shore of Lake Champlain in Addison County. Other 
 strips were shown on Grand Isle and Isle La Motte. 
 
 First Wing and later Brainerd and Seely extended our knowl- 
 edge of the occurrence and distribution of the Chazy rocks. 
 
 Wing found the Chazy well represented by fossils at West 
 Rutland in the "Eolian Limestone," and reported other fossils 
 from Leicester, East Cornwall and Middlebury. 
 
 On a map to accompany a paper entitled "Preliminary Report 
 of the Geology of Addison County," Seely later showed no Chazy 
 in Addison County east of the eastern boundaries of the towns 
 of Addison, Bridport and Shoreham. On page 308 of the paper 
 he wrote : "The deposits at the lime quarries near Leicester 
 Junction have been regarded as massive Chazy and yet the struc- 
 ture approaches the Beekmantown. As Beekmantown it may 
 remain until new light is thrown upon the obscure problem." 
 
 Wing described a "striped stratum" which was regarded as 
 a marked feature of the Chazy, "by which the rock may be recog- 
 nized without its fossils." This was found in Middlebury, in 
 northern Salisbury, in the western part of Brandon, and in west- 
 ern Pittsford. This stratum "doubtless reaches the marble quar- 
 ries of West Rutland and continues southward through Tinmouth 
 and the whole State." 
 
 Chazy fossils were also reported by Wing from West Corn- 
 wall, North Cornwall, Orwell, Weybridge Upper Falls and near 
 Bristol village. 
 
 In 1891 Brainerd described sections at Valcour Island, Crown 
 Point and Chazy, N. Y. and also at Isle La Motte, Cornwall, 
 Orwell and Highgate, Vt., and at St. Armand, Quebec. At 
 Valcour Island 890 feet of Chazy were measured and separated 
 into divisions de^gnated as A, B and C, corresponding to Lower, 
 Middle and Upper Chazy. 
 
 , , The distinction among the diiTerent divisions of the Chazy 
 was made on the basis of fossils and lithology. The lower and 
 upper boundaries of the formation were ultimately established 
 and when all the lower members are present it has now for its 
 recognized base a ferruginous sandstone which is prominently 
 developed at Isle La Motte and is known as the "Isle La Motte 
 sandstone." It carries Lingula limitaris, Seely, as a character- 
 
140 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 istic fossil. This sandstone rests, according to Seely, upon dif- 
 ferent members of division E of the Beekmantown, but usually 
 upon the upper ferruginous limestone of that division. The upper 
 strata of the Chazy, though varying somewhat, bear most, often 
 a tough, magnesian limestone, destitute of fossils, and weathering 
 with an iron stain, while just above is a layer of flinty sandstone. 
 At Valcour Island the Chazy is described as follows (abbre- 
 viated) : 
 
 1. Gray or drab-colored sandstone, usually with thin layers 
 of slate and with occasional thin layers of limestone at the base; 
 passing into massive beds made up of thin, alternating layers of 
 tough slate and of nodular limestone ; dark, bluish-gray, impure 
 limestone in beds of variable thickness ; gray, tolerably pure lime- 
 stone in beds 8 to 20 inches thick, separated by earthy seams. 
 Lower Chazy, Group A, 338 feet. 
 
 2. Impure, nodular limestone ; gray, massive, pure lime- 
 stone ; bluish-black, thick-bedded limestone, usually weathering 
 so as to show pure nodular masses in a somewhat lighter matrix ; 
 dark, compact, fine-grained Hmestone, with obscure bedding; 
 bluish-black limestone. Middle Chazy, Group B, 350 feet. 
 
 3. Dove-colored, compact limestone in massive beds ; dark, 
 impure limestone in thin beds ; tough, arenaceous, magnesian 
 limestone passing into fine-grained sandstone. Upper Chazy, 
 Group C, 202 feet. 
 
 Like the Beekmantown, the Chazy throughout its distribu- 
 tion at the present surface shows some variations in characters 
 and thickness of members and at some places only partial repre- 
 sentation of the formation. 
 
 In addition to the localities given above, exposures of Chazy 
 occur near Balls, MacNeils and Merriams bays, and from Basin 
 Harbor to Button Bay, along the east shore of the lake ; at the 
 northern end of Providence Island ; on Sawyer's Island ; and on 
 Grand Isle, where it is represented somewhat extensively, both 
 geographically and as a terrane. 
 
 After the discovery of characteristic Chazy fossils {Maclu- 
 reas) at the surface in the central and western parts of the West 
 Rutland valley fine, although somewhat distorted, specimens were 
 found on polished slabs from the bottom of the deep "Ripley 
 quarry." 
 
 South of West Rutland, in the town of Ira, at Day's quarry, 
 which was worked for a time, Walcott found sections of large 
 gastropods, probably Maclureas, in a bluish marble. 
 
 South of West Rutland in the Vermont valley recognizable 
 Chazy fossils, so far as the writer can determine, had not been 
 found up to the season of 1920. See beyond. Dr. Walcott dis- 
 covered fossils in the limestones south of Bennington, which were 
 assigned to the Chazy-Trenton, but no sharper distinction was 
 drawn. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 141 
 
 LowTille (Birdseye). 
 
 In the generalized time-scale for eastern North America the 
 Lowville succeeds the Chazy. 
 
 An elevation at the close of Beekmantown time, accompanied 
 by folding, in eastern North America, has been described as 
 probable. This elevation is thought to have raised much of the 
 middle Appalachian region and all of New York State except the 
 northeastern portion above water. In the Champlain region it is 
 held existed a trough at this time in which was being deposited 
 the Chazy. While the Chazy was being deposited in the Cham- 
 plain region and in another small (Ottawa) basin the lower 
 Stones River was depositing in Kentucky and Tennessee. 
 
 After the deposition of the Chazy in the Champlain region it 
 is thought an emergence there occurred, forming land, which 
 was not submerged again until the Black River brought the 
 Mississippian sea into the region. The Lowville, which is re- 
 garded as the time equivalent of the Upper Stones River of the 
 south, forms the basal member of the Trenton series (Mo- 
 hawkian) in New York and ushered in the Black River inva- 
 sion. 
 
 As mentioned in the discussion of the Chazy the Lowville 
 was theoretically included with Chazy and Black River in the 
 Vermont report. 
 
 The Lowville was at first described as very scantily repre- 
 sented in Vermont. Phytopsis tub'ulosum, Hall (a fossil which 
 has the appearance of a bird's eye and which gave the early name 
 to the formation), has been seen only in the northwest corner 
 of Benson in a bed about 6 feet thick. Elsewhere this horizon 
 is described as having only a few feet of pure, fine-grained, brit- 
 tle limestone with fine Hues of calcspar, lighter in color than the 
 known Black River strata just above, and without fossils. 
 
 Brainerd and Seely maintain that more than one horizon in 
 the Beekmantown and in the Chazy are lithologically similar to 
 the Birdseye, and have been wrongly assigned to that formation. 
 Assuming the rocks and fossils which had some appearance of 
 the Birdseye to belong to that formation they sought localities 
 where the Chazy approaches the Black River, thus hoping to 
 find the Birdseye between. But in every locality so sought they 
 found the Black River resting upon the Chazy, with no room for 
 the Birdseye. Instead they found the so-called Birdseye in places 
 to be underlain and overlain by members of their Calciferous. 
 They found fossils which have been figured as sections of Phytop- 
 sis tubulosum to be "spongoid" forms, known as Strephochaetus, 
 characterizing their middle Chazy. They could find no proof 
 of the Birdseye in Vermont, except the small exposure in Benson. 
 
142 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Black Eiyer. 
 
 In their description of the Beekmantown of Vermont, Brain- 
 erd and Seely frequently refer to the Black River as immediately 
 overlying their Cliazy. Northeast of Shoreham village they 
 mention Black River, carrying characteristic fossils, lying in a 
 trough of the Chazy. Half a mile south of this exposure the 
 trough widens and the Trenton appears flanked by the Black 
 River and the Chazy in succession. Again in Orwell, south of 
 Shoreham, Black River is described as resting against the Chazy, 
 the latter lying on the former at one place by overturn. Black 
 River is described at Larrabee's Point, Thompson's Point and 
 MacNeils Bay. 
 
 In his paper dealing with the Chazy of the Champlain valley, 
 Brainerd describes and shows graphically in sections the Black 
 River at Valcour Island, Isle La Motte and Highgate Springs, 
 resting upon or in close association with Chazy. 
 
 Professor Perkins has mapped five separate exposures of 
 the Black River on Grand Isle, and one on Isle La Motte, and 
 refers to it as occurring at Button Bay Island and at Benson. 
 
 The Black River strata are described as fine-grained lime- 
 stone, bluish at the base and jet black in upper layers. The 
 formation as a whole is nearly destitute of fossils, although some 
 thin layers are full of them. 
 
 Except in the vicinity of Lake Champlain the Black River 
 is not positively known in Vermont. 
 
 In the Champlain region the Black River has been thought 
 to lie disconformably upon the Chazy, the latter having been 
 elevated and probably somewhat eroded before the Black River 
 invasion. 
 
 Trenton. 
 
 This formation as identified by fossils differs in lithology 
 and degree of metamorphism at different places. Some ter- 
 rigenous rocks by reason of association with Trenton limestone 
 or other relations have been described as probably of Trenton 
 age. 
 
 The Vermont report shows the Trenton at Highgate, on Isle 
 La Motte, and on Grand Isle in Lake Champlain; in Charlotte 
 on the lake shore ; and in the western portions of Addison a,nd 
 Rutland counties. 
 
 Mr. Wing later added details of the Trenton in Addison 
 County and also found Trenton localities in the "Eolian Lime- 
 stone." West of or within the slate belt of the Vermont report 
 he identified the Trenton at localities only a few miles apart in 
 all the towns north of Castleton, including Hubbardton, Sudbury, 
 Whiting, Shoreham, Cornwall and Weybridge ; and on the east 
 of the slate belt' in Leicester, eastern Cornwall and Middlebury. 
 The presence of the Trenton at Benson, south of Orwell, left 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 143 
 
 little doubt that this formation exists "in long bands stretching 
 down on the west of the two belts of slate from Weybridge 
 southward." 
 
 From the relations of the "central slate belt" to the marbles in 
 Rutland County and farther south, Wing believed the Trenton 
 abundantly represented in the marble belt. Fossils (Trinucleus 
 concentricus) were described as found in limestones "interbedded" 
 in the slates 10 miles southeast of Sudbury, at Hubbardton, and 
 a mile or two north of the slate quarries at West Castleton. 
 
 In the summer of 1887 Walcott found fossils indicative of a 
 Trenton fauna at Pownal, Vt., a mile north of the Massachusetts 
 line, and also on the eastern side of Mt. Anthony about 3 miles 
 south of Bennington Centre. 
 
 In the papers by Brainerd and Seely on the Calciferous and 
 Chazy of the Champlain valley, frequent mention is made of 
 Trenton rocks. They are described as forming a wide strip east 
 of Shoreham, running through Cornwall and Whiting on the 
 west of the "central slate belt" ; also at Shoreham ; at Orwell ; 
 at Larrabee's Point; to the east of Balls Bay; at Cedar Branch, 
 north of MacNeils Bay; on Grand Isle, both inland and along 
 shore ; at Crane Point, opposite Port Henry, N. Y. ; and at Isle 
 La Motte. 
 
 Professor Perkins has shown wide exposures of this forma- 
 tion on Grand Isle and has also mapped its outcrops on Isle La 
 Motte. 
 
 Small exposures are mentioned as occurring at Highgate and 
 St. Albans, but they are in no cases extensive. The formation is 
 described as not occurring along the lake shore north of Charlotte, 
 
 Dale thinks that some of the limestones of the marble belt 
 are of Trenton age. On his map of the slate belt of eastern New 
 York and western Vermont, Ordovician limestone is shown as 
 an interrupted band along part of the western border. In Benson 
 this limestone, with a few small patches of slaty or gritty rocks, 
 is represented as a band 2 miles wide along the shore of the lake. 
 Just east lies the so-called "Benson Black Slate" over an area 
 about 2 miles wide and 5 miles long and this is bounded on the 
 east by an irregular strip of the limestone. These two areas of 
 limestone are shown as separated at the south from another area 
 of the limestone about 2^ miles wide south of West Haven. 
 The latter area narrows southward, and with only one inter- 
 ruption, extends to West Granville, N. Y. Fourteen miles south 
 of West Granville a narrow band runs from North Argyle to 
 Argyle in New York. In the text these areas are referred to as 
 the Trenton limestone. Outcrops are specially mentioned as oc- 
 curring in Hartford and at Carver's Falls in Poultney River. An 
 area is shown northwest of Hubbardton, surrounded by the slate, 
 phyllite and grit formation. At Carver's Falls and at several 
 other points near the Cambrian boundary, with which the lime- 
 
144 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 Stone is shown in contact over long distances, according to the 
 map, the Hmestone yields Trenton fossils. In several places this 
 limestone "may represent the entire Lower Silurian series and 
 should then be regarded as Trenton, Chazy and Calciferous." 
 The Trenton limestone is mentioned as occurring sporadically 
 within the Ordovician areas of the slate belt. 
 
 In general as thus far described the Trenton formation is 
 calcareous. Several observers have regarded limestone of this age 
 as interbedded with members of the slate formation. Dale says 
 that the limestone was probably in some places deposited con- 
 temporaneously with the "Hudson" grits and shales. In his table 
 and descriptions of formations, those designated as "Hudson 
 grits, Hudson red and green slates, Hudson thin quartzite," are 
 put in the Ordovician and in part referred to or described as 
 probably representing the Trenton limestone, described above as 
 occurring west of the slate belt. Dale describes what appeared 
 to him as indications of transition between Hudson grit and the 
 "Berkshire Schist" of the Taconic range, and from the areal rela- 
 tions infers that the latter is equivalent to the entire Ordovician 
 among the slates and grits and in addition to representing the 
 Calciferous, Chazy and Trenton includes also probably the Lor- 
 raine and Utica. 
 
 Foerste describes Trenton fossils as occurring in thin blue 
 limestone which forms intercalated bands in the base of the slate 
 formation. He gives 'two localities near Danby Four Corners, 
 12 miles south of Rutland, and another on the ridge west of 
 Otter Creek a little northwest of South Wallingford. He men- 
 tions branching bryozoa, crinoid beads, and sections of Stropho- 
 mena and Streptelasma. 
 
 IVormanskill. 
 
 Graptolite shales "interbedded or associated" with "Hudson" 
 grits in the slate belt are assigned to the Normanskill Zone 
 (Trenton) by Dale. 
 
 Utica. 
 
 The so-called "Utica" has a wide distribution in the region 
 of the lake. The Vermont report, which separates this forma- 
 tion from the "Hudson River," shows the Utica as forming 
 Alburgh peninsula, North Hero and much of Grand Isle, and on 
 the mainland of Vermont further indicates a strip extending from 
 the shore of Missisquoi Bay southward through Highgate and 
 Swanton to St. Albans Bay ; again at the mouth of the Winooski 
 River and from Charlotte on the east of the Trenton limestone 
 south to Shoreham. It is described as pjnching out in Orwell 
 near "Chittenden's Mills." A narrow strip is shown skirting the 
 lake on the west of the Trenton in Addison County, and a small 
 patch on the lake west of Bridport. 
 
 According to Professor Perkins what was mapped by the 
 Vermont Survey as "Hudson River" is also Utica. According 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 145 
 
 to Perkins : "Here and there the Utica appears on the Vermont 
 shore of Lake Champlain and in small patches away from the 
 lake." Juniper Island, the Four Brothers and Rock Dunder 
 in the lake are also formed of Utica slate. 
 
 Mr. Wing's investigations apparently dealt chiefly with the 
 Hmestone formation ("Eolian"), and only indirectly with the 
 slate. The slate of the great "central slate belt" of the Vermont 
 report he called "Hudson River" and showed it in sections and 
 discussed it as conformably overlying the Trenton formation. 
 At West Rutland "the Chazy adjoins the slate belt." The lime- 
 stones containing Trenton fossils "over the interior" of the slate 
 belt had the appearance of being "brought up from beneath by 
 anticlinals." 
 
 Brainerd and Seely maintained that all the rocks of the 
 Lower Silurian appear on the Vermont side of Lake Champlain, 
 sometimes showing in their natural order in great monoclinals 
 with Utica slate at the top, lying on the Trenton limestone. They 
 made the slate of the "central slate belt" which Wing called 
 "Hudson River" in the Shoreham section, of Utica age, thus cor- 
 relating it with the slate formation lying west of the "great fault," 
 or the slate of the Lake Champlain region proper. These ob- 
 servers show the Utica in faulted contact with the Chazy and 
 Trenton at Isle La Motte. Professor Perkins shows the Utica 
 widely distributed on Grand Isle, forming the larger part of the 
 island; also three patches along the east shore of Isle La Motte. 
 
 Within the roofing slate belt the Utica is not distinguished. 
 East of the slate belt the Berkshire Schist is made probably to 
 include this horizon. 
 
 On Grand Isle Professor Perkins has described characteristic 
 Trenton fossils and so-called "Utica" types occurring on the 
 same slab. 
 
 Later OrdoYician ("Lorraine," "Hudson Mirer"). 
 
 The presence of rocks of Ordovician age younger than so- 
 called "Utica" in western Vermont cannot be affirmed from the 
 rocks themselves. Perkins maintains that in the Lake Cham- 
 plain region all the slate formation is of Utica age (or older 
 perhaps). 
 
 In the Taconic range the Berkshire Schist is made provi- 
 sionally to include Lorraine, and many of the terrigenous rocks 
 of the roofing slate belt are not specifically assigned beyond in- 
 dicating that some of them are probably equivalent to the Trenton 
 (and the Calciferous and Chazy). They are usually referred to 
 by the non-committal term "Hudson," which term in its present 
 usage, includes Trenton and older and younger terranes. 
 
146 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 GENERAL STRUCTURAL CONSIDERATIONS. 
 
 Preliminary statement. Throughout their length and breadth 
 in western Vermont, from the Canadian boundary to the Massa- 
 chusetts line, and in their geographical extensions into Quebec at 
 the north and into Massachusetts and New York at the south and 
 west, the formations just discussed present a wonderfully fas- 
 cinating field with respect to the secondary deformations which 
 they have suffered. For a bold sweep of the imagination there 
 is no aspect of Vermont geology so inviting as that of the wide- 
 spread dislocations which have followed the action of compres- 
 sive stresses in the earth's crust. By these forces the rocks have 
 been piled on each other and shoved from east to west. 
 
 In the Taconic region the deformational history is very 
 complicated and difficult to read. Many views of the structure 
 have been given and there probably will always be divergence of 
 opinion. 
 
 The present erosional aspects of the region in many par- 
 ticulars seem clearly to be due to structure produced by ancient 
 processes of deformation and as one studies the topography and 
 geology together it becomes apparent that the physiography of 
 today had its genesis in crustal disturbances of a more or less 
 remote past. 
 
 Brief sum>mary of various studies that have been made in 
 the deformation of the earth's crust in various parts of the world, 
 and of certain theoretical aspects of the subject. In their work 
 of mapping the areal and structural relations of formations in 
 various parts of Europe and of this country during the past forty 
 or more years, geologists have in some cases readily come to 
 recognize and sometimes have been forced to reckon with the 
 existence of great displacements of the crust in order to account 
 for the field relations which certain regions show. Especially 
 noteworthy is that class of deformations comprising overturned 
 folds, shearing, reverse faults and thrusts. 
 
 All these secondary structural features often share with each 
 other the displacement changes of a given region and sometimes 
 apparently have a common general relation to a definite regional 
 deformation. Uncertainties will naturally arise concerning the 
 extent to which the various secondary deformations due to com- 
 pression, in a given region, are related to the same general epi- 
 sode ; or, if there is reason to think that pressure acted intermit- 
 tently, as to whether it acted in the same direction at various 
 times. Evidence has been offered to show that in certain regions 
 thrust movements have been widely separated in time and have 
 acted in practically diametrically opposite directions. 
 
 It is usually not easy to fix the precise, or even the proximate, 
 date for the chief displacement features of a region, or to appor- 
 tion the various deformations therein among different epochs in 
 those cases in which a region is known or suspected to have been 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 147 
 
 affected by crustal movements more than once and at more or 
 less widely separated times. The degree of probability rests 
 upon different conditions in different regions. In certain regions 
 where older formations now rest by thrust on younger masses, 
 these relations by themselves may serve to indicate only a general 
 limit of antiquity and other conditions may or may not give an 
 idea of the precise date at which the actual deformation occurred. 
 
 Sometimes the evidence points to the formation of a major 
 thrust whose plane was subsequently folded and suffered offsets 
 and other later disturbances. The latter may in certain regions 
 be reduced to a type characteristic of later orogenic movements 
 or other displacements and serve to show at least separate epi- 
 sides of disturbance, while they leave undecided the question of 
 how much earlier the major thrust occurred than did those move- 
 ments which modified it in various ways. 
 
 In certain cases perhaps the existence of a stratum com- 
 petent to transmit a great lateral thrust may serve to indicate the 
 limit of antiquity of the movement, while the relations at the 
 same time afford no means of telling at what time subsequent to 
 the formation of the competent stratum it was called upon to 
 exercise its influence. The problem might perhaps be further 
 complicated in some cases by the possible former existence of a 
 competent stratum which had been partially or wholly eroded and 
 which by reason of its original relation to the load which it 
 carried could have initiated a thrust which was participated in 
 by a lower stratum, also competent under proper conditions, 
 which obtained relief by the fracture initiated by the more super- 
 ficial part of the crust, the fracture of the latter changing the 
 relations between the deeper stratum and its load, which had pre- 
 vented fracture until the relief of the initial fracture was felt 
 by it. 
 
 In some cases a thrust movement may not have occurred 
 until erosion had so changed the relations of a stiff stratum with 
 respect to its load that it fractured, in which case the thrust 
 would be thought of as occasioned by reason of erosion preceding 
 or assisting compression. In a case in which erosion preceding 
 any compression seemingly made possible a thrust movement and 
 in which the erosion was apparently carried to a stage of pene- 
 planation prior to the thrust, the date of the peneplain, if ascer- 
 tainable, might serve to fix the probable date of thrust. 
 
 In some regions the fact of different dates of compression 
 might be perceived by reason of the difference in degree of dis- 
 placement produced as, for example, where it would be possible 
 to associate one class of fractures with the folding of an earlier 
 thrust of relatively large displacement. 
 
 While it is possible to imagine the formation first of a major 
 thrust whose plane was subsequently disturbed by folding and 
 thrusts, there are regions in which the conditions seem clearly 
 
148 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 to indicate that minor thrusting or reverse faulting along many 
 separate planes and apparently involving previous folding, oc- 
 curred first, piling the strata on each other, sometimes to 
 enormous thickness, and that a later thrust passed beneath the 
 whole and cut off the whole series of earHer minor thrusts whose 
 planes came to lie at oblique angles with the major thrust plane. 
 More than one series of minor thrusts, or reverse faults, and an 
 associated major thrust may exist in the same region, which sug- 
 gest different episodes, or periods of compression, for that region. 
 Moreover, in addition to these minor and major thrusts there 
 may be one or more later and still more powerful or "maximum" 
 thrusts, so formed that the later of these override the earlier, 
 while all may overlap the previous minor and major thrusts of 
 the region, at one or more places. A very complicated condition 
 is thereby produced. The maximum thrusts carry the older rocks 
 over the younger, but with various degrees of overlapping, and 
 the overthrusting may go so far as to carry the disturbed portion 
 of the crust over on undisturbed strata. While a common direc- 
 tion of movement and a sequential nature in these displacements 
 and therefore their relative dates might be apparent, the question 
 of their geological dates might still remain open. 
 
 A condition that might be inferred to be due to folding ante- 
 cedent to thrusting is frequent in such regions as just described, 
 but it is explained, sometimes at least, as occasioned by friction 
 along the unyielding plane over which the upper material moved, 
 so that there was a tendency for the upper part to curve under and 
 produce inversion of beds. 
 
 The outcrops of the maximum thrust planes under erosion 
 resemble boundary lines between unconformable formations 
 because of greater or less discordance between the strata above 
 and below the plane of fracture. 
 
 In regions of long-continued and profound erosion and in- 
 volving at the present surface very old rocks the problem of the 
 dates of various disturbances may shift to one of sheer uncer- 
 tainty, especially when a region is known or believed to have 
 been involved in two or more mountain building deformations 
 and one or more of these disturbances are also known to have been 
 a long time subsequent to the dates of formation of the rocks 
 which now lie in displaced relations to each other. It is con- 
 ceivable that a relatively recent orogenic movement might have 
 dislocated and deformed a region involving rocks of much greater 
 antiquity than the date of the movement itself and give results 
 not to be readily distinguished from those which would have 
 followed a compression of those rocks shortly after their forma- 
 tion. 
 
 Displacements have been described in the Canadian Rockies 
 in which an original width of 50 miles has been shortened to 
 half that distance by a succession of thrusts along a number of 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 149 
 
 parallel, longitudinal fractures which have produced a series of 
 huge oblong blocks resting on one another from west to east, and 
 apparently produced without much preliminary bending. Over- 
 turned folds were observed along the courses of some of the 
 faults, but were described as usually small and of minor structural 
 importance. Violent folding in the prolongation of a fault line 
 and undulations of major fault planes indicating disturbance 
 subsequent to the main faulting were observed. In the belt of 
 fracture there were recognized seven principal faults of varying 
 throws. There was observed a very striking apparent conformity 
 between beds zvidely different in age east of the axis of the 
 region. 
 
 It will appear, either in regions in which strata belonging 
 to epochs approximating in age relations the date of later defor- 
 mations have never been deposited, or in those in which such 
 strata though deposited have been eroded, as though only those 
 rocks which are now visible were involved ; but in one case it 
 will be necessary to recognize that a former load may have con- 
 trolled or modified the action of the deforming forces. It may 
 be that the only Hght one may be able to get upon such a pos- 
 sibility will come from considering the whole general region, of 
 which the province under consideration is apparently a genetic 
 part. Late Paleozoic rocks, for example, may be much more 
 sparsely represented today in New England than in the past. 
 The conditions in neighboring New York and the fact that we 
 are probably dealing with an upraised peneplain of a great up- 
 thrust segment of the crust should perhaps be remembered in 
 our studies in western New England. 
 
 The probability of difficulty in working out the dates of 
 deformations in a region as the result of the fact that nature 
 works, at least to some extent, with the same rock masses at 
 separate epochs and under various conditions is apparent. Such 
 conditions, in efforts to discriminate among the effects of possible 
 different crustal movements, will lead to differences of interpreta- 
 tion almost surely where present relations are greatly involved. 
 
 In passing it seems worthy of note that any principle which 
 assumes that the minor, secondary structural features of a region 
 may be taken as replicas of the larger deformations must be used 
 with caution. 
 
 The problem of the structure of a region often involves as 
 primary conditions the nature, sequence and thickness of sedi- 
 mentary formations and the complex nature of the substratum on 
 which these are deposited, such as rigidity, condition of previous 
 strain, irregularity of surface and admixture of crystalline 
 masses. It must further reckon with antecedent deformation of 
 any kind and frequently upon consequent strains in those cases 
 in which the structural features are of different dates. It must 
 take account of the possibility of variations in the strength of the 
 
150 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 compressive forces at different times, or in different parts of a 
 region during the same episode ; of metamorphism and resulting 
 crystallization or re-crystallization of rocks ; of erosion at dif- 
 ferent periods ; and of periods of tension stresses and normal 
 faulting. 
 
 DESCRIPTION AND DISCUSSION OF FIELD STUDIES 
 BY THE WRITER IN WESTERN VERMONT. 
 
 General plan of discussion. For convenience, general refer- 
 ence to field studies in this paper will be given by counties and 
 by towns which are shown on the accompanying map, plate XXII. 
 Observations and citations are based on the topographic, quad- 
 rangle sheets of the United States Geological Survey. Close 
 reference to localities mentioned will require the use of these 
 maps. Some assistance may also be had from the map showing 
 physiographic divisions, and from certain landmarks such as large 
 towns or cities, township boundaries and rivers. For the town- 
 ships of Brandon, Sudbury and Orwell a special map is offered, 
 Plate XXII. 
 
 ADDISON COUJfTT. 
 Orwell Township. 
 
 (Ticonderoga topographic sheet.) 
 
 Topography. The township has a somewhat diversified 
 topography. A spur of the foothills of the Taconic range enters 
 it from the town of Benson at the south. Over this spur the 
 contours of 600 and 700 feet run for long distances. The high- 
 est point is 1,000 feet. There are several scarps within the spur. 
 
 This high land extends nearly to the lake in southwestern 
 Orwell, but the surface of the northwestern part of the town is 
 a gently-rolling upland with contours at or below the 400 level. 
 The surface of East Creek over much of its length is practically 
 that of the lake. Along the creek and the lake shore are large 
 tracts of Champlain clays, which effectually conceal the under- 
 lying rock. 
 
 East of the spur described is a valley through which courses 
 the Lemon Fair River and which separates the spur from the 
 Sudbury hills. This valley has a minor ridge running in a 
 general north-south direction through it. 
 
 Mount Independence. The flattish position of the strata 
 forming this hill is noticeable. They dip about 10° northerly. 
 Forming the basal members at the southern end are thick-bedded, 
 whitish, quartzitic sandstones which Brainerd and Seely called 
 "Potsdam" and assigned a thickness of 170 feet. Then come 
 dark-gray, siliceous and magnesian rocks, in some cases almost 
 quartzites, and then interbedded dolomites and limestones. The 
 rocks of the hill above the so-called "Potsdam" were called Beek- 
 
152 
 
 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 mantown (Calciferous) by Brainerd and Seely and put in their 
 divisions A and B. The writer did not find along the lake shore 
 or at any other part of the base of this hill any contact with other 
 rocks than those which make up the hill. It seemed to be sur- 
 rounded on the landward portion by the Champlain clays. 
 
 w 
 
 Figure 9. Section to show interpretation of the relations at Mt. Independence. 
 U, "Utica" slate ; P, "Potsdam" ; "A" and "B," lower "Beekmantown." 
 The lower Ordovician has been thrust on the "Utica" slate formation. 
 A possible normal fault, F, is shown which displaced the whole series at 
 the west, including the thrust plane. 1-2, thrust plane. S-S, erosion 
 surface of the hard rock formations. 
 
 Chipman's Point. One and a half miles south-southeast of 
 Mt. Independence thick beds of dark-gray, magnesian limestone 
 emerge from the lake north of Chipman's Landing, with general 
 northerly dip and strike of N. 58° E. One-half mile southeast 
 of the landing these beds which seem to have suffered no break 
 within them, disappear into the lake with general southerly dip, 
 thus appearing to form a gentle arch with general direction of 
 its axis east and west. So far as observed along shore these beds 
 are similar to those lying above the "Potsdam" in Mt. Inde- 
 pendence. At many places the rocks dip abruptly into the lake. 
 No so-called "Potsdam" was observed. Eastward these rocks 
 pass beneath the clays. No contacts with other rocks were found. 
 The strata indicated only gentle deformation within them. 
 
 South of Chipman's Point. South of Chipman's Point are 
 three promontories known by campers along the shore as "The 
 Phoebes." These are composed of black, limy slates and shales 
 with bands of interbedded black hmestone. All are much dis- 
 turbed and show not only a highly-inclined easterly dip as a 
 rule, but internal crushing as well. The shaly members of the 
 southern promontory gave Graptolithiis pristis, and bowlders 
 of the interbedded limestone at the base of the cliff yielded 
 Plectambonites sericeus, Dalmanella testudinaria, and Trinucleus. 
 
 One hundred and fifty rods south of this promontory a brook 
 enters the lake. Slate outcrops in the bed a few rods from the 
 shore and is succeeded up the brook by a magnesian limestone, 
 dipping easterly and resembHng part of the lower Beekmantown 
 of the exposures at the north. In the field northeast of this 
 
KEPORT OF THE VERMONT STATE GEOLOGIST. 153 
 
 brook are dark, magnesian limestones. In lithology and presence 
 of chert, some of this rock resembles division A of Brainerd and 
 Seely's Beekmantown. This is succeeded eastward by other 
 magnesian limestone of general gray color and probably part of 
 the Beekmantown. 
 
 South of this brook is a hill known as "Blue Ledge" by the 
 campers. The ledge shows an almost perpendicular scarp from 
 150 to 200 feet above the surface of the lake. The west face 
 of the scarp to a height of 100 plus feet is composed of slate like 
 that of "The Phoebes" at the north. The shaly layers yielded 
 Graptolifhus pristis. The summit of the scarp and the eastern 
 slope of the hill is a magnesian limestone like that in the brook 
 bed just north and is probably Beekmantown. The topography 
 shows that "Blue Ledge" is bounded on the north and south by 
 east-west faults of the normal type. The limestone capping the 
 hill dips easterly. See figure 10. 
 
 Figure 10. Section to show relations at "Blue Ledge," on the Orwell shore 
 of Lake Champlain. A, "Utica" slate formation ; B, massive dolomite, 
 probably of "Beekmantown" age ; 1-2, thrust plane. Curved arrow in- 
 dicates folding of "Utica" strata ; straight arrow indicates bodily thrust 
 of massive "Beekmantown" on slate formation. 
 
 South of "Blue Ledge" is an abandoned farm. Just north 
 of the old barn is an exposure of the "Utica" and not more than 
 10 yards to the east of the slate is a low scarp in the dolomite, 
 but the contact is concealed. These relations are shown in 
 plate XXIV. 
 
 The relations at "Blue Ledge" and at the old farm thus give 
 clear and unmistakable evidence that the slate formation is over- 
 lain by the dolomite which is all regarded as forming some part 
 of the Beekmantown of the region, on the basis of the lithology 
 of the rock. The indication is that "The Phoebes" owe their 
 present topographic prominence to a protective covering of the 
 Beekmantown which has been removed at a relatively recent 
 epoch. For the Beekmantown to have its present position on the 
 younger formation an overthrust is assumed. 
 
 Questions then arise with reference to the former exten- 
 sion of the Beekmantown in the neighborhood. Is it present 
 
154 
 
 REPORT OF THE3 VERMONT STATE GEOLOGIST, 
 
 beneath the clays between Chipman's Point and Mt. Indepen- 
 dence? If not, was it once present there lying on the slate 
 formation and did it also once cover the slates to the east of the 
 lake shore over the areas now largely concealed by clays, but in 
 which along the various stream incisions the slates can be seen 
 to form the surface rock? East of these clays and west of 
 Orwell village, as will presently be described, the Beekmantown 
 occurs again and in apparent overthrust relation to the slates. 
 It therefore appears probable that these questions just asked as 
 to a probable, former, widespread covering of the slates by 
 Beekmantown may be answered in the affirmative. 
 
 The conditions at Mt. Independence, at Chipman's Point 
 and at other places indicate gentle flexures in the dolomite forma- 
 tion; while those at "Blue Ledge" and west of Orwell village 
 show that the formation has been fractured. It appears prob- 
 able that certain structural features permitted the removal of 
 Beekmantown beds over the areas intervening among its present 
 surface outcrops and that Mt. Independence, and perhaps also 
 the dolomite at Chipman's Point, are thrust-erosion inhers in the 
 slate formation. On the whole it appears probable that the 
 present exposures of the dolomite are the downthrow portions 
 of the formation as deformed by normal faulting and that many 
 of the flexures which the formation shows are products of the 
 same deformation. 
 
 Figure 11. Generalized section to show interpretation of relations along the 
 lake shore in Orwell just north of the Benson line. A, Black River ; 
 B, Trenton ; C, Trenton-"Utica" ; D, friable shales probably conform- 
 able with C; E, "Potsdam" and "Beekmantown" now lying by thrust 
 on A, B, C, and formerly also on D. A normal fault has dropped the 
 rocks at the left, including the thrust plane. On the upthrow side B has 
 been eroded and also part of D. 1-2, thrust plane. 
 
 Southeast of the old farm mentioned above is a very bold 
 precipitous scarp in the dolomite. In the face of this clifif the 
 rocks appear very massive and exhibit little appearance of 
 bedding. The scarp loses prominence southward owing to the 
 drift piled against it; but it was followed through the woods 
 
-J to 
 
 5^ 
 
 (f> 
 
 C 
 
 
 aS 
 
 
 
 ^ 
 
 C 
 
 
 
 d 
 
 <1) 
 
 U 
 
 cq 
 
 a> 
 
 - 
 
 X 
 
 
 ri 
 J 
 
 
 03 rS 
 02 O 
 
 gPQS 
 
 ° s S 
 
 01 -G 
 ' o g 
 
 "Geo 
 ra o cj 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 155 
 
 above the camp of Oscar Neemes to an apparent fault that will 
 presently be described. 
 
 Along the shore one-half mile south of "Blue Ledge" and 
 only a few rods north of Neemes' camp, very thick, bluish-black 
 limestone beds appear in the bank and dip into the lake. The 
 water line intersects diagonally the strike of these thick limestone 
 beds and as one walks along the shore one passes from syncline 
 to anticline, rather closely spaced and regular in their succession 
 and probably as strongly compressed as these heavy beds would 
 allow. South of Neemes' camp the beach is covered with many 
 boulders in which Bellerophon, Trinucleus, Plectambonites and 
 other fossils are common. Above the bank apparent Trenton 
 beds outcrop and many loose boulders are filled with Trenton 
 fossils. 
 
 South of an east-west line passing approximately through 
 Neemes' camp what are apparently Middle Ordovician strata have 
 a topographic level about the same as massive Beekmantown 
 north of that line. South of this hypothetical line, back in the 
 woods about one-fourth of a mile southeast of the old Walker 
 place, a quartzitic sandstone forms a low cliff. The scarp is 
 farther east of the shore than that of the massive Beekmantown 
 just north of Neemes' camp. There may be an east-west fault 
 with an offset, in the vicinity of the camp, and with differential 
 lateral displacement ; or, as the topography affords reason for 
 thinking, while there may be a fault the quartzite scarp south of 
 it may owe its present more easterly recessive position to erosion 
 of rocks left at a relatively higher topographic level after normal 
 faulting. 
 
 The thick-bedded, bluish-black limestones just described are 
 regarded as probably Black River, both from their lithology and 
 stratigraphic relation to apparent Trenton rocks. It is not wholly 
 certain whether they and the Trenton are part of the overriding 
 mass, or are beneath it like the "Utica" farther north. In figure 
 11 they are represented as beneath. They may have participated 
 in a thrust, or a reverse fault, and also be overthrust by older 
 rocks. 
 
 The evidence afforded by the relations along the Champlain 
 shore in Orwell favors the views : 
 
 1. That the Middle Ordovician strata (Trenton-Utica) are 
 overlain by early Ordovician (Beekmantown) or possibly even 
 older ("Potsdam") rocks; 
 
 2. That, as indicated by the absence of any but relatively 
 gentle flexures, which indeed were probably due to much later 
 deformation than that which produced its present superposition, 
 the older rock was thrust bodily over the younger strata and now 
 lies unconf ormably upon the latter along a thrust plane ; 
 
 3. That a later crustal disturbance deformed the whole 
 series, including the thrust plane, and caused irregular, gentle 
 
156 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 flexures in the thick overthrust mass, which as now eroded dis- 
 plays the basal Ordovician and perhaps Upper Cambrian lying 
 on the younger rocks ; 
 
 4. That, at the time of the disturbance just mentioned, or 
 later, there occurred some faulting with various degrees of dis- 
 placement, involving the rocks both above and below the thrust 
 plane ; 
 
 5. That the major thrust plane which parted the thick mass 
 of strata composing the Lower Ordovician of the region did not 
 shear always at the same stratigraphic level, but cut through it 
 so that the rupture was now through the Beekmantown and now 
 through the "Potsdam." 
 
 These conclusions seemed reasonably clearly established 
 before the relations in Orwell east of the shore were examined. 
 
 Relations west, northzvest and southwest of Onvell village. 
 East of the lake in the bottoms of ravines tributary to East Creek 
 are many small exposures of friable slates and shales with easterly 
 dip. Still farther east in the banks and bed of the North Branch 
 of East Creek in various parts of its course the slates again out- 
 crop and show frequent bands of interbedded black limestone. 
 These slates were traced eastward along East Creek and the 
 North Branch to the western margin of the limestone formations 
 west of Orwell village. 
 
 • One and a half miles west of the village, East Creek tumbles 
 over the edge of limestone and cataracts across upturned slates. 
 This place is the site of an old grist mill, formerly known as 
 "Chittenden's Mill." 
 
 At the summit of the falls the rock is a dark blue or black 
 limestone which breaks into splintery pieces. The beds strike 
 N. about 38° E. and dip southeasterly. This limestone carries 
 number of Prasopora lycoperdon on the eroded surface and 
 when broken gave Trinucleus and linguloid shells. About half 
 way down the cataract slopes in the brook bed a reading in the 
 slates and interbedded limestones gave N. 77° E. There has 
 clearly been disturbance. 
 
 About one mile northwest of HufT's Crossing, a few rods 
 east of the railway track is a high scarp in massive, siliceous 
 dolomite (see plate XXV). At the base are beds like those at 
 the base of Mt. Independence and probably representing the 
 "Potsdam" of Brainerd and Seely; but the slates on which this 
 rock presumably rests, by analogy with conditions farther south 
 on the lake shore, were not seen. Along the road east of the 
 scarp are beds like those overlying the "Potsdam" at Mt. Inde- 
 pendence. 
 
 In the bed and banks of the North Branch around Huff's 
 Crossing are exposed higher beds of the Beekmantown formation, 
 and three-fourths of a mile farther south some of these latter 
 beds are exposed in numerous outcrops in the fields near the road. 
 
(-> 
 
 m 
 
 _ 
 
 a 
 
 > 
 O 
 
 o 
 
 
 
 
 > 
 
 d 
 
 
 r> 
 
 , 
 
 c 
 
 
 » 
 
 <v 
 
 (V 
 
 In 
 
 
 ^ 
 
 rf, 
 
 CD 
 
 -^ 
 
 9r'^ 
 
 " m o 
 
 J O 
 
 bc.Si; 
 
 
 
 m .Ti C -^ 
 itj o o C 
 
 •+j !h oi oj 
 oo " C 
 
 » ^ •" CQ 
 
 2 ^ ^n 
 
 - m 0) 
 
 .1) '^ a Q 
 CQ^ O " 
 
 i^'5^ 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 1 
 
 These exposures have been described by Brainerd and Seely. 
 The blue limestone of their division D appears on the axis of 
 the anticline carrying Ophileta complanata, Maclureas and other 
 fossils. This member is succeeded on each Hmb by the other 
 members of this division, although those on the east limb are 
 most satisfactory for study. In the stream channels near Huff's 
 Crossing divisions D and E appear and in addition the top of 
 division C. 
 
 West of the highway bridge at Huff's Crossing the Beekman- 
 town beds, which directly beneath the bridge lie in a flat position, 
 as displayed in the south bank of the stream through a distance 
 of about 300 yards show gentle undulations with apparently 
 slight southerly pitch. Then appears an abrupt change from a 
 moderate dip to one about 65° W. along a strike of about N. 25° 
 E. About 60 or 70 feet of interstratified limestone and siliceous 
 beds are exposed across their strike in the bed of the stream. 
 About 100 paces west of these rocks are similar ones which show 
 a somewhat puddled arrangement which is attributed to the dis- 
 turbance which these rocks have suffered. Two hundred paces 
 downstream, after an interval of clay, appear the blackish slates 
 with limestone bands like those seen near the grist mill falls, 
 westward at intervals along East Creek, and at the lake shore. 
 
 A mile and half south of these exposures, north of the road 
 which runs westerly north of the grist mill falls, along the west 
 edge of the woods and west of Beekmantown beds, were found 
 numerous, well-preserved surface scrolls of Maclurea magna at 
 numerous places and other outcrops of striped, bluish limestone 
 like the Chazy as seen at other locaHties. West of this stratum 
 are limestones carrying hosts of surface markings of fossils and 
 which are regarded as probably representing the Trenton. These 
 various rocks seem more metamorphosed than the Trenton rocks 
 above and the slates below the dam at the grist mill and in some 
 cases, at least, have a highly-inclined westerly dip. 
 
 Figure 12. A section generalized to show interpretation of structure in the 
 overthrust Lower Ordovician limestones (here largely "Beekmantown") 
 west of Orwell village. The massive rocks were ruptured by reverse 
 faults which were subsequently truncated by a thrust, 1-2. The rocks 
 were carried westward over folded limestones and slates belonging to 
 the Trenton-"Utica" formations of the present lake region. 1-2, thrust 
 plane. 
 
158 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 From the general local deformation shown along the western 
 edge of this eroded anticline south of Huff's Crossing it would 
 appear that there was a rupture following compression of the 
 rocks composing it and that along the plane of rupture there was 
 differential movement and friction which occasioned more flexing 
 than these massive rocks usually underwent and which brought 
 about some overturning. So far as observed in the massive 
 strata found overlying the slate formation in this immediate 
 region, strong flexure does not appear to have been their mode 
 of deformation, from which fact the inference is drawn that the 
 structure just described was due to friction and of the nature of 
 a drag rather than one that preceded and initiated the break. 
 
 At the grist mill falls the eastern and western walls of the 
 gorge are apparently composed of massive beds lying rather 
 flat, and like those which extend with some interruption west- 
 ward and southwestward toward the lake, and which form a 
 noticeable scarp along the road to Montcalm Landing. From 
 general field relations and lithology most of these rocks are cor- 
 related with the Beekmantown, although their exact position 
 therein could not be made out with certainty. From the dis- 
 cordance in structure in the walls of the gorge it seems most 
 probable that the massive so-called Beekmantown rests uncon- 
 formably upon the slate formation and that it also once overlay 
 the fossiliferous rocks at the summit of the falls. The condi- 
 tions did not permit a good photograph. The massive strata 
 seem not to be so severely deformed as the similar rocks lying 
 north of them and it is regarded as probable that an east- west 
 break lies between. The interpretation of probable general 
 structure is shown in figure 12, which does not attempt to show 
 the probable normal faulting just mentioned. 
 
 The massive magnesian rocks that extend westerly from the 
 grist mill, about a half mile west of the dam are interrupted 
 along the road and in the fields by slates which in one outcrop 
 showed westerly dip. The field relations indicate that these slates 
 are surrounded by the dolomite and have been exposed by the 
 erosion of the latter. Westward the road to Montcalm Land- 
 ing descends over a scarp in the dolomite to the Champlain clays 
 that extend to the lake shore. This scarp is on a meridian a 
 mile west of that on which is located the axis of the anticline 
 south of Huff's Crossing. The rocks composing this scarp are 
 apparently in somewhat interrupted surface continuity with other 
 magnesian rocks which form the slopes and summit of a hill 
 about one mile south of it, the upper beds of which are yellowish 
 or somewhat chamois-colored rocks and which grade downward 
 into other rocks which could not be correlated with certainty on 
 account of drift and few exposures, but which towards the base 
 contain cherty dolomites like those of Mt. Independence, 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 159 
 
 Additional considerations concerning the general structure 
 of the region. From the outcrops and relations just described 
 for the areas inland from the lake and west of Orwell village 
 it seems that further support and suggestions may be drawn as 
 to the interpretations to be put upon the structure of the region 
 along the lake. 
 
 1. The structural relations at the grist mill gorge, taken 
 with the general procumbent position of the massive strata ; the 
 difference apparent in the metamorphism of the rocks which are 
 now in contiguity; and the patch of slates lying west of the 
 grist mill which is seemingly surrounded with massive magnesian 
 limestone beds and has therefore the character of an erosion out- 
 lier, give further support to the idea that the Beekmantown strata, 
 and possibly older rocks, now rest on the slate formation and 
 probably some Trenton rocks included or in addition, along a 
 thrust plane. 
 
 2. That the massive overriding strata, either during or 
 prior to translation, were broken along a reverse strike fault and 
 that a slight buckle occurred east of the fracture with some fold- 
 ing down of the edges of the beds along the western margin of 
 the block that was pushed against the adjacent beds on the west; 
 and that possibly some Chazy and possibly still younger beds 
 were involved in the frictional drag along this reverse fault 
 plane. 
 
 3. That there may have been some warping or faulting 
 later that dropped the strata between the gorge and the scarp 
 
 . north of Huff's Crossing and left the intervening beds at a lower 
 level than those on each side of these faults, or in the trough of 
 the warp, and thus preserved beds higher than the Beekmantown 
 at the present erosion surface. 
 
 4. That the various scarps in the dolomite formation stand 
 primarily for the major thrust relation which this formation bears 
 to the slates ; and that some structural features secondary to the 
 thrust favored the erosion of the Beekmantown between the de- 
 tached masses of these rocks near the lake shore and their sinuous 
 inland margin which is often marked by scarps. 
 
 5. That the massive character of the overthrust rocks pre- 
 vented much heaping up by reverse faulting under the com- 
 pression. 
 
 6. That the plane of major thrust is now and probably was 
 originally one of low angle to the horizontal. 
 
 Areas north, east and south of Orwell village. The Beek- 
 mantown rocks forming the anticline south of Huff's Crossing 
 were traced eastward by scattered outcrops across their strike to 
 the old ?tage road to Shoreham village and in places fossils were 
 noted on the weathered surfaces. These fossils appeared as 
 Maclurea- or Ophileta-like scrolls with others that resembled 
 cephalopods in the shape of the outlines and in the presence of 
 
160 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 septa. East of the stage road markings are less numerous and 
 distinct and outcrops fewer on account of drift. On the basis 
 of fossils and structure and also certain other exposures that 
 will be described presently lying to the eastward, the beds over 
 an east-west distance of a mile east of the road from Orwell 
 village to Larrabee's Point are regarded as Beekmantown in age. 
 
 East of the road from Orwell village to Orwell depot, lime- 
 stone outcrops are numerous and form a band a half mile wide 
 resting against the western slope of Deignault Hill. Maclurea 
 magna was found by the writer near the western edge of this 
 band. East of the beds carrying this fossil the limestone shows 
 abundant fossil markings on the weathered surfaces, but the 
 rock is so altered that nothing distinct could be seen on fresh 
 surfaces. At many places sections of shells both in the plane 
 of the spiral and at right angles to the axis, strongly resemble 
 Pleurotomaria and Murchisonia. A number of the more robust 
 Pleurotomaria-like forms were abraded to the plane of the 
 columella and left little doubt of their generic affinity. Spiral 
 coils at right angles to the axis of the whorls were very common. 
 Crinoid sterrts were frequent. From these characters the rock 
 is regarded as probably of Trenton age. It bears closest litho- 
 logical resemblance to other rock that will be described beyond in 
 which still more characteristic fossils were found with those just 
 described. 
 
 These limestone beds have a general north-northeast strike 
 and seem to occur in somewhat undulating open folds. There is 
 a prevailing easterly dip due to shearing deformation which has 
 greatly obscured the stratification dip. At some places an ap- 
 parent flattish position and at others a westerly dip of the bedding 
 were observed. 
 
 The limestones just described are succeeded eastward at the 
 surface by phyllites and schists on which they apparently rest, 
 although no contact was seen. Along the road from Orwell 
 village on the west slope of Deignault Hill outcrops of the phyl- 
 lites intervene between others of limestone, but a short way 
 beyond the eastern margin of the limestone is reached and may 
 be followed in a north-northeasterly direction just west of the 
 road running northerly at the top of the hill. The instance cited 
 above was the only one noted northeast of Orwell village where 
 the limestone has been eroded so as to expose a patch of the 
 underlying phyllite. East of the limestone margin all is phyllite 
 for a mile or more to the valley of the Lemon Fair River. 
 
 The limestones just described vary in degree of metamor- 
 phism along the strike and present certain interesting characters 
 in their outcrops in proximity to the phyllite. Just east of the 
 main village of Orwell, north of the road to Sudbury, the lime- 
 stones are strongly sheared and are almost slates. Many surface 
 exposures are "marbly" in appearance. Near the phyllite the 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 161 
 
 limestone is frequently seamed with many veinlets of calcite, a 
 feature which was observed at mariy places in this general region 
 where the limestone and phyllite are close together in surface 
 outcrops, or where there is good reason to think that the phyllite 
 is only a short distance beneath the limestone. 
 
 The limestones northeast of Orwell village continue along 
 the strike south and southwest of the village with prevailing 
 easterly dip which is for the most part a shearing deformation 
 structure purely. One-fourth of a mile south of the village 
 distinct easterly stratification dip is apparent and the rock carries 
 sections of Mure his onia-like forms. In general the rock south of 
 the village as far as the old stage road resembles the Trenton at 
 the north. 
 
 West of the road the limestone seems to be more metamor- 
 phosed generally, is strongly sheared and seamed with calcite in 
 many places, and often takes on a "marbly" appearance. At one 
 place a sort of flow-cleavage structure seemed to have been 
 developed nearly parallel to the bedding and both apparently 
 were subsequently folded. The fold is now cut by two sets of 
 fracture planes. 
 
 South of Orwell village the limestones give place easterly 
 at the surface to phyllites, schists and slates which are the south- 
 ward continuation of those in Deignault Hill. These terrigenous 
 rocks form the high hills in the southern-central part of the 
 township around Sunset Lake and its neighboring ponds, and 
 extend into Benson township at the south. Two miles south- 
 southwest of Orwell village, just east of the Benson-Orwell 
 road, begins a series of scarps, which increase in altitude south- 
 ward and which mark a normal fault displacement. At numer- 
 ous places in the hills east of these scarps are cliffs that are in- 
 terpreted as fault scarps and some of the ponds rest in what are 
 apparently primarily faulted basins. 
 
 About a mile north of the Benson line on the downthrow 
 side of the great fault the limestones along the valley of East 
 Creek give place at the surface to phyllites which extend westerly 
 as shown on the map. Over the phyllite lying west of the fault 
 and in the high hills east of it no limestone was discovered. 
 
 The wider surface exposure of the phyllite formation at the 
 south in Orwell township is to be associated with its present 
 higher altitude and conditions which favored the erosion of 
 limestone that once overlay it ; for the field relations east and 
 south of this spur of high land show that limestone of similar 
 age and character to that which in Orwell rests against or on the 
 schist at the west lies on entirely similar phyllite east of the spur 
 and indicate the former extension of the limestone over the 
 phyllite now forming the spur. 
 
 Eastern Orwell township. A strip of country about a mile 
 and a half wide in the eastern part of Orwell township presents 
 
162 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 many significant features. The northern part of this strip is now- 
 very largely buried by Champlain clays, but the southern part is 
 hilly and affords many interesting outcrops \v1iich serve to bring 
 out the general relations among the rock formations. 
 
 South of the Orwell-Sudbury road are two valleys separated 
 by a low range of hills. Along the western valley extends the 
 road from Abell corner to Bangall and Hortonville, The other 
 valley is occupied by the head stream of Lemon Fair River and 
 along its western margin is another road going also to Horton- 
 ville. Along these valleys and over the low range intervening 
 between them the surface rock is largely limestone, which can be 
 seen to have been much disturbed by folding and faulting and 
 to have been severely sheared in most places. The prevailing 
 rock is of a faded blue or gray color on weathered surfaces and 
 dark blue or bluish-gray on fresh surfaces. So far as observed 
 it does not often take on a "marbly" aspect south of the Orwell- 
 Sudbury road. Fossils were found at many places in this lime- 
 stone on the hills and in both valleys mentioned, chiefly on the 
 weathered surface. They all have a similar aspect and consist 
 of crinoid stems, scrolls representing shells of gastropods like 
 those found northeast of Orwell village, sections in the planes 
 of the axes of spirals resembling Pleurotomaria and Murchisonia, 
 Plectambonites, Orthis, a doubtful streptelasmoid form, a small 
 and a medium-sized Orthoceras, bryozoans like Stictopora and, 
 on fresh surfaces, many specimens of Triniicleus. The most 
 prolific localities were found on the adjoining farms of George 
 W. Felton and Horton Farnum along a side hill just west of the 
 eastern road mentioned above. Southeast and east of Farnum's, 
 similar rock extends east of the road across the Lemon Fair 
 valley and similar fossils were found at several places nearly to 
 the Hyde Manor road. 
 
 For the most part the limestone just described, so far as 
 the shearing structure permits observation, consists of beds of 
 moderate thickness and in this and in general lithologic features 
 as well, resembles the Trenton northeast of Orwell village and, 
 in fact, also that along the lake near Neemes' camp. But it 
 should be noted that metamorphism is clearly more pronounced 
 in the areas east of the lake shore. 
 
 In Horton Farnum's pasture were seen some massive beds 
 of limestone which from the field relations seemed to be inferior 
 to the fossiliferous beds lying north and south of them. There 
 was nothing seen to indicate whether the massive beds are of 
 the same age as those surrounding them or older. See plate 
 XXVL 
 
 At various places along both valleys mentioned, on each 
 side of both roads and within the low range of hills intervening, 
 phyllite or quartzite emerges at the present surface from be- 
 neath the broken and eroded limestones. The map does not 
 
,^ 
 
 ►^ 
 
 o 
 
 r^ 
 
 
 d 
 
 Otw 
 
 
 CO 
 
 fo 
 
 3 
 
 
 ^ 
 
 CD 
 
 ^ 
 
 (P 
 
 ;. 
 
 o 
 
 
 
 S 
 
 03 ai 
 
 
 
 
 
 %-l 
 
 o 
 
 3 C 
 
 r^ 
 
 3 
 
 S 
 
 o 
 
 •^ 
 
 ^ 
 
 CO 
 
 h^l 
 
 
 O 
 
 "w 
 
 <p 
 
 
 o 
 
 CD 
 
 j:^ 
 
 L< 
 
 o 
 
 
 
 
 o 
 
 
 m 
 
 "w 
 
 <4-l 
 
 
 CD 
 
 p 
 
 3 
 
 o 
 
 ci 
 m 
 
 H 
 
 o 
 3 
 
 o 
 
 0/ 
 
 
 
 o 
 
 CD 
 
 
 
 
 
 "5 
 
 S 
 
 a 
 
 >.'3 
 
 > 
 
 o 
 
 'C 
 
 cc! 
 
 -i--> 
 
 
 sh 
 
 
 ,Q 
 
 OJ 
 
 
 >- 
 
 o 
 
 ^ 
 
 (B 
 
 C 
 
 
 
 
 T 
 
 
 « 
 
 
 h 
 
 (p 
 
 CO 
 
 ^4 
 
 CD 
 
 •S 
 
 
 CO 
 
 "a! 
 
 ^ 
 
 f: 
 
 M 
 
 OJ 
 
 tC 
 
 CO 
 
 5 
 
 0) 
 
 5 
 
 CD 
 
 3 
 
 CD 
 
 d 
 
 J= 
 
 ^ 
 
 ■^ 
 
 3 
 
 fe 
 
 o 
 
 ^ 
 
 c 
 
 
 
 c 
 
 a; 
 
 
 'C 
 
 o 
 
 <D 
 
 Si 
 
 A 
 
 H 
 
 o 
 
 X, 
 
 CD 3 
 
 q-i 
 
 
 i O o 
 
 m 
 
 CO 
 
 CO 
 
 CO 
 
 
 ^ 
 
 m 
 
 ■S 
 
 C 
 
 <w 
 
 u 
 
 ^ 
 
 e 
 
 <D 
 
 o 
 
 a! 
 
 X 
 
 §g 
 
 £ 
 
 O 
 
 o 
 o 
 
 A 
 
 CD 
 
 
 CO 
 
 
 %4 
 O 
 
 m 
 
 
 
 CD 
 
 
 
 CP 
 
 ^ 
 
 2 
 
 A 
 
 3 
 
 S 
 
 
 
 
 
 r; 
 
 > 
 
 Ti 
 
 .2 
 
 "3 
 
 O 
 
 <D 
 
 S 
 
 .. 
 
 o 
 a; 
 
 (1) 
 
 ^ 
 
 
 CO 
 
 a 
 
 H 
 
 ^ 
 
 ."^ 
 
 
 o 
 m 
 
 
 O 
 
 CO 
 CO 
 
 
 |--] 
 
 n^s o3 
 
 s 
 
 
 >> 
 
 '^ 
 
 , 
 
 
 O 
 
 
 
 
 ^ 
 
 CD 
 
 s 
 
 X 
 
 .^ 
 
 
 
 f>i 
 
 CD 
 
 
 
 CO 
 
 
 +J 
 
 rw 
 
 C 
 
 d 
 
 ^_) 
 
 
 .— 1 
 
 a; 
 
 (D 
 
 O 
 
 
 O 
 
 m 
 
 
 c 
 
 O ^ t^-C CO 2, 
 
 ^Ph ^ CO o m 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 163 
 
 attempt to show fully the fragmentary nature of these outcrops 
 of terrigenous rocks. They appear sometimes as patches sur- 
 rounded by limestone, sometimes as scarps along the strike on 
 hill summits, sometimes but more rarely in sections across the 
 strike in gulleys of erosion, and again as narrow bands, as though 
 in faulted or infolded with the limestone. These terrigenous rocks 
 are entirely similar to those of the Orwell hills and to those of 
 the Sudbury hills lying to the eastward, and it was not possible 
 to draw any distinctions among them on the basis of difference 
 in age, or from their relations to the associated limestones. 
 
 North of the Orwell-Sudbury road the course of the Lemon 
 Fair has been constrained and controlled in the process of the 
 river's down-cutting by a few ledges which by the river's work 
 and that of general erosion have been opened to view. Some of 
 these ledges are of much interest. 
 
 Outcropping in the west bank of the Fair in the fields about 
 one and a half miles north-northeast of Abell corner and ex- 
 posed on the dip surface is the light blue limestone seen south of 
 the Orwell-Sudbury road. In the east bank of the stream the 
 beds are exposed along their edges and much of the rock is 
 seen to be a strongly-sheared limestone having the character of 
 a calcareous slate. Practically on the strike of these beds, a few 
 rods north in the same bank and in a somewhat higher scarp, 
 this sheared limestone takes on a "marbly" aspect and is infolded 
 or infaulted with patches of chamois-colored, dolomitic rock. 
 Near the base of the section light-colored, siliceous phyllites like 
 those so frequent in the Orwell and Sudbury hills, and outcrop- 
 ping through the limestones lying between, emerge from beneath 
 the marbly rocks and at one place a large solution hole has ex- 
 posed the phyllite underlying the limestone. Northerly the 
 sheared rock becomes still more "marbly" and lies above strongly- 
 sheared, slaty limestone. 
 
 In this general vicinity the limestone or "marble" is filled 
 with solution holes and channels along joints which give an im- 
 pression that the limestone lies in disturbed relation to some 
 stratum beneath. 
 
 The sheared "marble" extends through the fields eastward 
 from the Fair for several rods and gives place at the surface to 
 a sheared, light-blue rock like that noted on the west of the Fair. 
 It is infolded with gray dolomite mentioned above. 
 
 The sheared blue rock and "marble" are thus seen ap- 
 parently to pass into one another both along and across the 
 strike in these exposures and apparently both have essentially the 
 same relations to the gray or chamois-colored beds. The gray 
 rock is also found south of the Orwell-Sudbury road, but its 
 relations there are not impressive. Conditions similar to those 
 just described for the rocks in the banks of the Fair and adjacent 
 fields, north of the Sudbury road, prevail in the fields east and 
 
164 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 south and need not be cited in detail. It may be noted that 
 entirely similar types and relations extend through detached ex- 
 posures southeastward to the west slope of Sudbury Hill below 
 the stage road. 
 
 The field relations of the blue limestone or "marble" to the 
 gray dolomite suggests that the dolomite is not interbedded with 
 the other, but that it is usually above it and distinct from it. The 
 examination of some of the exposures in which the two are in- 
 folded, or infaulted, might give the impression that the two are 
 interbedded members of the same formation. 
 
 For some reason the rocks north of the Orwell-Sudbury road 
 have been more severely altered and fossils in them now seem 
 to be lacking. 
 
 RUTLAND COUNTY. 
 
 Benson Township. 
 
 (Whitehall topographic sheet.) 
 
 Topography. Hubbardton River and its head streams have 
 cut their valleys below the level of 300 feet among the hills in the 
 eastern part of the town, and a strip along the lake shore in the 
 northwestern part a mile wide and a mile and a half long marks 
 a small extension of the Champlain lowland into this area. Else- 
 where Benson topography is typical of the foothill country west 
 of the Taconic range. 
 
 Description of a section from Lake Champlain through 
 Benson village to Bangall, near Hortonville. Extending from 
 Benson Landing for a distance of one and a half miles eastward 
 along the road from the landing to Benson village the section 
 gives siliceous and magnesian limestones of Brainerd and Seely's 
 Beekmantown formation. The beds form a gentle arch and near 
 the lake dip at a low angle to the west. 
 
 At Benson Landing the Beekmantown rocks as exposed do 
 not reach the lake shore, but a mile north at Stony Point they 
 dip into the lake. A few rods east of Benson Landing are ex- 
 posed in a low west-facing clifif in a ravine south of the road 
 about 15 feet of dark, bluish-gray, siliceous limestone or dolomite, 
 weathering light gray, in beds about two feet thick which dip 
 gently to the west. About 20 rods to the east of this outcrop is a 
 somewhat higher cliff in the ravine showing from the base about 
 two-thirds the way up, massive beds of somewhat pitted, magne- 
 sian limestone which on fresh surfaces is mottled light and dark 
 gray. Above these beds are a few feet of limestone showing many 
 ridges parallel with the bedding. The dip is gently westward. 
 Above these rocks, in and beside the road and perhaps 20 feet 
 higher stratigraphically, near the junction with the Stony Point 
 road and in the yard of the William White place, are exposed 
 with westerly dip bluish-gray limestones frequently covered with 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 165 
 
 thick, reticulated, gray or reddish brown patches, which often 
 show as shallow, ringed craterlets in relief which give the weath- 
 ered surface a coarsely-pitted appearance. Among these pits and 
 patches and also on the smoothly-weathered rock are scores of 
 finely-coiled whorls of Ophiletas and some Maclureas. These 
 fossiliferous beds are interstratified with layers of sandstone. 
 Eastward about 200 yards along the road, dark, bluish-gray rock 
 somewhat like that noted in the first clifif outcrops beside the 
 road and a half mile east similar rock lies flat. Away from the 
 lake the outcrops are few and mere patches in the drift. The 
 precise sequence was therefore hard to determine; but it seemed 
 clear that probably the fossiliferous rock represents the lowest 
 subdivision of Brainerd and Seely's Division D, carrying Ophileta 
 complanata, Vanuxem. 
 
 The magnesian limestones lying beneath the fossiliferous 
 beds presumably represent Division C. All the rocks appear 
 conformable, but the conditions do not permit minute comparison 
 with similar rocks in the sections of Shoreham and Orwell. 
 
 Eastward along the road past the school house at William- 
 son corner and down the slope to a brook are occasional ex- 
 posures which are not readily identified or correlated in their 
 restricted outcrops. 
 
 South of the brook and the road are mud-colored slates 
 which a few hundred feet eastward up the brook give place to 
 bluish or dove-colored limestones intermingled with chamois- 
 colored dolomite. The dove-colored rock carries dirty, yellowish 
 patches and stripes often soiled to black and on its weathered 
 surface at places afforded many small fragments of indetermin- 
 able fossils and two recognizable specimens of Maclurea magna. 
 A reading gave the strike as N. 32° E. and the dip as 25° easterly. 
 
 East of these rocks a short distance, on the north side of the 
 road, are limestones resembling the Trenton beds near Horton- 
 ville, which will be described presently. No fossils were found. 
 East of these exposures, along the road, the rocks are slates, 
 some of which are mud-colored, friable rocks like those men- 
 tioned above as occuring at the present surface farther west 
 between probable Beekmantown and Chazy outcrops and which 
 have what appears to be a distinguishable difference from most 
 of the slates of the Benson hills. They have in fact a resemblance 
 to certain slaty or shaly rocks which were noted farther north in 
 Orwell, but which have not thus far been described in a special 
 way. In some of the ravines tributary to East Creek in Orwell 
 the friable shales did not appear precisely like the blacker so- 
 called "Utica" and led to the suspicion that there is a series of 
 beds in the formation that usually goes under the comprehensive 
 name of "Utica" which is marked by less carbonaceous matter 
 and whose members are of prevailingly different color. This 
 idea seemed to receive some confirmation when mud-colored slates 
 
 m. OF Mfcss. mm imm 
 
166 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 were found west of the grist mill on East Creek along the road 
 to Montcalm Landing and therefore lying west of the black, 
 compact Trenton limestone and associated black slates at the 
 dam and in the gorge of the creek and again when similar slates 
 were found on the meridian of those west of the grist mill two 
 miles to the south along the road to the lake that passes through 
 Frank Charleton's farm, and also a mile south of here on the 
 hill east of the Nefong farm (old Walker place) and east of the 
 road from the Nefong farm to Benson Landing. 
 
 The mud-colored slates along the road from Benson Landing 
 to Benson village lie on the general meridian of the various ex- 
 posures, of similar slates just mentioned as occurring in Orwell 
 and are now regarded by the writer as the same. Along the 
 Benson road they give place at the surface to black slates which 
 have been called "Benson Black Slates." An actual transition 
 was not noted. Outcrops of the mud-colored, friable slates, 
 however, occur close to those of the black slates ; but after the 
 latter begin, going eastward, there do not appear to be any more 
 outcrops of the lighter-colored and more friable slates. A similar 
 relation obtains at the north ; in northern Benson township, on 
 the downthrow side of the great scarp along the Benson-Orwell 
 road, a blackish slate is present and westward across East Creek 
 the other slates appear. 
 
 The black slates continue eastward through Benson village 
 and east of the village are succeeded by outcrops of lighter- 
 colored, siliceous phyllites like those that are intermingled with 
 the black phyllites of the Orwell, Benson and Sudbury hills. 
 The black slates are not exactly like any of the terrigenous rocks 
 that the writer has seen among the hills just mentioned. They 
 also appear different from the mud-colored slates or shales at the 
 west, not only in color, but in the fact of greater metamorphism. 
 On the strike or meridian of the black slates farther south in 
 Benson at Forbes Hill, however, occur the light-colored, siliceous 
 phyllites and grits so common at the east, but this is not con- 
 clusive of similar general age for them and the black slates ; for 
 it will be shown that the probability is that terrigenous rocks 
 have been overthrust on other terrigenous rocks in western Ver- 
 mont and it apparently cannot be affirmed whether the black 
 slates are beneath or on top in the examination of a surface 
 section of such an overthrust. It seems probable, however, that 
 the mud-colored, friable shales are of different age from the 
 phyllites at the east in Benson village and eastward, and that 
 they may belong to the same general formation that contains the 
 black, limy, fossiliferous slates along the lake shore in Orwell, 
 and also some of the Trenton rocks. If this is so, then the map 
 of Orwell which shows the slate of the Orwell hills extending 
 west of the scarp along the Benson-Orwell road should differ- 
 entiate among the slates west of the scarp and show some of 
 
 mmi mmti nm i .vj^i 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 167 
 
 them in the character used to represent the "Utica," just as was 
 done west of the grist jnill farther north. On such an interpreta- 
 tion some of the slates would be part of the mass that has been 
 overridden and therefore probably of different age from the 
 other terrigenous rock. It is, however, not easy to show any 
 sharply dividing line at the present surface. 
 
 Continuing the section eastward from Benson village, out- 
 crops are lacking east of the direct road from Orwell to Fair- 
 haven along the road to "Spoke Hollow" or "Howard Hill cor- 
 ner." Due north of this road in the high hills around and west 
 of Sunset Lake in the northern part of the township are phyllites 
 and quartzites which have been described at another place, and 
 south of these hills, across the valley^s of the head streams of 
 Hubbardton River, are entirely similar rocks which will be briefly 
 mentioned again beyond. Similar rocks are found on Howard 
 Hill. 
 
 On the southeastern slope of Howard Hill are exposures of 
 limestone bearing strong resemblance to rocks which a little way 
 to the eastward and elsewhere carry Trenton fossils. A half 
 mile east along the road through Bangall to Hortonville, on each 
 side of the road just northeast of Hall's corner, are ledges of 
 undoubted Chazy showing the lithological characters of this rock 
 and affording good samples of Strephochaetus and several recog- 
 nizable specimens of Maclurea magna, besides fragments of other 
 fossils. 
 
 Eastward from these ledges of Chazy, about half a mile, 
 near the standpipe of the Hortonia Power Company, greatly- 
 sheared, blue limestone has been blasted for the big conduit run- 
 ning to the power house, and still further east between Babbitt's 
 corner and Hortonville, north and south of the road, are ledges 
 of faded blue limestone which give evidence of arrangement in 
 undulating folds with easterly dip which is sometimes that of 
 stratification and sometimes very apparently that of shearing in 
 westward dipping beds. Fossils are numerous on the weathered 
 surfaces and include many small spirals and numerous sections 
 in the plane of the axes of the spire of Murchisonia- and Pleuro- 
 tomaria-\ike gastropods. In its fossil contents and in its other 
 characters the rock is like that which at the north and northeast 
 along the valley of the Lemon Fair and north of Horton Pond 
 carries numerous Trenton fossils. 
 
 Along the section just described it will be seen that at the 
 present surface there is wide separation by terrigenous rocks of 
 the calcareous rocks near the lake from those near Bangall, but 
 that the latter practically join the limestones of the valley of the 
 Lemon Fair, and actually do join the rocks in the valley along the 
 road that leads from Bangall to Abell's corner. Around Horton- 
 ville the phyllite formation frequently outcrops through the lime- 
 stone by erosion of the latter. The section does not reveal any 
 
168^ REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Beekmantown rocks away from the lake region at the present 
 surface. 
 
 The field relations of the rocks just described indicate that 
 the calcareous strata east and west of Benson village lie on a 
 formation of terrigenous rocks. That these latter rocks are all 
 of similar age seems improbable. The phyllites on which rest 
 the Chazy-Trenton rocks near Hortonville are entirely similar 
 to those of some of the Benson hills and those found in the hills 
 of Orwell and Sudbury; but nearer the lake the Beekmantown- 
 Chazy-( Trenton?) beds may rest in part on phyllites like those 
 at the east and in part on very different slates. See figure 14. 
 
 Some observations south and southeast of Benson village. 
 South by east of Benson village along the road from the village 
 through O'Donnell corner, black and lighter-colored phyllites in 
 the association that has been so frequently mentioned outcrop at 
 several places. At O'Donnell corner they occur together in the 
 same ledge in the exposures near the dam. These rocks con- 
 tinue eastward and form the hills east of the road from Howard 
 Hill to Fairhaven. For two miles along the Benson-Fairhaven 
 road, from the junction of the Howard Hill road with it, the hills 
 at the east drop by a high, steep scarp to the plain of Hubbard- 
 ton River. This scarp is the counterpart of those along the 
 Benson-Orwell road north of Benson. It diminishes in height 
 southward and the Fairhaven road ascends from the plain and 
 crosses the hill to Fairhaven. Near the top of the rise, west 
 of the road, are ledges of greatly-brecciated blue limestone. 
 Fossils have been destroyed, but the rock is lithologically like the 
 Trenton as observed at the north. The apparent dip is eastward. 
 West of these outcrops, along the road that goes over Forbes 
 Hill to Benson village, and north of it, are other ledges clearly 
 dipping easterly and composed of gray dolomitic beds and light- 
 blue limestone. The blue Hmestone is much altered and sheared. 
 One much-weathered specimen which was identified as Maclurea 
 magna was found and there seems little doubt that the beds be- 
 long to the Chazy. Westward and between these outcrops and 
 Hubbardton River there appear to be other ledges of Chazy, 
 but at the time they were examined circumstances did not permit 
 a prolonged study. 
 
 Across Hubbardton River, along the road up the east slope 
 of the hill, are phyllites like those in the hills east of the Fair- 
 haven road and believed to be the continuation of them beneath 
 the limestone that intervenes and to have been exposed by the 
 erosion of the limestone. They continue along the road over 
 Forbes Hill for a mile and a half where the limestones appear in 
 the fields to the west of them and then north of them along the 
 road towards Benson village. The latter rocks give place two 
 and a half miles south of Benson village to the phyllites again 
 which continue along the road towards the village. Limestone 
 
REPORT OF THE VERMONl' STATE GEOLOGIST. 
 
 169 
 
 was also noted forming detached hills in the plain of Hubbard- 
 ton River. 
 
 The exposures just described south of Benson village, by 
 a somewhat circuitous route it is true, connect the limestones 
 on the Hortonville meridian with those near the lake. They 
 carry the Chazy-Trenton beds nearer the lake rather than the 
 Beekmantown away from it. 
 
 Figure 13. Writer's interpretation of relations east of Renson Landing. A, 
 "Reekmantown," forming a low abraded anticline ; ' R, Chazy, separated 
 from A by a brook in which appear shales which are interpreted as ex- 
 posures of the formations that have been overlapped by thrust ; C, prob- 
 ably Trenton ; D, black phyllite, probably Lower Cambrian, interpreted 
 as unconformably subjacent to the Ordovician limestones. A thrust, 1-2, 
 has cut through D and from it into the overlying limestones and all have 
 been driven over E, Trenton- "Utica" slates. The rocks near the lake 
 were subsequently dropped by normal faults as shown. 
 
 The field relations of all the exposures now described, 
 though briefly, for Benson township indicate that the phyllite 
 formation, as in Orwell, and as will be indicated presently as 
 also in Sudbury and Brandon, once had a continuous covering of 
 limestone strata which was either thrust or deposited upon it. 
 There does not appear to be any essential difference in the ter- 
 rigenous rocks over all this somewhat extensive area, except as 
 indicated above for certain slates at the west. There seems tQ 
 be no indication that the limestone appears from beneath the 
 phyllite formation on account of folding and erosion or on account 
 of thrust. On the contrary, the various areas of Hmestone are 
 either purely erosion remnants, or thrust-erosion remnants, and 
 whether outliers or inliers depends upon the age assigned to them 
 and to the terrigenous formation on which they rest. 
 
 Short section north of Benson Landing. Before leaving the 
 Benson area it seems desirable briefly to record some observations 
 made north of Benson Landing. 
 
 One mile north of the landing, at Stony Point, siliceous 
 limestone of arenaceous texture forms a cliff rising from the 
 lake and lies nearly flat. Eastward from the shore surface de- 
 posits have covered the hard rock to a great extent, but through 
 the sugar orchard east of Sibbald's cottage and eastward to the 
 Chester Bishop place, are scattered ledges and the very gentle 
 
170 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 dip and rock exposures indicate the northward continuation of 
 the rocks and structure east of the Landing. In the northern 
 section within a distance of about a mile were seen at intervals 
 going eastward small exposures in the following sequence: 1, at 
 the water's edge a rather coarse, siliceous dolomite; 2, tough 
 sandstone, carrying many fragments of fossils looking like trilo- 
 bite fragments ; 3, siliceous limestone with ridges on the weathered 
 edges ; ^, blue limestone "conglomerate" with irregular frag- 
 ments of a hue slightly different from that of the matrix; 5, layer 
 with numerous whorls on the weathered surface ; 6, drab or buff- 
 colored dolomites. 
 
 From this sequence, although outcrops were usually limited 
 in number except at the east, it was concluded that this flat 
 arch is composed largely of Brainerd and Seely's Division D, 
 with possibly some of C at the west and some of E at the east 
 where the dolomite strongly resembles that associated with the 
 blue limestone of the Chazy. So far as observed the arch was 
 not broken or eroded to expose any slates through it. 
 
 EUTLAND COUJfTT. 
 
 Sndbnry Township, 
 
 (Brandon topographic sheet.) 
 
 Topography. This township includes most of the spur of 
 high land which forms the northern end of the Taconic range. 
 On the west and northwest the spur is bounded by the valley of 
 the Lemon Fair River, which is a southward extension of the 
 Champlain lowland between the Taconic hills. On the east and 
 northeast the spur is bounded by the low, swampy flood plain of 
 Otter Creek, along which the Champlain lowland merges with the 
 Vermont valley. 
 
 The spur falls off gradually in altitude northward into the 
 low schist ridge of Whiting, which is flanked on the east and 
 west by limestone. There are certain structural features both 
 within the spur and along its margins which will be described in 
 detail beyond. 
 
 General geological features. As one passes eastward from 
 the lake region through the Taconic range towards the Green 
 Mountains the confusion in field relations and the difficulty of 
 interpretation increase. The field worker experiences the need 
 of multiplicity of detail in critical relations in order to feel at 
 all sure of his views of structure and even then it will happen 
 that two persons will arrive at quite different conclusions with 
 respect to the meaning of presumably critical relations or will 
 stress quite different things as being of importance. It soon 
 becomes apparent to the student of the metamorphosed and 
 greatly deformed rocks lying east of the lake that the region 
 must be viewed more or less as one grand unit in order to see 
 
REPORT OF THE VERMONT STATE GEOLOGIST. I71 
 
 into the meaning of its smallest part. Recognition of the direc- 
 tion of the road which one must travel to get anywhere perhaps 
 will be conceded as an important step leading towards the destina- 
 tion. 
 
 Noi'th and south of Sudbury milage. The sheared blue lime- 
 stones and marble and associate^ gray dolomite in the valley of 
 the Lemon Fair River in eastern Orwell township that have 
 been described, continue into Sudbury township and give place 
 eastward to the terrigenous rocks of the Sudbury hills, which 
 are practically continuous northward with a low ridge of similar 
 rocks extending northward into Whiting township and south- 
 ward join with the entirely similar rocks of Hubbardton. The 
 map shows connection across the ridge of the limestone of the 
 Lemon Fair valley with that of Otter Creek. Whether one showed 
 the area, which on the writer's map represents a surface connec- 
 tion of the limestones, as there shown, or as schist, would depend 
 upon what outcrops were stressed, as will be seen presently; for 
 it appears .that schist lies beneath limestone in the area and also 
 outcrops through it. It will be convenient to say that both are 
 practically continuous, which, though literally impossible, when 
 so stated conveys important ideas. The schists outcrop every- 
 where along the road from Webster's corner in Sudbury nearly 
 to Whiting village, also westward nearly to Ketcham corner, 
 where they appear on the meridan marked by the marbles and 
 sheared limestones farther south. Eastward they extend one- 
 third of a mile from Webster's corner along the road to Brandon 
 and are then interrupted by the limestone for a short distance. 
 At this interruption the limestone is really a calcareous slate as 
 shown in pits along the road and in fields nearby and might be 
 mistaken for the schist or phyllite formation if hastily examined. 
 A little farther east the schist appears in the road, east of the 
 school house, but is again bounded by the limestone north and 
 south. 
 
 West of Sudbury Hill is an old road across the flats that 
 runs from the village to Ketcham's corner. East and west of 
 this old road are detached, knoll-like patches of limestone or 
 "marble" with associated gray dolomite projecting through the 
 clay of the old "lake" bottom and apparently to be regarded as 
 practically continuous westward beneath the clay with the similar 
 rocks described above as outcropping in the banks of the Lemon 
 Fair; but whether continuous with or surrounded completely by 
 limestone beneath the clay, or whether partly surrounded by 
 schist, could not be determined for they are now simply islands 
 in the clay. These exposures show varying proportions of either 
 sheared blue limestone, or "marble," with gray dolomite. On 
 the .west side of the main Sudbury road, on the west slope of the 
 hill below the village, the rock is often a whitish or salmon-pink 
 sheared "marble" and this and the rocks in general along the old 
 
172 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 road mentioned are entirely similar to those which extend around 
 the northern end of the schist spur and join with others at the 
 east. Directly west of Sudbury church the sheared "marble" is 
 overlain by a mass of thick, blocky, gray dolomite through which 
 the marble peeks at places and the structure was made out as 
 probably that of a local syncline of "marble" holding the super- 
 jacent dolomite. 
 
 South of the Sudbury church is sheared "marble" and asso- 
 ciated dolomite and this association in general continues along the 
 scarp slope east of the Hyde Manor road as far as Hyde Manor. 
 South of the Manor the "marbly" rock gives place apparently 
 along the strike to light blue limestones mostly sheared into 
 slaty-looking rocks and these, except for an occasional tongue 
 or patch of schist near the summit of the slope, and with obvious 
 faults and flexures, are continuous with the sheared blue lime- 
 stones, dovetailed with tongues of schist and carrying Trenton 
 fossils, north of Horton Pond and extending westward across 
 the upper valley of the Lemon Fair. 
 
 Directly east of Hyde Manor, along a brook that descends 
 from the hill, the phyllite formation has been exposed by erosion 
 of the Hmestone and is continuous eastward at the surface with 
 that of Government Hill. South of the road from Hyde Manor 
 over the hill to the Huff Pond road occur patches of limestone 
 surrounded wholly or partly by schist and the latter outcrops 
 through the limestone at the summit of the scarp slope just west 
 as a gray, pyritiferous rock much like that seen in the valley of 
 Sugar Hollow Brook east of Brandon in association with phyl- 
 lites quite similar to those of. the hill east of Hyde Manor. 
 
 An east-west section along a parallel about 300 rods north 
 of Sudbury church gives sheared blue limestone just east of the 
 stage road, which is succeeded eastward up the hill slope by 
 phyllite, and this in turn by limestone. But along this section 
 erosion has left few or no remnants of limestone on the higher 
 slopes, and eastward over the hill for a mile and a half all is 
 schist or quartzite. 
 
 At the northern end of the Sudbury spur, about a mile 
 northeast of the church, is an instructive east-west section along 
 which erosion has produced a mutually interrupted series of out- 
 crops of limestone and schist, as now exposed, and which is in- 
 dicative of what was probably once the condition over all the 
 higher portion of the spur to the southward. 
 
 One and a fourth miles north of Sudbury church, in a gulley 
 beside the main stage road, is sheared blue limestone. Eastward 
 up the slope this is succeeded by schist which is the northward 
 continuation of similar rock on the northwest slope of Govern- 
 ment Hill where it is often intermingled with patches of quartzite. 
 The schist forms a scarp which is topped by limestone. The scarp 
 is regarded as the northward expression of normal displacements 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 173 
 
 on the west of Government Hill, of which the one east and north 
 of Hyde Manor is the most clearly defined at the present time. 
 The Hmestone topping the scarp just referred to is a slaty, 
 sheared, blue rock in places and "marbly" in others. It is suc- 
 ceeded eastward by schist with contact concealed, but with the 
 two rocks only 9 paces apart. Then a short distance eastward is 
 the sheared blue limestone again with "marbly" aspect, then schist 
 once more, then sheared blue limestone with some dolomite 
 mixed with it, then schist, and once more sheared "marble" mixed 
 with dolomite, then "marble" which joins at the present surface 
 with extensive exposures of similar rock lying eastward and 
 northward to the road. On the map the phyllite or schist is 
 shown dove-tailing with the limestone along the section just 
 described, but such arrangement is somewhat schematic. The 
 implication is that the calcareous formation is superjacent to the 
 terrigenous rocks as is the case in the areas lying to the west. 
 This relation seems to be capable of reasonable proof by the 
 means so far employed without paying much special attention to 
 differences of dip and strike in the associated rocks. Many areas 
 of the "marbly" rock at the east of the section just described are 
 pinkish in color like that west of Sudbury church. Dolomite 
 is intermingled with it at various places and it passes laterally 
 into blue, sheared limestone. 
 
 East of the section just described, and east of the north- 
 south road that joins the Brandon road ("Otter Creek road"), 
 near the school house, are four large, conspicuous hills which are 
 composed largely of sheared Hmestones and marbles, and all 
 show, at some places more than at others, gray dolomite resting 
 on the blue limestone or marble in patches and intermingled 
 without any regularity. 
 
 It is reasonably apparent that the north end of this spur of 
 the Taconic range in Sudbury now has metamorphosed limestones 
 lying on the schist formation and that the latter has been exposed 
 at many places by erosion of the limestone, while the limestone 
 has been preserved from erosion at certain places by protection 
 through folding or faulting. South of the section at the north end' 
 of the spur which was just described to demonstrate these rela- 
 tions, and to show that the conditions prevailing west of the Sud- 
 bury hills also occur in them, limestone has not been found by the 
 writer within this spur in the township of Sudbury, except east 
 of Hyde Manor along the lower faulted portion of the western 
 slope of Government Hill, where the limestone which tops the 
 considerable scarp east of the Manor extends easterly to the Huff 
 Pond road. 
 
 The question of the age of the sheared, blue limestones and 
 marbles on the western, northern and northeastern slopes of the 
 Sudbury spur apparently cannot be readily affirmed from fossils, 
 as most of these rocks are extensively altered. None was found 
 
174 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 in them by the writer. The question is complicated by the pres- 
 ence of disturbances, some of which seem fairly easily defined as 
 to character, while others are very difficult to explain. There 
 are, however, some considerations which serve to establish the 
 identity of some of the limestone on the basis of probability. 
 
 The fossiliferous Trenton limestones in the southeastern part 
 of Orwell township, as discussed above, pass eastward across 
 the low, hilly land between the head stream of the Lemon Fair 
 and Horton Pond and join at the present surface with the sheared 
 blue and slaty limestones south of Hyde Manor, while these pass 
 northward along the face of and on top of the scarp east of the 
 Hyde Manor road through Sudbury village from which area, 
 when traced northeastward, they join with the limestone expo- 
 sures at the northern end of the Taconic spur and when traced 
 northwestward they join with the sheared blue limestones and 
 "marbles" in the valley of the Lemon Fair. The latter are to 
 all appearances the northern continuation of the fossiliferous 
 limestones to the south of them. Over this considerable area, 
 therefore, these various rocks may seemingly be traced with un- 
 important surface interruptions into each other. Added to this 
 is the important fact that at scores of places these various rocks 
 have substantially the same relation to an underlying schist- 
 phyllite formation, which is throughout essentially the same in 
 its characters. Moreover, there is associated with all these 
 various rocks a singularly similar gray dolomite which has held 
 to a more uniform appearance in the different localities, for some 
 jeaSon or other, and which lies on the fossiliferous as well as the 
 metamorphic rocks, although seemingly more abundant at the 
 east. Further, the strong indications of normal displacement 
 on the west of Sudbury Hill afiford explanation of any apparent 
 discontinuity at the present surface. The lithological differences 
 among these calcareous rocks require explanation, especially on 
 the assumption that the various rocks are essentially the same; 
 such differences might be seized upon to show that the rocks 
 could hardly be the same. But any effort to explain the differ- 
 ences may be postponed for the present. 
 
 Description of an irregular or composite section across the 
 northern end of the Taconic range passing through Government 
 Hill. The section begins for sake of completeness at the Hyde 
 Manor road and extends to the eastern boundary of the township 
 of Sudbury, across the schist formation. 
 
 At this point it will be convenient to call special attention to 
 and to discuss briefly certain lithological differences shown by 
 the members of the schist formation. Some of the terrigenous 
 rocks making up this formation are distinctly schistose, but per- 
 haps most of them are better called phyllites than schists because, 
 though obviously altered, crystalline rocks and while generically 
 speaking they are schists, they are prevailingly rather fine-grained 
 
(B m 01 IB o 
 
 £ ^ £ •;= ■*-> 
 
 .2 cd .S S C 
 0.0-^ °.2 
 
 ^ Oj be" 0} 
 
 .S b^-2 
 
 O 0;'^ O 
 m ^ .-^ 
 
 S .2 ■" <" 
 
 5 '■*-^ '•-' '5 IS 
 
 '^ m o 'S a 
 
 ti-tii 3 0) ;^ 
 
 ^ rf OJ +-1 72 
 
 o 
 
 0) 4) m*^X2 
 C O rf'g 
 
 3 > S a.^ 
 .n o 13 '-^^ -^^ o 
 
 3 O '^ 
 
 fj !-, PI <P O' c* 
 ■■j +^ QJ S-i r- ^ 
 
 "^ "2 S ^: K c 
 
 -] cc t. <p 5 
 " ci^ bJOC 
 
 s^^ bi] 71 M ^ 
 
 O o c; •" .2 
 
 5,G (B'3^ 
 
 iJ3,^ 3 
 
 m ^ 
 
 "-^ r^ ^ T'j ' 
 
 §^.2 Si 
 
 -M bD 
 CD aj oj { 
 
 uiJ^ O ' 
 
 3 c a ' 
 o Ctt-i.~.; 
 tiS ©'On 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 175 
 
 and do not show their minerals conspicuously when viewed with 
 the naked eye, except where they carry the large crystals of 
 pyrite which have been mentioned, or other phenocrysts. In the 
 older descriptions of these fine-grained, micaceous rocks they 
 were called "hydromica schists." Many, perhaps most, of these 
 phyllites are black and man}?- are light-colored, fissile rocks, 
 cleaving somewhat like slate, but more brittle and chipping into 
 many small pieces. A coppery-colored stain is abundant in both, 
 but usually more apparent on the lighter-colored variety. The 
 pyrite seems to be much more characteristic of the black phyllites. 
 It occurs, however, in some of the other terrigenous rocks of this 
 formation. 
 
 True slates are not abundant at the present surface over the 
 Sudbury hills, although they occur there and in the Orwell hills 
 as well. They have not been found good enough to quarry 
 profitably. Occasionally among these rocks there occurs a very 
 black, carbonaceous phyllite, rich in small pyrite grains, and 
 rather restricted in its lateral and horizontal extent. Quartzite 
 is abundant, sometimes in scattered small patches, but at other, 
 places continuous at the surface, or practically so, over con- 
 siderable areas. In a number of places white vein quartz in 
 irregular seams and patches is abundant within the quartzite. 
 Some of the black, pyritiferous phyllites, gritty schistose quartz- 
 ites, and more compact or massive quartzites are indistinguishable 
 from similar rocks found east of Brandon in the ridge west of 
 Sugar Hollow and near the base of the margin of the plateau. 
 
 While there is thus often a manifest difference in general 
 surface aspect of ledges in close proximity, both in color and 
 lithology, after an examination of hundreds of outcrops over the 
 Sudbury and Orwell hills and in other parts of the Taconic range, 
 the writer has failed to find any positive criteria by which to 
 separate one from another on the basis of age. The structural 
 relations and other considerations seem to afford sufficient ex- 
 planation of the variations seen at the present surface. In the 
 high scarps on the west of the hills in Orwell and northern Ben- 
 son, massive quartzite is interbedded with black phyllites and 
 other rocks which could not be satisfactorily irrspected on these 
 precipitous scarps ; but which together had an aspect very similar 
 to that given by a surface section across the summits of the ranges 
 lying east and similar to the association of phyllite and quartzite 
 east of Brandon. 
 
 As may be mentioned again beyond there appears no good 
 reason for regarding the phyllites along the low ridge that ex- 
 tends from Sudbury into Whiting as different from those in the 
 Sudbury hills, although along the Sudbury- Whiting road the 
 light-colored variety is rather in predominance. In a brook two 
 miles northwest of Whiting village occurs the same quartzite 
 
176 
 
 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 with its nests of white vein quartz that is so conspicuous on 
 Government Hill. 
 
 One-half mile north of Hyde Manor and east of the stage 
 road is a scarp. The steepest portion of the face near the top 
 is a sheared "marble." This continues over the summit and 
 eastward is covered at places with the gray dolomite. The cal- 
 careous rocks extend from the scarp eastward for about one-third 
 of a mile to the Huff Pond road. At the base of the scarp at 
 places near Hyde Manor the dolomite has a position that might 
 suggest an interbedded relation to the "marble," but as the super- 
 jacent position of the dolomite is more apparent the relations at 
 the Manor are interpreted as due to faulting as shown in figure 14. 
 
 w 
 
 
 E 
 
 
 F 
 
 ^^ ^OL. 
 
 :^^p^ 
 
 
 1 
 
 )^^^ 
 
 o 
 < 
 o 
 
 
 V 
 
 QOARTJJITC- SCHIST 
 FORMATION 
 
 Figure 14. Section just north of Hyde Manor, somewhat generalized as to 
 attitude of beds, showing gray dolomite as probably faulted with sheared 
 limestone, which produces appearance of being interbedded. The cal- 
 careous rocks are shown as being underlain by the quartzite-schist 
 formation of the Sudbury hills. 
 
 A little south of the section as just begun, along the cross- 
 road from the Manor to the Huff Pond road, and also east of the 
 main road from Sudbury village to the pond, on the western slope 
 of Government Hill, are black phyllites with bedding unusually 
 distinct and striking nearly east and west, N. about 70° E., and 
 farther up the slope near the summit thick-bedded quartzite 
 shows much disturbance from the prevailing strike of the rocks 
 roundabout. A reading here gave N. 70° W. 
 
 The surface rock on the western slope of Government Hill 
 is prevailingly a blackish phyllite, with some patches of quartzite, 
 but the latter forms most of the ledges north and south along 
 the summit of the hill, and in places carries much vein quartz in 
 irregular seams and bunches. 
 
 Government Hill descends over quartzite by a gentle slope 
 of irregular surface on the east about 150 feet through a distance 
 of less than one-third of a mile. Then comes an ill-defined 
 scarp, which does not appear on the topographic map, with the 
 black phyllite at its base and quartzite forming the higher portion 
 and summit. Eastward this hill descends over quartzite by irreg- 
 ular surface to a swamp with a sharp scarp facing west on the 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 177 
 
 t 
 
 east of the swamp and with the black phyllite at the base and 
 quartzite again at the succeeding summit. Then another east- 
 erly slope to a swamp with another scarp, sharper if anything 
 than those just mentioned and exhibiting similar geological rela- 
 tions. 
 
 East of the eastern slope of Government Hill, the section as 
 thus far described, is either through a dense, swampy tangle 
 or thick woods and very difficult to travel se, but while the ledges 
 are much covered with decaying vegetation the succession can 
 be made out. 
 
 At the east of the spur in the high hill north of Dolan's house, 
 two-thirds of a mile north-northeast of Landon's corner, the 
 quartzite seems thinner than farther west. This hill has a sharp 
 scarp on the east which is clearly visible from the road running 
 northerly from "Pond Hole" school house. Between the base of 
 the scarp and the road are abundant ledges of the black phyllite 
 with patches of quartzitic graywacke and some of the lighter- 
 colored phyllite intermingled with it. The map shows the fault 
 marked by the scarp just described. The schist has been dropped. 
 North and south on the downthrow side it gives place at the 
 surface to exposures of sheared blue limestone and dolomite. At 
 the north the latter lie now in great confusion and in places near 
 the schist are much mashed and broken. Eastward across the 
 road and brook the phyllite is succeeded by sheared and foliated 
 "marble," or blue limestone, and associated dolomite. 
 
 From the scarp just described a probable fault extends 
 northwesterly between the phyllite and limestone towards the 
 northern end of the Sudbury spur. This is marked by a scarp 
 for some distance, with a swamp at its base. The limestones east 
 of the north-south fault just mentioned are on a meridian oc- 
 cupied by "Long Swamp" at the north; while those north of 
 the probable fault running northwesterly lie on the meridian 
 of and are identical with those which have been described as 
 forming the high hills northeast of the Sudbury spur. 
 
 From the facts now recited, of the occurrence east of Sud- 
 bury church along the strike of the sheared "marble" at Hyde 
 Manor of black phyllite like that east of this marble at -the base 
 of Government Hill, and of the occurrence of similar phyllite 
 along the strike of the "marble" west of Burr Pond and north of 
 Horton Pond, and of field relations in Sudbury village and north- 
 east of it, as well as at other places, it is apparent that the phyl- 
 lite is, along the margins of the Sudbury hills, subjacent to lime- 
 stones that can be rather satisfactorily traced into one another at 
 the present surface and which present similar features and asso- 
 ciations. And a field examination leaves a strong impression, 
 almost no doubt, that the different members of the terrigenous 
 formation are components of a formational unit. 
 
173 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Composite section from the phyllites of southern Orwell 
 across the Taconic range to Otter Creek in Brandon. This sec- 
 tion, like the preceding one, is a broad band or belt from west to 
 east. 
 
 Beginning in the phyllite formation in southern Orwell, for 
 sake of completeness, the section passes from these phyllites over 
 a band of limestone, which is the northern extension of the Chazy- 
 Trenton rocks of Bangall in Benson township, with some irregular 
 outcroppings of phyllite through the limestone, then over phyl- 
 lites which are the northern extension of those in Hortonville, 
 then over a succession of limestone and phyllite bands dovetailed 
 in with each other, the limestones carrying probable Trenton 
 fossils, to the phyllites west and north of Burr Pond. The black 
 and associated light-colored phyllites forming the hill north- 
 northwest of Burr Pond are succeeded eastward at the eastern 
 base of the hill by massive quartzite with prominent ledges just 
 east of the brook that feeds Burr Pond, between the brook and 
 the road. Across the road is a softened scarp, facing west, then 
 for a mile schists with patches of quartzite to another scarp that 
 faces east and at the base of which is the sheared, blue limestone 
 extending south of "Pond Hole." This scarp is the southward 
 continuation of that which was described in the preceding section 
 as bounding the phyllite and quartzite formation on the east. 
 The fault which this scarp marks can be followed southward 
 with diminished scarp and passes just east of High Pond, about 
 two miles south of "Pond Hole." The map does not attempt to 
 show a number of scarps, which presumably mark fault lines 
 through these hills, because the writer wished to avoid a preju- 
 dicial impression which often comes from seeing many such 
 features represented on a map whose area is so small in compari- 
 son with that of the actual territory pictured. An examination 
 of the region would be sufficient to show how much these rocks 
 have been disturbed and the extent to which their present surface 
 succession and arrangement may be explained by disturbance. 
 
 Taking up the description at a point one-fourth of a mile 
 north of High Pond, along the fault line just mentioned as extend- 
 ing south of "Pond Hole," the section eastward is over black 
 phyllites on the west slope of the hill called "Stiles Mountain"^ 
 on the map, then over massiX^e quartzite in prominent ledges 
 through the woods along the east slope to the road, then across 
 the road and on phyllites and quartzites over a succession of 
 steep, scarp-like slopes facing west and gentle ones facing east, 
 including those of Stiles Mountain proper, for a mile and a half 
 to an old wood road. East of this road on the west of Castle 
 Mountain is a very steep scarp at whose base a brook runs 
 northerly. In the bed of this brook, perhaps 100 rods from its 
 junction with another brook, massive quartzite rests on black 
 
 1 The name Stiles Mountain, according to the residents, really belongs 
 to the second high hill east of this one. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 179 
 
 phyllite on the downthrow side of the fault, which is marked by 
 the scarp under which the brook flows. The west scarp of Castle 
 Mountain ascends oyer phyllites, which are succeeded at the 
 summit and down the eastern slope of the mountain by phyllites 
 and quartzite. Midway down the eastern slope are patches of 
 gray, siliceous dolomite of arenaceous texture. The phyllites 
 with quartzite continue to the base of the hill and are succeeded 
 eastward at the edge of the valley by marble and blue limestone 
 with associated gray dolomite. Along the section just described 
 the light-colored phyllites are frequent at more or less regular 
 intervals, but without any defined order. 
 
 Over the high hills along the southern boundary of Sudbury, 
 from Horton Pond to the valley of Otter Creek, which were sur- 
 veyed with care, no Hmestone was found by the writer except the 
 siliceous dolomite mentioned as occurring in patches on the east- 
 ern slope of Castle Mountain. Further evidence that the lime- 
 stone once rested on the terrigenous rocks is however obtained 
 from relations shown along the valley of the brook that flows 
 east in the hollow north of Stiles Mountain (proper) and Castle 
 Mountain to join Otter Creek. Along this valley, as shown on 
 the map, and separated by the phyllites and quartzites from the 
 limestones of the valley of Otter Creek, and surrounded by the 
 terrigenous rocks, are patches of sheared, bluish marble. The 
 valley of the brook is presumably a small, east-west trough- 
 faulted basin separating the hills north and south of it, and the 
 limestone has been dropped between them. 
 
 The road from Bressee Mill to Brandon, a half mile south 
 of the Dean farm, skirts the eastern base of a scarp in greatly 
 sheared and contorted marble, which at the top of the scarp rests 
 on quartzitic schist, while south of this scarp on both sides of the 
 road to Bressee Mill are ledges of massive quartzite. There is 
 a scarp running west-northwest from the road south of Dean's 
 place and which extends from the edge of the Otter Creek valley 
 to the embayment which is shown on the map as bounded rather 
 symmetrically by fault displacements. This scarp probably marks 
 a normal displacement and, although phyllite occurs on the down- 
 throw side, it substantially separates limestone on the north from 
 the terrigenous rocks of the hills. 
 
 The embayment mentioned, in which the limestone now ex- 
 tends southward at the surface between higher masses of phyl- 
 lite, is bounded at the south by another scarp along the high ten- 
 sion line of the Hortonia Power Company, just north of which 
 is a considerable swamp. South of these faults as just described 
 as bounding the phyllite hills on the north, the limestone has been 
 eroded on the upthrow side, except as shown on the map. North 
 of them the limestone has been preserved, as shown, by down- 
 faulting. On the northeast the Taconic hills are thus separated 
 from the low land west of Otter Creek by well-marked normal 
 fault displacements. 
 
180 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 .^ KUTLAND COUNTY. 
 
 Brandon Township. 
 
 (Brandon topographic sheet.) 
 
 Topography. The short spur of the Taconic range which 
 includes "Stiles Mountain" and "Castle Mountain," whose geology 
 was described under Sudbury, really belongs in Brandon township. 
 Bordering this spur on the east is the low, level flood-plain of 
 Otter Creek which extends into the northwestern part of the 
 township and there is largely occupied by extensive, wooded 
 swamps. 
 
 Except for a short distance near Brandon the Rutland R. R. 
 follows the eastern margin of the plain. At various places 
 ledges emerge from the plain as detached knolls, some of which 
 are of considerable size; but for the most part along the creek 
 the hard rock is hidden. 
 
 Along the eastern edge of the plain are low hills which offer 
 nearly continuous exposures. On the whole the land rises east- 
 ward to form a somewhat rolling upland which, with some inter- 
 ruptions due to ancient dissection of the rock surface, passes into 
 the foothills of the Green Mountain plateau. The Neshobe 
 River and other streams have in recent times terraced an old sand 
 plain that marks a period of glacial flooding or a submergence 
 of the old rock valleys among the hills east of Brandon village. 
 East of these streams the land rises more rapidly to the western 
 edge of the plateau, but east of Brandon a ridge of intermediate 
 elevation is separated from the steep scarps that border the 
 plateau by the valley of Sugar Hollow Brook. In general, how- 
 ever, a strip of hilly and mountainous land about two miles wide 
 extends in a north-south direction through the eastern part of 
 the township. 
 
 General geological features. In Brandon township many of 
 the rocks are marked and masked by still greater metamorphism 
 than that shown by the rocks of Sudbury. But this feature is 
 not true of all. In this township appears a series of beds that 
 has not been identified in Sudbury and is the northern con- 
 tinuation of the "interbedded series" of the Lower Cambrian 
 that will be discussed in connection with different parts of the 
 Vermont valley at the south. In their well-preserved, bedded 
 character and in other ways these rocks are in contrast to most 
 of the other calcareous rocks of the Brandon area, which, as 
 exposed both at the surface and in the quarries, give evidence of 
 great dynamic stresses in the flow structures which they exhibit 
 and in the obvious crushing and crystallization which they have 
 undergone. 
 
 With the terrigenous rocks in many cases there does not 
 appear to be distinguishable difference between those in the Sud- 
 bury-Orwell hills and similar types lying east of Brandon village ; 
 
^ - > j^ 
 
 ~ X ~ ^ ~ 
 
 
 '— Ti _ i 
 
 3=^-2 
 
 — X — 
 
 ^ •- a: I — - 
 
 
 :^T,?^^ = 
 
REPORT OF THE VERMONT STATE GEOLOGIST. Igl 
 
 but in the scarps of the western edge of the plateau and at other 
 places along its edge, quartzite and arkose have sometimes been 
 sheared into more or less foliated rocks. 
 
 General relations west of Brandon village. The sheared 
 "marbly" rocks and sheared blue limestone with associated gray 
 dolomite which compose the conspicuous hills in the northeastern 
 part of Sudbury township in some cases lie in faulted position 
 against the rocks that underlie the plain of Otter Creek, along 
 which a surface area two miles wide with few exposures, sepa- 
 rates the rocks on the west from those on the east of the creek, 
 although there are a few detached outcrops, or islands, which 
 serve in a measure to bridge the gap. The easterrimost of these 
 islands is at the southern extremity of "Long Swamp" and lies 
 on the meridian which farther north marks the western edge of 
 practically continuous surface exposures northwest of Brandon, 
 which edge is two miles east of the meridian along which lie 
 the conspicuous hills of Sudbury township mentioned above. 
 
 South of "Long Swamp" and north of the fault at the north- 
 ern end of the Taconic hills which lie southwest of Brandon 
 village, a continuous surface section from west to east spans 
 the distance between the two meridians and joins fairly closely 
 with other exposures which carry the limestones to the meridian 
 of Brandon village, while farther south detached exposures, 
 similar to those at the north, outcrop in the plain of Otter 
 Creek, which owing to the course of the creek is here two miles 
 or more east of the plain in the northwestern part of the town- 
 ship, and carry the section in limestone to a meridian which 
 passes a mile east of Brandon village. 
 
 The above-described relations may assist somewhat in under- 
 standing the geological features around Brandon village. 
 
 The calcareous rocks of the islands along the plain of Otter 
 Creek and along the continuous east-west exposiire south of 
 "Long Swamp," except some rocks which will be mentioned 
 later, are entirely similar to those which have been described for 
 the northern end of the Taconic spur in Sudbury. Making due 
 allowance for such disturbances as these rocks have experienced 
 since their present general relation to the phyllite formation had 
 been established, it has seemed possible to trace rather satis- 
 factorily the counterparts of the fossiliferous beds on the west 
 side of the Taconic spur around its northern end into the Brandon 
 area. Two considerations seem especially to warrant the pro- 
 priety of such procedure : 
 
 \. The invariable occurrence of a similar association of gray 
 dolomite with marble or blue limestone in all fairly extensive ex- 
 posures. 
 
 2. The fact that if we view the transition area from Sud- 
 bury into Brandon broadly, that is, so as to include an east-west 
 section as wide as the township of Brandon is long from north 
 
182 REPORT OF THE VERMONT STATE GEOLOQIST. 
 
 to south, we have rocks on the eastern side of the Taconic spur 
 having the same relation to the terrigenous formation as that 
 which obtains on the western side and at the northern end, and 
 not to be disguised by any faulting which has occurred on the 
 east. 
 
 The latter consideration seems to give further indication that 
 the same terrigenous formation that composes the Taconic spur 
 is present at depth beneath the marbles and their associated dolo- 
 mite beds of the Champlain lowland around Brandon village. 
 On such an assumption it becomes easy to account for the simi- 
 larity of the terrigenous rocks east of Brandon to those of the 
 Taconic spur and to support certain ideas of the down-faulted 
 character of the Vermont valley around Brandon and in other 
 places which will be offered later. If such an assumption should 
 prove plausible it must have far reaching significance in the inter- 
 pretation of the structure of the region. 
 
 The gray dolomite which has so frequently been mentioned 
 as occurring in association with the sheared blue limestone or 
 the marble rocks west of Brandon seems to be quite distinct from 
 any member of the interbedded series which, as will be described 
 later, consists of interbedded dolomitic limestones, calcareous 
 quartzites, and quartzites, and perhaps other dolomite not strictly 
 interbedded, like those occurring throughout the Vermont valley ; 
 and this distinction holds even in those places where the inter- 
 bedded series also is now clearly present above the marble. 
 
 In the Brandon area there are exposures in which this gray 
 dolomite is associated with a dove-colored rock, which is striped 
 precisely like the Chazy rock seen at Bangall in Benson township, 
 where it carries well-defined, probably middle, Chazy fossils, 
 and like that seen west of Bennington in southern Shaftsbury, 
 and elsewhere. One of the places near Brandon where this 
 striped rock may be seen to good advantage is one and a half 
 miles north of the village, about 300 rods west of the old race 
 course. The rock here is so greatly altered that all traces of 
 organic remains have been obliterated and do not appear with 
 any definite characters even in weathered outcrops. The stratum 
 showing this association continues southward to the angle of the 
 roads and across the west road. It also occurs a mile south, 
 west of the village, north of the "Otter Creek road,"' and at other 
 places west of the village. 
 
 This association had also been noted at places in Sudbury, 
 and at other places less distinctly in the Brandon area ; but what 
 now seems its probable significance was not grasped until the 
 examination of the Brandon area was well under way and until 
 the Brandon region had been reviewed in the light of relations 
 which are shown at the west. 
 
 If this association of dove-colored rock and gray dolomite 
 is the Chazy, as now seems to the writer likely, it appears to be 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 183 
 
 significant that it so often lies apparently on the marble, or 
 above the sheared blue limestone, as the case may be. In the 
 vicinity of Brandon, except where the interbedded series ' of 
 dolomite and quartzite has overlapped it, the dove-colored rock 
 and its dolomite roughly alternate across the strike with the 
 marble, with the result that each of these strata forms an indis- 
 tinct band or "vein" running somewhat parallel with the other 
 north and south. A greater width of the marble "veins" is now 
 seen along the meridians where this rock is quarried. 
 
 The marble bands are not, however, homogeneous in their 
 composition. Every quarry of any size in this area shows some 
 dolomite, either on top of the marble or as infolded blocks or 
 other involved fragments in the quarry rock. Where these 
 dolomitic or "flinty" masses are discovered in the course of quar- 
 rying they usually halt the work at that point and drive the 
 quarrying in a new direction. In Huntley's quarry at Leicester 
 Junction, where the rock is burned for lime, pink marble just 
 like that northeast of the Sudbury spur has sheared each side 
 of a huge block of dolomite which shows in the north a.nd south 
 faces of the quarry. This dolomite is often a drab-colored rock 
 and frequently occurs in close association with interbedded dolo- 
 mites and quartzites. In the quarries generally all bedded struc- 
 ture is greatly obscured or obliterated and profound dynamic 
 effects, such as mashing, flowage and crystallization, are every- 
 where manifest. 
 
 The explanation of the relations of the gray dolomite and its 
 associated dove-colored rock to the marble around Brandon seem- 
 ingly must account for the present apparent superposition of the 
 former in so many places on the assumption that the former is 
 Chazy and the latter probably Trenton. The agency of reverse 
 faulting or thrusting at once comes to mind. The effect of such 
 deformation would be to elevate the Chazy against the younger 
 rock and carry the former over the latter. If this deformational 
 process was repeated at intervals across what is now the general 
 line of strike of these rocks the immediate effect would be to 
 ease the stress, at least for a time, which was felt by the mass of 
 rocks in which these ruptures occurred and to heap the rocks by 
 piling some on others. Account must be taken of the possible 
 former presence of other limestone strata beneath what is called 
 "Chazy" and also of strata above what is called "Trenton" at the 
 time of this postulated faulting. The rough regularity of the 
 relations between the two strata, as now exposed, might be ac- 
 counted for on the basis of certain primary structural relations 
 which the mass of which they were a part had to the stress sus- 
 tained by it. 
 
 Certain assumptions have clearly been made as the premises 
 for the considerations just offered ; but it will be remembered that 
 effort was made to give a foundation of probability to the ages 
 
184 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 of the rocks in the Brandon area which have been discussed by 
 tracing the less altered rocks at the west into them through more 
 or less continuous surface exposures and by careful lithological 
 correlation and by general field relations. 
 
 The greater metamorphism of the rocks at the east in Bran- 
 don might be explained as due to several factors. These rocks 
 might have been involved in primary, or at least antecedent, 
 relations different from those at the west at the time they came 
 under kinetic stresses; or they might have been subjected to con- 
 tinued or repeated compression after new conditions, such as a 
 loading due to overthrusting, had been imposed ; or they might be 
 thought of as having been involved in the zone of most severe 
 crushing in the region. These rocks at the east give evidence of 
 having sustained pressure under confinement, whether this con- 
 dition was a special one present only at the east when the rocks 
 at the west were sheared into their present condition, or whether 
 it was a condition antecedent or subsequent to the operation of 
 those stresses which sheared the rocks at the west. 
 
 The deformational structure of the limestones west of Bran- 
 don, as far east at least as the present western margin of the "in- 
 terbedded series," is that of shearing chiefly. This shearing seems 
 to increase eastward towards the areas in which the rock has 
 taken on the characters which are shown by the marble of the 
 Otter Creek valley. It is practically along the meridian on 
 which falls the present eroded western margin of the "inter- 
 bedded series" west of Brandon village that the commercial 
 marble runs out westward at the surface southwest of Brandon, 
 and even the quarries, including the "old Goodell quarry," opened 
 at this western limit south of the "Long Swamp road," one- 
 fourth of a mile east of M. F. Phillip's house, were soon aban- 
 doned. One of these quarries shows very well the gray dolomite 
 folded as a small patch with the dove-colored rock and both of 
 these driven as one mass over the marble. The latter shows its 
 bedded structure much more distinctly than does the more 
 severely crushed rock farther east, which is a feature that falls 
 in line with other characters to mark a transition zone between 
 the rocks at the west and those of Otter Creek valley. South of 
 the "Long Swamp road," between it and M. F. Phillip's place 
 and about one-fourth of a mile southeast of Martin Ketcham's 
 place, is a clifif in the limestone facing north. In the face of the 
 cliff great irregular blocks of limestone rest against others along 
 irregular contacts and where two come together, big chunks fall 
 away, while the rock is broken throughout into small, irregularly 
 shaped pieces, usually with good faces, but with much irregularity 
 of shape, and the whole mass indicates beyond a doubt that it 
 has been greatly crushed and brecciated, but apparently not 
 under the same degree of confinement as the marble and other 
 rocks farther east. The surface exposures roundabout, parti- 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 185 
 
 cularly to the southward, show intermingled dove-colored rock 
 and its gray or chamois-colored associate, with occasional patches 
 of marble. Each is deformed by shearing, a feature which the 
 dolomite shows least, and all are much disturbed and involved 
 with each other. 
 
 A number of considerations make it appear that there is a 
 progressively increasing metamorphism from west to east in the 
 calcareous rocks in passing from Sudbury into Brandon ; but 
 whether the relatively moderate shearing shown by the rocks at 
 the west was a structure antecedent in the rocks at the east to 
 the greater deformation now shown by them, or whether the 
 two are different expressions of stresses acting at the same time 
 but under different conditions is a question involving other con- 
 siderations. In general it appears that all the various calcareous 
 rocks ^which have just been described, were obliged to accom- 
 modate stresses by some molecular adjustment as well as by 
 movement en masse; but accommodation by mashing and flowage 
 differed at different places and was much more pronounced at 
 the east, in those rocks which presumably are represented at the 
 west by the blue limestones and their associated dolomites and 
 dove-colored rocks. 
 
 On the assumption that these various calcareous rocks just 
 mentioned are in general equivalent over wide areas and rest 
 on essentially the same terrigenous formation throughout — an 
 assumption that seems to the writer to have gained a consider- 
 able degree of probability — the thoughts arise as to how this 
 relation came to be established and as to what is the age of the 
 terrigenous rocks. Some of the latter have been called Ordo- 
 vician and some of them Cambrian ; but a field examination will 
 show that it is hardly possible to separate them as belonging to 
 different terranes on the basis of the lithological features of the 
 rocks themselves, although certain types easily impress one as 
 being of Cambrian age from a likeness to those which have been 
 assumed with considerable positiveness to be Cambrian and the 
 same might be claimed for other types with respect to their in- 
 clusion in the Ordovician. Whether we call them Cambrian or 
 Ordovician, or both, the problem remains of accounting for the 
 calcareous rocks above them, and the postulates which are formu- 
 lated to explain the present relations will differ in the large for 
 the different cases. 
 
 It was about at this point in the writer's studies that the 
 need of certain more definite working hypotheses which could be 
 further tested in the field appeared. Certain similarities in field 
 relations insisted upon recognition; the terrigenous rocks, called 
 for a more definite status concerning possible or impossible divi- 
 sion and for a more definite assignment as to age ; and the ac- 
 cumulated evidence for the action of powerful compressive 
 stresses throughout a wide region and for clearly-defined thrust- 
 
186 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 ing in certain parts of that region made it necessary to ponder as 
 to the extent to which thrust movements were involved in the 
 entire region's history. 
 
 The following are examples of some of the questions which 
 came to mind : 
 
 1. Is there any evidence to show that the calcareous or the 
 terrigenous rocks which have been described were first broken 
 and heaped up by repeated reverse faulting and then carried 
 westward as a mass over other rocks along a low-angle thrust 
 plane so that they now rest by thrust unconformity on other 
 rocks? In this connection what emphasis is to be put upon the 
 apparent present contact surfaces of the calcareous rocks - and 
 the terrigenous formation on which they rest or the contact 
 surfaces where the conditions are reversed and terrigenous rocks 
 rest on limestone? 
 
 2. Is there any evidence to show that while the calcareous 
 rocks have been disturbed in position their superjacent relation 
 to the terrigenous formation was primarily due to normal marine 
 overlap on a floor of eroded older rocks? 
 
 3. What explanation is to be offered for the apparent ab- 
 sence of middle and later Cambrian in the general region ? 
 
 4. Is it likely that the Beekmantown as known near the 
 lake is now present at depth or at the surface around Brandon 
 and in the Vermont valley or the "slate belt"? Is it likely that 
 it was ever deposited at the east and is there any evidence on this 
 point ? 
 
 These questions and others grew out of a study of the field 
 relations in western Vermont and the possible answers to them 
 are part of the problems of the region. They will have to be 
 considered again. 
 
 The "interhedded series" of dolomitic limestones and quartz- 
 ites in Brandon. This series is present in great force in Brandon 
 township, north, east and south of Brandon village. In contrast 
 with the marble and for the most part with the dove-colored 
 rock and its associated gray or chamois-colored dolomite, the 
 bedded structure of this series is well preserved in Brandon, 
 in which feature it resembles other exposures of the series in the 
 Vermont valley. The field relations at Brandon perhaps indicate 
 its age less decisively than at other places, as at Bennington, for 
 example ; but the resemblance of the series to the entirely similar 
 rocks at Bennington leaves no doubt of the similar age of the two 
 and little doubt of the Lower Cambrian age of the series. 
 
 In the Bennington region a certain thickness of dolomitic 
 limestone intervenes between the quartzite and the interbedded 
 series. In Brandon neither the quartzite nor the dolomite are 
 in the same simple relations to the interbedded series. In some 
 places a dolomite is associated with the marble, as alluded to 
 above, and this rock does not appear to have the characters (3f 
 
REPORT OF THE VERMONT STATE GEOLOGIST. ^ 187 
 
 the Striped rock that has been described or those of the gray rock 
 associated with it. The dolomite referred to may be seen at 
 most of the quarries around Brandon lying on or in the marble. 
 It often separates the marble from overlying, interbedded dolo- 
 mites and quartzites. As first studied by the writer it seemed to 
 him to be a part of the Lower Cambrian series, but the field rela- 
 tions are much involved and not conclusive on this point. The 
 probability of its inclusion with the Lower Cambrian would seem 
 to depend to some extent upon the interpretation put upon the 
 present structure of the rocks of which it is a part. 
 
 In a few places members of the interbedded series seem to 
 lie directly on the marble. Such relation was noted in the field 
 just west of the old Goodell quarry in Brandon along the old 
 stage road to Leicester and SaHsbury, where stringers of quartz- 
 ite, irregularly disposed along the strike lie directly on marble. 
 In places this quartzite thins out to nothing along the strike and 
 at others widens out beyond any probable thickness of any of the 
 quartzite beds of the series. These stringers look in fact like 
 eroded remnants of members of the series which lay in a rather 
 flattish position upon the marble. East of the road a few feet 
 of dolomite lie on the marble in the old Goodell quarry and above 
 it is the interbedded series again. A few rods west of the expo- 
 sures showing the quartzite stringers is a ridge composed of the 
 gray dolomite and the dove-colored limestone on which no recog- 
 nized traces of the interbedded series is now present. Northwest 
 of this ridge, across the road, are outcropping ledges of a band of 
 marble which is succeeded westward by another ridge at the 
 south end of which, in the open pasture just east of the back 
 road to Morgan's Stock Farm, is an abraded anticline of what 
 is interpreted as the interbedded series. The western limb de- 
 scends across the back road to the plain of Otter Creek. Traced 
 northward along the axis of the fold the interbedded rocks give 
 place to the gray dolomites and associated dove-colored rock, 
 but farther north on the northern side of a crossroad appear 
 various eroded exposures of what appears to be the dolomite- 
 quartzite interbedded series. The relations as thus described show 
 the marble and its associated gray dolomite and limestone to be 
 overlain by an eroded mass of the interbedded dolomites and 
 quartzites northwest of Brandon village. 
 
 After an examination of the rocks in Orwell these relations 
 were reviewed. While the interbedded rocks northwest of Bran- 
 don bear some resemblance to members of the Beekmantown 
 west of Orwell village, they do not seem to be sufficiently like 
 them to change the writer's earlier assignment of them to the 
 Lower Cambrian. Moreover, they showed no traces of fossils. 
 They have some differences at places from the interbedded rocks 
 east of Brandon village, which seem, however, to be due to a 
 shearing more nearly parallel to the bedding. Rocks like those 
 
188 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 just described as probably Lower Cambrian also occur just 
 north of the Rutland R. R. track, and two miles south an "island" 
 in the plain of Otter Creek shows these rocks prominently ex- 
 posed again on precisely the same meridian as those at the north, 
 and farther south, still on the same meridian, northwest and west 
 of the Seager farm, they outcrop again. They may thus be 
 traced north and south through a distance of about three miles. 
 
 In places at the north, near the axis of the fold, there is 
 pronounced shearing structure developed across the bedding, 
 but at other places along the axis where the beds lie more nearly 
 flat and along the slopes of the western limb of the fold, shearing 
 seems to be more nearly with the bedding, producing thin, sheeted 
 structure, and at many places these thin sheets are distinctly 
 crinkled. Stringers and patches of salmon-yellow calcite mixed 
 with quartz occur abundantly over the eroded exposures of these 
 thinly-sheared beds. 
 
 Northeast, east and southeast of Brandon village, west of 
 the road from Forestdale to Pittsford, the interbedded series is 
 disposed in regular and irregular folds, often closely compressed, 
 frequently overturned, and ruptured at many places along the 
 strike, and probably also across it. A rupture along the strike 
 may frequently be seen passing into a fold. Over these parts 
 of the Brandon area the marble is wholly covered by these inter- 
 bedded rocks, which are generally marked by higher altitude and 
 greater thickness than elsewhere near Brandon. 
 
 Some of the ruptures in the series, just referred to, seem 
 clearly to be reverse faults, which are best shown at those places 
 where members of the series stand on edge, or are inclined at 
 high angle with easterly dip, while contiguous members at the 
 west dip at a moderate angle to the westward. One of these 
 localities is a mile east of Brandon village, at Cheney corner. See 
 section, figure 15. 
 
 Figure 15. Structure shown by members of the interbedded dolomites and 
 quartzites east of Brandon village, near Cheney corner ; close folding 
 and reverse faulting. 
 
 East of the Forestdale-Pittsford road. The interbedded 
 series as described for the area east of Brandon village is sue- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 189 
 
 ceeded on the east by terraced sand plains of old delta deposits 
 and east of the Forestdale-Pittsford road by heavy bowlder drift 
 which conceal outcrops. The heavy drift forms the lower west- 
 ern slopes of a series of high, ridge-like hills which begin in 
 Forestdale and extend southward through Coxe, Mountain in 
 Pittsford. This range of hills is separated throughout most of its 
 length from the steep, scarped slopes of the Green Mountain 
 plateau by the valley of Sugar Hollow Brook. 
 
 The exposures in these hills from Forestdale southward 
 present many features for comparison with the rocks forming the 
 Sudbury and Orwell hills of the Taconic range. It is possible 
 to identify some of the types in these foothills of the plateau with 
 characteristic ones of the range. In the eastern hills there occurs 
 a dolomitic limestone in association with the quartzite and phyl- 
 lite which is now apparently wholly absent in the Taconic hills 
 of southwestern Brandon, Sudbury and Orwell, except for some 
 doubtful rocks on the eastern slope of Castle Mountain which 
 have been mentioned. 
 
 Southeast of Forestdale are ledges of massive, brown quartz- 
 ite which are separated at the present surface by a space of nearly 
 a mile from the most eastern exposures of the interbedded series 
 east of the village. Four miles to the south, however, the inter- 
 bedded rocks are separated by only one-fourth of a mile from 
 the drift slope of the range of quartzite hills. Southeast of 
 Forestdale, back in the woods, is a considerable scarp and west 
 of it, in the open fields just outside the village, is a succession 
 of smaller scarps dropping off westward. West of the second 
 of these dolomitic limestone apparently rests on the quartzite, 
 but elsewhere in the vicinity the dolomite was not seen. Due 
 north of these ledges, along their strike, on the road to Goshen, 
 just east of Forestdale, are ledges of black phyllite and quartzitic 
 schist entirely similar to those seen in Sudbury and Orwell and 
 also at other places in this eastern range that will presently be 
 mentioned. 
 
 Going southeast . from Forestdale, ledges of quartzite are 
 numerous at many places and it is possible to trace this rock 
 through the woods and clearings along the low range of hills 
 to Coxe Mountain. Exposures are chiefly found along the higher 
 western slopes and summits. There are a number of significant 
 associations which should be mentioned. 
 
 The hill road going east from the Forestdale-Pittsford road 
 about two miles south of Forestdale crosses the summit of this 
 range of hills and descends to Sugar Hollow. The summit point 
 is known locally as "Birch Hill." 
 
 On the ridge north of Birch Hill, massive, brown quartzite 
 forms the higher part of the western slope and is in contact with 
 schist or phyllite which overlies the quartzite and extends east- 
 ward and northward along the ridge. The black phyllite or schist 
 
190 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 forms large exposures, but is roughly intermingled on a large 
 scale with quartzitic schist, or schistose quartzite, in which at 
 places are large, chunky veins of quartz which have been opened 
 by zealous seekers for gold. In one of the pits was noted a 
 black, graphitic schist carrying pyrite and quite like that seen at 
 places in Orwell. The dip of the rocks, which is probably 
 cleavage structure in part, is easterly. The western slope of the 
 ridge north of Birch Hill has scarps above the drift-covered por- 
 tion and the eastern slope is abrupt and regarded as marking a 
 fault displacement. No dolomite was found along the top of the 
 ridge; but northeast of Churchill's house on Birch Hill, on the 
 eastern slope, are small patches of dolomite, apparently in place. 
 South of Churchill's house, across the road, an east-west section 
 gives massive quartzite at the west, then eastward quartzitic schist 
 with a small patch of dolomite. 
 
 South of Churchill's house and west of the Sugar Hollow 
 road, patches of dolomitic limestone occur sparingly as remnants 
 of erosion on the eastern slope of the ridge. At places also the 
 same association of quartzitic schist and phylhte with massive 
 quartzite noted at the north occurs along the southern extension 
 of the ridge. East of an old road which joins the Sugar Hollow 
 road with the Birch Hill road, on the east side of a gulley, is 
 quartzitic schist carrying pyrite and overlain by dolomite, while 
 west of the gulley are big ledges of massive brown and granular 
 quartzite which continue on the strike to join the exposures north 
 of the Birch Hill road. 
 
 South of Churchill's corner the Sugar Hollow road descends 
 for a mile over a gentle slope nearly to the brook. The old road 
 over the ridge passes through a sort of col which may mark a 
 structural sag, for directly south of the point where the old road 
 joins the Hollow road the quartzite gave a reading of N. 72° E. 
 and a dip of 36° N., which is a marked deviation from the prevail- 
 ing north-south strike of the rocks. Directly north of the place 
 giving this anomalous reading, dolomite rests on the quartzitic 
 rock and its presence here leads to a suspicion that the low pass 
 just north may be due to erosion of dolomite lying in an irregular 
 sag. 
 
 Just south of the point where the old road joins the Hollow 
 road a scarp appears west of the Hollow road and continues south- 
 ward. 
 
 Two miles south of Churchill's corner a small basin in the 
 hills holds Sugar Hollow Pond. The basin is a faulted one. 
 Scarps bound it on the east, northeast and probably on the south. 
 East of the pond is a succession of low ridges broken by strike 
 faults which are marked by westward- facing scarps and inter- 
 vening swampy gullies. 
 
 The terrigenous rocks composing these hills of the ridge or 
 range just described present many similarities to those west of 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 191 
 
 Brandon in Sudbury, both in their lithology and structure. They 
 are evidently broken by numerous faults as well. Massive quartz- 
 ite is more abundant at the east and a dolomite is present at 
 places, but otherwise the student will be impressed by the very 
 strong similarities, amounting to identities so far as distinguishing 
 among them is concerned. 
 
 It has been suggested above that the terrigenous rocks of 
 Sudbury pass beneath the marbles of the Otter Creek valley to 
 join others at the east. This should be construed as only a 
 general statement; no implication was intended that the ter- 
 rigenous rocks at the east may not have been greatly disturbed 
 in position. 
 
 East of Sugar Hollozv Brook. East of the brook the to- 
 pography is marked by sheer precipices, steep slopes and a rugged 
 surface generally. Displacements by faulting are very evident. 
 The western scarps which were cleared by glacial action were 
 too high and extensive to be banked and covered with drift and 
 now offer a somewhat imposing view when observed nearby. 
 
 In common with other portions of the western edge of the 
 plateau the total displacement now apparent between general up- 
 throw and downthrow areas has often been effected along several 
 distinct planes. Along what appears as a single plane the amount 
 of displacement will vary at different places along the strike. 
 A scarp will often pass into a monoclinal fold and at some in- 
 definite distance across the strike will be replaced by another 
 scarp which will perhaps overlap the former along the strike and 
 perhaps also another which has in its turn replaced the second. 
 This arrangement impresses the observer of the topography east 
 of Sugar Hollow Brook. 
 
 From the junction of its head streams the brook flows at the 
 base of a prominent scarp on the west of the Chaffee Mountain 
 mass. The considerable height of the scarp may be seen very 
 clearly where a recent slide has cleared it of trees and other vege- 
 tation. This scarp is replaced eastward by another higher preci- 
 pice at whose summit is a shelf 'that on a clear day gives one of 
 the finest views in the Vermont valley. 
 
 Chaffee is best ascended along its northern slope from the 
 valley of the eastern tributary of Sugar Hollow Brook. Massive 
 quartzite forms the bed of this tributary and its valley and the 
 ascent of Chaffee is over similar quartzite, dipping easterly, 
 which can be followed to the shelf above mentioned and from the 
 latter place to the summit where the easterly dip still prevails. 
 
 The ascent of Chaffee was made, by the writer under trying 
 conditions ; the summit was enveloped in clouds and the rain 
 came down in torrents. The atmospheric conditions caused 
 some bewilderment so that observations could not be made with 
 the desired accuracy in the thick woods of the mountain. About 
 a mile as estimated, south-southeast of the summit of Chaffee 
 
192 
 
 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Mountain, along the upper portions and summit of an eastward 
 slope is dolomitic limestone, which here from the field relations 
 apparently lies on the quartzite. A sort of col here permits an 
 easy descent on the west side which is made over dolomite and 
 quartzite by zigzagging down slope among a number of small 
 scarps to the valley of Sugar Hollow Brook. 
 
 On a subsequent trip along the western slope of the "Moon- 
 shine"-Nickwaket range, along an old wood road that ascends to 
 the col mentioned above, black phyllite was found in a scarp 
 overlain by massive quartzite which was succeeded up the slope 
 by exposures of dolomite. There is a small settlement on the 
 mountain side above the contour of the scarp and at the base of 
 Nickwaket and in the cleared fields of these farms the dolomite 
 is extensively exposed. On the east side of a road through the 
 settlement, near its northern termination, the dolomite dips east- 
 ward at a moderate angle, but farther east up the slope the dip 
 is westward at a high angle. 
 
 A half mile southwest, west of this back road, the surface 
 rock shows undulating not much compressed interbedded dolo- 
 mitic and quartzitic layers which resemble the interbedded series. 
 These are bordered by a scarp on the west, at whose base is a 
 black, sheared quartzitic schist, which southward passes into 
 massive quartzite. Then westward the dolomite again forms the 
 surface rock which farther south on the slope and in the valley 
 of the brook can be seen grading downward into quartzite and 
 arkose, all dipping easterly at a moderate angle. West of these 
 outcrops is Sugar Hollow road and then the quartzite of Coxe 
 Mountain. 
 
 Figure 16. A generalized surface section of tlie margin of the Green Moun- 
 tain plateau southeast of Brandon village, from Nickwaket Mt. west- 
 ward through Coxe Mt. with offsets along the strike. Principal offset 
 shown by dotted line. A, dolomite; B, "interbedded quartzites and dolo- 
 mites" ; C, quartzitic schist ; D, quartzite and arkose ; E, quartzite ; 
 F, probable faults. 
 
 The observer passing northward along the Sugar Hollow 
 road, from the point where the back road referred to above joins 
 the Hollow road, would hardly fail to notice the conspicuous 
 

 ifM 
 
 o aj 
 
 55 
 
REPORT OP THE VERMONT STATE GEOLOGIST. I93 
 
 ledges of dolomite on the east side of the road and would hardly 
 fail to see that the beds are always folded and sometimes over- 
 turned to the west. Throughout the same distance on the west 
 side of the road the quartzite of the ridge extending northward 
 from Coxe Mountain is broken by a scarp on the east. Some 
 dolomite occurs on the west side of the road. The scarp ends 
 at the north at the place where the anomalous strike in the 
 quartzite was noted. East of the road at this point dolomite 
 dips at a gentle angle easterly, but on the west side of the road it 
 shows much confusion. 
 
 East of Sugar Hollow Brook then are found: 
 
 1. Massive quartzite forming the prominent scarps; 
 
 2. Dolomitic limestone at places on the summits and in large 
 exposures on the western slope of this mountainous strip, ap- 
 parently resting on quartzite; 
 
 3. Black phyllite and quartzitic schist in scarps overlain by 
 massive quartzite ; 
 
 4. Apparently some representatives of the interbedded 
 series, whose relations are not clear, but which presumably rest 
 on the dolomite. 
 
 This whole series has clearly undergone much disturbance, 
 in fact more than one deformation, but it seems reasonably clear 
 that the rocks all belong to one series and that they are of Lower 
 Cambrian age by analogy with other rocks having similar char- 
 acters and relations in other parts of the Vermont valley. The 
 original depositional sequence is not clear from the interrelations 
 shown east of Brandon. From the relations at Bennington we 
 have: 
 
 1. Massive quartzite, at the base; 
 
 2. Dolomitic limestone ; 
 
 3. Interbedded series. 
 
 The relation of the schist is not wholly clear. It seemed to 
 be a part of the basal quartzite formation and interstratified with 
 it. In explaining the present field relations, account must be 
 taken of erosion as well as deformation. 
 
 General structural relations of the interbedded series and the 
 rocks of the plateau east of Brandon. The interbedded series 
 just east of Brandon clearly shows within itself deformational 
 features of several kinds, most of which are due to compression 
 and some of which are the result of normal faulting. The effects 
 of compression may be summarized as follows: (a) buckling, 
 with frequent formation of tightly compressed folds, which are 
 often overturned; (b) shearing across the bedding of the folds; 
 (c) reverse faulting along the strike, which is indicated clearly 
 at several places. 
 
 The field relations which the interbedded series has to the 
 other strata with which it is now associated around Brandon 
 village, in the writer's opinion, could leave little doubt, after a 
 
J94 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 careful field inspection, that the former is superjacent to the 
 marble and the dove-colored limestone and its gray dolomite 
 associate. The interbedded series has been worn through over 
 many large and small areas, with the consequent exposure of the 
 other rocks on which it lay. The more or less detached exposures 
 of the interbedded rocks along its western portion west of Bran- 
 don are inliers of this formation on presumably younger rocks, 
 or are in process of becoming such. This relation makes the 
 marbles and their associated rocks outlying belts in an older series. 
 The number of contacts and outcrops that reveal this relation is 
 manifestly reduced by concealment under drift or by difficulty of 
 correlation of certain dolomites lying on the marble. There may 
 also have been some deformation of all these various rocks, in- 
 cluding their plane of contact, subsequent to that which super- 
 posed the older series on the younger strata. The evidence may 
 be summarized as follows : 
 
 1. The contrast in metamorphism and deformational fea- 
 tures which the two formations show when in proximity ; 
 
 2. Ragged erosional remnants of the resistant quartzitic 
 members of the interbedded series on the marble and its associated 
 rocks at various places ; 
 
 3. The interrupted outcroppings in bands of the marble 
 through the interbedded series and a probably related dolomite. 
 
 From the east- west width of the area in which the marble 
 outcrops through the interbedded formation we may infer with 
 some reason that the marble underlies the interbedded rocks east 
 of Brandon ; but how much farther east the marble extends at 
 depth is a question whose answer would depend a good deal on 
 the interpretation given to the relations of the rocks of the plateau 
 to those of the valley. 
 
 There is little hint of what lies at depth beneath the sand 
 plains and drift that occupy the space of varying width along the 
 Forestdale-Pittsford road between the interbedded series and the 
 range of quartzite hills east of the road. Farther north, east of 
 Lake Dunmore, a prominent scarp marks a normal fault and this 
 scarp falls precisely along the line of the projection of the Forest- 
 dale-Pittsford road northward. The great pile of drift that 
 extends along the western slope of the ridge south of Forestdale 
 suggests that a cliff has afford'ed a convenient place in which to 
 pile this debris. The slighter development of drift at the north 
 around Dunmore, in contrast with conditions east of Brandon, is 
 quite in consonance with the variability in this respect shown by 
 other portions of the Vermont valley. It is close to the line of 
 this assumed displacement east of Brandon that the kaolin mine 
 at Forestdale with its deposits of lignite and limonite occurs. 
 
 Prominent scarps bound the interbedded series on the east, 
 southeast of Brandon village, west of the Pittsford road. Their 
 significance is not clear. They suggest displacements. Pre- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 195 
 
 glacial and base-levelling forces and glacial plucking, evidently- 
 availed themselves of a general line of crustal weakness along the 
 region of the intervening surface space just described. The map 
 brings the interbedded series and quartzite in contiguity; but the 
 implication is general rather than precise, for there are indica- 
 tions at Forestdale that schist or phyllite lies beneath quartzite 
 and it is not unreasonable to think that the presence of more 
 friable schist, interbedded with the quartzite, might have been the 
 primary contributing cause of the space that has been mentioned. 
 
 The quartzite of the ridge south of Forestdale, which is 
 overlain and possibly underlain by phyllite and therefore inter- 
 bedded with it, joins at the present surface with the quartzite of 
 the higher plateau slopes east of Forestdale which affords some 
 reason for regarding them of the same age and therefore for 
 regarding the terrigenous rocks of the Orwell and Sudbury hills 
 as in part of the same age as the plateau rocks. But it seems 
 that too much reliability should not be placed upon the present 
 surface continuity alone, here or elsewhere in the Vermont val- 
 ley, in view of unquestionable deformation of more than one kind 
 and the probability of lateral as well as vertical displacement of 
 the rocks now forming the edge of the plateau. 
 
 It is not easy to fix the precise relation of the schist in the 
 ridge south of Forestdale to the associated quartzite by reference 
 to these rocks alone. It appears to be conformable. It is even 
 harder to be satisfied of the relation which the patches of dolo- 
 mite along this ridge have to the schist and quartzite. It seems 
 rather likely that the formation which forms the probable basal 
 member of this series of quartzite and phyllites, dolomites, etc., 
 as a depositional mass varied originally in composition, both later- 
 ally and vertically, not only as a result of overlap, but from other 
 causes as well and that a vast mass of sands and muds of dif- 
 ferent kinds was finally spread over the sea floor. 
 
 In general it would appear that the quartzite-phyllite forma- 
 tion is basal to the dolomite and that the former has been elevated 
 against the interbedded series by reverse faulting and that a 
 lateral thrust has carried the latter over the marble and its asso- 
 ciated rocks at the west. It does not seem possible to account for 
 the present superposition of the interbedded series on the marble 
 and its associated rocks on any other basis, if the conclusions 
 regarding the relative ages of these formations are in general 
 correct. Apparently the lateral thrust drove for some distance 
 above the schist and through the dolomite, for the schist appears 
 nowhere in the Brandon region between the marble and the 
 interbedded series, although it is entirely possible that the marble 
 extends at depth beneath the quartzite-schist ridge east of the 
 Forestdale-Pittsford road. 
 
 It seems reasonably clear that the interbedded series and the 
 quartzite-phyllite formation belong to one terrane from the rela- 
 
196 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 tions which they have to each other throughout the Vermont 
 valley. If the interbedded series has been thrust on younger 
 rocks we may reasonably infer that probably the quartzite has 
 also. The field relations of the interbedded series give the clue 
 to the meaning of the position of the quartzite and schist east 
 of it ; the latter have been brought up by reverse faulting as the 
 result of rupture following compression and probably a low angle 
 thrust plane cuts the reverse fault plane somewhere at depth. It 
 is not so apparent whether the quartzite with its overlying dolo- 
 mite east of Sugar Hollow Brook, which now form the rugged 
 edge of the plateau, are separated by a reverse fault from the 
 quartzite-phyllite west of the brook, because normal faulting ob- 
 scures the relations between the two ; but while the peculiar 
 pattern of these normal displacements, in which the faults pass at 
 the present surface into folds, suggests that except for normal 
 faulting these various terrigenous rocks east of the interbedded 
 series are not broken except by tension faults within the area of 
 the map, conditions at other places may lead to another conclu- 
 sion. 
 
 Approaching the question of the correlation of the terrige- 
 nous rocks on the west and east of Sugar Hollow Brook from 
 the viewpoint of their general associations, their similarity in age 
 and common membership in the basal formation gains consider- 
 able increase in probability, in the writer's opinion. So far as 
 the writer's observations go there is no reason to suppose that the 
 quartzite of Chaffee Mountain, "Moonshine" and Nickwaket, 
 and certain quartzites and arkoses in the valley of Sugar Hollow 
 Brook are any older than the quartzites and phyllites of the ridge 
 of hills west of the brook. The rocks west of the brook are 
 dismembered portions of the plateau, dropped down by faulting, 
 in the formation of a great downthrow region. In this down- 
 thrown mass the interbedded series, of course, also belong. 
 
 How far east the marble may extend beneath the rocks of 
 the plateau is a question whose answer rests wholly upon the 
 answer to the prior question of how Jar does the thrust plane, 
 whose existence seems to be established by the present relations 
 of the interbedded series, extend east of the present western edge 
 of the plateau. If the thrust arose in a reverse fault near the 
 present margin, then presumably on the basis of the relations 
 which the marble seems to have to these terrigenous rocks and 
 the equivalence of the latter to each other, the marble would not 
 be found at depth east of such a root fault. The thrust plane 
 cannot be traced eastward beyond the exposures of the marble 
 and its associated rocks from beneath the interbedded series 
 because its trace must be made from the surface. There does 
 not appear to be visible at the present surface any transection of 
 the plane. Reconnaissance trips by the writer in the plateau 
 have failed thus far to give anything that could be construed as 
 
REPORT OP THE VERMONT STATE GEOLOGIST. I97 
 
 the root of a great thrust. Its eastward extension is wholly 
 problematical. 
 
 It was suggested above that probably a lateral thrust in car- 
 rying the interbedded rocks over on the marble had sheared 
 above the basal formation into the calcareous members of the 
 Lower Cambrian rocks. An important principle seems to be 
 involved here. Probably we are inclined to look for too much 
 regularity in the manner in which a great lateral thrust would 
 drive through a mass of rocks. Because the thrust has apparently 
 cut in a certain way through the rocks now near Brandon is no 
 positive indication that the shear would have been just like it at 
 other places, while the general fact of an elevation of Lower 
 Cambrian rocks and overthrusting by them would still hold for 
 many places. In other words, we might expect that in some 
 cases the plane of thrust would have been such as to carry the 
 terrigenous rocks of the east over on the marble and its asso- 
 ciated rocks. The recognition of such a possibility in the pres- 
 ence of evidence for general overthrusting might greatly affect 
 the interpretation of relations at many places and such possibility 
 will be called to mind in dealing with certain relations farther 
 south in the Vermont valley. 
 
 In considering the ideas and possibilities which have just 
 been discussed, the question continually arises in one's mind as 
 to what extent these various rocks were covered by others at the 
 time of overthrusting. Did the overriding Cambrian carry with 
 it a heavy load of younger rocks ? Certain other questions arise : 
 Did the marbles which are now found west of the plateau once 
 extend over it to the eastward? Is there more than one thrust 
 plane, one by which the marble and its apparent counterparts 
 at the west, together with their associated rocks, were heaped up 
 and carried westward and another along which the Lower Cam- 
 brian rocks broke through the marbles and overrode them? Did 
 the latter rupture occur first and so bring an extra load on the 
 calcareous rocks now represented by the marble and thus cause 
 their greater metamorphism ? Were the marbles and their counter- 
 parts ever covered with other rocks, especially with terrigenous 
 rocks? They have been assumed to have been and the marble 
 has been assumed to have been thrust through the younger ter- 
 rigenous rocks or exposed on anticlinal folds through them. 
 Why do not terrigenous rocks appear between the marbles and 
 the interbedded series around Brandon, not by overthrust of 
 lower members of the Cambrian, but because the marbles were 
 overlain by terrigenous rocks? Is it because these were eroded 
 before the thrust of the Lower Cambrian? Was the thrust 
 which we now see evidence of around Brandon an erosion thrust, 
 that is, one consequent upon previous erosion of the various 
 rocks? If the terrigenous rocks that are found at places lying 
 above the marble and which have been described as Ordovician 
 
198 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 are such, why do not similar rocks appear above the less meta- 
 morphosed Chazy-Trenton rocks that have been described by the 
 writer on previous pages? Why are such rocks absent north of 
 the Taconic range in Leicester, Salisbury, Shoreham and neigh- 
 boring towns? Must we discount or discard the ideas that the 
 various calcareous rocks, which were described as lying on a 
 terrigenous foundation common to all, are actually in such relation 
 and essentially equivalent? Again in this connection what sig- 
 nificance has the similarity of the terrigenous rocks east of Bran- 
 don to those of the Sudbury and Orwell hills? If some of the 
 latter are of different general age than others, why does not 
 some pronounced structural arrangement appear among them so 
 that they may be separated? If it should prove more than 
 probable that rocks carrying fossils in Sudbury have been crushed 
 into marble in Brandon does it appear probable that difference in 
 degree of metamorphism among the terrigenous rocks is any sure 
 criterion of difference in age? Is there anything in the lithology 
 of the various terrigenous rocks that is positive enough to separate 
 them into different terranes? Has account been taken of pos- 
 sible overthrust bringing schists into contiguity with less meta- 
 morphosed terrigenous rocks ; or of an overthrust margin sepa- 
 rating rocks of one age from those of another on each side 
 of it, except possibly where rocks which have been overridden 
 now appear through the overthrust mass on account of erosion? 
 In a region of thrust displacements, how much value can be as- 
 signed to apparent surface transition? What relations have the 
 overthrust phenomena along the lake to those at the east? Are 
 there field relations anywhere in western Vermont that show 
 the Ordovician rocks resting or probably resting on Lower Cam- 
 brian strata? 
 
 Allusion has been made to the presence of a great downthrow 
 region bordering the Green Mountain plateau for a long distance 
 on the west. In the writer's judgment recognition of the reality 
 of this great structural feature is all-important and it seems to 
 him that failure truly to appreciate the extent of the region and 
 the significance of the principle involved has been an element 
 of confusion in his own thinking and that of others. 
 
 At the present time the Green Mountain plateau structurally 
 appears to stand as a great upthrow block of the crust with 
 reference to certain rocks that lie to the west of it. This relation 
 holds irrespective of whether the plateau has been thrust up or 
 the other area has sunk; but enough has probably been said al- 
 ready to show that it is the writer's idea that this present manifest 
 relation of upthrow and downthrow regions was produced by 
 a deformation quite separate from any of the great overthrusts 
 which have been described. It is necessary to appreciate that 
 the genesis of this relation is of much more ancient date than 
 any purely physiographic relations that now obtain between the 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 199 
 
 two, and that although crustal warping and other disturbances 
 may have caused minor movements and changes in their relations, 
 in a primary and larger sense the present general relation of 
 upthrow and downthrow areas probably antedates the destruc- 
 tion by erosion of a loftier region, although one cannot be so 
 positive about how long after the great thrust movements of the 
 general region the relation of upthrow to downthrow by normal 
 faulting was produced, because the date of the thrusts is so 
 uncertain. 
 
 The part of Vermont lying west of the Green Mountain 
 plateau includes the other physiographic divisions described in 
 a preceding section of this paper. From consideration of the 
 ways in which rock deformation is known to have occurred it 
 will appear that there are several purely theoretical possibilities 
 as to the relations which the rocks of these divisions might hold 
 to one another. 
 
 1. The Taconic range, Vermont valley and Champlain low- 
 land might all be interpreted as parts of a general downfolded 
 region with respect to the Green Mountain plateau and as owing 
 their present physiographic contrasts entirely to differential ero- 
 sion of a region of relatively simple folds, in which region the 
 rocks west of the plateau constituted a compound, structural 
 synclinorium and those of the plateau the complemental anti- 
 clinorium. Faulting and particularly thrusting played only minor 
 parts at any time in the history of the region. In connection with 
 this view the rocks at the west might be considered as originally 
 members of a great geosynclinal of deposition, while those of the 
 plateau belonged largely to a contemporaneous positive segment 
 of the crust. Sedimentation might have been interrupted with- 
 out changing the essential relations of these two regions, but 
 eventually produced a great thickness of rocks which were later 
 compressed without being profoundly displaced with respect to 
 one another. 
 
 2. The rocks lying west of the plateau might all be regarded 
 as parts of a great downfolded region without having suffered 
 much deformation by thrusting, as postulated under 1. At some 
 subsequent time great trough faults were formed producing the 
 structural outlines of what are now the Vermont valley and 
 Champlain lowland, which stand as downthrow regions with 
 respect to both the plateau and the Taconic range. The present 
 physiographic relations are thus primarily structural in thei'r 
 genesis and secondarily due to erosion. The rocks of the Taconic 
 range and the plateau have the same general relations to each 
 other that they had originally and prior to normal faulting, except 
 for folding. 
 
 3. On the basis of known overlap at certain places in west- 
 ern Vermont of older on younger strata the rocks at many other 
 places within the region might be considered as now remote from 
 
200 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 their original places of deposition as the result of deformation 
 of the crust by great thrust movements carrying the masses of 
 one segment of the crust over on those of another for con- 
 siderable but indeterminate distances, with or without much fold- 
 ing, thus bringing into juxtaposition rocks of widely different 
 ages. At some time subsequent to such deformation by thrust- 
 ing, normal faulting occurred and produced the structural out- 
 lines of the Vermont valley and Champlain lowland. These 
 faults literally chopped these overthrust masses along many planes 
 and introduced a confusion calculated to baffle any attempt to 
 explain the present structural relations. If in addition to these 
 deformations there were others, such as folding of irregular thrust 
 planes and repeated normal faulting a very tangled aspect would 
 undoubtedly be produced. Normal faulting in laterally thrusted 
 masses conceivably might give relations that would have strong 
 resemblance to such as would be produced by reverse faulting. 
 
 EUTLAND COUNTY. 
 
 Townships of Danby, Mount Tabor, Wallingford, Tinmouth, Clarendon, 
 Rutland, Proctor and Pittsford. 
 
 (Pawlet, Wallingford, Castleton and Rutland topographic sheets.) 
 
 Topography. The areas which will be described in the town- 
 ships mentioned in the heading for the most part lie in the Ver- 
 mont valley in its extension north of Dorset Mountain. The 
 rocks along the edge of the Green Mountain plateau at the east 
 and a few in the Taconic range will be briefly mentioned. 
 
 The Vermont valley north of Dorset Mountain is marked by 
 a ridge which extends northward from Danby to Rutland. The 
 place of this ridge is then taken by two shorter ones; one of 
 these separates the valley north of Center Rutland from that 
 at West Rutland and the other forms Pine Hill northwest of 
 Rutland. 
 
 Otter Creek enters Danby from Dorset at the south and flows 
 in a valley between the edge of the plateau and the ridge that 
 runs north from Danby; but at Rutland the stream turns west- 
 ward to Center Rutland and flows in the Center Rutland valley 
 west of Pine Hill as far as Proctor, where it enters the wide 
 v.alley in Pittsford. 
 
 By the ridges mentioned the main valley is thus broken into 
 several minor ones which have been excavated in softer rocks 
 than those which compose the ridges. The surface topography 
 of this portion of the Vermont valley therefore differs from that 
 south of Dorset Mountain, but the main outlines of the valley 
 between the plateau and the Taconic range are maintained 
 throughout, except for the interruption by the Dorset Mountain 
 mass. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 201 
 
 General note. North of Dorset Mountain the Vermont val- 
 ley in its extent from .Danby to Pittsf ord, including the detached 
 ridges that have been mentioned in the brief discussion of the 
 topography, presents a great number of most remarkable and 
 illuminating field relations that can be truly appreciated only 
 after an examination of them. An adequate discussion of the 
 geology of this part of the valley would speedily pass beyond the 
 limits, of a general paper like the present one. All that can be 
 done is to give what appears to be essential. Outside the Ben- 
 nington and Brandon areas the writer spent more time in this 
 than in any other part of the valley and devoted parts of five 
 days to a careful inspection of the region. 
 
 General description. North of Dorset Mountain lies Danby 
 Hill which, as will be discussed, is separated by an east-west fault 
 at the south from the mass of Dorset Mountain and which north- 
 ward joins the ridge which extends through Tinmouth, WaUing- 
 ford and Clarendon to Rutland. 
 
 Figure 17. Composite drawing designed to show structure of quartzite at 
 the foot of the plateau between Danby and South Wallingford and that 
 along eastern slope of the Danby-Clarendon intermediate ridge ; also that 
 of the overlying dolomite. The overturning is westward. 
 
 On the east, Danby Hill slopes rather gradually to the plain 
 of Otter Creek. North of Danby Hill the eastern slope of the 
 ridge is often much sharper and sometimes, near the base, abrupt. 
 
 Danby Borough is on the eastern edge of Danby township. 
 Danby station is in. the adjoining township of Mount Tabor. A 
 mile and a fourth east of the station begins the steep slope of 
 the plateau which is cut east of Danby by the gorge of the "Big 
 Branch." In the bed of this stream at Mount Tabor village the 
 compact, massive quartzite outcrops. Thence it may be followed 
 in the valley northward to large ledges along the railroad track 
 three miles north of Danby station. The boundary of the quartz- 
 ite then bends easterly away from the track at South Wallingford 
 and its place is taken here along the meridian of the ledges farther 
 south by members of the interbedded series and by limited out- 
 crops of marble. The ledges of quartzite along the track are only 
 a little over a mile, if that, east of quartzite-phyllite outcrops on 
 the northeastern slope of Danby Hill. Except for difference of 
 present altitude of Danby Hill and the erosion of its eastern 
 slope, the relations of plateau, narrow valley, and western ridge 
 
202 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 at some places in Danby is like that farther south, east of Dorset 
 Mountain. 
 
 The structure in the quartzite of the ledges along the track, 
 just referred to, is generalized in the accompanying sketch. See 
 figure 17. A mile west of these ledges, on the west side of the 
 creek at a sharp turn in the main road, dolomite shows the same 
 structure. We see the quartzite and the superjacent calcareous 
 beds buckling under compression to form overturned folds. 
 
 The marble outcrops on the northeastern and northern flanks 
 of Dorset Mountain give place northward under drift to quartzite 
 and to members of the interbedded series of the Lower Cambrian 
 in Danby Borough and along the eastern slopes of Danby Hill. 
 In the bed and banks of Mill Brook in Danby Borough, beds of 
 dolomite have a flattish position with very gentle arching, slight 
 easterly dip and apparently a slight southerly pitch. A mile and 
 one-fourth southwest of these outcrops along the brook road 
 from Danby Borough to Danby Four Corners, at the bend in the 
 road, what appear to be dolomitic members of the interbedded 
 series have been folded into a small anticHne and overturned so 
 as now to form an acute, recumbent fold. East and west of the 
 dolomite is quartzite. Along the meridian of these outcrops 
 about one and a half miles north of them on the eastern slope of 
 Danby Hill the interbedded members of the Lower Cambrian 
 series outcrop and here apparently mark the eroded edge of a 
 more extensive covering of these rocks. On Danby Hill they 
 extend eastward to join those in the valley of Otter Creek. 
 Further discussion of them may be given after following the 
 section as begun along the brook road and after noting certain 
 other exposures lying north and south of the road. 
 
 Westward along the brook road the outcrops of quartzite 
 west of the recumbent dolomite give place to a black schist, well 
 exposed in the bank at the second fork in the road and which 
 continues northward over the top of the hill along the same meri- 
 dian and joins the schist exposures along the higher eastern 
 slopes of Danby Hill. West of the schist outcrops in the bank 
 of the road in both of the high walls of the gorge of the brook 
 is somewhat massive quartzite. This quartzite was not carefully 
 traced northward at the surface, but on the meridian of this 
 quartzite in the gorge of the brook, on the southern slope of 
 Danby Hills, occurs the black schist or phyllite, and the latter 
 occurs westward along the road to Danby Four Corners. South- 
 ward towards Dorset Mountain along a back road are fine ex- 
 posures of massive, brown quartzite which are surrounded by 
 drift and whose actual extension could not be followed. A mile 
 west of these outcrops the bed of Mill Brook, which flows east- 
 ward, is strewn with quartzite boulders. Hosts of big quartzite 
 boulders fill the drift south of Danby Hill, which is a feature 
 doubtless associated with the action of the ice in stripping the 
 
REPORT OF THE VERMONT STATE GEOLOGIST. ' 203 
 
 slopes and summit of the hill and parts of the ridge at the north. 
 
 One-third of a mile south of Danby Four Corners and east of 
 the hamlet on the southwestern slopes and northward along the 
 lower western slopes of Danby Hill is a bluish-gray or bluish 
 limestone, weathering gray and appearing in many outcrops. 
 Fossils were not found in this rock by the writer, but they have 
 been reported by Foerste,^ and regarded by him as having a 
 Trenton aspect. A mile and a half north of the Corners a crys- 
 talline limestone shows a brecciated condition on the gray, weath- 
 ered surface, but is quite healed and without obvious fragmenta- 
 tion on the fresh surface, which is of dark blue color. From 
 t;he writer's acquaintance with other areas this blue rock would 
 have been tentatively correlated with Trenton and certainly not 
 with the Cambrian. 
 
 Above the blue limestone outcrops at the base of Danby Hill, 
 along the path up the hill traversed by the writer, outcrops are 
 lacking until about half way up when black phyllite or schist 
 appears which continues over the summit and outcrops at intervals 
 therefrom down to about the 1,100 feet contour, when the topog- 
 raphy changes somewhat in passing from the schist to some out- 
 crops of sheared, bluish marble standing on end and then a short 
 distance eastward appears the characteristic association of the jn- 
 terbedded series of the Cambrian, which is traceable south by west 
 as the eroded edge of the Lower Cambrian series along the slope 
 of Danby Hill alluded to above. Some conspicuous ledges of 
 massive quartzite also standing on end appear just west of the 
 margin of the interbedded rocks. The surface succession is thus 
 within a fourth of a mile or less across the strike from west to 
 east, with slight offsets to include outcrops: 1, schist; 2, sheared, 
 blue marble; 3, massive quartzite; 4, interbedded series. 
 
 A half mile north of the exposures just described the schist 
 outcrops east of the marble. There is, in fact, at this place a 
 confusing intermingling at the present surface of marble, schist 
 and quartzite. 
 
 North of these ledges, bearing to the west across Baker 
 Brook, the schist or phyllite forms most of the surface outcrops, 
 with occasional patches of limestone or marble, to the summit of 
 Clark Mountain. Here on the summit and western slopes mas- 
 sive, heavy quartzite forms a continuous outcrop over large areas 
 with the phyllite or schist lying to the east. Thick quartzite dip- 
 ping about 30° westerly was traced for a rnile along an old lumber 
 railroad at the summit of the western slope. The western surface 
 slope of the mountain is fairly steep and bevels across the west- 
 erly dipping quartzite. Across the road at the western base of 
 the mountain the interbedded members of the Cambrian were 
 noted dipping 66° westerly along a strike of N. 19° E. 
 
 lAmer. Jour. Sci., 1893, vol. 46, pp. 435-444, 
 
204 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 West of Danby Hill and Clark Mountain is the Tinmouth 
 valley, much of which is low, swampy land. It joins at the north 
 with the valley of Clarendon River. 
 
 At the southern end of the Tinmouth valley, one mile west of 
 Danby Four Corners, black phyllite or schist outcrops along the 
 road to Tinmouth for a mile and a half north of the Pawlet road. 
 Between the schist and Danby Pond there appears to be some 
 "marbly" limestone. About two miles southwest of Danby Four 
 Corners is blue limestone. The phyllite is precisely Hke that 
 which occurs in the ridge at the east and in the various localities 
 described on previous pages. 
 
 Three miles north of the road from the Corners to Pawlet, 
 and 75 rods west of the Tinmouth road, and along the same gen- 
 eral contours northward are exposures of strongly-sheared lime- 
 stone or marble. At many places these ledges of marble do not 
 at all appear like the outcropping edges of thick masses of the 
 rock, but rather as a broken covering to some rock on which it 
 lies. Two miles west of the Tinmouth road, within the main 
 range, at the southern end of Harrington Hill, is what appears to 
 be an isolated patch of marbly rock lying on the terrigenous 
 formation. On the trip which was made to inspect these rela- 
 tions there was not time to map the country with the care neces- 
 sary to show the extent to which the marble or its probable 
 equivalent occurs in scattered exposures over the hills, or to as- 
 certain to just what extent it is interrupted at the surface by the 
 phyllite along the western edge of the Tinmouth valley. It was 
 hoped that there would be another opportunity to investigate the 
 relations within the hills at the west. There are indications of 
 considerable massive quartzite on the west side of the Tinmouth 
 valley in the general vicinity of Tinmouth. 
 
 On the eastern slope of Clark Mountain are patches of bluish 
 limestone not so severely metamorphosed as the marbles of the 
 region usually are. They appear to rest on the schist. In the 
 valley of Otter Creek on the west side of the stream at South 
 Wallingford are exposures of the heavy marble, including a 
 quarry. Adjacent to these and extending eastward from them 
 are the interbedded rocks of the Lower Cambrian, and east of 
 these, less than a mile away, is the quartzite of the plateau. 
 
 The interbedded members of the Lower Cambrian continue 
 northward from South Wallingford on the east side of Otter 
 Creek, forming conspicuous hills two miles north of the village. 
 In these the beds have been compressed so that they now stand on 
 end. Northward between these exposures and the village of 
 Wallingford the quartzite of Green Hill comes down close to the 
 railroad track with a low but good scarp on the wept. 
 
 Westward across the creek and its flat flood plain, near Wal- 
 lingford village, three-fourths of a mile away, is a sharp ascent 
 from the level of the plain which the writer at the time of in- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 205 
 
 spection put down as a probable fault. It runs along the eastern 
 base of the ridge that extends northward from the Clark Moun- 
 tain portion for 4 or 5 miles. The rock along this slope is schist 
 or phyllite; but northward, southwest of Clarendon village, the 
 place of the sharp slope is taken by a more gentle one and that of 
 the phyllite by quartzite. The base of the sharp slope referred 
 to is marked by swampy land for part of its extent and south- 
 west of Wallingford by Fox Pond. 
 
 Westward from Wallingford village over the ridge the sur- 
 face rock is largely schist or phyllite, with some quartzite. The 
 boundaries of these two rocks were not traced along the ridge 
 for 4 miles north of the road that crosses the ridge from Wal- 
 lingford village to Tinmouth village, except on the west slope 
 where the road descends diagonally across massive quartzite. 
 
 Clarendon village in the Otter Creek valley is 4 miles north 
 of Wallingford village. West of the former the eastern slope 
 of the ridge that lies to the west rises rapidly but gradually from 
 the level of the creek over quartzite which shows the structure 
 given in Bgure 17. About 300 or 400 yards up the slope from the 
 main road, members of the interbedded series of the Cambrian ap- 
 parently lie on the quartzite as they do on the eastern slope of 
 Danby Hill. The prevailing surface rock over the ridge to Chip- 
 penhook is quartzite ; but on the west slope east of Chippenhook 
 appears the interbedded series which continues westward into 
 the valley of Clarendon River. At Chippenhook, in the valley 
 and east bank of Clarendon River, the beds of the interbedded 
 series stand at a higher angle than farther east. A similar rela- 
 tion was noted between the quartzite of Clark Mountain and the 
 interbedded series lying west of it. It appears that these rocks, 
 both in their larger and smaller folds, show overturning west- 
 ward. 
 
 Southeast of Clarendon Springs, east of the road that ascends 
 from Chippenhook over Boardman Hill, black schist or phyllite 
 ledges are intermingled with others of gneissic-looking quartzite, 
 and the two are often together and in contact in the same ledge. 
 Northward down the hill to the bed of a brook is massive, thick- 
 bedded, jointed quartzite, dipping easterly at a low angle. East- 
 ward along a road that follows the brook to Otter Creek is quartz- 
 ite dipping easterly and apparently extending to the eastern base 
 of the ridge. The rock is often gneissic at the east. 
 
 East of Clarendon Springs at Flat Rock and northward, east 
 of the road over Boardman Hill to Center Rutland, is quartzite, 
 often gneissic in appearance, having essentially the same rela- 
 tions to schist or phyllite as noted above, but with the resistant 
 ledges of the quartzite often forming knolls of higher elevation 
 than the adjacent schist and giving a strong impression of quartz- 
 ite pushed over on schist. 
 
206 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 The road from Chippenhook to Center Rutland over Board- 
 man Hill makes a steep ascent diagonally across the western slope 
 of the ridge. The outcropping rock along it is phyllite or schist, 
 specimens of which at most places would not be distinguishable 
 from similar rock at scores of places in the Sudbury hills. The 
 schist outcrops appear in the road about a mile north of Chip- 
 penhook and thence continue along the road and east of it and 
 farther north also in ledges west of it, to a point about a mile 
 and one-fourth north of Flat Rock. Here the quartzite, which 
 was mentioned above, crosses the road to Boardman Hill whence 
 it continues northward west of the road and along it towards 
 Center Rutland. Some outcrops of the phyllite appear east of 
 the western outcrops of quartzite. The dip of the quartzite and 
 the apparent dip of the schist is easterly. The boundary between 
 schist and quartzite is in fact irregular and modified somewhat 
 by promiscuous intermingling or interchanging of areas of schist 
 and quartzite. Near and on Boardman Hill the ledges of quartz- 
 itic schist or thin-bedded quartzite show severe crumpling with 
 small folds in more or less recumbent position, but more massive 
 beds farther east have not been deformed so much, although the 
 quartzite has taken on frequently a gneissic structure. 
 
 West of Flat Rock and Boardman Hill the western slope of 
 the ridge descends to the valley of Clarendon River, first over 
 schist, then on marble. Outcrops of the latter were noted near 
 Austin's house between the 900 and 1,000 feet contours. Marble 
 outcrops occur east and west of the stream and at one place along 
 the road to West Rutland the rock is quarried (Clarendon Marble 
 Co.) and at other places east of the stream it has been opened. 
 But northward along the road the phyllite appears and intei*venes 
 between the marble exposures just mentioned and the great quar- 
 ries of the Vermont Marble Co. at West Rutland along the valley 
 of the head stream of Castleton River. To what extent, if any, 
 the marble is interrupted in its north and south surface extension 
 between Clarendon Springs and Center Rutland was not inves- 
 tigated. 
 
 Along the ridge north of Boardman Hill the quartzite was 
 traced to within a mile of Center Rutland, but was not followed 
 down the northern slope of the hill where it presumably occurs ; 
 for the rock was noted in the bed of the creek at Center Rutland. 
 
 About a mile north of Tinmouth village a gap in the range 
 leads to Middletown Springs. Along the road the terrigenous 
 rocks at the northern end of Tinmouth Mountain are precisely 
 like those in the hills at the north in Hubbardton, Sudbury and 
 Orwell, and while lithological distinctions may be drawn among 
 the rocks in both places any separation on the basis of age seems 
 impossible at the south as at the north, as well as between the 
 two. About a mile west of the Tinmouth-Chippenhook road, 
 "marbly" limestone appears. Its boundaries were not traced. It 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 207 
 
 seemed surrounded with terrigenous rocks, at the surface. No 
 limestone was found at Ira, although it is reported from there 
 and undoubtedly would have been seen by careful search. 
 
 As previously mentioned, east of Otter Creek near South 
 Wallingford the steep slope of the Green Mountain plateau bends 
 northeastward. The edge is marked southeast of Wallingford 
 by a high scarp known locally as the "White Rocks." While 
 the valley thus widens out between the plateau and the ridge that 
 extends northward from Danby Hill, the western boundary in 
 the eastern quartzite swings to the valley and is now marked east 
 of Otter Creek and south of Wallingford village by the western 
 edge of "Green Hill" which has the same general relation to the 
 plateau that the valley quartzite has at Bennington, except that 
 at north there are scarps in the valley as well as in the plateau. 
 The scarps at the north have been freshened by ice action. 
 
 The rocks were not examined north of Wallingford village 
 east of Otter Creek, between that town and Rutland. In the 
 valley of Otter Creek no marble was seen between South Walling- 
 ford and Rutland ; nor was any noted between South Walling- 
 ford and Danby. But the interbedded rocks were frequently seen 
 from Danby Borough northward to Wallingford village, more 
 particularly east of Otter Creek. 
 
 The quartzite which was noted in the bed of the creek at 
 Center Rutland was found two-thirds of a mile north in the cut 
 of the Rutland R. R. Later on a trip from Rutland city over 
 Pine Hill to Proctor village this rock was traced from a point 
 about one mile north of the outskirts of the city, from outcrops 
 just west of the Pittsford road, up the eastern slope of Pine Hill 
 along the cable line to the schist outcrops on the summit and 
 higher western slope at the northern end of the hill. Schist 
 was noted, apparently in place, while ascending the eastern slope 
 along a wood road to the cable line. 
 
 The quartzite on the eastern slope dips easterly and eastward 
 is overlain apparently conformably by dolomitic limestone, in 
 which one reading gave the strike due north (magnetic) and the 
 dip 42° easterly. As examined just east of the Pittsford road 
 the limestone at places contains many grains and sometimes larger 
 patches of silica. The quartzite apparently has some interbedded 
 schist. 
 
 North of Pine Hill there is apparently a structural break. 
 Pine Hill occupying the upthrow side. 
 
 At the northern end of Pine Hill the sharp descent on the 
 west is over schist for a distance and then over calcareous rocks 
 that apparently belong to the dolomite and dolomite-quartzite 
 members of the Lower Cambrian, which around Proctor and 
 southward, east and west of Otter Creek, are in association with 
 marble. The interbedded rocks were traced northward into Pitts- 
 ford, where their relations to the marble is the same as it is 
 
208 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 around Brandon; outcrops of the marble occur east of the west- 
 ern margin of the interbedded rocks. South of the Brandon 
 township line, except for a brief distance in Pittsford, the west- 
 ern margin of the interbedded rocks was not minutely traced 
 in its relation to outcrops of marble. Around Proctor the inter- 
 bedded rocks will often be seen in almost vertical attitude as has 
 been described for the areas both north and south. Two and a 
 half miles north of Proctor they were seen lying in an almost 
 flat position. South of Proctor marble outcrops and has been 
 opened along the lower western slopes of Pine Hill east of Otter 
 Creek. Between these exposures and other marble outcrops far- 
 ther west the calcareous membefs of the Lower Cambrian inter- 
 vene, affording, apparently, another instance of exposure of mar- 
 ble by the erosion of its covering of Lower Cambrian rocks. 
 
 Otter Creek has clearly availed itself of structural features 
 in its course, particularly around Rutland. At the city it turns 
 from a northerly course to a westerly one as far as Center Rut- 
 land, whence it again flows northerly west of Pine Hill through 
 Proctor and on to Pittsford. 
 
 The marble and the dolomite and interbedded rocks of the 
 valley of Otter Creek, north of Center Rutland, lie between the 
 mass of Pine Hill and a ridge of schist and phyllite. This ridge 
 northward is broken to a slight extent topographically, but ge- 
 ologically joins with the quartzite-phyllite rocks in eastern Pitts- 
 ford township, which in turn join with those of Brandon on the 
 north and Hubbardton on the west. On the ridge west of Proc- 
 tor village are some patches of "marbly" rock and a mile west of 
 Fowler, farther north, is another patch of calcareous rock sur- 
 rounded by the schist. Northward the terrigenous rocks are 
 faulted at places west of Brandon, as has been described on pre- 
 vious pages, against the sheared blue limestones and marbles and 
 finally disappear under these rocks in northern Sudbury town- 
 ship. 
 
 West of the schist ridge just mentioned lie the marbles of 
 West Rutland between this ridge and the main mass of ter- 
 rigenous rocks lying to the west in Castleton. In these marbles 
 have been found bluish-gray rocks with abundant specimens of 
 Maclurea magna. The calcareous rocks of the West Rutland 
 valley extend as a narrow band about five miles long and termi- 
 nate at the present surface at the north and south against the 
 phyllite formation. 
 
 Westward the phyllite rocks along the Castleton River valley 
 give place at the surface to the slates of« Castleton and Fairhaven, 
 but the slates are more or less associated with phyllite rocks just 
 as they are north of Castleton in Hubbardton and Sudbury and 
 north of Fairhaven in Benson, as described on previous pages. 
 
 Summary. Some of the details and some of the general 
 relations which have just been given in the preceding description 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 209 
 
 of certain portions of the townships now being considered have 
 been noted by other writers. The studies which have been only 
 in part briefly presented by the writer, were made for the pur- 
 pose of gaining from direct observation first-hand knowledge by 
 which comparison could be made with the rocks and their rela- 
 tions at other places and really represent only a part of what it 
 was hoped to make. They are offered for their general bearing 
 on the question of the interpretation of the broad structural 
 features of western Vermont. 
 
 In general it appears that the structural features of the dif- 
 ferent portions of the Vermont valley will have to be reconciled 
 with each other. The assumption of similar genesis with respect 
 to the main features of the valley throughout would seem to rest 
 upon strong probability. 
 
 It further appears from features which have been and will 
 be cited that the general structural relation of plateau to valley is 
 the same all along the contiguous margins of the two. The Ver- 
 mont valley now in its relation to the plateau is a downthrow re- 
 gion and a dismembered portion of the plateau. Probably this 
 statement expresses only a portion of the truth, however, as it 
 appears probable that the western side of the valley is faulted 
 also, so that the valley is primarily a great structural trough 
 between the plateau on the east and the mountains on the west. 
 If this is the fact then in our thinking we must in imagination by 
 taking account of probable displacement and erosion restore the 
 valley floor to its approximate original position and in such way 
 strive to visualize what the former relation of the plateau and 
 the masses west of the valley would have been through the con- 
 necting mass which was displaced. 
 
 It may be asked, what evidence is there that the western 
 side of the valley is faulted? West of Brandon there is evidence 
 to show that the sheared limestones and marbles north and east 
 of the phyllite hills are downfaulted, the fault being sometimes 
 in the marble and sometimes between the phyllite and the marble. 
 There is evidence on the east of Mt. Anthony in Bennington and 
 Pownal of downfaulting of the valley rocks. It happens that 
 along the west side of the valley it is not so easy to tie up some 
 formation in the valley floor with one in the Taconic range as it 
 is in the case of the valley quartzite with respect to similar rock 
 in the plateau. At Dorset Mountain, however, we see the marble 
 at its high level there and find its counterpart beneath the surface 
 of the valley. With the fairly satisfactory evidence at the east 
 of downfaulting why assume that Dorset Mountain has primarily 
 been thrust up with respect to the valley ? Dorset Mountain pre- 
 sents evidence by itself of displacement between it and adjacent 
 rocks on the north and south. This fact rather argues against 
 any such idea as that the whole region west of the plateau margin 
 is downfaulted with respect to the plateau, which view might 
 
210, REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 permit the explanation of the valley as an erosion feature purely. 
 There is no reason for selecting Dorset Mountain out of the 
 Taconic region and assuming for it upthrow displacement with 
 respect to adjacent rocks. On the whole it seems most probable 
 to the writer that in view of the displacement between plateau 
 and valley there was also displacement between the valley and 
 the masses now at the west and that such is the significance of 
 the relations shown at Dorset Mountain and at other places. 
 
 The marble is at different levels. In the valley it appears 
 to be at about the same level at most places, but varies somewhat 
 even there. In the Dorset Mountain mass it is much higher and 
 perhaps repeated. In Tinmouth valley it is intermediate between 
 its level in Dorset and in the main valley. This general state- 
 ment of the levels at which the marble occurs refers only to the 
 general Vermont valley region and its extension into the Cham- 
 plain lowland and passes by for the moment the detached patches 
 in the hills at the west. 
 
 The surface of the Vermont valley is controlled at various 
 places by the peculiar structural conditions which there prevail. 
 North of Bennington and through to Manchester, and in fact 
 practically all along its eastern border, the Lower Cambrian rocks 
 shape its surface. North of Dorset Mountain the main general 
 valley widens and new features appear. 
 
 The steep northern slopes of Dorset Mountain, except as 
 affected by general weathering, stream incision, and by drift, pass 
 rather abruptly to a more gradual and gentle slope, which except 
 for the incision of Mill Brook and the lateral erosion consequent 
 upon it, continues without important change of level to the sum- 
 mit of Danby Hill and northward to Pine Hill and the schist 
 ridge west of it in Rutland. This somewhat varying level marks 
 a surface of intermediate altitude in a ridge intermediate between 
 the plateau and the main mass of the Taconic range. This ridge 
 is bounded on the east for most of its length by the Otter Creek 
 valley and on the west by the valleys of Tinmouth Channel and 
 parts of Clarendon and Castleton Rivers. 
 
 North of Dorset Mountain a region marked out by an east- 
 west line just north of the mountain, a north-south hne running 
 probably along the western edge of the Tinmouth valley and its 
 extension, another north-south line at the east, and an irregular 
 line at the north, represents an area of downthrow in which the 
 displacement has been differential. The intermediate ridge just 
 mentioned is on the downthrow side with respect to Dorset 
 Mountain, the plateau and the main mass of schist at the west, 
 and on the upthrow side with respect to the rocks underlying 
 Otter Creek. Its relation to the narrow valley on the west of 
 it may be discussed later. Pine Hill is probably on the upthrow 
 side with respect to the area in Pittsford north of it and poten- 
 tially so with respect to the valley of Otter Creek south of it. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 211 
 
 One of the first efforts at a restoration, such as has been 
 suggested, of the original conditions prevaihng between plateau 
 and the mountains at the west would be to get the surface of the 
 valley quartzite back at its former level, so to speak. If this 
 were done all along the valley and lowland, beginning at Ben- 
 nington and extending to Brandon, a great mass of rocks would 
 be lifted. Along the eastern portion of the valley at least the 
 calcareous members of the Lower Cambrian that now lie at 
 places on the valley quartzite would be elevated to a level some 
 distance above the eroded surface of the plateau and would in 
 effect restore a part of the surface now gone from the plateau. 
 Some account would have to be taken of erosion of the plateau, 
 but the quartzite is a resistant rock. 
 
 Passing for the present what particular effects would be pro- 
 duced in the southern portion of the valley and in the region of 
 the Cham'plain lowland, and considering only what would be the 
 results in the regions of Dorset Mountain and the part of the 
 valley north of it to Pitts ford, the elevation of the upper surface 
 of the valley quartzite even to the present sky line of that forma- 
 tion in the plateau would bring it to about the level of the schist- 
 quartzite mass that partially caps Dorset Mountain. The cal- 
 careous members of the Cambrian would be above the quartzite. 
 What is now beneath or adjacent to the quartzite which would be 
 elevated with it? 
 
 In such an attempt at reconstruction there must necessarily 
 be a large number of elements of uncertainty. This number 
 should be reduced as much as possible. 
 
 We may assume, but only assume, that there has been no 
 displacement between the marble of Dorset and that in the valley 
 other than that which dropped the latter ; or in other words, that 
 the plateau and Dorset retain their relative positions practically 
 unchanged since the displacement of the block between them. 
 
 If no\v we take the relations shown at South Wallingford of 
 interbedded rocks resting on marble at their face value, and 
 recall the conditions east of Brandon and those which apparently 
 obtain around Proctor and Pittsford, it appears that in the neigh- 
 borhood of Dorset Mountain we have probable overlap of the 
 calcareous members of the Lower Cambrian on the marble. At 
 Pine Hill we see a terrigenous mass consisting of a sort of con- 
 glomerate and a quartzite with interbedded schist, overlain by 
 dolomitic limestone and interbedded rocks lying against marble at 
 the west with the interbedded series apparently .lying on the 
 marble just west of the hill. The sequence which we have from 
 the plateau through Pine Hill and the Center Rutland marble 
 strip is not very different from that which is present east of 
 Brandon ; but at the south, west of the Center Rutland marble 
 strip, we have conditions different from those near Brandon in 
 
212 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 the presence of a ridge of schist intervening between the marble 
 of the Center Rutland strip and that of the West Rutland strip. 
 
 In restoring the conditions in thdvalley east of Dorset Moun- 
 tain it would appear that between the quartzite as elevated and 
 the mass of Dorset there should intervene a narrow block of 
 marble with interbedded rocks overlying it. In Dorset Mountain, 
 schist with thick beds of quartzite tops the marble and the rela- 
 tive meridianal positions of the different rocks are made to cor- 
 respond between the restoration of plateau to Dorset Mountain 
 and what now prevails near Pine Hill. 
 
 The schist on Dorset Mountain and northward has usually 
 been regarded as younger than the marble. The fact that it 
 lies on the marble probably by itself is not a sure indication that it 
 is younger ; for it now appears practically certain that the marble 
 is at many places in the valley overlain by Lower Cambrian cal- 
 careous rocks. The argument assumes that the marble is younger 
 than the interbedded series of the Cambrian, evidence for which 
 is had in the specimens of Maclurea magna of the West Rutland 
 quarries, if the evidence as deduced from surface continuity for 
 the Brandon region and as afforded from other relations is not 
 conclusive. 
 
 On what does the marble of Dorset Mountain rest? It is 
 sometimes represented as passing beneath a schist formation as 
 though it continued indefinitely westward from the Vermont val- 
 ley in that relation to the mass of schist composing the Taconic 
 range and its foothills, and as though it passed at depth discon- 
 formably, or otherwise, into other calcareous rocks with Cam- 
 brian dolomites at their base. When the marble is found among 
 the terrigenous rocks of the hills west of the valley it is explained 
 as emerging from beneath, or as interbedded with the schist. 
 
 Examination of some of the patches of "marbly" Hmestone 
 within the terrigenous rocks west of the valley often does not 
 convey the idea of its being beneath, or of its being interbedded ; 
 but gives the distinct impression that it rests on the phyllite 
 formation. In fact it would appear that marble rests on schist 
 and that the latter rests on marble. The point would naturally 
 be raised as to whether the schist above is the same as or like 
 that below : that is, are limestone and phyllite usually really inter- 
 stratified ? 
 
 At West Mountain in Shaftsbury and at many other places 
 within areas which are mapped as "Berkshire Schist," the pre- 
 vailing terrigenous rocks are not distinguishable at all from those 
 of other areas on which fossiliferous limestone, sheared, blue 
 limestone, or "marbly" limestone now rest or certainly did rest 
 at one time. In Brandon, Sudbury, Orwell and Benson are ter- 
 rigenous rocks having to limestone the relation just mentioned, 
 which the writer regards as so like the phyllites and schists of 
 Danby, Clarendon and Rutland, that it is not possible to make 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 213 
 
 a sharp separation. They in fact join with each other at the 
 present surface. These terrigenous rocks in Sudbury, Orwell 
 and other places consist of interstratified schists, phyllites and 
 quartzites. The schists which top Dorset are interbedded with 
 thick beds of massive quartzite. Those which form the ridge 
 from Danby Hill northward also seem to be. 
 
 If we accept as valid the evidence that has been offered on 
 previous pages for a wide extension of calcareous rocks, includ- 
 ing the marble along the Vermont valley and the Champlain 
 lowland, over a terrigenous formation that is over large areas 
 quite similar in its general characters and of probably similar age, 
 and if on this basis we accept the idea that a section from the 
 plateau westward is essentially the same, whether it is along a 
 parallel passing through Leicester, Whiting and Shoreham, or 
 along one through Dorset Mountain, Rupert and westward, ex- 
 cept for differences of metamorphism of the limestone or the 
 terrigenous rock and for differences in the present attitudes of 
 the rocks, with consequent scarcity of hmestone on schist at the 
 south and consequent small exposure of schist through limestone 
 at the north, and perhaps also for differences due to original 
 lateral variation in the terrigenous rock, then if we think of the 
 phyllite of the Sudbury hills passing beneath the marble of Bran- 
 don we may also think of it as passing beneath the marble of 
 Dorset Mountain and that of the valley east of the mountain. In 
 connection with conditions in the Vermont valley, we especially 
 recall that at places among the hills at the west masses of lime- 
 stone which rest on the terrigenous formation have also been 
 preserved through protection by downfaulting. 
 
 The Vermont Report (page 412) states that "the limestone 
 from West Dorset is continuous, through a notch on the west 
 end of Mount Eolus, with the limestone and marble in the central 
 part of Danby, upon the west range of the limestone formation." 
 The map so shows it. Along the valley of the Mettawee a few 
 miles due west from Dorset Mountain, as discussed on a subse- 
 quent page, limestone (here the dove-colored rock with gray 
 dolomite) rests on the phyllite. The Vermont Report (page 412), 
 apparently on the authority of the elder Hitchcock, gives the 
 limestone as extending from Dorset over the mountain to Sand- 
 gate. 
 
 Accepting the idea of overlap along the eastern edge of the 
 valley, from such evidence as we have, we have nothing to tell 
 us how far the marble extends eastward beneath the older rocks. 
 The important fact is that of overlap. If the marble lies on a 
 quartzite-phyllite formation and practically the same kind of 
 rocks now lie on the marble at any place in or west of the Ver- 
 mont valley, one of the ways in which this relation might possibly 
 be explained, involves an extension of the quartzite-phyllite for- 
 
214 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 mation on which the marble lies eastward beneath the margin of 
 the overlap. 
 
 An effort has been made to get before the reader a certain 
 amount of evidence which goes to show a widely-prevailing rela- 
 tion between apparently related calcareous rocks and a terrige- 
 nous formation that is similar over wide areas and which in- 
 dicates that the normal position is limestone on the phyllite 
 formation. Attention was then called to the resemblance, as it 
 appears to the writer, which such terrigenous formation has to 
 similar rocks that have an inverse relation to the limestone and 
 that now at certain places rest on it, that is, on marble. 
 
 It seems to the writer that a certain amount of assumption is 
 involved when the schist on the limestone is called younger. 
 We have seen that superposition may not be regarded as conclu- 
 sive evidence in this region. The age of the "Berkshire Schist" 
 seems to have been determined indirectly in all cases, either from 
 field relations or in some other way. From relations which it has 
 to limestones at many places it would seem clearly on such a 
 basis to be older and in no wise interbedded. It has apparently 
 been assumed that the Cambrian dolomite and dolomite-quartzite 
 series passes directly beneath marble along certain parts of the 
 Vermont valley and that the calcareous rocks thus make up a 
 conformable or disconformable "Cambro-Ordovician" limestone 
 series on which lies a conformable "Berkshire Schist." Such 
 views, in the writer's opinion, leave in the air the explanation of 
 such relations as overlap of the Cambrian rocks on the marble 
 at numerous places ; the undoubted superposition of related lime- 
 stones including marbles on terrigenous rocks which are similar 
 to and many of which are correlated with the "Berkshire Schist," 
 and the relations which have been described in more or less detail 
 for Orwell, Benson, Sudbury and Whiting. They further seem 
 to ignore great thrusts, or at least, the wide extent of obvious 
 movement of older on younger rocks, which the region every- 
 where exemplifies. 
 
 Even if the general and normal superposition of the lime- 
 stone on the terrigenous formation over a wide region is admitted, 
 it is not of course necessary on that account to give up the idea 
 that the schist resting on marble is younger than the marble, 
 because it is conceivable that conditions of deposition permitted 
 the succession from limestone to terrigenous rock, or from ter- 
 rigenous rock to limestone and again to terrigenous rock, perhaps 
 over a wide region. Nothing in this summary has been said 
 about the age of the quartzite-phyllite formation except that it 
 often appears to be older as a whole, as now eroded, than the 
 limestone which rests on it, including the marble. Further than 
 the suggestions offered on previous pages the consideration of 
 its probable age may be postponed. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 215 
 
 One of the things that is perhaps confusing in explaining 
 the relations along the Vermont valley on the basis of overlap 
 by thrust of older rocks on younger ones is the fact that erosion 
 apparently nowhere has uncovered a clear overlap of Cambrian 
 quartzite on marble ; something sharp and distinct like that of the 
 quartzite on the "Utica" at Burlington. Another thing that is 
 bound to be confusing, if it occurs, is overlap of terrigenous rocks 
 on other entirely similar rocks, by thrust. 
 
 It has been implied above that the marble which underlies 
 the valley, for example, that at South Wallingford, has been 
 dropped from a higher level. North of Rutland the marble on 
 the meridian of that of South Wallingford is apparently covered 
 by the quartzite-schist and its overlying calcareous rocks in Pine 
 Hill. At South Wallingford only the interbedded series can be 
 seen to have any relation like that of overlap on marble. 
 
 The marble along Otter Creek north of Dorset Mountain has 
 been assumed by some to pass beneath the intermediate ridge 
 lying to the west and to emerge in the Tinmouth-Clarendon River 
 valley. This is the view given in the Vermont Report. By others 
 the intermediate ridge has been regarded as an anticline under- 
 lain by the basal Cambrian quartzite and the underlying pre- 
 Cambrian and overlain by the "Stockbridge" limestone and 
 "Berkshire Schist." Overthrust of Cambrian quartzite on schist 
 is described and indicated and inclusion of limestone and schist 
 in the older rocks is shown as occurring by the younger rock 
 being faulted down into the older rock. 
 
 The structural pattern of the valley north of Dorset Moun- 
 tain is unquestionably complicated and hard to analyze. It seems, 
 however, that one of the first steps would be to try and make a 
 restoration on the basis of the valley being a downfaulted region. 
 Along the eastern side the Cambrian quartzite and interbedded 
 schist could be thought of as elevated, carrying the Cambrian cal- 
 careous rocks above it and presumably at places at least, as at 
 Pine Hill, the subjacent marble to a higher level. In other areas 
 with more or less indeterminate boundaries on account of irregu- 
 larity of early overlap the interbedded rocks of the Cambrian and 
 its subjacent marble could be imagined as elevated. In still other 
 areas, probably in different measure according to amount of dis- 
 placement, the schist-quartzite masses of the intermediate ridge 
 would be elevated, and by assumption, subjacent marble with it. 
 
 By these imaginary processes it would seem that we should 
 get an extensive mass of marble over the area north of Dorset 
 Mountain, approximately back to former levels one of which is 
 now marked by the marble of the Dorset mass. It would seem, 
 too, that the quartzite-schist of the intermediate ridge would be 
 restored to a higher level and on this quartzite-schist with prob- 
 ably some overlying "marbly" limestone we should find a capping 
 of dolomite and interbedded rocks, which we have come to asso- 
 
216 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 date with the Lower Cambrian, the whole mass of Cambrian 
 showing the buckling so characteristic of the interbedded series, 
 as has been described so many times. We should recall that the 
 same kind of deformation exhibited by the quartzite on the inter- 
 mediate ridge is shown also by the quartzite east of Otter Creek, 
 and that in fact one is the replica of the other. At places we now 
 find lying on the schist of the intermediate ridge, small patches 
 of limestone younger than the Cambrian, sometimes fossiliferous, 
 sometimes "marbly," and it would appear that some of these were 
 formerly overlain by quartzite, which in turn was and is now at 
 places, overlain by the interbedded rocks of the Cambrian. In 
 some places we now find all these various rocks within the space 
 of a few acres, intermingling at the present surface, but in rela- 
 tions which suggest that the schist is lowest, the "marbly" or other 
 limestone next, the quartzite next and finally the interbedded 
 series. Underneath all, presumably, is other massive marble. 
 Farther west in the Tinmouth valley are some indications that 
 the interbedded series rests on massive marble, but this is not so 
 certain ; the massive marble may be deeper down. Except for 
 erosion or lack of it, and minor details, this brief description 
 would seem to apply to the whole ridge from Danby Hill north 
 to Center Rutland. At Center Rutland the massive quartzite 
 apparently swings to Pine Hill and does not touch the West 
 Rutland ridge; but the latter presumably gives marble at depth, 
 then the schist and on top of the latter, patches of marbly lime- 
 stone, with possibly som^e of the interbedded rocks along its east- 
 ern base. 
 
 It would seem from such a restoration as has been attempted 
 that north of Dorset Mountain there would have been overlap of 
 Cambrian rocks as far west as Tinmouth valley, with younger 
 rocks underneath. Sometimes this overlap apparently carried the 
 interbedded rocks on the marble with no quartzite or schist in- 
 tervening. Sometimes interbedded quartzite may have been car- 
 ried over on schist with limestone or "marbly" rock intervening. 
 Sometimes quartzite with overlying calcareous rocks may have 
 been carried over the schist with "marbly" limestone intervening. 
 
 On the general idea of overlap of Cambrian rocks as just 
 developed, recalHng the conditions north of Dorset Mountain, it 
 would seem that a restoration at Dorset Mountain would involve 
 ^an overlap on its summit of calcareous members of the Cam- 
 brian series, perhaps on younger limestones that have been eroded. 
 
 The ideas developed up to this point clearly depart from the 
 view that the Cambrian rocks of the valley, as now exposed, are 
 members of a series that is subjacent to the schist-phyllite forma- 
 tion, and suppose rather that a portion of the Cambrian floor 
 has moved from the east over on younger rocks and now lies by 
 unconformable thrust overlap on younger strata. Overlap seems 
 fairly plain ; its extent is less certain. From what has been said 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 217 
 
 above it is further regarded as probable that the normal position 
 for the marble is above a terrigenous formation like that which 
 caps it. On this view the terrigenous formation is also beneath 
 the marble of Dorset Mountain and extends eastward beneath 
 the margin of the overlap of older rock and also beneath the 
 valley marble, for an indeterminate distance, but perhaps not very 
 far. How far is wholly problematical. 
 
 Now it seems possible to imagine that the conditions which 
 seemingly would be present, after such a restoration as has been 
 attempted was made, over the region under discussion, could be 
 explained by a series of thrust displacements. The quartzite- 
 phyllite formation and its overlying probably younger limestone 
 were broken by reverse faults which probably were usually minor 
 thrusts, and along the planes of these thrusts the quartzite-phyllite 
 formation and the overlying younger limestone were driven west- 
 ward through and over similar rocks until they came to overlie 
 the younger limestone at the west. Or the plane may conceivably 
 have cut in such way as to carry the phyllite against other but 
 similar terrigenous rocks — cutting downward, for example, at 
 places beneath the limestone, or into the terrigenous rock, and 
 pushing the sliced-ofif portion on the "toe" of the thrust. It seems 
 not difficult to imagine that there may have been several such 
 thrusts, some of which may now be covered eastward and some 
 of which may have been wholly or partly eroded westward. On 
 meridians farther east a series composed of quartzite-phyllite 
 with overlying dolomite and interbedded rocks was broken by 
 reverse faults and finally, after ease of stress had been partly ac- 
 complished in this way, along an extensive, irregular plane, 
 which truncated earlier planes within the series at depth and cut 
 through different members of it, a great mass of rock was driven 
 westward over previous thrust masses at the west and may pos^ 
 sibly at places have overlapped several earlier thrusts. During 
 these' deformations probably some folding occurred as a result 
 of compression and some perhaps as the result of friction along 
 the surface of movement. On the hypothesis of repeated thrust- 
 ing, as thus outlined, the possibilities of some of the marbles 
 being separated from each other by thrust planes should be con- 
 sidered. During this overriding may have been the time when 
 the marbles acquired their particular metamorphic characters 
 which distinguish them from the apparently related rocks which 
 carry fossils, or are less metamorphosed, and which lie, so to 
 speak, west of the probable margin of the thrust overlaps from 
 the east. 
 
 In the section from the plateau westward through Pine Hill 
 apparently we should have, after restoration by elevation, quartz- 
 ite-schist with overlying dolomite elevated along a reverse fault 
 against the interbedded dolomites and quartzites, and the whole 
 series cut by and resting along a thrust plane which had cut 
 
218 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 through what is now marble overlying phyllite which together by 
 a minor thrust had been previously and independently pushed 
 over other calcareous rock now represented by the marble of the 
 West Rutland valley, which may have its normal position on the 
 terrigenous formation. These various rocks are probably now 
 much disturbed from their thrust relations on account of later 
 normal fault displacements. 
 
 Whenever the schist which had thus been thrust was brought 
 by thrust or by later normal faulting against phyllite or schist 
 which had been overridden it would probably not be possible, 
 oftentimes, to tell the two terrigenous rocks apart, except possibly 
 by difference in metamorphism of the moved rock. 
 
 , South of Pine Hill minor thrusts would have broken and 
 dislocated parts of the Lower Cambrian series with respect to 
 each other and another deeper thrust would have truncated these ; 
 but the various thrusts, cutting and thrusting here in different 
 ways from those at . the north, would presumably have pro- 
 duced the peculiar minor features present at the south. The 
 overlap of Cambrian on the marble would, however, have been 
 produced. 
 
 If at some subsequent time these overthrust rocks were 
 broken by differential tension faulting and dropped, as has been 
 argued, the marbles under the overthrust would have been carried 
 down, except at Dorset Mountain, perhaps, and at other places 
 south of it, and after erosion we should see the conditions as 
 they are today. It seems possible that portions of the main part 
 of the Taconic range may be overthrust masses that are now 
 protecting younger limestone (marble) at depth. West of the 
 preserved overthrusts the limestone, because unprotected, has 
 largely disappeared by erosion. 
 
 BENNINGTON AND RUTLAND COUNTIES. 
 
 Townships of Shaftsbury, Arlington, Snnderland, MancLiester, Dorset, 
 Kupert and Pawlet. 
 
 (Equinox, Londonderry, Wallingford and Pawlet topographic 
 
 sheets.) 
 
 Topography. The areas examined in these townships lie 
 mostly in the Vermont valley or that of the Mettawee River. For 
 the most part the topography has been sufficiently described in 
 speaking of the physiographic divisions of western Vermont. 
 
 Observations in certain parts of the Vermont valley through 
 northeastern Shaftsbury, Arlington, Sunderland, Manchester and 
 Dorset. The observations of the writer to be noted of the ex- 
 posures and relations of the rocks in the towns mentioned in the 
 heading of this section were made chiefly along the eastern part 
 of the Vermont valley. The rocks along the western part were 
 only casually inspected. It was the purpose to make a more 
 
■^o- 
 
 5 3 
 
 o o 
 
 
 ftS 
 
 C cS cS 
 ■- > <u 
 
 :^ C CD 
 
 .5 as 
 
 0) ^ 
 
 oj O CD 
 p p « n! 
 
a; ^ 
 
 > o ^ 
 
 be 
 O 
 
 4J OJ 
 
 
 O M C 4-1 
 
 i: =S 3 
 
 ^ « p, O 
 con 
 
 ^2 
 
 -^ 
 
 cS C — ' 
 
 M 
 
 to CJ r—l-' 
 
 O O 
 
 S be. 
 
 ) O g CD - 
 .C -^/S CD 
 
 CO" 
 
 ftp-, " o <u 
 CD m" P 
 
 o 15 Cj r-x: 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 219 
 
 critical examination of them later during the same season (1918), 
 which illness prevented, in connection with the mountain rocks 
 on the west side of the valley. 
 
 The surface covering is heavy along the eastern side of the 
 valley most of the way from Shaftsbury to Manchester. On this 
 account it did not prove possible to work out much concerning 
 the precise interrelationships of the hard rocks. 
 
 The interbedded dolomite-quartzite series of the Lower Cam- 
 brian as seen in the eastern parts of Bennington and Shaftsbury 
 was traced northward into Manchester and it was noted that 
 the rocks continue to show northward at many places the charac- 
 teristic topographic form of elongated arches which will be de- 
 scribed for the areas at the south. 
 
 East of Shaftsbury village the folds of members of this 
 series exhibit overturning to the west as was noted so often far- 
 ther south and which is a very characteristic attitude which has 
 been acquired by these interbedded rocks along the valley. Plate 
 XXXIV shows this overturning on a small scale and in this case 
 is a perfect repHca of what occurs all along the valley on a larger 
 scale, but which in the larger folds is obscured by abrasion. 
 Any further description of these hills of the interbedded rocks 
 throughout their extent from Shaftsbury to Manchester would 
 be largely repetition. 
 
 It should be noted that the hills of these rocks do not lie 
 snugly along the base of the slope of the Green Mountain plateau 
 that fronts the valley on the east, but are separated from it by a 
 space of varying width in which there is much modified and other 
 drift material. 
 
 East of East Arlington village, north of "Kansas," streams 
 have worn through from 75 to 100 feet of sand and gravel with- 
 out exposing the basement rock. Plate XXXIV shows the present 
 character of some of the kame and terrace covering that sur- 
 rounds the hills of Lower Cambrian rocks and apparently over- 
 lies other parts of the series. Other areas are bowlder strewn 
 and have apparently a relatively thin covering of bowlder drift. 
 The quartzite and overlying members of the Lower Cambrian, 
 in relations like those in Shaftsbury and Bennington, doubtless 
 underlie the drift and the series probably extends all along the 
 eastern side of the valley through these towns. 
 
 Quartzite was traced at several places up the steep slopes of 
 the plateau. All the relations indicate that the valley rocks are 
 dismembered portions of the plateau as is the case at the south 
 near Bennington and at the north near Brandon. Although the 
 quartzite was not noted in the valley between Bennington and 
 Manchester in actual surface outcrops, southeast of Manchester 
 the abundance of quartzite bowlders over certain areas suggests 
 that the quartzite is not far below the surface there. 
 
 " The Vermont valley widens out in Manchester and about 4 
 miles north of Manchester Center, marble outcrops extensively 
 
220 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 at the surface and is worked in quarries at South Dorset. Other 
 quarries have been opened between South Dorset village and the 
 southern base of the Dorset Mountain mass and still others high 
 up on the southern slopes. While the quarries at South Dorset 
 are in some cases below the 1,000 feet contour, some of those 
 near Owl's Head on Dorset Mountain are about on the 1,900 
 feet contour. 
 
 The different elevations at which the marble is worked on 
 the south of the Dorset Mountain mass and the topographic out- 
 lines suggest a probable displacement by which the marble of the 
 valley has been dropped from a higher level. 
 
 At the old Norcross quarry (see plate XXXV) a certain 
 thickness of dolomite now rests with sharp contact on the marble 
 and is well exposed in the north face of the old part of the quarry. 
 The dolomite is infolded somewhat with the surface of the mar- 
 ble. The rock has much the same relation that a similar rock 
 has to a marble in Swinington's quarry at Leicester Junction, 
 which is right on the western margin of the calcareous members 
 of the Lower Cambrian series in the township of Leicester. 
 
 In the quarries examined around South Dorset the marble 
 shows the same internal deformation in the form of flow struc- 
 tures that marks the marble nearly all the way along the Vermont 
 valley. It is in contrast to the interbedded series of the Lower 
 Cambrian just as it is near Brandon. It is more metamorphosed 
 in most cases than the dolomite that at certain places lies on it. 
 
 Observations along the valley of the Mettazvee in Dorset, 
 East Rupert, North Rupert and Pawlet to Granville, N. Y. Scat- 
 tered observations were made along the valley of the Mettawee 
 from South Dorset to Granville, N. Y. Some features of interest 
 were observed. 
 
 Limestone or marble was noted along the road a mile east 
 of East Rupert. 
 
 From East Rupert to North Rupert the hill slopes along the 
 valley road were only casually inspected, but no difference was 
 noted between the terrigenous rocks that compose them and those 
 which have been described on previous pages for the hills in the 
 northern part of the range. 
 
 Northwest of North Rupert the hill slopes on the south side 
 of the road were more carefully examined. Here are the black and 
 light-colored phyllites, the crinkled and more massive quartzites, 
 making up precisely the same assemblage as to be found in the 
 Sudbury and Orwell hills. They cannot be told apart. Two and 
 a half miles northwest of North Rupert, south of the valley road 
 to Pawlet, at the end of a short, blind road, limestone rests on 
 the phyllite. A mile north, south of the main road, are excellent 
 exposures of dove-colored limestone with gray patches of dolo- 
 mite and other exposures in which- the gray rock makes up prac- 
 tically the entire visible mass. More careful examination than 
 
S5 
 
 3P 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 221 
 
 the writer was able to give on a day's tramp would undoubtedly 
 disclose more extensive outcrops of the calcareous rock in a rela- 
 tion to the phyllite similar to that which has been noted at so 
 many places. 
 
 From the outcrops last described, the hill slopes along the 
 road through Pawlet give the phyllites. At Indian Hill and a 
 mile east of it along the road are crinkled quartzites and light- 
 colored, siliceous phyllites. 
 
 From North Pawlet a fine series of scarps can be seen bound- 
 ing Burt, Cleveland and Lincoln hills and Pond Mountain on the 
 west, and an east-west scarp on the south of Haystack Mountain. 
 
 Summary. Whatever its meaning may be, a section from the 
 Green Mountain plateau east of Manchester carried northwest- 
 erly through Dorset along the valley of the Mettawee to Granville 
 gives a repetition of the section from the Green Mountain plateau 
 east of Brandon carried over the Sudbury and Orwell hills with 
 certain differences that are less impressive than the resemblances. 
 The Lower Cambrian rocks have practically the same relation to 
 the marble, the calcareous rock rests on essentially the same ter- 
 rigenous formation, and the latter presents the same difHculty of 
 division into parts on the basis of age or other characters. More 
 slate appears in the southern section (west of North Pawlet) 
 and because of size of exposure permits easier arbitrary field 
 division and mapping, but similar slate occurs in the northern 
 section at several places. 
 
 The Verm,ont valley and eastern slopes of Dorset Mountain 
 in Dorset and southern Danby. The valley narrows north of 
 Manchester between the plateau and the mass of Dorset Moun- 
 tain. The interbedded series continues northward in the narrow 
 space between the steep western slope of the plateau and the 
 abrupt eastern slope of Dorset. 
 
 In East Dorset village along the road and just above the 
 buildings of the East Dorset Marble Co. are beds of dolomite. 
 At the later place they pitch in a northerly direction. The writer 
 was unable to decide what this dolomite represents, unless it is 
 below the interbedded series and a part of the Cambrian. 
 
 North of the road from East Dorset village up the eastern 
 slope of the mountain (Green Peak) and some distance up the 
 slope the interbedded series is plainly visible. The writer's notes 
 give a westerly dip for these beds at a point well up the slope. 
 Schistose limestone with some slaty rock were noted a short 
 distance up the eastern slope from East Dorset station near the 
 road. 
 
 The eastern slope of the mountain impresses one as being 
 bounded by normal faults. The great apparent thickness of cal- 
 careous rocks that appears along the slope may be due to dis- 
 placements along more than one plane as the rocks now in the 
 valley at the east and south were dropped, leaving the marble 
 
222 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 and associated rocks after erosion in view at the higher levels 
 and the interbedded rocks at the surface on the lower slopes and 
 in the valley where the marble is now concealed beneath them. 
 The idea of faulting is borne out by the general relations round- 
 about as well as by the aspect of the mountain slope itself. 
 
 The marble on the east face of Green Peak and northward 
 is quarried at about the same level as that at Owl's Head. The 
 fact of the same general level for the quarries may be made out 
 from the valley road. At the Dorset Hill quarry the same feat- 
 ures of metamorphism that have been mentioned for the marble 
 elsewhere were noted, as also the facts that while bedding is now 
 largely gone and flow structure and crystallinity have been in- 
 duced, the marble stratum or mass lies in a fiattish position as a 
 whole, indicating that the metamorphic structures which it shows 
 were probably induced under confinement of the mass and sug- 
 gesting that similarity of relations or conditions prevailed over 
 the wide area in which similar marble now occurs while these 
 features were in process of formation. 
 
 Overlying the marble in Green Peak and northward practi- 
 cally continuously to Dorset Peak, is the so-called "Berkshire 
 Schist" which, it is here interesting to note, is really a mass of 
 interbedded schistose and phyllitic rocks with thick beds of quartz- 
 ite and which as a whole, except for their aspect of somewhat 
 greater metamorphism, do not look conspicuously unlike the 
 quartzite-phyllite assemblage of the Hubbardton, Benson, Orwell 
 and Sudbury hills. 
 
 Figure 18. Sections to show different attitudes at different, places of the 
 interbedded series of the Lower Cambrian along the summit of an anti- 
 clinal ridge in the valley between Dorset Mt. and the plateau. 
 
 In the valley two miles north of East Dorset and east of Dor- 
 set Pond, on the strike of the northward-pitching dolomites at 
 at East Dorset station, light-gray dolomite of the interbedded 
 series forms a ridge. The rock is rather thinly-bedded at many 
 places. Along the summit or upper portions of the western 
 slope the beds may at one place be seen dipping rather gently 
 easterly, at another westerly, and still another standing on end or 
 dipping easterly at a high angle (figure 18). There has clearly 
 been overturning to the westward, as is indicated by the variations 
 in the dip of these anticlinal beds along and near the axis of the 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 223 
 
 fold. The same structure in these interbedded rocks is shown in 
 the narrow valley here as in the wider portions at the south and 
 north. 
 
 North of North Dorset a clear scarp defines the basal portion 
 of the eastern slope of Dorset Peak. The ridge of interbedded 
 rocks described in the preceding paragraph continues northward 
 east of the railroad track for two miles north of North Dorset 
 and then drops gradually off into the lowland of Otter Creek. 
 Near its northern termination it is marked on the west by a 
 moderate but steep scarp. West of the track and the highway, 
 a hill of the same rocks rests against the scarp at the base of 
 Dorset with a low scarp on the south. These rocks appear 
 greatly crushed. 
 
 In the Vermont valley in Dorset one finds in the same rocks 
 evidence of strong compression and also of displacement by 
 normal faulting. Along the lower contours some of the scarps 
 have been cleaned apparently at a relatively recent date. Ero- 
 sion prior to the glacier had so softened the outlines of the higher 
 eastern slopes of Dorset that although they are now steep, the 
 probable fault planes do not now emerge as pronounced scarps 
 even after ice action. 
 
 The observer is impressed in Dorset, as elsewhere, with the 
 contrast between the plainly-bedded although withal strongly- 
 folded Lower Cambrian rocks and the severely altered marble, 
 and, in addition, senses some important structural significance in 
 the presence of the high mass of this Taconic mountain flanked 
 by Lower Cambrian quartzite so close to the plateau, and the 
 narrow valley in between surfaced with the upper members of 
 the Lower Cambrian series which also extend up the eastern slope 
 of Dorset Mountain. 
 
 BENNINGTON COUNTY. 
 
 Towns of Pownal, Stamford, Bennington, Woodford, Shaftsbury and 
 
 Glastenbury, 
 
 (Bennington and Hoosic topographic sheets.) 
 
 The geological relations in southwestern Bennington County 
 were examined by the writer in 1912 and made the subject of a 
 paper entitled, "Notes on the geology in the vicinity of Benning- 
 ton, Vt."^ The map and descriptions therein given included the 
 township of Bennington, the major parts of Pownal and Shafts- 
 bury, and portions of Stamford, Woodford and Glastenbury. It 
 will therefore be convenient to review under one heading certain 
 relations described in the paper mentioned which bear upon the 
 present discussion, as well as to place on record some later ob- 
 servations made in the region and to offer some modifications of 
 conclusions previously offered. 
 
 * Ninth Report of the State Geologist, 1914. 
 
224 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 Topographic features. This area includes the southern por- 
 tion of the Vermont valley, which is hemmed in on the east by 
 the steep slope of the plateau except where this is cut by the 
 valley of Walloomsac Brook, East of Bennington and north of 
 Walloomsac Brook the western margin of the plateau is offset 
 to the west about two miles from its course south of the stream. 
 
 The valley narrows south of Bennington and is intercepted 
 by a ridge of schist which separates it from the valley of Hoosic 
 River that enters Vermont from the Berkshire valley in Massa- 
 chusetts. This schist ridge abuts against the plateau in Pownal. 
 Thence it extends northwestward and terminates in Mt. Anthony 
 in Bennington. The valley which comes down froiji the north 
 through the towns of Manchester, Sunderland and Shaftsbury is 
 bounded on the west by a high range which terminates west of 
 Shaftsbury Center in West Mountain. Between West Mountain 
 and Mt. Anthony is a wide open valley area which marks the 
 extension of the Vermont valley into the Hudson valley region. 
 
 Relations southeast, south and southwest of the town of 
 Bennington. In Stamford Mountain a gneiss that is believed to 
 be of pre-Cambrian age is exposed at many places. Flanking 
 this gneiss on the west and also extending around the southern 
 end of the mountain into Massachusetts and then northward into 
 Vermont again on the eastern side of the mountain is quartzite, 
 which at many places in what appear to be basal beds is a massive, 
 coarse, white, granular rock or a massive, compact, thick-bedded, 
 brown formation. This passes upward into thin-bedded, schistose 
 quartzite. 
 
 Glastenbury Mountain, north of Stamford Mountain, is also 
 flanked on the west by scarps of quartzite. Faults separate these 
 mountain masses from each other and bound them on the west. 
 At the bases of the scarps on the west of the plateau lies a series 
 of rocks which, when all members are present, has a quartzite at 
 the base, essentially similar to that of the plateau, overlain by a 
 certain thickness of dolomitic limestone, which is succeeded by an 
 interbedded series whose members are sometimes dolomites, 
 sometimes calcareous quartzites, and sometimes almost pure 
 quartzites. Unless disturbed these rocks apparently are con- 
 formable. 
 
 When the series just mentioned was first described by the 
 writer, owing to the limited time which was spent in areal map- 
 ping and lack of opportunity to check up certain portions of the 
 area, it was not possible to speak positively respecting the west- 
 ward extension of the series and its present western surface 
 boundary. Much of the calcareous rock outcropping in limited 
 exposures through the heavy surface mantle, in the western half 
 of the valley, both north and south of Bennington, was simply 
 termed limestone, in the absence of certainty as to correlation 
 with the interbedded series or its subjacent dolomitic limestone, 
 or of any fossil evidence as to age. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 225 
 
 As surface outcrops this interbedded series is present in 
 greatest force and is best exhibited northeast of Bennington. As 
 first mapped by the writer it was shown as a rather regular strip 
 about two miles wide along the eastern side of the valley north- 
 east of Bennington and as a somewhat narrower strip southeast 
 of Bennington, with its western boundary and the relation of 
 the calcareous members to the quartzite not clearly defined. 
 South of Bennington a strip about two miles wide was shown as 
 "limestone formation," with only two rather limited exposures 
 of the inbedded rocks at somewhat widely separated places along 
 the eastern edge of the strip. At one of these places, which is 
 southeast of Barber's Pond, the rocks are overlain by a black, 
 shiny, graphitic-looking phyllite, which appeared conformable to 
 the underlying beds. This is the only place in western Vermont 
 which the writer has noted where the interbedded series is over- 
 lain by a schist or phyllite. 
 
 In Pownal the calcareous rocks of the valley are intercepted 
 or interrupted at the present surface by the schist of Mason Hill 
 and by the quartzite of the plateau which come together along a 
 fault plane. 
 
 From their relation to the quartzite in which Lower Cam- 
 brian fossils have been found the calcareous rocks of the series 
 just described are regarded as of Lower Cambrian age. 
 
 Some revision of the writer's previously-held ideas has 
 proved necessary for the extension of the Lower Cambrian rocks 
 around Bennington. Observations which were made during a 
 short trip in the season of 1920, after a further acquaintance with 
 Vermont rocks had been gained, may be oflfered here as some of 
 them have an important bearing on the present paper. 
 
 Just south of Main street in Bennington, near the cemetery, 
 dipping easterly at an angle of about 54°, are beds which were 
 originally called simply limestone, but which now are regarded 
 as members of the interbedded series. Similar beds outcrop 
 along the road leaving Main street for Camp corner and again 
 in a quarry besides the road three-fourths of a mile south of 
 Main street. In the latter place the beds can be seen to be 
 greatly disturbed and standing at a high angle, apparently over- 
 turned. One-half mile south of this quarry, on the northern 
 slope of the hill, the same rocks lie in a flattish position, showing 
 hardly any buckling and apparently pitching slightly to the south. 
 One mile south-southeast of these flattish beds the interbedded 
 rocks stand on end about 40 or 50 rods west of the old lumber 
 mill on South Stream. 
 
 Within less than a mile therefore, east and west across the 
 strike, allowing for a few offsets north and south within a mile, 
 the interbedded rocks pass from a closely-compressed fold 
 through almost flat position to highly inclined beds. It is certain 
 that the drift conceals disturbed structural relations among these 
 
226 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 beds. Along the hill road from Bennington to Morgan's corner 
 and in the fields outcrops are few. Along the east-west road 
 from Morgan's corner to the main road from Bennington to 
 Pownal were observed some westward-dipping beds which were 
 also apparently members of the interbedded series. 
 
 About two and a half miles south of Bennington, just south 
 of Robinson's cross-roads and west of the main Pownal road, 
 a hill shows a series which was examined and finally assigned to 
 the interbedded stratum. The rocks are largely dolomitic but 
 carry some siliceous beds. They dip westerly on the east side, 
 but westward within the distance of half a mile the rocks show 
 confusion and brecciation and then a marked change in the char- 
 acter of the rock, which will be described beyond. The confu- 
 sion and brecciation are approximately on the line of strike of 
 greatly brecciated rocks two miles to the north near Bennington. 
 
 It further seemed to the writer that certain calcareous beds 
 and associated rocks, two and a half miles south of these out- 
 crops in the hill just described, north of Pownal Center, at the 
 base of the hill road running westward to Petty Corner, also 
 belonged to this interbedded stratum. Perhaps a hundred and 
 fifty yards up the steep hill, in the bed of the brook, south of 
 the road, are quartzite, schistose quartzite and sericite schist or 
 phyllite, apparently all conformable with each other and dipping 
 easterly at a low angle near the top of the hill. At the top of the 
 hill along the road to Petty Corner and northward along the road 
 west of Carpenter Hill are ledges of sheared quartzite and quartz- 
 itic schist which the writer now considers to be of probable Lower 
 Cambrian age from their resemblance to other rocks in the re- 
 gion. When first described and mapped in 1912, these rocks 
 were simply designated as a part of the terrigenous formation 
 that forms the Mt. Anthony-Mason Hill ridge. 
 
 The writer would now draw the western boundary of the 
 Lower Cambrian calcareous rocks of the valley, from Pownal 
 Center north to the Pownal township line, close to the base of the 
 schist ridge. 
 
 The observer passing along the main road from Pownal 
 Center towards Bennington would hardly fail to note the low 
 but steep, eastern, scarp-like margin in the ridge which extends 
 from just north of Pownal Center north to Carpenter Hill. At 
 Pownal Center the schist-quartzite formation crosses the highway 
 to join the schist of Mann Hill. The scarp just mentioned is 
 low at Pownal Center but increases in height northward. At 
 some places the members of the calcareous series give a false 
 impression of passing beneath the quartzite-schist formation of 
 the ridge, but at other places they seem rather clearly to be faulted 
 against it. The rocks at the surface of both valley and ridge 
 from Pownal Center to Carpenter Hill now appear to be mem- 
 bers of the Lower Cambrian series of the general region. It is 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 227 
 
 the writer's opinion that an east-west section at the surface in the 
 northern part of Pownal township from the quartzite of the 
 plateau across the valley to and including the terrigenous rock 
 of the eastern part of the ridge probably gives only Lower Cam- 
 brian rocks. 
 
 In Pownal Center along the road to North Pownal is a 
 schistose quartzite, which from the coarseness of its laminations 
 might be called a quartzitic gneiss. To the writer it appeared 
 quite the same as other rock found in the plateau and at other 
 places in the Taconic hills. This rock gives place westward to 
 blackish, pyritiferous, gritty schist or phylHte. The latter, greatly 
 crumpled and jammed and carrying much quartz in seams and 
 bunches, occurs along the western slopes of Mann Hill and is 
 particularly well shown along the highway and trolley road from 
 Pownal to North Pownal and in cuts along the road from Pownal 
 to Pownal Center. The rock at the summit of Mann Hill is a 
 silvery, often greenish, sericite schist. Its apparent counterpart 
 was observed, one and a half miles north of Pownal Center in 
 the beds of the brook coming down from the hill south of the 
 road from Petty Corner to the valley road, and was there ap- 
 parently interbedded with schistose quartzite, (see above). 
 
 The schistose quartzites, gritty schists and black, pyritiferous 
 phyllites of this ridge, at least from the latitude of Carpenter 
 Hill southward, bear close lithological resemblance to rocks which 
 are very common in the hills of the northern portion of the 
 Taconic range and which are described above. The lighter- 
 colored, finer-grained, more homogenous, siliceous phyllites com- 
 mon at the north were not so frequently observed in the exposures 
 examined in Pownal. 
 
 It is very hard to decide on the basis of lithology alone 
 whether all the schist and phyllite belong to one formation. It 
 seems clear that field relations among the various rocks may 
 simulate something very different from what they really are on 
 account of complex deformation and that in the absence of definite 
 criteria, assignment must be made on the basis of probability. It 
 has been particularly noted above that in the Taconic hills farther 
 north in Benson, Orwell, Sudbury and Brandon the black phyl- 
 lites, finer-grained, light-colored, sihceous phyllites, grits and 
 schists appear to pass into one another at the surface and that it 
 becomes practically impossible to discover any particular arrange- 
 ment or field relations among any of them that could be used to 
 separate them as belonging to different formations or terranes. 
 Moreover, in the Bennington region on West Mountain in Shafts- 
 bury, the schist formation carries the lighter-colored phyllite with 
 the other members and it appears to be still an open question 
 whether the schist formation of this mountain is in whole or in 
 part Lower Cambrian as mapped by Walcott, or Ordovician as 
 
228 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 mapped by Dale and formerly suggested also by the writer (1914). 
 
 East of Pownal Center, on the northeastern slope of Alann 
 Hill, limestone rests on the schist in patches and the two show 
 much intermingling of outcops and great confusion. It was not 
 possible to make any correlation of the limestone on the basis of 
 lithology. The dip of schist and limestone often seem the same. 
 Near Irish corner some early notes indicate the presence of a 
 bluish or dove-colored limestone carrying gray patches Hke the 
 rock to be described beyond. 
 
 At North Pownal village a scarp of limestone begins a short 
 distance south of the mill of the Pownal Lime Co. and runs 
 northerly parallel with and east of the main road through the 
 village to Whipple's corner. In the quarries of the Pownal Lime 
 Co. the limestone is without definite bedding, appears mashed and 
 shows black, pyritiferous phyllite overlying it and jammed in 
 with it. Plate XXXVI. 
 
 Under the highway, between it and the raiload track, in 
 North Pownal village is greatly crumpled schist and the lime- 
 stone seemingly rests on it. Although no contact was observed 
 here two miles south, west of the Hoosic River, limestone and 
 schist were found in relations which permitted no other inter- 
 pretation than that the limestone rested on the schist formation. 
 East of the high limestone hill in North Pownal village there 
 are occasional areas in which limestone and schist outcrops in- 
 termingle at the present surface. Except for some outcrops of 
 dove-colored rock carrying wavy stringers or layers of quartz 
 one-half mile north of Wright Bridge corner, nothing was ob- 
 served in the limestone in the vicinity of North Pownal that as- 
 sisted in its correlation. In the writer's first description, from 
 the general field relations and apparently isolated character of this 
 limestone, it was regarded as a? faulted inlier. It will be referred 
 to again in the discussion of the possible general structural re- 
 lations of the Bennington region. 
 
 The rocks southeast of Bennington present some further 
 features of structure and arrangement which should be men- 
 tioned." 
 
 The writer's first map showed the valley quartzite southeast 
 of Bennington as bounded by a fault on the west and there is 
 still reason to think from the flattish position of the interbedded 
 calcareous and quartzitic rocks in the bed of South Stream, as 
 shown near the lumber mill and nearby, that there is a rupture 
 between these flat beds and the closely-compressed similar rocks 
 that lie just west, as above described. What was shown on the 
 map as valley quartzite southeast of Bennington may and prob- 
 ably does have at various places some of the calcareous members 
 of the series resting on it, as is the case in the bed of South 
 Stream ; but east and southeast of Bennington stream deposits, 
 

 i^-r; 
 
 ^"- 
 
 Q ar; 
 
 .S tuoS 
 
 '^^ 
 
 3^ ^ 
 
 o <D <u 
 343 ^ 
 
 ^^ 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 229 
 
 carried into the valley at the time of glacial flooding, largely con- 
 ceal outcrops except as exposed in the beds of streams. 
 
 West of Harmon Hill the valley quartzite from a scarp in 
 the gneiss dips gently westward and passes beneath this mantle 
 of stream deposits, but southward on the east, along a strike 
 fault plane within the valley quartzite, a scarp appears which 
 continuing southward rises in altitude and seems to form the 
 main displacement that separates the quartzite of the plateau from 
 that of the valley. 
 
 No apparent distinction is to be drawn between the quartzite 
 of the plateau and the valley. They are the same in all essential 
 characters and one in fact merges into the other where a strike 
 fault scarp, for example, along the edge of the plateau dies away 
 into a slope or monocline of the plateau quartzite. In the writer's 
 first descriptions of this region the obvious displacements along 
 the western edge of the plateau were regarded as reverse faults 
 by which the gneiss and its overlying quartzite were thrust up 
 into younger rocks, with repeated breaks along the strike. The 
 valley quartzite was also thought of as having been elevated in- 
 dependently against younger rocks at the west and dropped later 
 by normal faulting. 
 
 While there seem to be probable ruptures in the rocks of the 
 valley by which they now stand in displaced relations to each 
 other, some modification of the original description, which the 
 map therewith attempted to show, is necessary if the Lower 
 Cambrian series has the westward extension suggested in pre- 
 ceding paragraphs. 
 
 In the first description of the region a sort of assumption 
 was made that in the vicinity of Bennington there is now a con- 
 siderable but unknown thickness of Ordovician terrigenous rocks 
 at the surface. For the pre-Cambrian gneiss and its associated 
 Lower Cambrian quartzite to have their apparent present relations 
 to the so-called younger masses, reverse faulting was assumed to 
 have occurred along what is now the western edge of the plateau 
 and also along planes that now lie within the valley. To the 
 writer there still appears much field evidence to bear out the 
 idea of an elevation of the pre-Cambrian floor; but the deforma- 
 tion by which the rocks of the Bennington area, and of western 
 Vermont generally, came to.be as they are, seems to be capable 
 of comprehension, if at all, only through the study of a wide 
 region. 
 
 Southwest of Bennington town are numerous puzzling rela- 
 tions which bear upon both the stratigraphy and structure of the 
 region. 
 
 In an area just southwest of Bennington, bounded by South 
 street, Dunham avenue and the Pownal road, occurs a bluish 
 or dove-colored limestone carrying many small streaks and 
 patches of gray or chamois color, and associated with beds of 
 
230 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 gray or light chamois-colored rock. These rocks have been noted 
 elsewhere near Bennington, as will be discussed beyond. In one 
 outcrop what appeared to be a few encrinal stem fragments were 
 found. This rock is greatly sheared and near the Pownal road 
 carries bands of brecciated Hmestone. On account of the sheared 
 structure it was usually not possible to decide whether the east- 
 ward dip is that of shearing or bedding, in the sheared rock itself ; 
 although in one place the dove and gray seemed clearly to be 
 interbedded and to dip easterly. In another place, perhaps two 
 hundred yards south of mixed sheared and brecciated rocks, and 
 along their general strike, were somewhat thick-bedded, gray 
 limestones dipping westward about 20 degrees. 
 
 On the east side of the Pownal road, just south of the junc- 
 tion with Dunham avenue, dark, bluish limestone forms a ledge 
 beside the road and the bedding planes can be distinguished stand- 
 ing at a high angle, sinuously bent along the strike and apparently 
 slightly overturned. Strong shearing along many planes close 
 together has greatly obscured the bedding and produced a sort 
 of slaty limestone, (figure 19). 
 
 vv 
 
 Figure 19. Schematic section of limestone as shown in a ledge near the 
 junction of the Bennington Center-Pownal road and Dunham avenue in 
 Bennington. Limestone is close to or involved in a zone of crushing 
 and an easterly-dipping shearing has nearly obliterated bedding. 
 
 The general strike of the rocks just described is approx- 
 imately north and south. Just east of the Bennington Center- 
 Pownal road, in the fields between Dunham avenue and the next 
 road north, are many ledges over an area several acres in extent, 
 in which the limestone is greatly brecciated, some of the frag- 
 ments being several inches in diameter. West of the Pownal 
 road, a few hundred yards northwest of these brecciated outcrops, 
 the limestone shows a strike of N. 81° W. and a dip of 24° south- 
 erly which correspond in general with the strike and dip of the 
 heavy limestones and marbles that form the northern slope of 
 Mt. Anthony. 
 
PLATE XXXVII. 
 
 Various fossils found in the vicinity of Bennington. Numbers 1, 2, 3 and 4 
 collected in South Shaftsbury about 2 miles north of North Bennington 
 village. Numbers 5 and 6 found 3 1/^ miles south of Bennington town 
 near Carpenter Hill. The forms are described in the text and are re- 
 garded as probably of Chazy age. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 2'6l 
 
 The sheared blue or dove-colored limestone described above 
 is traceable, with long interruptions, from the outcrops north of 
 Dunham avenue for two miles south-southwesterly to some ledges 
 just west of the road over Carpenter Hill and one mile south- 
 west of Robinson's cross-roads. At this place the sheared, patchy, 
 dove-colored rock and its gray associate occupy a prominent 
 knoll and form conspicuous ledges. In the blue rock were found 
 distinct fossil markings, including a much-worn spiral of the size 
 of and identified as Maclurea magna, a smaller probable Maclurea 
 about two inches in diameter (fig. 5, plate XXXVII), and two 
 specimens like that shown in number 6, plate XXXVII. On the 
 basis of fossils and the resemblance of the rock to Chazy beds 
 examined elsewhere in Vermont these rocks are put in that terrane 
 and regarded as probably Middle Chazy. These rocks may be 
 represented east of Pownal Center near Irish Corner, (see above). 
 
 North of these outcrops, along the eastern slope of Mt. 
 Anthony the relations are very obscure. At some places, partic- 
 ularly towards the northern end, thick-bedded marbles dip west- 
 erly into the mountain. The dip changes northward to south- 
 westerly and then to southerly. The mountain gives the appear- 
 ance of being of synclinal structure with southerly pitch and of 
 being composed of thick limestone or marble beds at the base, 
 which are capped with schist. In a quarry in the woods on the 
 east side of the mountain and west of the Everett mansion, and 
 also in Colgate's quarry on the northwest side, along the North 
 Pownal road, a blue, crystalline limestone stratum is seen to lie 
 just beneath the schist. This rock is of uncertain thickness, but 
 its strike and dip seem to indicate that it is conformable to the 
 marbles below it. It has not been identified in the region in any 
 other relations than those just described. 
 
 Notes taken in 1912 indicate absence of noticeable crushing 
 in the schist at Everett's quarry and describe the contact between 
 it and the limestone as apparently conformable. The phyllite 
 contact was described as disturbed at places in Colgate's quarry, 
 although in the northeastern part of the quarry a contact similar 
 to that in Everett's quarry could be seen. Internal deformation 
 in the schist is more apparent than in the limestone, as perhaps 
 would naturally be expected, whether in place or not. The cal- 
 careous rocks beneath are all highly crystalline, but apparently 
 not deformed like the marbles that have been noted as occurring 
 farther north. The contrast which the calcareous rocks under- 
 lying Mt. Anthony, as well as others which occur north of it 
 and have much the same dip, have to the sheared and brecciated 
 rocks of the general vicinity is very marked and goes with other 
 field relations to show that most of the strata of the region have 
 been greatly disturbed. 
 
 It should be noted that the drift covering is heavy over the 
 western part of the valley south of Bennington and that on that 
 
232 
 
 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 account much uncertainty must exist as to the extent to which 
 Lower Cambrian rocks form the hard rock substratum over this 
 area. Moreover, there are outcrops of Hmestone over this re- 
 gion which cannot be assigned with certainty to the Lower Cam- 
 brian or to any other terrane. In the Bennington region what is 
 immediately subjacent to the Lower Cambrian of the valley can- 
 not be stated in any measure, so far as the writer's knowledge 
 goes. Farther north in Vermont there is good reason to think 
 that the marble formation, whatever its age, is overlain by Lower 
 Cambrian rocks, as has been shown. 
 
 Ea^t, northeast and north of Bennington. It has not ap- 
 peared necessary to modify in any essential particulars the rela- 
 tions as described in the author's previous paper for the areas 
 east, northeast and north of Bennington. They may be very 
 briefly reviewed. 
 
 A broad band of Lower Cambrian rocks extends along the 
 eastern side of the valley under the scarp of the plateau. In its 
 southern part, except for a small area of dolomitic limestone and 
 overlying interbedded rocks near Bennington, quartzite forms the 
 only surface rock over a distance of about 4 miles. In the south- 
 ern portion of the band there is apparent a low southerly pitch 
 and the arrangement of quartzite, limestone and interbedded 
 rocks shows a conformable series, (figure 20). 
 
 Figure 20. A generalized north-south section of the southern portion of the 
 Lower Cambrian series north of Bennington, as displayed just east of 
 the Bennington Poor Farm. Southward pitch exaggerated. A, quartz- 
 ite ; B, dolomitic limestone ; C, interbedded dolomites, calcareous quartz- 
 Ites, and quartzites. All apparently conformable. 
 
 The quartzite at its northern end forms an anticlinal buckle 
 which presents great ledges of white, granular quartzite on its 
 eastern slopes. These have complete similarity with similar 
 quartzite in the plateau just east of the valley quartzite and the 
 latter is looked upon as a dismembered portion of that now flank- 
 ing the plateau. Southward towards Bennington the coarser 
 quartzite passes upward into somewhat thinner and more schistose 
 beds and thus gives the same transition that may be observed on 
 the western quartzite slope of "The Dome" in Pownal. On the 
 west the surface slope of this valley quartzite descends across the 
 edges of the beds. 
 
 At the north the valley quartzite just described, in the town 
 of Shaftsbury, is apparently cut off by a tranverse fault. The 
 quartzite is succeeded abruptly at the surface by limestone which 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 233 
 
 form a series of arches elongated along the strike. Farther north 
 these are replaced by similar arches of the interbedded rocks. 
 The succession going north is thus seen to be from quartzite 
 through limestone to the interbedded members of the series ; but 
 the members have been more disturbed with reference to each 
 other than is the case over the southern portion of the strip. 
 Moreover, there is apparent a series of displacements along the 
 strike as well as folding and faulting across it. 
 
 The arches described consist of compressed folds of lime- 
 stone or of the interbedded rocks and the beds frequently show 
 overturning to the west. The arches, including the one in the 
 quartzite and those south of Bennington, are all of similar genetic 
 type. Northward these arches give a characteristic topographic 
 form to the surface of much of the Vermont valley as has been 
 mentioned. 
 
 The members of the Lower Cambrian series north of Ben- 
 .nington, just described, were not positively identified in any part 
 west of the westernmost exposures of its basal quartzite member 
 as this outcrops along the South Shaftsbury road. Much surface 
 material covers the rock northwest of Bennington in the central 
 and western parts of the valley. The probable correlation of cer- 
 tain outcrops southeast of South Shaftsbury village and in the 
 cuts of the Rutland R. R. north of the village is not now ap- 
 parent. In the writer's map of the Bennington region a probable 
 fault was shown as bounding the whole Lower Cambrian series 
 on the west from Bennington north to the limit of the map. For 
 the most part the line to mark this fault was drawn some distance 
 to the east of South Shaftsbury road. Near Bennington, how- 
 ever, it crosses that road at the junction with the "Stony Hill 
 road." The boundary as thus shown was drawn partly to em- 
 phasize the close age relations of the rocks forming this broad 
 hand along the east side of the valley and partly to record the 
 surface features indicative of displacement along their apparent 
 western margin at the northern end of the strip. 
 
 It might be noted here that some fragmentary outcrops of 
 siliceous and dolomitic rocks somewhat resembling the members 
 of the interbedded series were observed one and a half miles 
 north of North Bennington village; but it did not seem possible 
 to determine whether they are in place. 
 
 West and northivest of Bennington. The general southerly 
 dip that marks the limestone and marble beds on the northern 
 slope of Mt. Anthony was traced northward to and across the 
 Bennington-Hoosic road and was noted distinctly three-fourths 
 of a mile northwest of the monument at Bennington Center. 
 While the rock in North Bennington, which will be mentioned 
 presently, shows some difference in strike and dip from that 
 south of it, the two bear resemblances with respect to absence of 
 
234 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 pronounced internal deformation such as other rocks of the 
 region show. 
 
 Along the banks and in the bed of Paran Creek, south of 
 North Bennington village, the limestone beds have a strike, ac- 
 cording to one reading selected as fairly representative, of about 
 N. 80° E. and a dip of about 11° south-southeasterly. On the 
 west side of the road west of the creek, opposite the office of the 
 Cushman Furniture Company, are beds of dark gray limestone 
 ranging in thickness from about two feet at the base of the expo- 
 sure to about 10 inches or a foot near the top. Similar beds out- 
 crop just below the dam of the Stark Paper Mill and above It 
 farther up stream. No fossils were found and no correlation 
 seemed justified on any basis. 
 
 In Shaftsbury a mile and a half north of North Bennington 
 village, in the woods on an east hill slope, southwest of Twitchell's 
 corner, were found a few ledges of the same sheared, patchy, 
 dove-colored rock and its gray associate seen southwest of Ben- 
 nington, west of the road over Carpenter Hill. The dip is west- 
 erly into the hill about 25° and the strike N. 40° to 50° E. The 
 exposures are limited with drift all about. The dove-colored rock 
 is plainly fossiliferous, but the markings are obscure. Spiral 
 lines and patches representing coiled shells of some kind were 
 noted at several places. These were hard to remove. Figure 3, 
 plate XXXVII, gives an indication of the markings, but some of 
 those found at the locality now being described were much more 
 plainly shown to be sections of coiled shells. At this locality 
 occurs a thin bed with abundant sections of small encrinal stems 
 (fig. 1). This same bed at one place yielded two orthoceras- 
 like specimens (figs. 2 and 4) which, however, it is hardly pos- 
 sible to identify. Some of the rock seen on surfaces cutting 
 across the bedding is distinctly striped in appearance. It was 
 at this locality that some fragmentary dolomitic and siliceous 
 rocks, very limited in exposure, were noted. They bear some 
 resemblance to the interbedded members of the Cambrian farther 
 east ; but from observations made about a mile farther west 
 where more extensive siliceous beds seem to belong with a series 
 which includes also the striped and dove-colored rocks, their 
 Cambrian age was regarded as improbable. The fossiliferous 
 rock and its associates are regarded as probably Chazy. It 
 seemed likely that Maclurea magna might be found but a care- 
 ful search did not reveal it. 
 
 Northwest of the limited exposures just described, over the 
 hill, across a road and down a northwestern slope to a brook, 
 for a distance of about a mile is nothing but drift. Just west 
 of this brook and north of the road to Cold Spring Corner are 
 low-lying ledges of black, pyritiferous phylHte. This rock passes 
 northward beneath greatly jammed and distorted limestone in 
 which the patchy, dove-colored rock appears again in association 
 
REPORT OB' THE VERMONT STATE GEOLOGIST. 235 
 
 with gray dolomite beds, which are infolded and otherwise in- 
 volved with the other rock. These beds of hmestone clearly rest 
 on the phyllite. The deformation of the limestone beds is very 
 severe; they are folded and overturned, profoundly sheared, 
 jointed and mashed. Fossils have not escaped. In one exposure 
 only, a small slab about 6 feet square, and perhaps not in place, 
 although lithologically resembling some of the ledges and quite 
 like some rock seen a mile east, showed some coils, most of which 
 ' were thick patches but clearly fossils. A piece of this slab is 
 shown in figure 3, plate XXXVII. The ledges at this place were 
 similar to those described above as carrying fossils. 
 
 Westward across a narrow swamp, in some woods and in 
 the field north, are many ledges of similar rocks, although inter- 
 bedded quartzite is frequent here. These rocks have resemblance 
 to some that were noted west of Brandon just east of the Rutland 
 R. R. track on both sides of the road through Morgan's Stock 
 Farm and also to some others on the strike of the latter on the 
 west side of Otter Creek along the eastern margin of Long 
 Swamp ; also with others found west of Orwell village. These 
 latter rocks in Shaftsbury were hard to correlate with others of 
 the vicinity. 
 
 The suggestion is strong from the field relations that the 
 phyllite mentioned above lies beneath all these various calcareous 
 rocks north of the road to Cold Spring Corner. 
 
 It seems probable that the various outcrops of dove-colored 
 rocks carrying gray patches and fossils, and the associated gray 
 beds, and perhaps also those with the interbedded quartzite, 
 belong to the Chazy, on the basis of similarity with the outcrops 
 south of Bennington and at places northward in the State. 
 
 An especially interesting feature of the exposures in Shafts- 
 bury described above is the subjacent position of the black phyl- 
 lite, in view of relations which have been described for areas 
 farther north. At places west and southwest of North Ben- 
 nington the relations between limestone and schist afiford reasons 
 for thinking that the limestone rests upon the schist formation. 
 
 On the lower portion of the southern slope of West Mountain 
 are calcareous rocks similar to those just described. They are 
 greatly sheared and "splintered." Up the southeastern slope of 
 the mountain the limestone gives place at the surface to phyllite. 
 At the top of the mountain is a light-colored, siliceous phyllite 
 very similar to rock found associated with quartzite and black 
 phyllite in the Sudbury hills except that the former is more 
 micaceous and schistose. 
 
 Summary of the Bennington region. Both the rocks and the 
 relations which they have to each other in this region show many 
 resemblances to those which have been described for the region 
 around Brandon. There are also differences. In general the 
 Lower Cambrian series along the east side of the valley, in its 
 
236 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 lithological characters and its structural features, much resembles 
 the other in each case. At Brandon black, and often pyritiferous, 
 schist is associated with the quartzite along the plateau margin. 
 At Bennington, except for a small patch lying on members of the 
 interbedded series against the edge of the plateau, southeast of 
 Barber's Pond, and the schist of Mason Hill, phyllite was not 
 noted as involved with quartzite in proximity to the plateau. But 
 it should be noted that much of the rock making up the Mt. 
 Anthony ridge, south of the latitude of Carpenter Hill at least, 
 is not to be distinguished from that found along the plateau east 
 of Brandon. It is apparently the same schist which is found in 
 both places and which also underlies the calcareous rocks de- 
 scribed above north of the Cold Spring road in Shaftsbury. This 
 schist has a marked similarity throughout a wide distribution, as 
 has been l^rought out fully above. 
 
 A section south of Bennington, in Pownal, from the plateau 
 on the east across the valley and the Mt. Anthony schist ridge, 
 gives gneiss with overlying quartzite, faulted with quartzite and 
 overlying calcareous rocks, which are faulted with each other. 
 These latter rocks apparently extend to the base of the schist 
 ridge on the west of the valley and here now apparently are 
 faulted again against quartzite and phyllite which form the scarp 
 and the surface rock along the eastern portion of the ridge. 
 Farther west lies the limestone of North Pownal which is much 
 involved with schist, sometimes intermingling with it in surface 
 outcrops, sometimes underlying it, and here and there jammed in 
 with it. 
 
 Another section north of the latter, passing through Mt. 
 Anthony proper, shows sheared and brecciated limestones, some 
 of which are of probable Chazy age, lying just west of the appar- 
 ent western edge of the Lower Cambrian series and containing 
 a long and strongly-marked zone of crushing, as well as the 
 shearing characteristic of the whole mass, and west of this de- 
 formed strip gives the thick-bedded, crystalline marbles of Mt. 
 Anthony apparently not greatly deformed internally, or as a mass, 
 and overlain by schist in apparent conformity. 
 
 An east-west section north of Bennington, passing just south 
 of North Bennington village, gives the Lower Cambrian as before, 
 then an interval of unknown (drift-covered), then the fiattish, 
 dark gray limestones of Paran Creek. Farther west the indica- 
 tions are that limestone rests on schist. 
 
 A section passing about two miles north of North Benning- 
 ton gives Lower Cambrian as before, an interval of unknown, 
 then the rocks which were described above as probable Chazy 
 and others associated with them. These at places lie on black, 
 pyritiferous phyllite and probably are over much of the area now 
 resting on the phylhte. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 237 
 
 Farther north still,.along a section passing through Shafts- 
 bury Center or Shaftsbury Depot and West Mountain, the Lower 
 Cambrian series Hes on the east side of the valley, then certain 
 limestones near the foot of West Mountain, then the schist 
 of West Mountain. Except for one small patch just west of 
 Shaftsbury Depot along the lower eastern slope, the schist of 
 West Mountain was not found to have any limestone resting on 
 it, although the writer's search was not exhaustive. 
 
 The Lower Cambrian series of the valley is clearly a dismem- 
 bered part of a mass to which the quartzite of the plateau also 
 belonged ; whether the result of reverse or normal faulting has 
 already been discussed for its northern extension. The evidence 
 in this Lower Cambrian series shows that it has been under strong 
 compressive stress, and that some of its deformational features 
 are due to such stress. The conditions exhibited south of Ben- 
 nington and in North Pownal show the action of powerful com- 
 pressive forces in the region. Some rocks seem to be crushed 
 more than others, as though caught and confined and made to 
 deform internally because they could not get away. Other rocks 
 seem to have escaped great internal crushing although meta- 
 morphosed by other processes, such as recrystallization. 
 
 The apparent minor displacements in the Lower Cambrian 
 series, involving overturned folds and probable reverse faults, 
 are evidence of former compression. The overturned folding in 
 some cases, however, may have been due to friction instead 
 of having preceded and initiated the rupture. In the Ben- 
 nington region the evidence of upthrust of older into younger 
 rocks is strong; but the evidence for lateral thrust, or better, 
 lateral movement, is not so apparent. Farther north, marble 
 that is almost certainly younger in age- outcrops from beneath 
 overthrust Lower Cambrian rocks. These relations were not 
 established for the Bennington area. While the limestones west 
 of North Bennington seem to be thrust on schist in some cases, 
 and have undoubtedly been under compression, the field relations 
 do not show that the limestone may not have rested on the ter- 
 rigenous rocks prior to the deformation of the former. 
 
 In the writer's first description of the geology of Bennington, 
 the character of the Vermont valley as primarily a structural 
 valley was recognized ; but the break between the plateau and the 
 valley was regarded as primarily a reverse fault and the normal 
 displacement producing the present relations was thought to have 
 utilized the earlier reverse fault plane. This does not seem likely 
 from the relations shown in other areas. 
 
 The present lateral distribution of the calcareous members of 
 the Lower Cambrian series in the valley has no necessary rela- 
 tion to their original extension eastward or westward. Such 
 extension must be decided by other considerations. The prob- 
 ability of primary upthrust of Lower Cambrian and of later 
 
238 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 normal faulting of a part of the series, together with the fact of 
 erosion, calls for an original extension of the Lower Cambrian 
 series as a whole to the eastward. Whether they extend west- 
 ward at depth is perhaps another question. Whether they ever 
 had a great westward extension by thrust is certainly an inde- 
 pendent consideration. 
 
 Certain other matters may be postponed until the general 
 summary for western Vermont is offered. Enough has been said 
 to show that the relations are complex and that one is practically 
 driven to inspect other areas to obtain light on this one. 
 
 ADDISON COUNTY. 
 Whiting and Shoreham Townships. 
 
 (Brandon and Ticonderoga topographic sheets.) 
 
 Topography. These townships lie just north of the Taconic 
 hills of Sudbury and Orwell, in the southern part of the Cham- 
 plain lowland. The surface is low for the most part in Whiting ; 
 the eastern boundary of the township in fact for a distance of 
 four miles is Otter Creek. In Shoreham there are a few low 
 hills. 
 
 General observations in Whiting and Shoreham. There has 
 been a much more extensive preservation of the limestone strata, 
 which have been noted in fragmentary areas in Orwell, Benson, 
 Sudbury and elsewhere, northward in the portion of the Cham- 
 plain lowland extending through Whiting, Shoreham and neigh- 
 boring townships. On this account, some of the relations and 
 the ages of the various rocks were early worked out in these 
 areas, first through the work of Wing and later that of Brainerd 
 and Seely. In the town of Shoreham was established the type 
 section of the Beekmantown of western Vermont. 
 
 In the course of his studies the writer reviewed some of the 
 field relations in Whiting and Shoreham. 
 
 The phyllites north of Sudbury village at and around Web- 
 ster corner, which have already been described, were followed 
 northward along the road to Whiting village by frequent out- 
 crops nearly to the village. Along the road running west two 
 miles north of the village the same phyllites were traced from 
 the school house on the Middlebury road past Hitchcock's resi- 
 dence to school house corner. In the valley of the brook one- 
 fourth of a mile west of Hitchcock's place, the phyllite forma- 
 tion showed patches of quartzite with vein quartz like that on 
 Government Hill in Sudbury and at other places in the Sudbury 
 hills. In general no essential difiference could be discerned be- 
 tween the rocks composing the low ridge which extends north- 
 ward from Sudbury into Whiting and those which make up the 
 hills of Sudbury, Orwell and Benson. 
 
REPORT OF THE VERMONT STATE GEOLOGIST, 239 
 
 West of the phyllite formation in Whiting just described, 
 the section described by Brainerd and Seely for eastern Shore- 
 ham can be fairly easily followed if side excursions are made 
 frequently enough to get exposures of beds which are soil-covered 
 at other places along the strike. The apparent monoclinal char- 
 acter with easterly dip and the apparent thickness as described, 
 can be made out and duly appreciated. 
 
 One-third of a mile west of school house corner, mentioned 
 above, the road which goes westerly past Hitchcock's place turns 
 sharply to the south to join the main road from Whiting village 
 to Shoreham village. Along and east of this road leading south 
 are exposures of the blue Trenton limestone dipping easterly 
 at an angle of about 40° and extending along the strike practically 
 north and south. West of the road are ledges of the Chazy and 
 others which have many similarities to the Chazy, but which 
 Brainerd and Seely called division E of their Beekmantown. 
 Along another road just west appears division D with many fos- 
 sils at numerous places. Then follow divisions C, B and A 
 westward over Cutting Hill towards Richville. Just east of 
 Richville is exposed with easterly dip along the main road the 
 whitish, quartzitic sandstone which was called the "Potsdam," 
 and which is described as forming the base of the section. 
 
 At the bridge at Richville, east of the road and in the river 
 bank, and northward the rocks show great confusion, and north 
 of Richville at places beds belonging to division D show westerly 
 dip just west of this zone of disturbance. As recognized and 
 shown by Brainerd and Seely a fault or thrust has elevated the 
 "Potsdam" against younger beds. 
 
 West of Richville the "Potsdam" outcrops again along the 
 road to Shoreham, apparently along the axis of a ruptured anti- 
 clinal buckle for the sandstone apparently rests at the west 
 against division C, and possibly D, This broken anticline, how- 
 ever, seems to belong to a larger mass of beds which has ridden 
 westward along a deeper and more extensive thrust plane, cut- 
 ting through the Beekmantown and still higher beds. Just east 
 of Shoreham village, near and east of the Catholic Church, are 
 Trenton rocks succeeded eastward by Chazy beds dipping west- 
 erly, which in turn are succeeded eastward by Upper Beekman- 
 town, dipping at a high angle easterly, according to the writer's 
 observations. It would seem that beds which stood at a high 
 angle of westerly dip at the time of rupture would have had this 
 increased and even reversed by the drag along a thrust plane. 
 
 In the center of the village the "Potsdam" appears again 
 on the eastern margin of an extensive swamp which westward 
 is succeeded by hills of "Utica" slates. 
 
 South of Shoreham in the town of Orwell, field relations 
 which have been described above, indicate that a limestone series 
 like that which occurs in Shoreham has been broken by reverse 
 
240 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 faulting and minor thrusting which have brought the lower mem- 
 bers of the series against and over higher ones, and that as now 
 affected by erosion at some places the younger rocks are shown 
 beneath and the older on top. Moreover, other more extensive 
 thrust planes have carried the previously faulted series over still 
 younger rocks on which it may now be seen resting at several 
 places. 
 
 From the description of the relations as inspected in Whiting 
 and Shoreham the similarity to the condition in Orwell appears. 
 The same phyllites occur at the east succeeded westward by an 
 unusually regular series of calcareous rocks from the Trenton 
 down through the gray sandstone called the "Potsdam," while 
 still farther west near the lake are hills of "Utica" slate. Except 
 as affected by erosion the arrangement and sequence are ap- 
 parently the same and it would seem that the structural relations 
 of both areas must have been due to similar causes. 
 
 The conditions in western Shoreham and western Orwell 
 townships raise two questions : 
 
 1. How is the preservation of the hills of rather frail 
 "Utica" shales and included limestone bands along the edge of 
 the lake to be explained unless by assuming their protection per- 
 haps until relatively recent times by a more durable covering? 
 
 2. What explanation is to be given of the absence at the 
 west of the phyllite formation found at the east beneath the lime- 
 stones ? 
 
 ADDISON COUTfTY. 
 
 Townships of Leicester, Salisbury, Middlebury, Cornwall, Bridport, 
 Weybridge, Addison, IVew Haren, Walthara and Tergennes. 
 
 (Brandon, Ticonderoga, Port Henry and Middlebury topographic 
 
 sheets.) 
 
 Topography. The topography of the areas examined in 
 these townships is for the most part typical of the Champlain 
 lowland. Snake and Buck mountains are somewhat conspicuous 
 elevations whose structural significance will be discussed beyond. 
 
 Observations between Lake Dunmore and Snake Mountain. 
 In the summer of 1918 two days were spent in as careful an ex- 
 amination as a walking trip would permit of the country between 
 Brandon village and Vergennes. The first part of the trip was 
 along an irregular traverse from Brandon by way of Lake Dun- 
 more to Snake Mountain through the townships of Leicester, 
 Salisbury, Middlebury, Cornwall and Weybridge. 
 
 North of Forestdale the western boundary of the quartzite 
 formation swings from the plateau to the Champlain lowland 
 and marks the beginning of a westward extension of this forma- 
 tion that in the lowland becomes even more pronounced at the 
 north in Monkton. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 241 
 
 The Structural breaks between the plateau and lowland north 
 of Brandon exhibit their own peculiar pattern, but in it can be 
 discerned a similarity to that at the south, m the overlapping along 
 the strike of normal fault displacements of varying throw. North- 
 ward the western margin of the plateau is farther west than it 
 is east of Brandon. The dismembered portions of the quartzite, 
 or rather the Lower Cambrian series, along the eastern margin 
 of the lowland take the form of hills and ridges which begin west 
 of Lake Dunmore and gain in prominence northward. In gen- 
 eral the relations are similar to those shown along the eastern 
 margin of the Vermont valley from Bennington, through Shafts- 
 bury, Arlington and farther north. Observations were not made 
 with sufficient thoroughness to show conclusively whether or not 
 outcrops of marble, or the rocks associated with it, occur within 
 the area chiefly occupied by the Lower Cambrian series, and there- 
 fore whether actual overlap occurs as it does around Brandon, 
 although probable overlap by thrust is suggested. 
 
 Dolomite like that associated with the marble around Bran- 
 don and farther south in Dorset was noted at Leicester Junction 
 and at other places and the interbedded series was found a mile 
 west of East Middlebury village along the road from that village 
 to Middlebury. The valley quartzite, however, northwest of Lake 
 Dunmore extends westward to a meridian a mile west of East 
 Middlebury village, at least. 
 
 East of Lake Dunmore is a prominent scarp in the quartzite 
 and the lake appears to lie in a structural basin. North of Lake 
 Dunmore the place of this scarp is taken by another lower one 
 which breaks the quartzite a mile west of Bryant Mountain. The 
 basin in which the lake Hes appears to be the counterpart of those 
 at the south near Arlington and Manchester which are filled with 
 drift. 
 
 Three miles northwest of East Middlebury village, and two 
 miles from outcrops of the interbedded rocks of the Lower Cam- 
 brian series west of the village, along the road to Middlebury, are 
 exposures of sheared, blue limestone, carrying gray, woolly 
 patches which after a short distance are succeeded by outcrops 
 of marble that lie about a mile southeast of Middlebury village. 
 The relations thus far noted present a strong similarity to those 
 found around Brandon. 
 
 In the fields a mile west of Middlebury are abundant expo- 
 sures of the bluish or dove-colored rock showing the same shear- 
 ing and the same gray patches that have so frequently been men- 
 tioned and which are associated with other limestones resembling 
 the Trenton. Many ledges were examined for fossils, but nothing 
 definite was noted. The prominent structural feature is strong 
 shearing with easterly dip. 
 
 Two miles west of Middlebury were observed outcrops of 
 phyllite. Some of this rock is like the light-colored phyllites seen 
 
242 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 in the Whiting and Sudbury exposures, in texture, but darker in 
 color. It was found along the valley of Ledge Creek. No at- 
 tempt was made to trace the boundaries of this formation with 
 adjacent rocks and no contacts were found. 
 
 West of the phyllite is a ridge known as "The Ledge." The 
 dove-colored rock was noted here. West of "The Ledge" the 
 surface sinks to the level of the Lemon Fair River in Weybridge. 
 West of the Fair the surface rises very gradually to the eastern 
 slope of Snake Mountain. 
 
 Observations near Snake and Buck mountains. In the north- 
 eastern part of Bridport the eastern slope of Snake Mountain is 
 formed of cherry-red or brick-red quartzite which dips easterly. 
 On the west the mountain presents a good scarp of varying alti- 
 tude fronting the lowland, but at places the drift is piled rather 
 high against it. 
 
 Along and near the east road to Addison, west of the moun- 
 tain, are good exposures of the' grayish-blue limestone carrying 
 Maclureas, Ophiletas and other fossils. 
 
 Two miles east of Addison village, along the road to New 
 Haven Junction, north of the mountain, were noted black shales, 
 weathering gray, and these one-half mile farther east in an ex- 
 cavation beside the road one-half mile west of Otter Creek gave 
 many graptolites, identified as G. pristis. Above the shales in 
 this pit is limestone apparently lying on the shales and which in 
 lithology resembles some of the higher Beekmantown. At the 
 bridge across Otter Creek is dove-colored limestone which ap- 
 pears again northward along the road to Vergennes apparently 
 dipping easterly. Farther north, three and a half miles south of 
 Vergennes, the limestone dips easterly about 20° and is full of 
 fossils, including Maclurea magna. The rock does not appear 
 to be so badly sheared as is its apparent counterpart east of Snake 
 Mountain and southeast of Middlebury. 
 
 Buck Mountain shows a conspicuous scarp on the west which 
 is not so sharp as that of Snake Mountain. 
 
 East of the limestone at the bridge over Otter Creek, along 
 the road from Addison village to New Haven Junction, limestone 
 gives place to quartzite, "Red Sandrock," which forms the east- 
 ern slope of Buck Mountain and dips easterly. This gives place 
 eastward to limestone. 
 
 Near the northern end of Buck Mountain a road crosses it. 
 North of this road, quartzite forms the base of the eastern slope, 
 but a short distance west up the slope it gives place to large ex- 
 posures of the bluish or dove-colored rock with its gray associate 
 and the former carries indistinct fossils. Field notes indicate 
 that the limestone is sheared and that it continues westerly and 
 apparently forms an anticline, for easterly dip occurs on the 
 east and one-fourth of a mile west the dip is westerly. North- 
 ward along the strike of the westerly dip the lirnestone presents 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 243 
 
 an abrupt, abraded edge 500 yards south of the house at the end 
 of the private road. About three-fourths of a mile farther 
 north and one mile south of Vergennes, in a pit east of the road, 
 shale appears. Here the rock has a larger exposure and is more 
 limy than that noted farther south, north of Snake Mountain, 
 but in general resembles that in which graptolites were found 
 two and a half miles east of Addison village. The shales appear 
 on a meridian intermediate between limestone outcrops farther 
 south which suggests that they were once covered by limestone 
 or quartzite which has been eroded. In the south wall of the 
 pit the rocks show that the formation has been greatly crumpled. 
 
 Summary. The faulted and scarped western edge of the 
 Green Mountain plateau continues northward from Brandon and 
 fronts a wide Champlain lowland lying to the west. Along the 
 eastern margin of the lowland lies a series of rocks whose basal 
 quartzite member is like the quartzite forming the escarpments 
 of the plateau. In the lowland and on the edge of the plateau 
 the quartzite is overlain by a dolomite and in the lowland there 
 is present also a series of interbedded dolomitic and quartzitic 
 rocks like those that have been described for Brandon and areas 
 farther south. The lowland rocks are dismembered portions of 
 those forming the plateau. The relations in the main are like 
 those at the south throughout the long extent through which 
 they have been traced in the descriptions of this paper. 
 
 Although conclusive evidence from field relations examined 
 by the writer may not be offered to show that the Lower Cam- 
 brian series at the east overlaps other rocks along a thrust plane, 
 such as was described for Brandon, a dolomite was seen during a 
 subsequent season at Leicester Junction, lying on the marble, and 
 the resemblance of the former to the dolomites so frequently 
 noted around Brandon in association with the marble was noted. 
 It does not resemble the rocks which seem to be Chazy and its 
 counterpart was not found west of the meridian of Middlebury 
 village. During a subsequent season also were inspected some 
 outcrops along the road from Leicester Junction to Whiting 
 village which bear strong resemblance to the interbedded rocks 
 seen northwest of Brandon village. They occur south of the 
 road about a mile west of the Junction and the exposure is limited. 
 In fact, drift very thoroughly hides the hard rock between Otter 
 Creek and the brook farther west, and the exposures are not at 
 all satisfactory for study. Two and a half miles west of the 
 Junction, just east of the railroad track, limestone shows a pud- 
 dled appearance and carries salmon-pink or buff-yellow patches 
 of calcite like those northwest of Brandon. In Huntley's quarry 
 at the Junction a dolomite is involved with pinkish marble and 
 west of the quarry, at some old quarry holes, beds of ochre-yellow 
 dolomite are involved with pinkish marble. 
 
244 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 South of the Leicester Junction-Whiting road some of the 
 few exposures along the road to Foster corner show the sheared 
 blue limestone of the Sudbury exposures farther south. 
 
 If the various outcrops indicated above belong to the Lower 
 Cambrian series they carry the margin of it west of the meridians 
 along which the marble and its associated rocks outcrop at Leices- 
 ter Junction, and southeast and northeast of Middlebury village. 
 
 At Swinington's quarry near Leicester Junction the dolomite 
 shows a structure like that at the old Norcross quarry at South 
 Dorset. They both offer structure to be considered in connection 
 with the characteristic deformations of the rocks of the region. 
 See plate XXXV. 
 
 The bluish-gray or , dove-colored limestone and associated 
 gray dolomite southeast and west of Middlebury village are re- 
 garded as the equivalents of similar rocks around Brandon and 
 west of it. West of Middlebury they have apparently the same 
 relations to sheared blue limestone as in eastern Sudbury and 
 the whole series bears the same relation to the phyllite in eastern 
 Cornwall that the calcareous rocks at the south do to the phyllite 
 formation of the Sudbury and Orwell hills. In eastern Corn- 
 wall, in fact, the phyllite band simply interrupts at the present 
 surface the continuity of entirely similar calcareous rocks that 
 now lie each side of it. These calcareous rocks lie on the phyllite 
 and are not interbedded with it. Westward in the valley of the 
 Lemon Fair the hard rocks largely or wholly disappear from 
 surface view and the next outcrops westward are the quartzitic 
 rocks of the "Red Sandrock" formation on the eastern slopes of 
 Snake Mountain. Farther north, however, on the meridians of 
 the phyllite and the limestones west of Middlebury the "Red Sand- 
 rock" of Buck Mountain appears at the surface with every in- 
 dication at its northern end that limestones similar to those lying 
 on the phyllite west of Middlebury village also lie on it, while the 
 quartzite on the eastern slope of Buck Mountain passes eastward 
 beneath similar limestones. Whatever it may mean, there is a 
 substratum to these similar limestones which shows a lateral 
 variation within not very long distances from phyllite to quartzite. 
 
 The published descriptions show that with minor surface in- 
 terruptions the quartzite of Buck Mountain connects northeast- 
 erly with similar rock in Monkton, which in turn is described as 
 "merging" with the quartzite of the plateau. Account should 
 be taken, of course, of the normal and other probable displace- 
 ments at the east. 
 
 Snake and Buck mountains are the topographic counterparts 
 of the interbedded quartzite and phyllites composing the Orwell 
 hills. They also lie along practically the same meridian. 
 
 West of Snake Mountain are calcareous rocks apparently 
 similar in important respects to those at the east, but less altered, 
 and fossiliferous; the dove-colored rocks yield Chazy fossils. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 245 
 
 North of Snake Mountain are black shales giving "Utica" grapto- 
 lites and this rock is overlain by limestone, which is probably 
 of Beekmantown or Chazy age. Along a meridian lying a mile 
 to the east are dove-colored rocks which northward west "~of 
 Buck Mountain give Maclurea magna and other Chazy fossils. 
 And still farther north and on a meridian lying east of the Chazy 
 outcrops are shales like those at the south carrying Graptolithus 
 pristis. 
 
 There is apparently a fault in the quartzite on the north of 
 Snake Mountain, but it is not apparent that there is any structural 
 lateral offset. The physiographic offset between Snake and Buck 
 mountains appears to be due to the irregular course of the dis- 
 placement that bounds those eminences on the west and which 
 north of Snake Mountain swings eastward and then again north- 
 ward. There are minor scarps and surface interruptions between 
 Snake and Buck mountains. Around Snake and Buck mountains 
 there were not noted by the writer any places at which the quartz- 
 ite and shales are in contact and only one place, as described, was 
 seen where the shales had limestone above them. The probable 
 relations of the quartzite, and the limestone which probably lies 
 on it, to the "Utica" rest upon probable conditions shown else- 
 where which will be described beyond. 
 
 The displacements marked by the scarps on the west of 
 Snake and Buck mountains have been described or pictured as 
 reverse faults by which the quartzite was elevated to its present 
 position with respect to the surrounding rocks. They will be 
 discussed beyond so as to show that they are probably in char- 
 acter, and relations to earlier thrusts, similar to those which broke 
 the rocks along the western edge of the plateau at the east and 
 the Orwell and Benson hills at the south. 
 
 CHITTENDEIf COTI\W. 
 
 Burlington. 
 
 (Burlington topographic sheet.) 
 
 Observations near Burlington. Vergennes was the most 
 northern point reached by the writer in the course of a trip on 
 foot through western Vermont in the summer of 1918. There 
 has been no opportunity since to make close field observations 
 between the parallels of Vergennes and Burlington. Some men- 
 tion may be made in the final summary of certain published ac- 
 counts of the relations shown in the territory intervening. At 
 Burlington trips were made to points along the lake shore and to 
 the valley of the Winooski, which may be mentioned here for 
 sake of completeness. 
 
 The celebrated Rock Point locality at Burlington should be 
 visited by anyone who is interested in the problems of rock 
 deformation in western Vermont. Here is exposed a relation 
 
246 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 that is often concealed along the lake shore. The phenomenon 
 of overthrust falls within the range of easy understanding as 
 one surveys the sharp contact of the Cambrian sandstone on the 
 Ordovician shale formation, and the inspection is helpful in 
 visualizing the relations at other places where the aid of the 
 imagination is needed more. 
 
 The massive quartzite-dolomite, "Red Sandrock," often with- 
 out any marked visible internal deformation, rests on greatly 
 crushed and crumpled, black slates and shales, with stringers and 
 nests of quartz and calcite. The color of the quartzite varies in 
 this vicinity ; while often red it is frequently gray and brown. 
 The shore section at Rock Point is a detached one ; north and 
 south of it the shore is in Champlain clays. 
 
 East of the lake shore the best exposures near Burlington 
 are along the Winooski River. At the Lower Falls, red and gray 
 quartzite in massive ledges in the stream and along the banks lie 
 in a flattish position, dipping gently in a general easterly or 
 jiortheasterly direction. East of Winooski village the gray 
 quartzite is succeeded by limestone of uncertain age. 
 
 FEANKLIN COUNTY. 
 St. Albans Bay. 
 
 (St. Albans and Milton topographic sheets.) 
 
 Some observations along the lake shore south of St. Albans 
 Bay. Some apology seems necessary for the very brief original 
 notes offered for the country north of Burlington. A part of 
 one rainy day was spent along the lake shore near St. Albans 
 Bay south of Melville Landing. Heavy weather prevented much 
 being done on the trip and illness from influenza practically closed 
 field work for the season. 
 
 From Melville Landing southward the shore as followed for 
 three miles towards Camp Rich in Milton is formed of "Utica" 
 slates and shales which form low cliffs and minor headlands. 
 The road hugs the shore for the distance mentioned and advan- 
 tage has evidently been taken of the level topography in laying 
 the road out. Back from the shore at varying distances &re ex- 
 posures of limestone which were not examined except as men- 
 tioned beyond. The slates were inspected casually for fossils 
 but none was found. 
 
 About two miles north of Camp Rich, above a shore clifif of 
 the shale and only a few rods from the shore, were noted light- 
 colored, siliceous phyllites or slates which at once recalled the 
 similar rocks in Whiting and Sudbury. This exposure seemed 
 somewhat isolated and surrounded landward by limestone. 
 Ledges of the latter occur only a few feet away from the slate, 
 but the contact was not seen. The relations were not absolutely 
 conclusive as to whether the limestone or the slate was superior 
 
REPORT OP THE3 VERMONT STATE GEOLOGIST. 247 
 
 in position. The shore road is here a fourth of a mile from the 
 bank. Limestone apparently continues eastward to the road and 
 across it. East of the road a low ridge of gray, "marbly" lime- 
 stone is succeeded by a fairly high escarpment of gray dolomite. 
 From the general relations as noted here and northward, east of 
 the shore road, it was concluded that the phyllite is beneath the 
 limestone and that the former rests on the "Utica." The phyllite 
 is correlated in the writer's mind with similar ones farther south 
 in Addison County and is thought of as, in general, equivalent to 
 the quartzite or "Red Sandrock" which farther south in Milton 
 and Colchester comes to the shore, either resting on the "Utica" 
 or dipping into the lake. The phyllite north of Camp Rich as 
 just described is apparently very limited as a surface formation 
 in the immediate vicinity of the outcrops noted. Northward 
 towards St. Albans Bay, limestone apparently rests on the 
 "Utica," to judge by general field relations ; but both phyllite and 
 limestone are regarded as resting by thrust on the "Utica" forma- 
 tion. 
 
 GRAND ISLE COUNTY. 
 South Hero and Grand Isle. 
 
 (Plattsburg topographic sheet.) 
 
 During the season of 1920 some examination was made of 
 the formations on the island of Grand Isle, often in the company 
 of the State Geologist. The geology of this interesting island 
 has been most recently studied by Professor Perkins, whose ex- 
 cellent and careful descriptions will be found in his Second and 
 Third Reports. In this paper the writer wishes to record only a 
 few observations which bear more particularly upon the deforma- 
 tion of the rocks. 
 
 The surface mantle on the rocks of Grand Isle is largely com- 
 posed of the deposits of an old "lake" bottom. The exposures of 
 the hard rocks, however, are sufficiently numerous inland, even 
 over the lowest portions, to permit an apparently fairly accurate 
 delineation of the boundaries of the different formations ; but 
 the covering is heavy enough to conceal in most places such 
 critical features as contacts over considerable distances. 
 
 In a general way the formations may be divided into the 
 shale formation, which occupies the northern, eastern and south- 
 eastern portions of the island, and the limestone strata which 
 stretch as a wide strip along the western side from its south- 
 western end northward two-thirds the distance across the island 
 from south to north, and which at the north extend towards the 
 east into the central portions. The present apparent surface 
 distribution, in a large way, of the rocks just mentioned, in itself 
 appears to have some structural meaning which apparently could 
 hardly be grasped in its true signification from the study of this 
 
248 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 island alone. Especially confusing would probably be a close 
 age relation of some of the members of the shale-slate formation 
 with some members of the limestone strata and an apparent 
 transition between the two at many places, not only in lithological 
 characters, but in the fossils as well. In addition to these features 
 of general distribution there are some details which will be men- 
 tioned presently. 
 
 The limestone strata include the Beekmantown, as a small 
 patch at the southern end, which is better exposed on Providence 
 Island a mile and a half away, the Chazy, Black River and Tren- 
 ton. In general as seen along the shore and also inland a short 
 way from it the beds of these different terranes have not been 
 greatly deformed internally. An almost continuous section in 
 limestone extends from Phelps' Point at the southwest to Wilcox 
 Cove along shore, and more or less widely interrupted exposures 
 occur to the eastward a short way from the shore along an old 
 "lake" bottom and along the old beach and some ridges that bound 
 it on the east. 
 
 The Chazy rocks are usually impressive in their massive- 
 ness. Some of the beds are several feet thick ; in one case a 
 bed is as much as 20 feet through. These strata are prevailingly 
 quite flat in position along shore, and so far as examined are 
 free of pronounced internal deformation, although they show 
 more evidence of it inland so far as the more limited exposures 
 permit observation. 
 
 The Black River beds are limited. They too are somewhat 
 massive, but less so than the Chazy rocks. They might be con- 
 sidered as somewhat intermediate in this respect between the 
 Chazy and the Trenton. Along shore these beds are also pre- 
 vailingly almost fiat in position. They are very smoothly and 
 symmetrically jointed as a rule. An occasional outcrop of rock 
 with some characters of the Black River, but much crushed and 
 filled with veins of calcite, occurs near the west shore ; but a con- 
 sideration of general relations makes it seem doubtful if such 
 rock is in place. 
 
 By far the larger part of the limestone as mapped for the 
 present surface belongs to what is called Trenton, and which 
 probably is Trenton, but perhaps not all there is on the island 
 that should be included in this terrane. Professor Perkins has 
 been impressed with the Trenton or transitional character of 
 some members of the shale-slate formation and has been at 
 work on the problem of a clearer separation of the Trenton 
 from the so-called "Utica" of the island. From what will be 
 indicated beyond it may appear that structural features among 
 some of these rocks will have to be considered in working out 
 their age and other relations. 
 
 The Trenton rocks that are readily recognized and have been 
 mapped as such have, like the Black River and Chazy, where 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 249 
 
 they occur along shore a nearly horizontal position. A fine sec- 
 tion is exposed from Rockwell Bay northward, in which there 
 appears to be only gentle but variable incHnation of the beds. 
 The exposed portion of the stratum is composed of limestone 
 beds of varying thickness, ranging from 2 through 4 or 6 to 8 or 
 10 inches with intercalated shaly layers. The rocks in their dark 
 gray and somewhat monotonous appearance throughout are in 
 contrast with the dense and more heavily-bedded Black River and 
 the massive and often more distinctly marked Chazy. 
 
 Deformation of the Trenton beds, including visible shearing 
 within them, is found in the shore section and now and then a 
 small fold or buckle appears which sometimes appears to be asso- 
 ciated with a fault displacement. In one case the latter appeared 
 to be a tension fault ; at another place, near Wilcox Cove, there 
 was suggestion of thrusting and therefore of compression. On 
 the whole, however, along shore there is less evidence within the 
 various limestones of the action of compressing forces upon them 
 than farther east. There is some evidence of norrnal faulting 
 across the general strike of the rocks, both within formations and 
 between them, and some of these are apparently marked by shore 
 indentations at the present time, as well as by juxtaposition of 
 rocks of different ages. How far most of these displacements 
 may run inland it is difficult to find out. 
 
 It has been assumed and would probably by many observers 
 be assumed that these various limestone beds and formations 
 have at the present time their original stratigraphic interrelations 
 and primary geological sequence, and that they are probably near 
 the place of their deposition ; that, in other words, they have not 
 been greatly disturbed from the place where they were laid down, 
 though bearing some evidence of deformation. 
 
 The careful systematic examination which would be neces- 
 sary to show it was not made to find out to what extent, if any, 
 the primary interrelations of the rocks of different ages which 
 these limestones represent, may have been changed by the action 
 of thrusts ; but in addition to the insignificant disturbances which 
 have been mentioned, effects distinctly to be attributed to the ac- 
 tion of compression were observed in the limestones at other 
 places on the island. 
 
 Along a ridge about one-half-mile east of the west shore and 
 east of Sawyer's Bay, and eastward from this ridge in more scat- 
 tered exposures, beds of Trenton limestone give satisfactory evi- 
 dence of internal deformation, not only in their sheared structure, 
 but in the compression, distortion, fragmentation, or obliteration 
 of their fossils. Minor buckling may be seen and an easterly dip 
 due to shearing can be readily distinguished from that of strati- 
 fication. Some of the fragmentation of fossils may have oc- 
 curred during or prior to deposition ; but in the field it is possible 
 within short distances across the strike, and sometimes apparently 
 
250 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 along the strike, to pass from one ledge with excellently pre- 
 served fossils, such as Bellerophon, to other ledges in which, at 
 the distance of only a few hundred yards at the most, alteration 
 will vary from compression, as shown by a flattened Bellerophon, 
 nearly to obliteration. Account is taken in this statement of dif- 
 ferences in fossil contents due to natural variation in passing 
 from bed to bed across the strike. 
 
 Observations seemed to indicate that in the Trenton beds, 
 because of their more thinly-bedded character, deformation due 
 to buckling and crushing, and probably shearing, found expres- 
 sion more readily than in the more massive Black River and 
 Chazy. It hardly needs more than a casual inspection of the 
 limestone rocks as one goes east from the lake towards their 
 eastern edge to discern the evidence of the greater disturbance 
 and deformation which they show over those along the lake at 
 the west. Along their eastern margin some of them are clearly 
 crushed and carry many calcite veins. 
 
 The limestone formations whose deformational features have 
 just been discussed are those which may in the field be separated 
 clearly from those which have some similar lithologic and struc- 
 tural characters, but which are in more intimate major structural 
 association with the shale-slate formation. Along the lake shore at 
 places between Rockwell Bay and Wilcox Cove beds of not ap- 
 preciably deformed rocks of probable Trenton age pass into 
 other apparent Trenton rocks which are rather strongly sheared, 
 and between these and other rocks which have been called "Utica"^ 
 there is sometimes difficulty in drawing any decided lithological 
 distinction. 
 
 The so-called "Utica" slates and included limestones, perhaps 
 together with some Trenton rocks, may apparently as a forma- 
 tion be differentiated somewhat sharply from the limestone strata 
 which border the lake, as just described, on the basis of the de- 
 formation which it has suffered. In general, these rocks present 
 much the same aspect with respect to deformation wherever ob- 
 served. Under severe compression the beds of the shale-slate 
 formation have not only been folded and tilted, but apparently 
 because of pronounced difference in behavior of beds of different 
 thickness and strength under stress of pressure and probably also 
 load, there has been frequent rupture with much crushing and 
 frequent movement of one part of the mass over another part, 
 producing great confusion. An exposure of great interest as 
 showing this behavior of the slate formation is to be seen in the 
 cliffs south of the Grand Isle end of Sand Bar Bridge, and which 
 is pictured in the Third Report. In lithological and deforma- 
 tional aspects the members of this formation are like those along 
 the shore of the mainland south of St. Albans Bay and at Burling- 
 ton and in essentials like those farther south in Addison County. 
 The lithological differences and resemblances among the dif- 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 251 
 
 ferent slates and shales through the distances separating the 
 localities just mentioned are of the same order and character as 
 those which appear in comparing the slaies of western Vermont 
 with those of some parts of the Hudson valley. 
 
 Interpretation. In the course of the writer's examination 
 of Grand Isle the question arose very early in his mind as to what 
 is the present structural relation which the limestones have to the 
 slates. Search did not show any of the limestones resting on the 
 slates. So far as the writer's observations have gone, and also 
 the descriptions of others, it appears that the structure of the 
 island as a whole is best explained by the relations shown at the 
 east on the mainland and at other places in western Vermont 
 which have been described in this paper. 
 
 In the first place, one notes the relatively great deformation 
 of the shale-slate formation already referred to and the contrast 
 which it bears to the limestone strata viewed as a mass. The 
 contrast recalls the relations on the mainland where a dolomite- 
 quartzite showing little visible internal deformation rests on 
 greatly crumpled slates and shales in all essential respects like 
 those of Grand Isle only a few miles to the west. The slates of 
 the mainland having the inferior position to older rocks that has 
 been noted at so many places, but in this connection, especially 
 along the lake shore from St. Albans Bay to Burlington, undoubt- 
 edly once had connection across what is now the lake surface 
 between the mainland and Grand Isle with the slates of the latter. 
 Did the Cambrian quartzite ride over the slates, or rather did 
 the thrust plane along which it was driven cut through the slate 
 formation above the limestones now exposed at the surface on 
 Grand Isle, or did it cut through it along what is the plane of 
 contact of these limestones on the slates? In other words, do 
 the limestones of Grand Isle structurally lie below the "Utica" 
 of the island or above it? If above it, they he unconformably 
 along a thrust plane and are not in their original position. The 
 considerations ofifered all suppose the slates to be younger than 
 the limestones. On such a supposition as overthrust there prob- 
 ably will not be in most cases, of course, actual transition from 
 undeformed Trenton limestone into deformed "Utica" slate or 
 limestone. There might, however, be transition from sheared 
 Trenton limestone into continuous, unsheared limestone, but all 
 within the mass that had been moved. The idea of overthrust 
 does not preclude the inclusion of Trenton rocks in the "Utica," 
 but such rocks would presumably have to be thought of as having 
 once been separated from the undeformed Trenton rocks by a 
 greater or less interval. 
 
 In connection with the idea of overthrust the question of the 
 relations of the limestone strata of Grand Isle to the quartzite 
 on the mainland calls for consideration. A better knowledge 
 than the writer has of what lies on the quartzite east of the lake 
 
252 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 might help in answering this question. Published accounts are 
 not conclusive. Conditions farther south that have been exam- 
 ined may give some suggestions. 
 
 Did the quartzite which now lies on the slate formation along 
 the mainland at Malletts Bay and Burlington once extend over 
 both the slates and the limestones of Grand Isle? Or did its ex- 
 tension westward by thrust stop short of Grand Isle? Its ab- 
 sence west of the mainland is not conclusive, but is suggestive. 
 It would seem that if this durable formation once extended any 
 distance west of the eastern shore of the lake some remnant of it 
 would be preserved. In this connection may be recalled the ap- 
 parent contact of limestone on the slates around St. Albans Bay 
 with apparently no quartzite or phyllite intervening, and other 
 places southward where either some phyllite, or slate, or quartzite, 
 lies between limestone and the "Utica." Again may be noticed 
 the eastward extension of the lake surface to form St. Albans 
 Bay where apparently only limestone rests on the slate formation. 
 It would appear, even from the few observations made by the 
 writer in northern Vermont, that either limestone, or quartzite, 
 or phyllite may rest on the "Utica," presumably by thrust, along 
 the mainland. In view of this probability it is not difficult to 
 imagine the limestones of Grand Isle as lying on the slate-shale 
 formation by thrust. 
 
 In the areas farther south that have been described, it will be 
 recalled that along the lake region it is some member of the lime- 
 stone that lies on the "Utica" and that at only one or two places 
 of obscure relations is there suggestion of visible contact of any 
 member of the quartzite-phyllite formation on terrigenous rocks 
 of younger age. 
 
 The correlation and unification of the phenomena of these 
 various localities will have to be undertaken in the closing sum- 
 mary. 
 
 At places on Grand Isle the Chazy and apparently the Black 
 River are shown to have such relations to the slates, when mapped 
 and when inspected in the field, that it is difficult to draw any 
 other conclusion than that the two are in contact. At other places 
 it is the Trenton that is or appears to be in contact with the 
 slates. Judging again by conditions as shown farther south, 
 some of the relations of limestone to slate on Grand Isle may be 
 the results of displacements due to normal faulting; but all of 
 them apparently may hardly be explained on such a basis. There 
 is nothing to suggest that the limestones have been completely 
 inverted ; they retain at least their depositional attitude. When 
 one finds a mass of Chazy limestone surrounded on three sides 
 by the slate formation and remembers that the latter is unques- 
 tionably the younger rock, two possible explanations suggest them- 
 selves ; either younger rock has simply been dropped by normal 
 faulting so as to surround the older rock, partly by slates perhaps 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 253 
 
 and partly by younger Hmestone, as is the apparent case north of 
 Keeler Bay ; or the older rock has been thrust on the younger 
 strata. The first hypothesis is entirely adequate to explain the 
 present relations, if perhaps we recognize the possibility of dif- 
 ferential faulting, for there is apparently nothing in the interrela- 
 tions of the different limestone strata which opposes such a view. 
 On either view the limestones are presumably present at depth, 
 but in one case the limestones are different at depth from those 
 at the surface with respect to their original relations to the slates 
 of the island and in the other case the rocks at the present surface 
 and at depth have presumably simply slipped by one another along 
 planes of normal faulting. The latter view would of course have 
 to assume some disturbance as the result of compression in order 
 to account for the features shown by the various rocks, but might 
 in the minds of some, not appear inconsistent with the contrasts 
 exhibited by the two principal formations of the island with 
 respect to their deformation. Such a view, however, does not 
 seem to take sufficiently into account the obvious thrust deforma- 
 tions of the region of which the island is a part. Whether we 
 assume or not that the big mass of Trenton rocks in the western 
 part of the island is underlain by Chazy beds, the explanation of 
 relations seems to be possible on the basis of thrusting. Prob- 
 ably we should have to take into account that the map to show 
 the distribution of the formations is not absolutely accurate, 
 although as much so as conditions at the present time allow in 
 view of the surface covering and the non-committal or doubtful 
 character of isolated and small outcrops. Where the present 
 conditions suggest Trenton in contact with slates may not be 
 really the case ; but even if it should be normal faulting subse- 
 quent to other deformation might readily account for such con- 
 ditions, although normal faulting is perhaps not necessary to 
 explain them. 
 
 If on the mainland it is quartzite-dolomite that rests by 
 thrust on the slate formation there appear at least two possible 
 ways to account for the relations on Grand Isle and of Grand 
 Isle to the mainland by thrusting: 
 
 1. Prior to the major thrust, as it may perhaps be called, 
 that carried the quartzite over on the "Utica," as now shown 
 along the mainland, there was reverse faulting and minor thrust- 
 ing by which the limestones lying east of what is now Grand Isle 
 were broken, perhaps because of the massive character of the 
 Beekmantown-Chazy strata, and thrust up and over the "Utica." 
 In this deformation the slates were tilted and overturned. As 
 the heavy limestone strata rode over them they were further 
 jammed beneath the load and by the drag and often broken and 
 mashed. The limestones themselves were broken and moved 
 more or less against each other. At this time were formed the 
 deformational features which they show. Subsequently there 
 
254 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 occurred some normal faulting, perhaps differential in the same 
 episode, and as a deformation perhaps repeated. Before the 
 normal fault displacements presumably thrusting had ceased. 
 Before it had ceased perhaps the stresses which had been only 
 partially eased by the reverse faulting and minor thrusting just 
 referred to produced a great thrust that carried the basal Cam- 
 brian up through the "Utica" and drove the former westward 
 over the younger rocks, and over those which now form Grand 
 Isle. But it has already been remarked that if the quartzite once 
 extended very much farther west of its present edge along the 
 shore of the mainland it seems somewhat remarkable that some 
 remnant of its westward extension has not been preserved, unless 
 the mainland is a downfaulted block with reference to the lake 
 region which does not seem probable. According to this postu- 
 late, however, it is not necessary to assume that the quartzite once 
 covered what is now Grand Isle. 
 
 2. The limestone strata of Grand Isle once belonged to a 
 region that lay eastward from Grand Isle and the "Utica" slate 
 formation on it, one may not say how far. They may have had 
 a relation to the quartzite-phyllite formation entirely similar to 
 that now shown by the limestones which have been described as 
 lying on the phyllite formation at the south in Benson, Orwell, 
 Sudbury and other parts of Addison County. At the time this 
 region was undergoing the compression that produced the various 
 thrusts which may now be seen, there was at first ease of stress 
 by shearing and minor faulting and thrusting. Then came a 
 great thrust, widely extended, cieep and powerful, and strongly 
 resisted by the combined masses of the quartzite-phyllite forma- 
 tion and the heavy strata of limestone which lay on the former. 
 The great thrust cut through the various rocks along an irregular 
 plane that often intersected the quartzite, but often also passed 
 from that formation into the overlying limestone strata and cut 
 irregularly through them. As this rupture developed, the mass 
 above rode over the mass below. Sometimes the quartzite and 
 sometimes the limestone was brought to rest upon the slate. 
 When the thrust left the quartzite-phyllite formation and cut 
 into the limestone the former was left at depth west of the pre- 
 sumable line of emergence of the thrust at its surface. Not only 
 would such a thrust plane as has been postulated be very irre- 
 gular as a plane, but the line at which it cut the surface originally 
 and its trace after erosion would probably be very irregular and 
 sinuous. It is even conceivable that such a plane would have cut 
 through a great thickness of Beekmantown, Chazy and Trenton 
 beds in such a way as to carry Beekmantown here. Chazy there 
 and Trenton at still other places on the "Utica." After, and 
 perhaps a long time after, such thrusting as has just been sup- 
 posed had ceased, there would have occurred normal faulting. 
 The laterally disturbed masses were now chopped more or less 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 255 
 
 vertically and displaced. Some of the relations on the island 
 now existing or apparent, might thus be explained. By such an 
 hypothesis of thrusting as just developed, the quartzite probably 
 never lay over what is now Grand Isle, although it may once 
 have overlain a part of what is now lake between the islands 
 
 Figure 21. A generalized section to show the writer's interpretation of the 
 present relations of formations along the eastern shore of Lake Cham- 
 plain north of Burlington. The relations shown on the mainland are 
 drawn from studies near St. Albans Bay. A, gray dolomite ; B, gray, 
 "marbly" limestone ; C, light-colored, slaty phyllite (Lower Cambrian) ; 
 D, limestone capping an island and resting by thrust on folded "Utica" 
 slate, E. 1-2 thrust plane. 
 
 and the mainland. At St. Albans Bay apparently we have the 
 thrust plane cutting through the limestone except at certain 
 places where a bit of the phyllite was caught beneath it ; but 
 farther south at Malletts Bay and Burlington, the plane passed 
 well down in quartzite and opposite here the quartzite conceiv- 
 ably once extended farther westward. The region now repre- 
 sented by the lake has been excavated in "Utica" shale and slate 
 after the removal of overthrust rock that was partly quartzite 
 and partly limestone. The writer has not had opportunity to 
 inspect the mainland on the New York side in a critical way ; but 
 certain relations seen farther south, near Benson Landing, sug- 
 gest that part of an overthrust mass of Ordovician limestone 
 now rests against the Adirondack mass north of Putnam Station, 
 and one wonders how far overthrust may have affected the New 
 York side. According to this view of the relations at Grand Isle 
 the limestones there could hardly have been exposed to view by 
 erosion of overlying slate; but presumably limestones similar 
 to those at the surface exist at depth below Grand Isle. 
 
 That the various considerations just offered are more than 
 speculations is proved by overthrust farther south. Practically 
 on the meridian of Grand Isle and 60 miles south of it along the 
 east shore of Lake Champlain in Orwell, as has been described, we 
 find the "Utica" formation and in some cases, apparently, Black 
 River and Trenton, rocks, overridden by members of the Beek- 
 mantown formation and perhaps older beds which also have been 
 cut through in such a way as now to carry one horizon and now 
 another over on the slates. The erosion of the overthrust lime- 
 stones at places in western Orwell has exposed the "Utica" slates 
 which are sometimes inundated and sometimes not. Here again 
 the quartzite-phyllite formation lies to the east and over it the 
 
256 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 limestones of western Orwell seem to pass eastward, as has been 
 described. Similar relations are shown in Shoreham, but in this 
 township, and in Whiting on the east, the limestones have been 
 better preserved. The quartzite-phyllite formation emerges at 
 the present surface only as a low ridge through Whiting. At the 
 west the "Potsdam" of Shoreham village fronts a wide lowland 
 partly swamp and partly hills of slate. Here we have in process 
 of formation the kind of hard rock surface and topography which 
 the unglaciated bottom of the lake would present, and it becomes 
 apparent that the lowest portion of the Champlain lowland is the 
 surface of the rock bottom of the greatest depth of the lake. 
 
 * The various detached masses of limestone found now at 
 various places in the region of the lake seem to be not simple 
 erosion inliers of rock substantially resting where it was formed, 
 but rather thrust-erosion inliers of rocks now more or less re- 
 moved from the places of their deposition. Whether it is likely 
 that these displaced rocks have been moved more than once for 
 any distance from their original sites may be discussed in the 
 final summary. 
 
 Mention has been made of probable normal faults cutting 
 across the strike of the rocks of Grand Isle. These undoubtedly 
 pass down into the slate formation. Numerous dikes of igneous 
 rocks cut through the slates and limestones along the shore and 
 inland. These dikes usually show no evidence of great disturb- 
 ance after their formation. They were formed after the lime- 
 stones came to have their present relations to the slates and 
 probably after or during the subsequent period of normal fault- 
 ing. In the clifif south of the Grand Isle end of Sand Bar Bridge 
 there is a dike that gives some suggestion that it has been dis- 
 turbed, but not greatly. Perhaps it would be possible to explain 
 its features as due to the character of the original fissure; in the 
 limestones, while there is some offsetting here and there, it is 
 evidently due to the dike rocks following a previous small lateral 
 displacement. Igneous intrusion in the form of dikes is wide- 
 spread on the island, and on the mainland even southward to and 
 in the Taconic region. 
 
 GENERAL SUMMARY. 
 
 The studies offered in the preceding pages were begun with 
 the definite idea of trying to get some light on the plan of struc- 
 ture of the rocks of western Vermont. As details accumulated 
 it became apparent that many different areas presented similar 
 phenomena involving similar rocks and the search began for 
 some principle that would unify the various features of the field 
 relations and explain the apparent anomalies. 
 
 Suggestions have been offered in the preceding discussion 
 at several places as to interpretations that might be put upon 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 257 
 
 field relations ; but it has been the writer's experience that hardly 
 a single area sufficed to explain completely its own structural 
 features. At several places also certain questions which the 
 field relations raised have been formulated and the statement 
 made that answers to them might later be attempted. 
 
 The preceding descriptions have shown the confusion that 
 prevails in the field, but at the same time have tried to make it 
 plain that when the surfaces of different areas are carefully com- 
 pared there is at many places over a wide region much apparent 
 uniformity in the relation which certain rocks bear to each other 
 when such differences as metamorphism and present condition of 
 erosion are taken into account. Careful examination also brings 
 out the existence of certain kinds of deformation in the rocks of 
 the region which having once been seen are readily recognized 
 at many places and soon impress one as being characteristic. 
 The resemblances that appear from place to place grow upon 
 one and the differences stand out less prominently until the time 
 comes when it seems possible to discern some order in the midst 
 of the confusion. 
 
 The first working hypothesis which suggests itself is that the 
 key to the present relations is that of secondary deformation of 
 the rocks. They have been profoundly disturbed. Underneath 
 their present static relations and immobility it seems possible in 
 imagination to see them once more in action. While the changes 
 which have been wrought throughout the long time that has 
 doubtless elapsed since the rocks underwent their major deforma- 
 tions have greatly dimmed the complete picture, and the light 
 from scattered localities gives only an uncertain illumination of 
 some features, encouragement is experienced in the fact that the 
 main outlines come out with increasing sharpness as new areas 
 are examined. 
 
 In presenting this summary and in inventing hypotheses 
 by which to try and explain the various structural features and 
 the history of the region as a whole, there are several apparently 
 important field relations that should be kept in mind more par- 
 ticularly to bring out unity of structure. With these it would 
 seem the minor differences must be reconciled. 
 
 1. The great north and south extent along the western edge 
 of the Green Mountain plateau and eastern portion of the Ver- 
 mont valley in Vermont, from Pownal to Middlebury and beyond, 
 of a similar series of rocks comprising conformable, thick-bedded 
 and thin-bedded quartzites and interbedded schists at the base, 
 followed by dolomites and interbedded dolomites and quartzites. 
 
 2. The conformability, as shown at Bennington, of the dif- 
 ferent rocks named in 1 in the order of (a) quartzite-schist 
 formation; (b) dolomite or dolomitic limestone; (c) interbedded 
 dolomites and quartzites. 
 
258 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 3. The occurrence of this series at the present time chiefly 
 in the areas mentioned in (1) and the predominance of the upper 
 members in the valley and lowland, where they appear sometimes 
 in conformable relation with the quartzite member of the series 
 and where sometimes the interbedded rocks rest directly on 
 marble, or directly on quartzite, and apparently at some places 
 on an interbedded quartzite-schist formation. The frequent oc- 
 currence of a dolomite resting on the marble or involved with 
 it, which dolomite differs from other dolomite with which it is in 
 frequent proximate field association and seems to belong to the 
 same general formation to which the quartzite and interbedded 
 dolomites and quartzites belong. 
 
 4. The present absence of this series just described, in its 
 completeness, west of the Vermont valley. 
 
 5. The wide distribution west of the Vermont valley, in- 
 cluding parts at least of the main Taconic range, of a terrigenous 
 formation made up of black phyllites or schists, lighter-colored, 
 fissile or slaty phyllites, and more or less massive quartzite which 
 are rather plainly interstratified, as shown in surface sections 
 at numerous places from the latitude of Pownal to that of Sud- 
 bury and which can be discerned in fault scarps at places west of 
 the range in the Taconic hills. 
 
 6. The striking similarity among black phyllites and other 
 members of this terrigenous formation at most places over the 
 region of its present distribution, with certain variations appear- 
 ing on account of greater metamorphism in some areas. The 
 close geographical and geological association which this forma- 
 tion has with the quartzite-dolomite series described above and 
 the similar north and south extension of the two in this associa- 
 tion at the east along the region of the Vermont valley. 
 
 7. The practical restriction of the outcrops of the marble 
 formation to the region of the Vermont valley, or to the incisions 
 along the eastern border of the Taconic range, or to the eastern 
 part of the Champlain lowland ; and the exposure by erosion of 
 patches, belts, or other outcrops of the marble from beneath the 
 calcareous members of the quartzite-dolomite series described 
 above (3), and apparently also from beneath masses of terrige- 
 nous rocks having the interbedded structure and composition 
 mentioned above (5). 
 
 8. The probable Lower Cambrian age of the quartzite- 
 dolomite series on the bases of fossils found in the quartzite and ' 
 at some places in the calcareous members, in connection with the 
 conformability shown by the members of the series. 
 
 9. The clearly disturbed condition through compression of 
 the Lower Cambrian series along the western margin of the 
 plateau, involving displacements of one part in relation to another 
 part of the series and the displacement of the whole series or 
 parts of it by overlap on other rocks ; the former to be observed 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 259 
 
 all along the western edge of the plateau and the latter to be 
 noted at many places, at some more clearly than at others. 
 
 10. The practical impossibility of separating on any basis, 
 except somewhat different mineralogical composition clearly due 
 to metamorphic changes, rocks found on the edge of the plateau 
 and others found in the Taconic range and its physiographic out- 
 liers and also in the hills of southwestern Brandon, and of Sud- 
 bury, Orwell, Benson, Hubbardton, Pownal, Bennington, Shafts- 
 bury, Pawlet, Rupert, and other townships, some of which have 
 been mapped as "Berkshire Schist" and some as "Cambrian." 
 The wide distribution at the present erosion surface of all the 
 characteristic members of this terrigenous formation from Pownal 
 to Sudbury and possibly also to the northern part of the State, 
 although the writer's examination of the region along the lake 
 north of Burlington gave only the quartzite and the lighter- 
 colored phyllites, and between Whiting and Burlington only the 
 quartzite ("Red Sandrock"). 
 
 11. The apparent wide distribution, with interruptions over 
 large areas clearly due in part to erosion and probably in part 
 to previous disturbances which affected the ways in which erosion 
 could work, of Ordovician limestones and their metamorphosed 
 derivatives on the terrigenous formation which has been described, 
 found in Whiting, Sudbury, Brandon, Orwell, Benson, West 
 Haven, Hubbardton, Danby, Tinmouth, Rupert, Shaftsbury, and 
 also at the north near St. Albans. The occurrence of similar 
 limestones on the quartzite, or "Red Sandrock," of Snake and 
 Buck mountains, and in their vicinity. The greater continuity at 
 the present surface of the Ordovician calcareous rocks in Shore- 
 ham, Whiting, northern Sudbury and Orwell, and the much 
 more fragmentary condition of the same rocks at the south in 
 the Taconic hills. 
 
 13. The impossibility of assigning age to the terrigenous 
 rock on the basis of the limestone associated with it in all the 
 places examined. 
 
 14. The overlap in some places of quartzite of Lower Cam- 
 brian age (at and north of Burlington) and at other places of 
 Ordovician limestones, like those which rest on the terrigenous 
 rocks, including the quartzite, on the slates and shales of the 
 so-called "Utica" formation, to be seen at various places along or 
 near the eastern shore of Lake Champlain. 
 
 15. Evidence of repeated normal and reverse faulting in the 
 quartzite-dolomite series, the latter sometimes causing the quartz- 
 ite, sometimes phyllite to rest against the dolomite or against the 
 interbedded members, various aspects of which faulting may be 
 seen at different places from Bennington to Salisbury, along the 
 eastern portion of the Vermont valley. 
 
 16. Evidence of repeated reverse faulting and of normal 
 faulting in the overlapping Ordovician strata near the lake, to 
 be seen in Shoreham and Orwell townships and at other places. 
 
260 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 17. Evidence of disturbance by normal faulting, and prob- 
 ably also by reverse faulting, of the quartzite-phyllite formation 
 among the Taconic hills. 
 
 18. Evidence of internal deformation by strong shearing 
 of the calcareous rocks lying on the the terrigenous rocks which 
 increases somewhat gradually as one goes eastward from the lake 
 region. 
 
 19. The highly-metamorphosed character of the marble at 
 the east. 
 
 20. The more schistose condition of the rocks of the main 
 Taconic range. 
 
 21. The relatively unaltered character in most cases of the 
 rocks near the lake. 
 
 22. Absence of recognizable Beekmantown east of the im- 
 mediate vicinity of the lake. 
 
 One of the first difficulties that was encountered in applying 
 any hypothesis to explain present structure as a result of defor- 
 mation was that of arriving at a feeling of certainty as to the 
 age of the terrigenous formation with which the fossiliferous 
 Chazy-Trenton limestones are so frequently associated and in' 
 such apparent relations as to leave no doubt of the superjacent 
 position of the limestones with respect to the terrigenous rocks. 
 Some of these terrigenous rocks have been called Ordovician and 
 and others Cambrian in areas in which the writer was unable to 
 see a valid distinction. The writer has satisfied himself on the 
 point that the age of the terrigenous rock cannot always be told 
 from the limestone associated with it — it may be in some cases 
 apparently (Cambrian) ; but if this is the fact it leaves the age 
 of quartzite-phyllite formation as a whole still a question. Espe- 
 cially should it be noted that the presence of Ordovician hme- 
 stone with phyllite is not indicative of a similar age for the latter 
 in any cases which the writer has examined. The limestone has 
 the character of an overlapping formation on the terrigenous 
 mass. The next difficulty in applying an hypothesis is to get the 
 limestone on the terrigenous formation. How did it come there ? 
 In trying to answer this question another difficulty appears. The 
 writer was unable to find any visible contacts of limestone on 
 the quartzite or phyllite. In southern Shaftsbury the two are 
 very near at the present surface and the limestone here is greatly 
 mashed and broken, affording a suggestion that it was thrust on 
 the phyllite ; but the field relation is not conclusive. In other 
 words, there is nothing to show that the limestone might not have 
 been deposited on the phyllite, or at least on contiguous phyllite, 
 and have been slightly disturbed later, or that it must have come 
 to its present position from some more or less remote place. In 
 other places the two rocks are near together, but the question of 
 whether the apparent overlap is one of deposition or one of thrust 
 apparently may not be positively settled by the contact relations. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 261 
 
 although it has not proved possible to find any rock that might 
 be thought of as representing the shore accumulation along the 
 transgressing strand line of a sea advancing upon terrigenous 
 rock. If the ovferlap i.s one of depositon it would seem that the 
 limestone was probably laid down upon the terrigenous formation 
 without definite and continuous basal overlapping member. 
 
 It would probably be argued that the fact of a subjacent 
 position for the terrigenous formation with respect to Ordovician 
 litnestones is not conclusive evidence of its greater age, in a 
 region in which thrust deformation is regarded as the key to the 
 structure. This probably must be admitted. What is the prob- 
 ability as one views the region as a whole? 
 
 The Brandon-Sudbury-Orwell region is one of great interest 
 in connection with the question of the relation of quartzite-phyl- 
 lite formation to the Ordovician limestones. As has been de- 
 scribed, the terrigenous rocks pass beneath the limestones north- 
 ward in Orwell, and also in Sudbury, except for a narrow ridge 
 that passes northward through Whiting to Weybridge. Little 
 doubt remains that the extensive areas of limestone north of 
 Orwell and Sudbury rest on the northward continuation beneath 
 them of the terrigenous rocks of the hills at the south. The latter 
 rocks also, except for normal faulting, pass beneath the marbles 
 and their associated rocks in Brandon and appear again east of 
 Brandon village. At this place the intimate association which 
 they have with Lower Cambrian rocks makes the presumption 
 of a similar age very strong. 
 
 The quartzite of Snake and Buck mountains apparently has 
 the same relation to the Ordovician limestones that the phyllites 
 of Whiting have and the quartzite joins northeastward with lin- 
 important interruptions at the surface through Monkton with the 
 rocks of the plateau, and southward after a more extensive sur- 
 face interruption under the limestones with the quartzite-phyllite 
 hills of Orwell. Through the quartzite of Charlotte and Shel- 
 burne and northward, the southern quartzite joins with that north 
 of Burlington which carries Lower Cambrian fossils. Southward 
 the hills of Orwell join with similar rocks that carry Lower 
 Cambrian fossils. It would certainly seem that from surface con- 
 tinuity, or what amounts practically to it, since the fact of similar 
 limestone resting on the different terrigenous rocks is apparent, 
 the probability of the Lower Cambrian age of the quartzite- 
 phyllite formation underlying the limestones of Benson, Orwell, 
 Sudbury, Brandon, Whiting, and probably even Bennington and 
 Shaftsbury, is strongly indicated, as well as the equivalence of 
 the quartzite ("Red Sandrock") farther north to the rocks of 
 the Taconic hills. The case would be stronger if depositional over- 
 lap of the limestones could be proved or shown to be very prob- 
 able. It is hard to prove the point. In Orwell and Benson the 
 limestones have unquestionably been greatly disturbed and per- 
 
262 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 haps moved some distance from the east, if the contrast which 
 they exhibit with the rocks of the lake region that have been over- 
 ridden means anything in this connection ; but they do not give 
 an impression that is at all conclusive of having been transported 
 from a distance and superposed on the terrigenous rocks on which 
 they lie. If the point of the former widespread covering of the 
 terrigenous rocks by the limestones be accepted as probable, then 
 there is involved a long distance from east to west for these 
 limestones to have been moved bodily across it over the rocks on 
 which they now lie, although it is quite conceivable that they could 
 have been disturbed from their original positions and probably 
 were. It would appear more probable from the appearance 
 which they now present that if they had a movement of transla- 
 tion from the east it was one in which the mass beneath par- 
 ticipated ; that, in other words, they really "rode" along the thrust 
 plane on a mass of terrigenous rock that transported them. From 
 all the viewpoints that the writer could utilize after a careful field 
 study, it appears to him quite as if not more probable that 
 the limestones were deposited on the terrigenous rocks. All the 
 field relations suggest such a history rather than that they have 
 come to be distributed on the quartzite-phyllite formation by 
 thrust. On this view then the latter formation is older than the 
 limestones and if it may be made to appear extremely probable 
 that there is unity in the terrigenous formation over all the areas 
 where it shows essentially the same characters, except perhaps 
 for difference in metamorphism, then the principle of thrust as 
 the key to structure in the presence of what may be actually seen 
 of overlap in the region seems to apply. Some applications of it 
 have already been made without, however, stating much about 
 the probable relative age of the terrigenous rocks, except that 
 they had suggestive association with the Lower Cambrian rocks 
 at the east and that they seemed unquestionably to be normally 
 beneath the limestones, including the marble. 
 
 In connection with the discussion or argument just given it 
 should be remembered that on previous pages it has been con- 
 tended that there is nothing which the writer has been able to 
 see in the terrigenous rocks of the Orwell-Sudbury hills that 
 supports the idea that two terranes are there represented. The 
 rocks seem to compose a formational unit. The question is, What 
 is the age of the unit? Whether one regards it as Cambrian or 
 as Ordovician, the problem remains of accounting for the superior 
 position of the limestones. Accordingly, the field relations were 
 considered from the point of view of any of the terrigenous rocks 
 being of Ordovician age to see if the principle of thrust which 
 has to be recognized could be applied on that basis. 
 
 At this point it seems advisable to call attention again to one 
 other relation which, in the writer's opinion, argues against the 
 terrigenous rocks under discussion being younger than the lime- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 263 
 
 stones, including the marbles. Over the extensive limestone areas 
 north of Brandon, Sudbury and Orwell we do not find any schist 
 above the limestone. The strongest argument for the younger 
 age of the schist appears to be its superior position at places 
 farther south. This relation has already been discussed. 
 
 The idea that any of the terrigenous rocks under discussion 
 are of Ordovician age assumes that the limestones are in general 
 older than such terrigenous rocks and that the latter represent 
 changed conditions of deposition in a sea which first laid down the 
 limestones on an older base, conformably or unconformably. How 
 could the conditions have permitted change from limestone to 
 sand and mud rocks so that now in what is the Taconic range the 
 limestones could have a covering of younger schist and so that 
 conditions elsewhere in the vicinity, such as north of the range, 
 could be as they now are? It is still conceivable, if Ordovician 
 limestones were succeeded and covered by terrigenous deposits, 
 that during a period of compression and thrust, Cambrian rocks 
 could have been brought to lie on the Ordovician schists, while 
 the Cambrian rocks passed under the limestone at depth. 
 
 If the schist capping Mt. Anthony in Bennington and Dorset 
 Mountain and the ridge in between be regarded as of Ordovician 
 age, passing by resemblances which much of this schist shows, 
 except for metamorphism to rocks that have been shown as 
 Cambrian on maps which represent the schist as Ordovician, 
 many of the field relations are apparently not impossible of ex- 
 planation while allowing the presence of deformation of the re- 
 gion by thrusts. 
 
 One may first imagine an eastward transgression of an Or- 
 dovician sea probably over an eroded Cambrian floor with depo- 
 sition of limestone. If after the deposition of a certain amount 
 of limestone an elevation should have occurred landward, it is 
 possible to imagine that terrigenous deposits would have been 
 carried westward out over the limestone which had been over- 
 lapping the older land. Deposition of limestone would have been 
 halted landward but might have continued at the west and at other 
 places, so to speak, while the muds and sands under the new con- 
 ditions were making at places at the east. It is of course pos- 
 sible to imagine that these terrigenous rocks were restricted in 
 their distribution and were not laid down everywhere along the 
 changing strand. While some effort is required to imagine dif- 
 ferent conditions of deposition in such close proximity as to give 
 originally the same abrupt passage from schist to limestone that 
 is now to be seen at the northern end of the Taconic range, it is 
 not inconceivable. In some way, according to the terms so far 
 given of this hypothesis, the absence of the schists over the mar- 
 bles and limestones at the north must be explained, it being 
 assumed that the limestones at the north and those underlying the 
 schist at the south are essentially the same and that both rest on 
 
284 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 a similar base. We may further imagine that the westward 
 distribution by seaward overlap of muds and sands was re- 
 stricted, perhaps in some places more than others, in its extent 
 and that at the west these deposits graded laterally into more 
 limy muds which graded downward into Trenton and upward 
 into the so-called "Utica." We may imagine that at certain 
 places the deposition of limestone continued practically during 
 the whole time that the schists were making at other places, or 
 that at places the limestones were succeeded by other deposits 
 which were of such character that they could be easily eroded and 
 therefore do not now appear above the limestone, as north of the 
 Taconic range for instance. 
 
 The hypothesis just considered is in reality the theoretical 
 extension of another involving other field relations and considera- 
 tions, more especially the occurrence of essentially equivalent 
 limestone strata lying on a terrigenous mass, composed every- 
 where of parts indistinguishable in one place from those of an- 
 other, and which seems to be a formational unit, and which 
 occurrence, as discussed above, seems to be due to the deposition 
 during the Ordovician period, and perhaps the latter part of the 
 Cambrian period, of the limestones of those periods on the mass 
 of terrigenous material which now underlies the limestones. The 
 field relations indicate unconformity of contact although actual 
 contact was not found. 
 
 If now we take such evidence as we have of the age of the 
 terrigenous substratum, some of which was given above, and re- 
 gard it as of probable Cambrian age and probably largely Lower 
 Cambrian, from what we know of the geology of surrounding 
 regions as well as that of western Vermont itself, we may formu- 
 late more definitely another hypothesis to explain certain primary 
 relations which preceded the disturbance of the region by great 
 thrusts. 
 
 We may imagine the Paleozoic history of the region to have 
 begun with the deposition of extensive masses of terrigenous 
 materials marked by a thick sandstone at the base overlapping 
 from the west on an older land north and south all along through 
 what is now western Vermont and certainly also beyond its con- 
 fines. As the sea deepened offshore, muds mingled with the 
 sands until a great thickness was accumulated. Oscillations of 
 level or other conditions, perhaps a combination, finally produced 
 a mass of interstratified mud and sand. We may further imagine 
 that there was lateral variation in these terrigenous deposits. 
 Possibly where rivers flowed into the sea the sands were carried 
 farther offshore and formed deltas between deposits of finer 
 materials extending in either direction, north and south. On 
 these deltas the ebb tides and periodic diminution of river floods 
 exposed the sands to the weather and the oxidizing agencies pro- 
 duced the red color now marked by certain members of these 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 265 
 
 rocks on which the Hmestones now seem to lie. Finally, condi- 
 tions would have permitted the deposition of the dolomitic lime- 
 stones and interbedded dolomites and quartzites so widely present 
 north and south in association with the quartzite-schist series. 
 The hypothesis as thus far developed does not assume that the 
 present geographical relations between the rocks of the Taconic 
 region that are being regarded as Lower Cambrian and the Lower 
 Cambrian rocks along the western edge of the plateau and in the 
 Vermont valley was the one which obtained when these respective 
 rocks were forming; but on the contrary recognizes that they 
 are now separated by thrusts. Nevertheless, the calcareous rocks 
 of the Lower Cambrian series were probably once present over 
 the Lower Cambrian terrigenous rocks of the Taconic hills. 
 
 After deposition of Cambrian sediments had continued for 
 a time, perhaps for Middle and part or all of Upper Cambrian 
 time as well as during the Lower Cambrian period, a disturb- 
 ance may be thought of as having folded or otherwise deformed 
 the Cambrian beds and raised them above the sea. Erosion 
 would have followed and a considerable but unknown mass of 
 rocks presumably would have been removed, exposing the Lower 
 Cambrian rocks. The changes which the Cambrian rocks under- 
 went during this disturbance could be thought of as having pro- 
 duced some of the differences now apparent between them and 
 the limestones which rest on them at many places. It is notice- 
 able, from east to west, that the terrigenous rocks on which the 
 limestones lie are more uniformly altered than are the limestones ; 
 they present less variation in metamorphism over the same areas. 
 
 Finally came a submergence of this denuded Cambrian sur- 
 face and the deposition of a series of calcareous rocks, one can 
 hardly say at just what time because the bottom of series is not 
 now present in western Vermont, as the oldest Ordovician lime- 
 stone or sandstone usually rests by thrust on much younger strata. 
 One cannot say what may be present at depth underneath a prob- 
 ably great thickness of Ordovician rocks in the lake region which 
 have been overridden by great masses of other rocks, including 
 some Ordovician. The hypothesis of Ordovician deposition that 
 is being developed is in fact erected on the basis of the overriding 
 mass, in largest part. 
 
 Near the lake the great thrust plane along which were car- 
 ried the rocks from the east over on those at the west, sheared 
 away from the terrigenous rock into and through various Ordo- 
 vician horizons, but apparently through nothing older than the 
 so-called "Potsdam" which has been described. 
 
 The deposition of the limestones apparently proceeded by 
 overlap eastward, laying down first, at the west, the Beekman- 
 town and by progressive advance farther east some Chazy and 
 Trenton. What may have come above the limestones at the east 
 has already been discussed. At the west we have evidence that 
 the Trenton was followed by the "Utica," but this rock apparently 
 
266 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 does not now appear east of the erosion margin of the great thrust 
 except from beneath by exposure from erosion, as south of Mt. 
 Philo in Ferrisburg and Charlotte. 
 
 Such an hypothesis seems to offer a ready and simple ex- 
 planation of the occurrence of Chazy-Trenton beds apparently 
 resting directly on the terrigenous formation in Orwell, Sudbury 
 and Benson, if the latter formation is the Cambrian. It also 
 permits the interpretation that the fragmentary areas of Ordo- 
 vician limestone in the Taconic hills are erosion outliers resting 
 unconformably upon the rocks beneath. The hypothesis does 
 not necessarily call for the interpretation of schist now resting 
 on the limestone, or marble, as younger, in view of the possibili- 
 ties of modifications by thrust deformation. One thing that 
 seems to support the idea of depositional overlap is the geograph- 
 ical extension of tlfe limestone over the terrigenous formation, 
 if erosion is taken into account. 
 
 To some it would seem almost incredible that the Beekman- 
 town which has such a tremendous apparent thickness near the 
 lake was not deposited over what are now the Taconic region and 
 the Vermont valley. Seely, in fact, could not believe it. The 
 fact remains that the Beekmantown has not been positively recog- 
 nized away from the lake in what is to be regarded as the mass 
 that has been in some degree transported from the eastward. Is 
 it possible that it could have been deposited? Is it possible, for 
 example, that the marble is the Beekmantown? Allowing again 
 the necessity for recognizing thrusts, is it possible to explain the 
 present relative position of Chazy-Trenton limestones and the 
 terrigenous rocks of the Taconic hills in Orwell and Sudbury and 
 still have the Beekmantown in the marbles at the east ? It would 
 seem that in this connection it is necessary to consider the prob- 
 ability of down faulting of the marble and that some restoration 
 of the rocks along the eastern border of the Vermont valley would 
 have to be made, as has been done above, in order to weigh the 
 question properly. When such restoration is made the probable 
 Ordovician calcareous rocks of the valley are apparently raised 
 to the level of those which lie on the rocks of the Taconic hills 
 and the presumption grows that the marbles are younger. 
 
 To some the explanation of the occurrence of the hmestones 
 on the quartzite-phyllite formation by deposition might not ap- 
 peal. It would then be necessary to account for the relation in 
 some other way, say by thrust. Could a thrust plane have cut 
 through a mass of rocks that lay to the eastward of the present 
 Taconic hills in such way as to carry everything that lay above 
 the calcareous rocks that now occur in the Taconic hills on the 
 toe of the thrust and further in such way as to superpose these 
 Chazy-Trenton limestones on Lower Cambrian, at the same time 
 pushing what lay on the Lower Cambrian still farther west, the 
 mass pushed now having disappeared by erosion? It might be 
 possible, since there seems to be no necessary rule to govern the 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 267 
 
 way in which a thrust plane would cut having once been initiated. 
 Such explanation might leave Beekmantown at depth somewhere 
 at the east. It magnifies more than ever the principle of thrust 
 and the distance of movement. That we must suppose that such 
 thrust, if it occurred, carried Ordovician limestones on Cambrian 
 seems best shown north of the Taconic hills, where the evidence 
 is strongest for the terrigenous rock ("Red Sandrock") being 
 Cambrian. If it carried the limestones on Cambrian there is it 
 probable that it would have elevated them to Ordovician schists 
 only a few miles to the south in the Taconic hills? 
 
 The idea of depositional overlap fits the conditions at Snake 
 and Buck mountains if we recognize the possibility of lateral 
 variation of the Lower Cambrian sands and muds. 
 
 The proximity of the phyllite in the Whiting- Weybridge belt 
 to the quartzite of Snake and Buck mountains offers no particular 
 difficulty. The hypotheses mentioned have not been knowingly 
 stretched to meet the facts. They take careful account of studied 
 field relations. Any discrepancies may be put down for the most 
 part as due to differences of assignment of age to certain rocks 
 and to other differences of interpretation. 
 
 In the descriptions of the various areas given in the preced- 
 ing pages, application has been made of some of the ideas that 
 have just been developed. In the lake region there is acceptable 
 evidence which has long been recognized of westward thrust. 
 Perhaps some of the details offered in this paper are new, and 
 perhaps some of the explanations are original. It is plain that 
 we must recognize the present juxtaposition of masses that were 
 once more or less separated. When we find the "Utica" exposed 
 from beneath the mass, which we look upon as having moved 
 from the east, at some distance east of the present lake shore, the 
 probability of extensive movement appeals strongly. We are 
 bound to consider the possibility that much of the calcareous 
 rock now exposed in the lake region is transported rock. If 
 such could be established with much certainty, our ideas of 
 sedimentary provinces might require modification in some 
 measure. We do not now view the rock where it was originally 
 deposited. 
 
 In Benson and Orwell it may appear that we should recognize 
 the probability that a phyllite of Cambrian age now rests on a 
 slate of Ordovician age by thrust. It may be that we shall have 
 to do the same or something similar at the east, but there the 
 conditions are more obscure. 
 
 The possibility of extensive thrust or of any geographically 
 extended thrust between the plateau and the Taconic range does 
 not seem to have received much attention or credence. The evi- 
 dence for thrust overlap has been cited and the question discussed 
 above. It remains to consider a few localities more specifically 
 than has been done. 
 
268 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Apparently, without doing violence to the hypothesis of Cam- 
 brian or post-Cambrian folding and erosion and subsequent Or- 
 dovician overlap, or even to the idea that the latter in some way 
 brought terrigenous rocks to rest on the limestone that rests on 
 supposed Cambrian, it is possible to imagine that at some time 
 after the overlap occurred, possibly after a period of erosion, but 
 not necessarily, during a period of compression a part of the 
 Cambrian quartzite-schist formation was broken and thrust 
 through and over the limestone. In this way a schist could have 
 come to overlie a limestone or a marble and might appear in a 
 greatly disturbed region to be conformable. But the possibilities 
 seemingly do not end here. If the Ordovician limestone were 
 succeeded upward by terrigenous rock, in some such way as 
 described above, or otherwise, these might even be overthrust by 
 older terrigenous rocks so that Cambrian quartzite or schist 
 might come to lie on Ordovician schist, while the former underlay 
 the limestone at depth. 
 
 It appears that the metamorphism shown by the schist of the 
 Taconic range, which it should be noted in many cases, does not 
 exceed that shown by the rocks of some of its foothills, could 
 readily have been produced in muds of Cambrian age and if these 
 should have by thrust been elevated and shoved westward on 
 Ordovician calcareous rocks, they might readily have come into 
 such relation with less altered or originally somewhat different 
 terrigenous rocks as to give an appearance of being wholly dif- 
 ferent in age, which aspect would be heightened by the fact of 
 their position relative to the limestone. In a region of thrust 
 lithological transitions as indications of increasing metamorphism 
 in relatively undisturbed rocks and therefore as indications of 
 similar age, may have unsuspected significance. 
 
 The relations around Bennington are very complicated and 
 those are apparently most so which at first appear simple. It 
 would appear on the basis of general unity of structure of the 
 rocks over a wide region that the conditions at Bennington should 
 be capable of any explanation which should essentially satisfy 
 the conditions farther north in the Vermont valley. On the basis 
 of downfaulting, evidence for which is as strong at Bennington 
 as at any place in the valley, one may attempt a restoration like 
 that which was imagined for the valley around Dorset. The 
 elements of uncertainty are many. The conditions south of the 
 latitude of North Bennington are somewhat different from those 
 north of it, which lends some support to the idea of transverse 
 or east-west faulting between Mt. Anthony and West Mountain. 
 The elevation of the surface of the valley quartzite south of 
 Bennington to that of the plateau would carry a certain amount 
 of the calcareous rocks of the Cambrian upward, but it is not 
 clear that it would carry all as the interbedded rocks along the 
 western side of the valley south of Bennington may not rest on 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 269 
 
 quartzite. The proximity of the sheared and otherwise greatly 
 deformed dove-colored limestone and its associated rock just east 
 of Mt. Anthony, south of Bennington town, to interbedded 
 rocks practically contiguous with them on the east, certainly 
 suggests overlap such as is found and more plainly seen at the 
 north. In the imaginary elevation of the interbedded rocks of 
 the valley along the western portion south of Bennington, ap- 
 parently beneath them would be carried upward some younger 
 rock which had been overlapped by them. The conditions so 
 far imagined give us apparently old rock resting against younger 
 rock along a reverse fault and a thrust plane. Perhaps on the 
 principle of differential normal faulting in the region, the Mt. 
 Anthony ridge would have to be elevated somewhat in this process 
 of restoration. The crystalline limestones and marbles underly- 
 ing Mt. Anthony are relatively undeformed internally, presenting 
 in their clearly-bedded condition a contrast to the marbles farther 
 north ; they are highly crystalline, but to a • large extent not 
 mashed and crushed. Directly east of them the bluish-gray 
 limestone and its gray associate are greatly deformed internally, 
 largely through shearing and brecciation. It would appear that 
 this evidence of compression with the general field relations could 
 be taken to mean that there had been a movement of one rock 
 mass on another and the two masses which seemingly would have 
 been involved are the marbles of Mt. Anthony and the sheared 
 rocks just east of them. The marbles are presumably younger 
 than the other rocks. Walcott found certain fossils (Trenton) 
 which would seem to indicate such a probability ; the writer found 
 certain fossils which indicate Chazy age for the sheared rocks 
 (see above). The Chazy has apparently broken and ridden up- 
 ward on the Trenton along a reverse fault plane now marked by 
 the rather extended zone of strong brecciation south of Benning- 
 ton. 
 
 The marbles of Mt. Anthony are capped by schist or phyl- 
 lite. Along the ridge southward near Carpenter Hill the rocks 
 along the summit and eastern slope are interbedded black phyllite, 
 sericite schist and quartzite. Along a scarp which extends from 
 Carpenter Hill nearly to Pownal Center these terrigenous rocks, 
 for some of the distance at least, rest against the interbedded 
 series of the Lower Cambrian. South of Pownal Center the 
 surface rocks of the ridge are largely crushed black phyllites, 
 often pyritiferous, or chlorite-sericite schist. The schist mass 
 bends southeasterly and cuts across the strike of the interbedded 
 and other rocks northward, finally abutting against the massive, 
 granular quartzite of the plateau. 
 
 West of Carpenter Hill is the crushed limestone of North 
 Pownal with some sheared, bluish or dove-colored rock along the 
 eastern part of the mass. On this limestone and jammed in with 
 it is the black, pyritiferous phyllite, the same rock that surrounds 
 
270 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 it. Between Carpenter Hill and the limestone hill at North 
 Pownal are areas in which patches of phyllite and limestone are 
 intermingled at the present surface. In North Pownal the lime- 
 stone rests on the schist ; it does also west of the Hoosic River, 
 north of Pownal station. The field relations all about speak with 
 emphasis of former strong compression of the region. 
 
 Reckoning with the idea of an overlap of Ordovician cal- 
 careous rocks on an old Cambrian surface, as developed in con- 
 nection with apparent relations at the north, and with the evi- 
 dence of severe compression which is everywhere manifest, the 
 present relations seem to be capable of at least partial explanation. 
 It would seem that except for normal faulting their relations 
 must recognize deformation by powerful compression and that 
 the structural characters of the rocks show that deformation took 
 place largely in the "zone of fracture." The evidence is good that 
 many of the rock masses have come to be where they are now 
 as the result of disturbance by rupture and displacement. 
 
 The interbedded terrigenous rocks on Carpenter Hill are 
 counterparts of similar rocks on which the Ordovician limestones 
 rest in the northern part of the Taconic hill region. The schist 
 of Mann and Mason hills, except for its more abundant chlorite, 
 is like that of West Mountain. The dove-colored rock and its 
 gray dolomite are like those in Benson and OrAvell, except for 
 greater metamorphism ; they are much like those in Brandon. 
 
 Proceeding with the strong feehng that has come from actual 
 and extensive examination of the whole region it seems that the 
 Bennington area does not dififer essentially from other areas of 
 the Taconic hills near the Vermont valley that have been dis- 
 cussed. It appears that under compression the rocks of the 
 region were broken by reverse faults. It would seem that the 
 members of the Lower Cambrian series were displaced with 
 reference to each other and that the members of the overlying 
 Ordovician rocks were also displaced with reference to each 
 other. It seems possible to imagine that the quartzite-schist mass 
 was either ruptured without much folding or that it was folded 
 and overturned and then ruptured. The marbles of Mt. Anthony 
 were protected from pronounced deformation by a great fracture, 
 probably a reverse fault, that cut up through them. At Carpenter 
 Hill and southward the crush zone apparently dies away. The 
 quartzite-schist mass was apparently either folded and overturned 
 or ruptured and pushed up, perhaps both. The calcareous rocks 
 of North Pownal were caught and mashed and the schist jammed 
 in with them and carried over them ; it was also apparently, 
 carried over Mt. Anthony. On the basis of restoration, the 
 Lower Cambrian calcareous rocks may once have overlapped the 
 rocks that formerly lay on the Mt. Anthony ridge. In testing the 
 validity of the interpretation, one must recall contrasts in the 
 different rocks with reference to metamorphism. The schist and 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 271 
 
 for the most part the Ordovician calcareous rocks were subjected 
 to conditions different from those within the mass that over- 
 rode them. The probabihty of overlap by lateral thrust is strong, 
 on the basis of what is known farther north, but its extent is 
 wholly uncertain. All thrust relations have been thoroughly dis- 
 guised by normal faulting. Whether any of the Ordovician 
 calcareous rock has been much displaced by lateral thrust it is 
 not possible to tell. 
 
 North of North Bennington we find the counterpart of the 
 dove-colored rock which occurs south of Bennington, and which 
 seems to be Chazy, resting on the phyllite, although greatly de- 
 formed. Whether this rock is substantially in place it is not pos- 
 sible to decide. On the basis of a restoration it would be lifted 
 to some extent and might come to the level of similar rock now 
 found on the southern slopes of West Mountain. Erosion, as 
 well as faulting, have operated to obscure relations here. 
 
 It is still maintained that by a combination of reverse fault- 
 ing and lateral thrusting, a portion of the floor on which the Or- 
 dovician rocks apparently lie, whether by deposition or otherwise, 
 could be carried over the limestone and perhaps give the appear- 
 ance of being something very different from what it really is. 
 
 Regarding apparent conf ormability ; this might be simulated. 
 Logan has distinctly called attention to the superposition of cer- 
 tain rocks on others which seem to be conformable, but which 
 give the strongest possible impression of being very different in 
 age and speaks of the probable greater age of those which are 
 superior in position. . . 
 
 There is apparently nothing which requires that a thrust 
 plane should cut in any particular way through the rocks that 
 are interposed, so to speak, in its path except a variable resist- 
 ance. It might have undulated in the most irregular fashion at 
 some places and have been fairly regular at others. At times it 
 might have passed from a horizontal direction to one nearly ver- 
 tical, and might have cut downward as well as upward. In cases 
 where patches of limestone rest on a schist, which in turn rests on 
 a marble presumably by minor thrust and where all are overlapped 
 by thrust, it is possible to imagine that these patches either repre- 
 sent rock that is where it was before overlap by a thrust which 
 cut above them, or that it has been carried there by the thrust 
 cutting down into limestones farther east and moving some of that 
 rock with the overriding mass. They would belong in a different 
 category in one case from what they would in the other, being 
 simple or displaced erosion outliers in the former case and thrust 
 erosion outliers in the latter. The question of the extent to which 
 thrusts may have moved masses of Ordovician limestone or mar- 
 ble, small or large, it is of course impossible to decide. The 
 possibility apparently needs to be recognized. 
 
272 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 North of Brandon the thrust apparently did not raise Cam- 
 brian schist and push it on marble, but only the interbedded series 
 was thrust on the marble. 
 
 Northward it may be that the thrust along the western edge 
 of the plateau disappears and that there is only one thrust plane. 
 The eastern thrust at the south may be a minor one compared 
 with that which drove the Lower Cambrian rocks and their load 
 over the "Utica," and possibly may have been of widely different 
 date. 
 
 It is interesting to note that apparently nowhere west of the 
 plateau and east of the margin of the thrust as now developed 
 by erosion along Lake Champlain or in the Laconic hills has the 
 base or basement of the presumably Lower Cambrian been ex- 
 posed. 
 
 In the early stages of the deformation which was to cul- 
 minate in lateral overlapping thrusts of the Cambrian rocks, the 
 whole floor of these rocks and their overlying load under the 
 tremendous compression were probably folded and crumpled. 
 There were probably developed many reverse faults of varying 
 throw, some of which were probably very small. At this time 
 the rocks undoubtedly also were strongly sheared. Schistose 
 structure was developed in the impure muds, cleavage in the slates, 
 and folds and ruptures in the quartzites. Similar deformations 
 were produced in the overlying limestones. 
 
 The dates of these displacements may only be conjectured. 
 In view of the apparent nature and magnitude of the regional 
 deformation one cannot be sure that some later Paleozoic strata 
 may not have once been present in the region. 
 
 At some post-Ordovician period the strata were cut by dikes 
 of igneous rock, which in many places cut through the displaced 
 rocks from the substratum beneath. So far as the writer knows, 
 there is no evidence that sets the date of the. intrusion and it 
 may have been post-Carboniferous. 
 
 It is not easy to discern how much deformation of the thrust 
 planes by folding occurred subsequent to their formation. East 
 of Brandon the apparent plane of overlap of the interbedded 
 series of the Cambrian does not seem to have been much de- 
 formed. Irregularities in thrust planes, which are more prob- 
 ably irregular than regular at the outset, by subsequent compres- 
 sion of the region seemingly would not be easy to see. If the 
 thrusts were of pre-Devonian date it seems as though there would 
 be more evidence than is apparent of subsequent deformation in 
 the Appalachian folding of post-Carboniferous time. The prob- 
 ability of a late date for the big thrusts on this basis grows 
 stronger. 
 
 The presence of thrusts in the region on the scale that has 
 been described in part and postulated in part greatly complicates 
 the question of the character and extent of any folding that has 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 273 
 
 been assumed to have occurred at the close of Ordovician time 
 in this region. The assignment of date to the structural features 
 of the rocks of a region like that of western Vermont depends 
 upon one's viewpoint. 
 
 It seems reasonably clear that at some time subsequent to 
 the production of the major features of the region that are due 
 to compression, there came a period of extensive deformation by 
 normal faulting. It would seem that it was at this time that the 
 structural outlines of what are now the Vermont valley and 
 Champlain lowland were formed. Between what is now the 
 western edge of the Green Mountain plateau and the region now 
 represented by the Taconic range, the rocks were dropped, pro- 
 ducing a great structural trough. Northward was formed the 
 outlines of the Champlain lowland between the plateau on the 
 east and the Adirondacks on the west. Considering the down- 
 faulted region as a whole the movement was differential and 
 involved flexures as well as actual ruptures. The date at which 
 this deformation occurred again can only be conjectured. Pos- 
 sibly it occurred at the time when similar deformations outlined 
 the great Triassic troughs of our Atlantic border. 
 
 It seems not unlikely that during the time of post-Triassic 
 faulting_in the eastern part of the country there might have been 
 renewed disturbance of this general region and that some of the 
 fault lines now marked by scarps in the Taconic hills and else- 
 where may belong to this period of disturbance. Such displace- 
 ments are not to be confused, however, with reverse faults. It 
 is, however, often not possible to decide whether certain obvious 
 displacements between interbedded quartzites and phyllites of the 
 Taconic hills are reverse or normal faults. 
 
 Some of the displacements along Lake Champlain which have 
 been regarded as reverse faults or thrusts and are marked by 
 scarps are apparently really normal faults within thrusted masses. 
 The margin of the thrust is really at a distance from the scarps 
 in question. For example, the displacements on the west of 
 Snake and Buck mountains and west of the Orwell and Benson 
 hills are probably normal faults cutting through a great lateral 
 thrust. These masses were covered at one time and have been 
 exposed by erosion. They stand higher now than the rocks at 
 the west of them because the latter were dropped and the quartz- 
 ite was carried downward beneath them. The thrusts extended 
 west of these scarps an indeterminate distance, and apparently 
 often, if not usually, across the lake, at least. 
 
 There is apparently nothing definite in the region to tell 
 whether any of the thrusts were the results of previous erosion. 
 It is true that east of Brandon and at other places the inter- 
 bedded series lies on the marble and it is probable that other 
 Cambrian rocks lie on marble ; but it seems conceivable that these 
 conditions could have been produced even though there were a 
 
274 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 mass of rocks above the limestones now represented by the mar- 
 bles by reason of the way the thrust plane could have cut through 
 the mass. 
 
 It is not necessary that we should assume that the marbles 
 were not covered by other rocks when these thrusts occurred. 
 Such has not intentionally been the argument; the explanation 
 of the particular kind of terrigenous rock that now covers the mar- 
 ble at places is apparently one problem to be solved. A great 
 shear seemingly might have been as effective as erosion in trun- 
 cating a folded series. This statement would seem to apply gen- 
 erally and to fit the conditions along the lake as well as those near 
 the plateau. 
 
 The present physiography. It has been a widely-accepted 
 theory that during middle and late Mesozoic time a large por- 
 tion of the Atlantic border of our country was reduced by the 
 forces of subaerial erosion to a great peneplaned region, and 
 that in succeeding Tertiary time the region was elevated by an 
 extensive warping movement. According to this theory the 
 present physiography is to be explained as the result of the re- 
 newed action of the base-levelling agencies as the region was 
 gradually elevated. For certain regions it does not appear that 
 any better theory has been advanced to explain the present con- 
 ditions within them. 
 
 Accepting this view, the present physiographic outlines of 
 western Vermont apparently must have been shaped along lines 
 that had been determined by the great deformations which the 
 region had suffered. The rocks in the different parts of western 
 Vermont, whether the region was one of early folding and much 
 later thrusts or one of folds and thrusts independent of pro- 
 nounced earlier deformation, had been brought into such relative 
 positions that during late Mesozoic time, allowing for some ero- 
 sion, there was produced much the same relation that we see 
 today from west to east across the State : a great truncation of 
 perhaps lofty masses and exposure of rocks of one age here and 
 another there. We note the oldest rocks at the east and the 
 youngest at the west, as far as exposure has gone. The structural 
 outlines of the Vermont valley and Champlain lowland had pre- 
 sumably already been laid down by the downfaulting of great 
 blocks of soft rocks between masses of more resistant crystallines. 
 Although all were alike presumably reduced to a peneplain in 
 late Cretaceous time, upon later elevation the forces of erosion 
 discovered the downfaulted masses of softer rocks and wore 
 them rapidly away. 
 
 The present physiography of the region gives some hints 
 of the deformations which it has undergone, and a gross surface 
 section across the State adds something more ; but it must be ap- 
 parent that the physiography by itself is wholly insufficient to 
 explain the complicated structure of the rocks of western Ver- 
 mont. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 275 
 
 SUPPLEMENTAKT NOTE. 
 
 Some of the names in this paper designating fossils from exposures 
 studied by the writer are used chiefly as general descriptive terms for 
 forms whose identities the nature of the material would often make it 
 difficult to establish. As indices to the horizons of the containing rocks 
 their values have been recognized in many instances by reason of con- 
 comitant features, such as reasonably apparent stratigraphic associa- 
 tions with other rock whose identity could seemingly be more conclu- 
 sively fixed, and from' occurrence in similar rocks at other places in the 
 same region with other and different fossils whose identities were 
 more obvious. Particularly among terms used for such general descrip- 
 tive purposes the names Pleurotomaria and Murchisonia were applied to 
 markings which strongly resemble either some of the species of Pleuro- 
 tomaria or some of those of Murchisonia as described in the older 
 literature to which the general reader probably would most likely first 
 refer, such as the Paleontology of New York by James Hall, or early 
 publications of the Geological Survey of Canada by Billings, as well as 
 the early descriptions of the formations of Vermont. Most of the forms 
 assigned to Murchisonia by earlier writers are now referred to other 
 genera (Lophospira, Eormotoma, etc.), and the same is true for Pleuro- 
 tomaria. 
 
 Other names which have been used in reference to fossils are 
 obviously citations from the literature and in such connection are 
 employed without presuming to pass upon their validity or synonymy. 
 
 Certain other names have been employed also because of their use 
 by others with reference to Vermont formations in describing certain 
 characteristic fossils and in making comparison thereby with rocks of 
 other regions. In such cases attempt has not usually been made to 
 establish with absolute positiveness just what names in the latest 
 synonymy of Ordovician fossils should apply to the forms referred to. 
 In the list given beyond certain probabilities are indicated. 
 
 The general structure of the region suggests that, so far as preserva- 
 tion of fossils in certain disturbed and somewhat metamorphosed strata 
 permits, it may prove desirable to undertake studies designed to draw 
 comparisons among fossils of different localities and rocks in the gen- 
 eral Champlain region in order to obtain further light on the probable 
 extent of the thrust deformations which the region has obviously 
 suffered, and to ascertain if any peculiar or anomalous faunal features 
 exist in the region which could be ascribed to such disturbances as the 
 foregoing paper has discussed. 
 
 It may perhaps be said that the older names have an historical 
 value in tracing the progress of knowledge of the rocks of western 
 Vermont; but better knowledge of the exact affinities of the fossils 
 is doubtless required before the ancient geographic relations of those 
 rocks may be fully understood. 
 
276 
 
 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Name used. 
 
 Bellerophon sp. 
 
 Ophileta complanata, Vanuxem. 
 
 Maclurea magna, Emmons. 
 Strephochaetus sp. 
 
 Trinucleus concentricus, 
 {Trinucleus concentrica of various 
 
 authors). 
 Graptolithus pristis. 
 
 Prasopora sp. 
 
 Possible oe probable emendation. 
 
 Probably Sinuites cancellatus, 
 
 Hall. 
 Possibly equivalent to som-e one 
 
 of the forms described as 0. 
 
 compacta, Salter. 
 Maclurites magnus. Lesueur. 
 Girvanella, probably ocellata, 
 
 Seely. 
 Cryptolithus tesselatus, Green. 
 
 Graptolithus pristis, Hall. 
 
 (Possibly Diplograptus sp. or 
 Glossograptus sp.) 
 
 P. simulatrix, var. orientalis, 
 Ulrich. 
 
 (Some specimens collected by the 
 writer at South Hero were ex- 
 amined by Dr. Ruedemann of 
 Albany in connection with 
 studies of Trenton fossils from 
 Grand Isle and identified as P. 
 simulatrix, var. orientalis, Ulr.^ 
 In view of the recognition of 
 this form in the Champlain val- 
 ley the writer prepared radial 
 and tangential sections of speci- 
 mens collected by him at the 
 grist mill, one mile west of Or- 
 well village, and on the lake 
 shore in Orwell just north of the 
 Benson line, and compared with 
 the descriptions and figures 
 given by Ulrich in the Geology 
 of Minnesota, vol. 3, part 1, 
 1895, pp. 245-248, plate 16, and 
 found his specimens also to be 
 P. simulatrix, var. orientalis, 
 Ulr.) 
 
 1 Personal communication. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 277 
 
 BIBLIOGRAPHY. 
 
 1845 — Adams, C. B. First, Second, Third and Fourth Annual Reports 
 on the Geology of Vermont. 
 
 1846 — Emmons, E. Agriculture of New York. 
 
 1861 — Hitchcock, E., and Others. Geology of Vermont, 2 vols. 
 
 1861 — Baeeande, J., Logan, Sir W., Hall, James. Correspondence on 
 the Taconic System and the age of the Fossils found in the 
 Rocks of Northern New England and the Quebec Group of 
 Rocks. Amer. Jour. Sci. Vol. 31. 
 
 1861 — Baebande, J. Documens Anciens et Nouveaux sur la Primordiale 
 et le Systeme Taconique en Amerique. Bull. Soc. Geol. de 
 France. Vol. 2. 
 
 1863 — Logan, Sir W. E. Geology of Canada, Text and Atlas. 
 
 1877 — Dana, J. D. An Account of the Discoveries in Vermont Geology 
 of the Rev. Augustus Wing. Amer. Jour. Sci. Vols. 13 and 14. 
 
 1877 — Dana, J. D. On the Relations of the Geology of Vermont to that 
 of Berkshire. Amer. Jour. Sci. Vol. 14. 
 
 1879— Dana, J. D. On the Hudson River Age of the Taconic Schists. 
 Amer. Jour. Sci. Vol. 17. 
 
 1880— Dana, J. D. Note on the Age of the Green Mountains. Amer. 
 Jour. Sci. Vol. 19. 
 
 1882 — Dana, J. D. The Geological Age of the Taconic System. Quart. 
 Jour, of the Geol. Soc. Aug., 1882. 
 
 1884 — Geikie, a., Peach, B. N., and Horne, J. The Crystalline Rocks 
 of" the Scottish Highlands. Nature. Vol. 31. 
 
 1884 — Dana, J. D. On the Southward Ending of a Great Synclinal in 
 the Taconic Range. Amer. Jour. Sci. Vol. 28. 
 
 1885— Ford, S. W. Great Fault, Schodack Landing, N. Y. Amer. Jour. 
 Sci. Vol. 29. 
 
 1885 — Dana, J. D. On Taconic Rocks and Stratigraphy, with a Geolog- 
 ical Map of the Taconic Region. Amer. Jour. Sci. Vol. 29. 
 See also Vol. 33, 1887. 
 
 1886— McCoNNELL, R. G. Report on the Geological Features of a Por- 
 tion of the Rocky Mountains. Ann. Rept. Geol. Surv. Can. 
 Vol. 2. 
 
 1886 — Dana, J. D. Berkshire Geology. A paper read before the Berk- 
 shire Historical and Scientific Society, Pittsfield, Mass., Feb. 5, 
 1885. 
 
 1886 — Brainerd, E. and Seely, H. M. Notice of Geological Investiga- 
 tions along the Eastern Shore of Lake Champlain. Bull. Amer. 
 Mus. Nat. Hist. Vol. 1. 
 
 1888 — Peach, B. N., Horne, J., Gunn, W., Clough, C. T., Hinxman, L., 
 Cadell, H. M. Communicated by Geikie, A. Report on the 
 Recent Work of the Geological Survey in the North-West 
 Highlands of Scotland. Quart. Jour, of the Geol. Soc. Vol. 44. 
 
 1888 — Walcott, C. D. The Taconic System of Emmons and the Use of 
 the Name Taconic in Geologic Nomenclature. Amer. Jour. Sci. 
 Vol. 35. 
 
 1888 — Dana, J. D. A Brief History of Taconic Ideas. Amer. Jour. 
 Sci. Vol. 36. 
 
 1888 — Margerie et Heim. Dislocations de I'ecorce terrestre. Zurich, 
 1888. 
 
 1888 — Eixs, R. W. Second Report on the Geology of a portion of the 
 Province of Quebec. Ann. Rept. Geol. and Nat. Hist. Survey 
 of Canada. Vol. 3, Part 2. 
 
 1890 — Walcott, C. D. The Fauna of the Lower Cambrian or Olenellus 
 Zone. Tenth Annual Report of the Director, U. S. G. S. 
 
 1890 — Brainerd, E. and Seely, H. M. The Calciferous Formation in the 
 Champlain Valley. Bull. Amer. Mus. Nat. Hist. Vol. 3. 
 
278 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 1891 — Hayes, C. W. The Overthrust Faults of the Southern Appala- 
 chians. Bull. Geol. Soc. Amer. Vol. 2. 
 
 1891 — Bbaineed, E. The Chazy Formation in the Champlain Valley. 
 Bull. Geol. Soc. Amer. Vol. 2. 
 
 1891 — Wolff, J. E. On the Lower Cambrian Age of the Stockbridge 
 Limestone. Bull. Geol. Soc. Amer. Vol. 2. 
 
 1891 — ^"Walcott, C. D. Correlation Papers, Cambrian. Bull. U. S. G. S. 
 No. 8L 
 
 1892 — WiLus, Bailey. The Mechanics of Appalachian Structure. 
 Thirteenth Annual Rept. of the Director, U. S. G. S. Part 2. 
 
 1892 — Van Hise, C. R. Correlation Papers, Pre-Cambrian. Bull. U. S. 
 G. S. No. 86. 
 
 1893 — Dakton, N. H. On two Overthrusts in Eastern New York. Bull. 
 Geol. Soc. Amer. Vol. 4. 
 
 1893 — Willis, B. and Hayes, C. W. Conditions of Appalachian Fault- 
 ing. Amer. Jour. Sci. Vol. 46. 
 
 1893 — FoEESTE, A. F. New Fossil Localities in the Early Paleozoic. 
 Amer. Jour. Sci. Vol. 46. 
 
 1893 — Dale, T. Nelson. On the Structure of the Ridge between the 
 Taconic and Green Mountain Ranges in Vermont. Fourteenth 
 Ann. Rept. of the Director, U. S. G. S. Part 2. 
 
 1894 — PuMPELLY, R., Wolff, J. E., and Dale, T. N. Geology of the 
 Green Mountains in Massachusetts. Monograph U. S. G. S. 
 No. 23. 
 
 1894 — Whittle, C. S. Algonkian Rocks in Vermont. Jour. Geol. 
 Vol. 3. 
 
 1895 — Dale, T. N. Structural Details in the Green Mountain Region 
 and in Eastern New York. Sixteenth Ann. Rept. of the Director 
 U. S. G. S. Vol. 4, Part 1. 
 
 1895 — Van Hise, C. R. Principles of North American Pre-Cambrian 
 Geology. Sixteenth Ann. Rept. of the Director U. S. G. S. 
 Vol. 4, Part 1. 
 
 1896 — Bbaineed, E. and Seely, H. M. The Chazy of Lake Champlain. 
 Bull. Amer. Mus. Nat. Hist. Vol. 8. 
 
 1898 — Dale, T. Nelson. The Slate Belt of Eastern New York and 
 Western Vermont. Nineteenth Ann. Rept. of the Director 
 U. S. G. S. Part 3. 
 
 1899 — Emeeson, B. K. The Geology of Eastern Berkshire County, 
 Mass. Bull. U. S. G. S. No. 159. 
 
 1899 — 'White, Theodobe G. Upper Ordovician Faunas in Lake Cham- 
 plain Valley. Bull. Geol. Soc. Amer. Vol. 10. 
 
 1901 — ^RuEDEMANN, R. Hudson River Beds near Albany and their 
 Taxonomic Equivalents. N. Y. State Mus. Bull. No. 42. 
 
 1902 — Willis, Bailey. Stratigraphy and Structure, Lewis and Livings- 
 ton Ranges, Montana. Bull. Geol. Soc. Amer. Vol. 13. 
 
 1902 — Peekins, Geoege H. The Geology of Grand Isle. Third Report 
 of the State Geologist. 
 
 1904 — Dale, T. Nelson. The Geology of the North End of the Taconic 
 Range. Amer. Jour. Sci. Vol. 17. 
 
 1905 — Raymond, P. E. The Fauna of the Chazy Limestone. Amer. 
 Jour. Sci. Vol. 19. 
 
 1906 — Meeeill, G. p. Contributions to the History of American Geol- 
 ogy. U. S. Nat. Mus. Report for 1904, No. 135. 
 
 1906 — Edson, G. E. Geology of St. Albans and Vicinity. Fifth Report 
 of the State Geologist. 
 
 1906 — Seely, H. M. Beekmantown and Chazy Formations in the 
 Champlain Valley. Fifth Report of the State Geologist. 
 
 1907 — Keith, Aethue. Roan Mountain Folio. Geological Atlas of the 
 U. S. No. 151. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 279 
 
 1908 — Perkins, Geokge H. Preliminary Report on the Geology of Chit- 
 tenden County. Sixth Report of the State Geologist. 
 1908 — Edson, G. E. Geology of the Town of Swanton. Sixth Report 
 
 of the State Geologist. 
 1908 — Perkins, George H. Preliminary Report on the Geology of 
 
 Franklin County, Vt. Sixth Report of the State Geologist. 
 1909 — RuEDEMANN, R. Types of Inliers Observed in New York. Bull. 
 
 N. Y. State Mus. No. 133. 
 1909 — Van Hise, C. R. and Leith, C. K. Pre-Cambrian Geology of 
 
 North America. Bull. U. S. G. S. No. 360. 
 1909 — ScHUCHERT, C. Paleogeography of North America. Bull. Geol, 
 
 Soc. Amer. Vol. 20. 
 1910 — Dale, T. N. The Cambrian Conglomerate of Ripton in Vermont. 
 
 Amer. Jour. Sci. Vol. 30. 
 1910 — Seely, H. M. Preliminary Report on the Geology of Addison 
 
 County. Seventh Report of the State Geologist. 
 1910 — Perkins, George H. Geology of the Burlington Quadrangle. 
 
 Seventh Report of the State Geologist. 
 1910 — Kemp, J. F. and Ruedemann, R. Geology of the Elizabethtown 
 
 and Port Henry Quadrangles. Bull. N. Y. State Mus. No. 138. 
 1911 — Ulrich, E. O. Revision of the Paleozoic Systems. Bull. Geol. 
 
 Soc. Amer. Vol. 22. 
 1911 — Gordon, C. E. The Geology of the Poughkeepsie Quadrangle. 
 
 N. Y. State Mus. Bull. No. 148. 
 1912 — Willis, Bailey. Report on an Investigation of the Geological 
 
 Structure of the Alps. Smithsonian Miscellaneous Collections. 
 
 Vol. 56. 
 1912 — Richards, R. W. and Mansfield, G. R. The Bannock Overthrust. 
 
 Jour. Geol. Vol. 20. 
 1912 — Dale, T. Nelson. The Ordovician Outlier at Hyde Manor in 
 
 Sudbury. Amer. Jour. Sci. Vol. 33. 
 1912— Dale, T. N. The Commercial Marbles of Vermont. Bull. U. S. 
 
 G. S. No. 521. See also Ninth Report of the State Geologist, 
 
 1914. 
 1913 — Keith, A. Further Discoveries in the Taconic Mountains. Ab- 
 stract. Bull. Geol. Soc. Amer. Vol. 24. 
 1913 — Dale, T. N. The Ordovician Outlier at Hyde Manor in Sudbury. 
 
 Second paper. Amer. Jour. Sci. Vol. 36. 
 1914 — Gordon, C. E. Notes on the Geology in the Vicinity of Benning- 
 ton. Ninth Report of the State Geologist. 
 1916 — Perkins, George H. The Geology of Western Vermont. Tenth 
 
 Report of the State Geologist. 
 1917 — Emerson, B. K. Geology of Massachusetts and Rhode Island. 
 
 Bull. U. S. G. S. No. 597. 
 
THE GE0L06Y OF LAKE WILL0U6HBY. 
 
 Elbridge C. Jacobs, 
 University of Vermont. 
 
 Lake Willoughby lies in the western part of the town of 
 Westmore, near the eastern boundary of Orleans County, and 
 some twenty-three miles north of St. Johnsbury. It is one of 
 the most beautiful sheets of water in the United States and would 
 not suffer by comparison with the Alpine lakes of Switzerland. 
 To quote from Mr. Walter Crockett's "Lakes of Eastern Ver- 
 mont," we have here /'a rare combination of lake and mountain 
 scenery, a lake (five miles long and from one-half to one and 
 one-fifth miles wide) of exquisite loveliness set amid bold and 
 rugged mountains, the dark tints of the evergreen forests and the 
 delicate silvery whiteness of the birches being reflected as in a 
 mirror in Willoughby's deep waters. *****" "Qn either side, 
 at the southern extremity of the lake, like giant guardians, stand 
 Mount Pisgah and Mount Hor, with their Scriptural names, 
 keeping watch over this vision of scenic loveliness." The slopes 
 of these mountains are densely wooded save where erosion re- 
 veals nearly vertical cliffs of dark, bronze-colored rocks, slashed 
 with bands and patches of a lighter material. Below the cliffs 
 are enormous talus heaps of granite and other material. Rock 
 falls are frequent, a fall in July of this year blocking the road 
 for several days. 
 
 The lake may be likened to the section of a giant calabash 
 gourd, with its broad end lying in the relatively open country and 
 its curving neck penetrating and forming a gap in the mountain 
 range at its southern extremity. The lake shores were formerly 
 impassible to vehicles, communication between the eastern and 
 western valleys being either by boat or else by a mountain road 
 running east of Mount Pisgah. But some sixty years ago a 
 road was built along the eastern (Mount Pisgah) shore and now 
 forms part of the main highway between St. Johnsbury and New- 
 port. Numerous summer cottages and the Westmore Hotel are 
 located along this road towards the northern end of the lake. • 
 "Westmore," a girls' camp, was built in 1919 on a commanding 
 hill on the northwestern shore. The camp is closed this season 
 owing to financial difficulties, but will probably be reopened. This 
 
r/. 
 
 -/' 
 
 "■ -t"^ 
 
 ,..^.... 
 
 ;-=?^'^ 
 / 
 
STUDIES IN THE GEOLOGY OF WESTERN VERMONT 
 
 Second Paper. 
 
 Clarence E. Gordon, 
 Massachusetts Agricultural College 
 
 TABLE OF CONTENTS. 
 
 Introduction. 
 
 Descriptions and discussions of observations made by the writer within 
 the Charaplain lowland and adjacent portions of the Green Moun- 
 tain plateau. 
 Grand Isle County. 
 
 South Hero and Grand Isle. 
 
 North Hero. 
 
 Alburgh. 
 
 Isle La Motte. 
 Franklin County. 
 
 Highgate. 
 
 Swanton. 
 
 St. Albans. 
 
 Georgia. 
 
 Fairfax. 
 Chittenden County. 
 
 Milton. 
 
 Colchester. 
 
 Essex. 
 
 Burlington. 
 
 South Burlington. 
 
 Williston. 
 
 Shelburne and St. George. 
 
 Charlotte. 
 
 Hinesburg. 
 Addison County. 
 
 Ferrisburg and Vergennes. 
 
 Monkton. 
 
 Starkshoro. 
 
 Panton. 
 
 Waltham. 
 
 New Haven. 
 
 Bristol, including parts of Lincoln. 
 
 Addison. 
 
 Weybridge. 
 
 Middlebury. 
 
 Bridport. 
 
 Cornwall. 
 
 Shoreham. 
 
 Whiting. 
 
 Salisbury. 
 
 Leicester. 
 General Summary. , 
 
144 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 INTRODUCTION. 
 
 A description of the principal physiographic divisions of 
 western Vermont and a general statement of the characters dis- 
 tribution and certain other features of the various rock formations 
 found in those divisions may be found in the first paper under 
 this title, published in the Twelfth Report of the State Geologist. 
 These were intended to serve for guidance in following the de- 
 scription and discussion, offered in the same paper, of a number 
 of observations made in certain parts of western Vermont which 
 dealt chiefly with the deformations of the different rocks. For 
 the present paper, which gives an account of studies of the field 
 relations of the rocks in other parts of western Vermont, the 
 general statement made in the preceding report is considered sufifi- 
 cient and need not be repeated nor amplified in this one. 
 
 The physiographic divisions mentioned are the prominent 
 ones of the present surface of this part of the state. Each, of 
 course, shows many minor topographic variations incident to the 
 character and structure of the underlying rock and the modifying 
 effects of erosion and other agencies, such as glaciation. Except 
 for a quarry here and there the average observer is probably 
 impressed only by the grander features of the surface ; it is their 
 charm that invites the tourist to motor through this part of Ver- 
 mont or impels the summer resident to build his camp on some 
 hill or mountain side. 
 
 So conspicuous indeed are these larger divisions of the land- 
 scape they may easily impress the geological student as possessing 
 a significance beyond that which they really have. Geological 
 accounts of different parts of the region often accentuate these 
 more or less modern features and it seems as though in a provin- 
 cial treatment of them their true geological history and connec- 
 tions have been more or less obscured. The more ancient second- 
 ary structural features of the rocks bear no necessary relation to 
 the present physiography of the region, which is due in part to 
 later deformations or disturbances and in part to repeated erosion. 
 
 Over the present surface of western Vermont there is shown 
 a confusion in the arrangement of the rocks that is very baffling. 
 This confusion is very clearly due in large measure to the various 
 deformational and metamorphic changes which the rocks have 
 suffered and to certain primary features, such as lateral variations 
 in certain members. Added to these are the effects of erosion 
 and glaciation. Over large areas correlation may not be made by 
 direct aid of fossils, and one must rely upon other criteria of 
 various sorts. Particular mention should be made of the exten- 
 sive mantle of surface material, either bowlder drift, sand or 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 145 
 
 clay, which conceals large areas and imposes great difficulties in 
 working out the structural details of most localities. 
 
 The student who confines his studies to a small portion of 
 the region may gain a glimpse of the nature of the structure of 
 the rocks in some cases ; in 'others he may be quite confused. It 
 is necessary to carry one's studies over a wide area to see into 
 the plan that apparently prevails over the region as a whole. 
 
 The studies described in this paper and the earlier one were 
 undertaken in the hope that it would eventually prove possible to 
 examine in a somewhat critical way a large number of outcrops 
 in all four of the different divisions of the region, which the 
 writer has defined, with the purpose of getting light on the gen- 
 eral plan of structure of the rocks and in order to discover if any 
 marked degree of unity prevails throughout. For reasons that 
 will generally be understood it has been necessary to publish ac- 
 counts of the work at various stages of its progress. At this 
 writing there still remains the larger portion of the mass of rocks 
 contained within what is known as the Taconic range, which is 
 a territory which the writer had reserved in his mind for future 
 study. From studies already made in parts of the range it seems 
 likely that in its main features it may finally be reduced to a plan 
 of structure like that of other divisions which now bear little 
 physiographic resemblance to it. Finally, it seemed probable that 
 a more careful inspection than has yet been possible could be 
 given to the western ranges and other masses of the Green Moun- 
 tain plateau to see to what extent the rocks now lying west of 
 the plateau could be traced into it and whether the deformations 
 present in it are similar in plan to those found among the rocks 
 now lying west of it. Experience has served to show that ap- 
 parently only by a broad survey of the region as a whole is it 
 likely that one may grasp the true significance of the relations 
 within and among its different parts. 
 
 The general similarity shown by the field relations in widely 
 separated areas indicates a fundamental unity of structure in all 
 of them. Moreover, excursions into areas contiguous to Vermont, 
 such as western Massachusetts and southern Quebec, as well as 
 published descriptions for other adjoining territory and for dis- 
 tricts still more remote suggest that a common plan of structure 
 may prevail over a much wider region than western Vermont. 
 
 The work and writings of Professor J. D. Dana,^ in which he 
 aimed to show the relations (general similarity or unity of plan) 
 between the geological features of western Vermont and those of 
 Berkshire County, Massachusetts, and other areas as well, are 
 well known. The writer's conception of the similarity that exists 
 in the areas described by Dana follows him in maintaining that 
 
 ^ On the relations of the Geology of Vermont and that of Berkshire, 
 A. J. S., Vol. XIV, July, 1877. 
 
146 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 the "western half of the whole Green Mountain region is emi- 
 nently a natural area," and that in many primary features, such 
 as general age and general original interrelations, the rocks 
 throughout are similar. The purpose of this paper is to indicate, 
 if possible, the kind of structure in which western Vermont pos- 
 sesses unity and to show the apparent nature of the chief deforma- 
 tions which have disturbed the rocks. Numerous descriptions of 
 field relations, in addition to those given in the first paper, will 
 be offered to show the dominant influence of thrust displacements 
 of various magnitudes and of kindred phenomena due to pressure 
 acting upon highly elastic and resistant rock formations asso- 
 ciated with weaker and less "competent" strata. 
 
 Extent and certain other features of the region described in 
 this paper. A rough estimate of the dimensions of the irregular 
 territory which has been surveyed gives about 900 or 950 square 
 miles. It includes either the whole or large portions of the fol- 
 lowing-named topographic sheets of the U. S. G. S. : — Rouses 
 Point, St. Albans, Plattsburg, Milton, Willsboro, Burlington, Port 
 Henry, Middlebury, Ticonderoga and Brandon. In a north to 
 south direction it extends from the Canada line approximately to 
 the southern boundary of Leicester in Addison County, and west 
 to east from the New York State boundary to the western margin 
 of the Green Mountain plateau. 
 
 The ground gone over has not, of course, all been studied in 
 minute detail; but much of it has been examined with more 
 thoroughness than will appear in the descriptions, in the search 
 made for clues of different sorts, especially for fossils in the 
 more altered rocks found in the eastern portions of the region. 
 
 Some parts of the territory have been described more or less 
 fully in the first paper ; but in most cases these areas have been re- 
 examined. 
 
 The lake region proper, which is included within the physi- 
 ographic division called the Champlain lowland, seems to call 
 for some sort of specific definition, as it will be frequently men- 
 tioned in the following pages. In addition to the lake with its 
 islands there are along its border many areas of various dimen- 
 sions, often small but again of considerable size, which are under- 
 lain by rocks similar to those which form the islands and the lake 
 bottom. Many of these areas are now covered with Champlain 
 clays, or sands brought in by streams entering the lake. In many 
 places outcrops are few, especially where the underlying rock is 
 clearly or apparently the soft shale formation, but at many places 
 limestone beds like those found on the islands project above the 
 surface deposits, forming knolls and ridges. It seems likely that 
 if the clay which is so plentiful over portions of the mainland 
 near the lake were removed these areas would be more or less 
 inundated by the lake waters, even at their lower levels, and that 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 147 
 
 there would be produced a very different shore Hne, more numer- 
 ous islands and a larger water body. A similar operation on the 
 islands would in some cases partition them into smaller units. 
 
 Some of the streams which enter Lake Champlain, such as 
 Lewis, Little Otter and Otter Creeks, are for greater or less dis- 
 tances from their mouths hardly more than inundations by the 
 lake waters of narrow channels in the clays, with hardly head 
 enough at the present time to give them perceptible currents ; and 
 Dead Creek, a tributary of the Otter, is practically all its way 
 a sluggish stream of this. sort. In the case of the Otter the 
 inundation extends from its mouth to the city of Vergennes, 
 where the stream tumbles over a scarp in massive dolomite to the 
 graptolite shales below. For a large part of its course below 
 Vergennes the river flows through a sand plain of its own making 
 and at its mouth it has formed delta levees by which it has tied 
 Fort Cassin to the mainland. 
 
 Hog Island, so-called, in the township of Swanton, is a land- 
 tied island, accomplished in this case by the delta deposits of 
 the Missisquoi River. 
 
 It thus appears that some islands have become secondarily 
 attached to the mainland and that large areas of the mainland 
 differ from the lake only in the fact that clay takes the place of 
 water. Such considerations may prove helpful to the reader 
 when in the succeeding pages different areas are described and 
 compared with one another. 
 
 The studies which were described in previous papers were 
 scattered rather generally over the western half of the state 
 and were conducted in much more detailed and systematic manner 
 in some places than in others. This resulted from the way in 
 which the general problem was from time to time approached. 
 
 The rocks first examined were those in the difficult region 
 around Bennington, in the southwestern portion of the state. 
 Six years later (1918) a trip was made through the Vermont 
 valley and parts of the Champlain lowland, Taconic range, and 
 Green Mountain plateau with the definite purpose of searching 
 for a general plan of structure among the rocks over a wide 
 region which might serve as a key to the relations around Ben- 
 nington. Much that was planned for this trip had to be aban- 
 doned on account of illness. In the seasons of 1919 and 1920 a 
 somewhat systematic study was made of a wide surface section 
 from the Green Mountains to Lake Champlain, in the towns of 
 Brandon, Sudbury and Orwell. 
 
 From these several studies, especially from those made in 
 Brandon, Sudbury and Orwell, various inferences were drawn, 
 some of which were given a broad application in the interpretation 
 of the structure of the region. The views expressed were based 
 on personal work. Some found support in the writings of other 
 
148 REPORT OP THE AT'ERMONT STATE GEOLOGIST. 
 
 workers while others were apparently new and clearly called for 
 such substantiation as further study might give. 
 
 The brief studies wdiich it had been possible to make in 
 various parts of the Champlain lowland, up to the season of 1921, 
 had tended to strengthen the belief that the whole of western 
 Vermont is "eminently a natural area" and had suggested that 
 the lowland would probably afford the field relations that would 
 serve best in testing certain views regarding structure. 
 
 The Champlain lowland makes up a large portion of western 
 Vermont. It merges quite imperceptibly with the Vermont valley, 
 both physiographically and geologically, and except as disguised 
 by certain primary differences of the rocks and by faulting may 
 reasonably be shown to merge with the Taconic range, whose 
 foothills as well as the main range itself still show vestiges of the 
 features that are now best preserved over the lowland. The low- 
 land then seems to be only a physiographic subdivision of a large 
 region whose genetic features are essentially identical throughout. 
 Even in its relation to the Green Mountain plateau the designation 
 of lowland should not be understood to convey the idea of strong 
 contrast between the two, for over long distances there is a most 
 gradual transition topographically and almost complete identity 
 or unity geologically between adjacent portions of them. 
 
 Notwithstanding these recognizable transitions between the 
 lowland and the higher lands of the Taconic range and the Green 
 Mountain plateau and the presence of high hills at many places 
 in the lowland this division is structurally a sunken region with 
 respect to surrounding higher surfaces. The Vermont valley 
 may be viewed as the southward extension of the lowland between 
 the plateau and the Taconic range. Since in its breadth from 
 west to east the lowland therefore comprises counterparts of the 
 marginal portion of the plateau, of the Vermont valley and of the 
 Taconic range one finds within it relations that are often pre- 
 served only in much more fragmentary conditions in the other 
 divisions, for one reason or other. 
 
 The meaning of the comparisons which have just been made 
 of parts of the region with each other really comes out only after 
 careful field study ; but it is hoped that the discussions which will 
 follow, taken with those which were given in the first paper, will 
 enable the reader to see the force of the contention that difTerent 
 parts of western Vermont possess strong similarities in a number 
 of ways. 
 
 A survey of the lowland was carried on during the seasons 
 of 1921 and 1922, together with some study of the marginal por- 
 tions of the plateau. The territory covers many square miles. 
 It was necessary to confine attention to those field relations that 
 bear particularly upon structure, simply in order to get over the 
 ground and not leave untouched any large number of places that 
 
PLATE XVIII 
 
 ^yj^-^'ST-^eT-......^^ 
 
 2 PAr ^^7i5^^>=- '^ ^'^"'^ 
 
 ..v^rs'r^^^^^ 
 
 W^ '^^'■ 
 
 
 
 
 Township map of Vermont. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. ]49 
 
 might throw Hght on the main problem. Naturally during- the 
 work many other fascinating problems appeared which it was 
 necessary to pass by. 
 
 DESCRIPTIONS AND DISCUSSIONS OF OBSERVA- 
 TIONS MADE BY THE WRITER WITHIN THE 
 CHAMPLAIN LOWLAND AND ADJACENT POR- 
 TIONS OF THE GREEN MOUNTAIN PLATEAU. 
 
 General plan of discussion. As the field studies described 
 herein were the continuation of those discussed in the first paper 
 it has seemed best to make no marked change in mode of treat- 
 ment. General reference will be given by counties and town- 
 ships which are shown on the accompanying township map of 
 Vermont. Citations of localities are based chiefly on the topo- 
 graphic quadrangle sheets of the United States Geological Survey. 
 
 It may prove useful in some cases to cite observations or in- 
 terpretations of others in order to develop the writer's viewpoint 
 in respect of relations and structure, and in this paper this will 
 be done along with the discussions of different areas rather than 
 in the form of a general preliminary review, such as was given in 
 the first report. 
 
 Because there is often a close relation between topography 
 and geology the topographic features that are of interest in, re- 
 gard to structure will be mentioned at appropriate places. 
 
 GRAND ISLE COUNTY. 
 
 Townships of South Hero and Grand Isle. 
 
 (Plattsburg and Rouses Point topographic sheets.) 
 
 General remarks. From observations made in the season of 
 1920 on the island which includes the townships of South Hero 
 and Grand Isle, suggestions were offered as to how the relations 
 among the formations there present might possibly be explained. 
 These suggestions were made not only on the basis of conditions 
 on the island, but also in the light of careful studies of the field 
 relations at other places in the lake region, particularly in Shore- 
 ham and Orwell. 
 
 While camping on the island in the summer of 1921, parts of 
 it which had not been personally visited before were inspected 
 and excursions were made to the New York side of the lake. 
 
 Principal geological features of the island. The geology of 
 the island has been described in detail by Professor Perkins.^ 
 
 ' Third Report of the State Geologist, 1901-02, pp. 102-17? 
 
150 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 The formations of the island may be briefly described as 
 follows : 
 
 1. Limestones, mostly gray or gray- weathering, generally in 
 rather thick beds, frequently very massive, more or less altered 
 by granulation and, perhaps, somewhat in certain cases by dy- 
 namic agencies ; but generally not marked by clearly visible in- 
 ternal deformation due to shearing. These rocks include a small 
 portion of Brainerd and Seely's "Beekmantown," which is more 
 fully developed on Providence Island just to the south of Grand 
 Isle and parts at least of the same authors' divisions A, B, and C of 
 the Chazy. These rocks occur in somewhat disconnected masses, 
 chiefly in the central and southwestern portions of the island. 
 The Chazy shows much variation in color and the different divi- 
 sions are recognizable on the basis of fossils. The small area 
 of Beekmantown at the south end of the island was considered by 
 Seely and Perkins to belong to division E of Brainerd and Seely's 
 classification. 
 
 2. Other limestones, generally in contrast with those of 
 1 in being composed of prevailingly much thinner beds, but in- 
 cluding somewhat massive blackish rocks of Black River age. 
 All belong to a series which is apparently marked at the base by 
 heavy Black River beds and overlying fairly pure limestones of 
 Trenton age and which ascends through a sequence of mud rocks, 
 all more or less limy, but including fairly pure limestone beds. 
 The members vary in color from gray to bluish-black, the latter 
 usually weathering to a gray. In these rocks granulation is not at 
 all marked. The sequence from base to top is interrupted by dis- 
 placements so that it is not as well shown on this island as at some 
 other places in the lake region which will be mentioned beyond. 
 The alternations from one kind of rock to another, from fairly 
 pure limestone to more argillaceous material, suggest oscillations 
 of level and other conditions which operated to cause changes in 
 the character of the deposits from time to time and changes in 
 the character of the fauna as well. As would be supposed, there 
 are also shown lateral gradations or variations in the same beds. 
 Frequently limestone apparently takes the form of small lenses 
 in more argillaceous rocks. All the conditions indicate that dur- 
 ing the times of deposition of this series, muds were contending 
 with limestones, over which they finally gained ascendency. Some 
 portions of this mud-limestone series are barren of fossils. In 
 others they are scarce. There is an interesting recurrence in 
 low horizons within the shales of forms marking the basal beds 
 which have a typical Trenton fauna ("Glens Falls".) 
 
 This formation of limestones and irregularly repeated muddy 
 limestones and limy muds passes upward into the rocks described 
 under 3. 
 
 3. Prevailingly blackish, shaly mud rocks, still often if not 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 151 
 
 usually limy, effervescing with cold dilute acid, but characterized 
 by persistently finer grain. In their bedded features they are 
 not, however, uniformly thinly-bedded shales. The beds can be 
 seen to vary in thickness from a fraction of an inch to an inch or 
 more and are interbedded with siliceous bands of tougher texture 
 which break with subconchoidal fracture and are often from six 
 to eight or more inches thick. These various shaly rocks have 
 over wide areas a splintery character due to pronounced shearing 
 across the bedding, giving a kind of slaty structure. 
 
 Contacts of the members given under 1 with those of 2 and 
 3 are mostly wanting and their structural relations are, therefore, 
 more or less problematical and open to such interpretation as the 
 general structural features of the region might suggest. The 
 higher members of 2 probably pass upward into the lower beds of 
 3, but there are present well-defined displacements which actual 
 contacts do not seem necessary to demonstrate. 
 
 Attention has been directed by different observers to 'the 
 differences shown at the present time among the formations of 
 the island with regard to the extent to which or the manner in 
 which they have been respectively affected by dynamic agencies. 
 
 The rocks belonging to group 3, as defined above, perhaps 
 make up the larger part of the island. They are generally char- 
 acterized by pronounced deformation. Folding and tilting are 
 common; but even in places where neither of these is marked, 
 they are when only slightly buckled or lying nearly flat distin- 
 guished by a strongly developed cleavage. But this shearing struc- 
 ture is not confined to the members of group 3 alone ; it is found 
 in much of fine grained limestone of category 2. 
 
 This shearing structure has undoubtedly led to confusion in 
 the field among different horizons of the younger members of 
 the Ordovician series. In surface outcrops, particularly small 
 ones projecting through the clay or drift, all that may be visible 
 is an irregular erosion surface of apparently more or less flatfish 
 beds which have been sheared into slates which do not differ much 
 in appearance, whether they belong to group 2 or group 3. This 
 circumstance is of importance because without appreciation of 
 it the real character of a rock in its present surface exposure 
 may not be recognized. 
 
 From the conditions shown on Grand Isle, Perkins^ was early 
 led to regard a considerable portion of the limestones with inter- 
 bedded muds as forming a transitional series between the Tren- 
 ton and the "Utica." The probable occurrence of such a "transi- 
 tional series" in the Champlain basin has also been suggested by 
 other observers.^ From a study of fossils from the younger lime- 
 stones and shales of the Champlain region, Ruedemann^ came to 
 
 1 Perkins, Third Report, 1902, The Geology of Grand Isle 
 
 2 White, Bull. Geol. Soc. Amer., No. 10, 1899, pp. 452-462. 
 
 = Ruedemann, Twelfth Report Vt. State Geol., 1920, pp. 90-100 
 
152 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 the conclusion that the "Ordovician series ends in Vermont with 
 beds no younger than the Trenton group." The thinly-bedded 
 limestones of the basal beds are true Trenton ("Glens Falls hori- 
 zon"). The black mud rocks of the Champlain basin in the 
 south (for example, around Panton) consist entirely of Canajo- 
 harie shale ; in the north they are "prevailingly of the 'Stony Point' 
 shale. In the middle they meet, the 'Stony Point' shale resting 
 upon the Canajoharie shales on Grand Isle and in the Vermont 
 portion of the northern part of the basin." 
 
 Most of the rather barren black shale in the northern part 
 of the basin, carrying Triarthnis becki and Glossograptus qiiadri- 
 mucronatus as its prominent fossils, which extends from the 
 Canadian line southward over the islands of the lake and along 
 the mainland of Vermont, is thought by Ruedemann to be the 
 equivalent of his "Stony Point" shale and to be homotaxial with 
 late Trenton and, therefore, older than true Utica. Ulrich con- 
 curs with Ruedemann in the opinion that no true Utica exists in 
 the Champlain basin. 
 
 On Grand Isle the thinly-bedded basal Trenton rocks form a 
 ridge about a mile east of the west shore of the island, running 
 from a point southeast of Sawyer's Bay, where they are in prox- 
 imity to Chazy beds, northward to the latitude of Gordon Land- 
 ing. At numerous places they yield characteristic basal Trenton 
 fossils. For the most part these beds are not crushed nor sheared, 
 although at some places they have buckled and sheared somewhat, 
 showing clearly that they have experienced lateral pressure. 
 Except where buckled into small folds these rocks appear to lie 
 in a flattish position, dipping gently easterly. They do not ap- 
 pear to form a part of a true anticlinal fold. The western out- 
 crop of the beds forms a slope of variable inclination as now 
 eroded. This slope east of Sawyer's Bay clearly marks" a former 
 shore of the Champlain water body. There is a topographic 
 breach in this Trenton ridge northeast of Rockwell Bay. It seems 
 probable that these rocks formerly had an extension west of their 
 present western margin. 
 
 The muddy limestones with included shaly layers which occur 
 along shore north of Rockwell Bay appear to be younger than the 
 beds forming the ridge just described. They also lie in flattish 
 position, but take on a slight northerly pitch about one-fourth of 
 a mile north of Rockwell Bay. These rocks have strong resem- 
 blance to beds which lie above the basal Trenton near Crane 
 Point in Addison County, which will be described more fully 
 later. Around Gordon Landing the rocks are of more muddy 
 texture than are those southward and are even more thickly- 
 bedded. Near Gordon Landing, although bedding is distinct, the 
 rocks are sheared with easterly dipping cleavage, so that surface 
 exposures away from shore have the appearance of slates. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 153 
 
 A little way north of Rockwell Bay, in a layer near the 
 water, Isoteliis occurs with Prasopora, paralleling the conditions 
 near Crane Point where Prasopora, which sometimes makes up 
 almost an entire bed in the basal series, as it does also on 
 Grand Isle, recurs occasionally in certain layers of the muddy 
 rocks which lie above the basal series. 
 
 Between the west shore of the island at Gordon Landing 
 and the slope of the ridge of basal beds east of it there is much 
 surface covering; but from the general field relations and the 
 attitude of the layers along shore and in the ridge there is nothing 
 that suggests an anticlinal fold so that the so-called younger 
 beds along shore could be interpreted as lying above the basal 
 beds on the western limb of such fold. 
 
 North of Gordon Landing the rocks in some places have 
 resemblance to the basal Trenton and at others to the beds north 
 of Rockwell Bay. At the Grand Isle landing of the Cumberland 
 Head ferry in a thick layer near the water-level there were found 
 specimens of Sinuites cancellatus, fragments of Calym-ene, and 
 small orthocerata. The thick layer just referred to is succeeded 
 northward and upward by an imperfectly alternating series of 
 layers, some of which are dark colored and sheared, while others 
 are lighter colored, as weathered and usually non-sheared. It is 
 somewhat surprising to observe these rather strongly sheared 
 layers lying between others which show no marked cleavage. 
 Among the mud rocks this condition not infrequently occurs 
 within a considerable thickness of beds which do not show any 
 prominent mass deformation and which often lie nearly flat. 
 
 Although the beds near the ferry landing are not greatly 
 deformed, in general there is more evidence of disturbance from 
 pressure in the rocks between Gordon Landing and Camp Ver- 
 mont than in the shore section south of the landing. This dis- 
 turbance is shown in the form of minor buckling and occasional 
 ruptures, as^^well as by mashing and by the shearing which has 
 been mentioned. 
 
 There is acceptable suggestion of an east-west fault at Rock- 
 well Bay, the "transition beds" lying against the Chazy, although 
 the contact is not visible. There is also suggestion of a break at 
 Gordon Landing, with the beds at the north occupying the up- 
 throw side. 
 
 The ridge that has been described above as composed of 
 the basal Trenton beds can be followed only a short distance 
 north of the latitude of Gordon Landing. Northward over areas 
 that have been mapped as "Utica" the surface outcrops are few 
 and usually not clear as to horizon. In some places the rock 
 might without much hesitation be correlated with the "transi- 
 tional series" of limestones and shales rather than with the higher 
 black shale beds ; but extensive shearing and absence of fossils 
 
154 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 make it difficult to decide the matter, particularly in low surface 
 outcrops, such as these rocks usually present. 
 
 From Wilcox Cove northward the shore section displays a 
 series of beds which are predominantly shaly, with some bands 
 of siliceous rock, the whole lying nearly flat. While there is some 
 crushing these rocks are not much tilted. 
 
 The formation of black shale on this island, and in most of 
 its exposures among the islands to the north, as well as on the 
 mainland, has primary structures which serve to distinguish it 
 from the more limy rocks that are thought to be transitional from 
 the basal Trenton beds into it. Even when strongly sheared the 
 black shale formation may be seen to comprise members of 
 variable thickness, as has been mentioned above, some of which 
 are distinctly shaly, while others are of firmer character and more 
 siliceous. These different members are separated by distinct 
 parting planes which come out most sharply when the rocks have 
 been folded or tilted. But the more shaly or muddy beds are 
 marked in addition by fine laminations which often give an ap- 
 pearance of fine-grained wood. These laminations show most 
 clearly when the rock has been weathered, the weathering process 
 having the effect of emphasizing the slight differences in the com- 
 position of the laminae. One is tempted to speculate on the con- 
 ditions that could have produced these laminations which have 
 so much resemblance to seasonal accumulations. 
 
 The "primary" shaly character of these muds is due to 
 these laminations, but there is often shown an imperfect separa- 
 tion under impact which may be an expression of a tendency to 
 minor lenticular segregation of the more limy from the less limy 
 portions of mud in a sea in which limy deposits were contending 
 with argillaceous material, but in which there was always more 
 or less admixture of the two. Many of the laminations in the 
 beds so distinguished are of rusty brown color, in which they 
 resemble the more siliceous bands interbedded with the shales. 
 
 Over the eastern part of the island the rocks which have been 
 mapped as "Utica" probably include some beds which belong to 
 the "transitional series." The rocks at Allen Point may be such. 
 
 North of South Hero station, in the railway cut near the 
 overhead bridge, are outcrops of rock much like that north of 
 Rockwell Bay, and similar rock occurs just east of the station 
 along the main highway. The beds in these outcrops have not 
 been much disturbed from the horizontal and in the railway cut 
 on both sides the dip may be plainly observed at an angle of 
 about 15 degrees easterly. The rock is sheared, giving a splintery 
 structure. 
 
 Again, along the road from South Hero station to Sandbar 
 Bridge, a mile east of the station, some of the low-lying ledges 
 seem to be sheared limy rocks like those of the cut just mentioned. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 155 
 
 Towards Sandbar Bridge the rocks are blacker and more shaly. 
 It would, therefore, seem that there is a gradation eastward from 
 the basal Trenton through a "transitional series" to blacker, more 
 shaly rocks hke that which with some interruptions may be traced 
 along the west shore of the island from Rockwell Bay northward. 
 
 Cedar and Fish Bladder Islands. These islands were visited 
 with a suspicion that they would be found to be made up of the 
 shale formation ; but as they would serve to carry the inspection 
 of the lake rocks eastward towards the Vermont mainland it 
 was kept in mind that possibly some overthrust rocks might be 
 found. There was seen no evidence of any kind to indicate that 
 at the present time the slates of these islands have any traces of 
 older rocks lying on them. 
 
 On these small islands the rocks which are shales are exposed 
 in high cliffs around their shores, but are concealed by clay over 
 their central portions. Savage Island was not visited. The 
 Vermont Report shows it to be composed of the shale. 
 
 The rocks of Cedar and Fish Bladder Islands are entirely 
 similar, and are laminated muds with firmer layers, such as have 
 been described. Recognizing in these laminations a primary char- 
 acter it is clear that the beds of these islands have been terribly 
 jammed and mashed, and distorted in the most amazing manner. 
 The deformation is largely that of fracture; once continuous 
 layers have been broken into chunks which have been separated 
 from each other and mashed together, producing a sort of brec- 
 ciation. Cleavage is also pronounced. At some places it appears 
 that small blocks have moved over other parts of the formation, 
 but such displacements were never very extended. 
 
 Kibbie Point. At Kibbie Point on the main island are rocks 
 similar in their several structural features to those south of Sand- 
 bar Bridge and those of the islands just described. Distortion 
 and shearing are plainly manifest. At this place a minor thrust 
 was noted which did not appear to pass beyond the immediate 
 exposure involved. 
 
 Robinson Point. At Robinson Point, four miles north of 
 Kibbie Point, in the northeastern part of the island, the laminated 
 shales are apparently not so badly mashed as in the southeastern 
 part. They are disposed in rather gentle folds as can be deter- 
 mined from the laminations, which are usually the only means of 
 identifying the stratification. The bedding is very often obscured 
 by cleavage. This cuts the bedding at different angles as a con- 
 sequence of buckling which preceded the shearing. At Robinson 
 Point the stratification dip is about 15 degrees westerly, while that 
 of the cleavage is 60 degrees easterly. Shearing has often pro- 
 duced a rough jointing which might be mistaken for bedding. 
 
156 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 It is, however, uneven, giving a ragged, splintery structure. In 
 many places bedding and cleavage dip in the same direction, 
 although the two dips do not coincide in most cases. 
 
 In common with all the areas in the lake region the north- 
 eastern part of this island shows at some places local disturbances 
 of the slate by folding and minor crushing, but these particular 
 features are not so marked in present exposures in this part of 
 the island as at other places. 
 
 Occasionally in these rocks one of the firmer siliceous beds 
 will be seen to have buckled into gentle, wavy folds, while the 
 laminated muds above and below show no apparent folding, but 
 instead a more or less prominent cleavage induced by the same 
 pressure that folded the firmer band. This is but one instance 
 of the ease with which the shales accommodated themselves to 
 pressure by shearing. 
 
 Calcite veining is very common among the shales in the east- 
 ern part of this island and sometimes indicates mashing when 
 such is not very apparent from any other structures. 
 
 As well seen in clifif exposures the way a mass has behaved 
 under shearing stress, even when bedding structure is largely 
 destroyed, affords a means of telling whether the rocks were 
 originally shaly or somewhat more massive. The more thinly- 
 bedded rocks will give a slaty or finely splintered rock, while the 
 thicker beds will be coarsely splintered, or sometimes roughly 
 jointed. 
 
 A rather careful inspection of Grand Isle, joined with an 
 examination of the rocks of North Hero, Alburgh peninsula. 
 Isle La Motte, some of the smaller islands, and the Vermont main- 
 land, shows that the Ordovician rocks of the Champlain basin, 
 above the Beekmantown, are well represented on Grand Isle, 
 and that some of the shales belong in the higher portions of the 
 shale formation. On Grand Isle fossils from these higher hori- 
 zons are rare, probably largely because of shearing ; but in litho- 
 logical characters the rocks are closely comparable to and seem 
 susceptible of indentification with similar rocks in the upper part 
 of the shale formation in many of the other parts of the region 
 as named above. 
 
 The shore sections of the islands and the rocks along the 
 mainland from the Canada line to the southern limit of the lake 
 show that the various submerged channels, passages and bays that 
 now form the basin known as Lake Champlain are practically 
 throughout excavated in the softer rocks belonging to the transi- 
 tional series of limestones and shales or to the higher black shales 
 of the basin. But on both the islands and the mainland, some- 
 times forming parts of the present lake shore, are areas of older 
 and very dift'erent kind of rock whose relations to the shales form 
 some of the problems of the region. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 157 
 
 Structure of Grand Isle. Certain apparently possible in- 
 terpretations of the structural relations of the rocks of Grand 
 Isle were discussed in the writer's first paper in the light of such 
 studies as it had been possible to make up to the time of its publi- 
 cation. Attention was directed to the secondary structural dif- 
 ferences shown by the rocks of the island. It was pointed out 
 that a large portion of the formation including the transitional 
 series and overlying black shales might be somewhat sharply dif- 
 ferentiated from the massive strata of Beekmantown and Chazy 
 ages. The deformational features shown by much of the transi- 
 tional and shale series were noted and it was indicated that in the 
 crushed condition of these rocks, now manifested by minor fold- 
 ing and tilting, minor reverse faulting, mashing and coarse brec- 
 ciation, and different modes of shearing, they stand in contrast 
 to the more massive strata of the island. The Beekmantown and 
 Chazy beds were shown to have a generally flattish position in 
 most of their exposures, particularly in the western half of the 
 island, and not to be notably sheared, although somewhat de- 
 formed by pressure along or near their eastern margins. The 
 Black River and the basal Trenton beds making up the ridge that 
 has been described above, were also shown to lie rather flat, 
 although the latter were described as showing minor buckling 
 and shearing at some places. 
 
 Before passing to the discussion of the possible significance 
 of the structural differences shown by these Grand Isle rocks as 
 the result of differences in behavior under dynamic stresses it 
 may be worth while to consider other differences of secondary 
 character which some of them show. 
 
 The Beekmantown and Chazy rocks give an impression of 
 having suffered certain alterations before the formation of the 
 younger beds. The features referred to do not seem to represent 
 on a minor scale or to be in the same class with those which in 
 similar rocks of the region have more or less clearly been due 
 to dynamic pressure, which in addition to producing metamor- 
 phism by crystallization also caused flowage and cleavage in dif- 
 ferent degrees, with the formation of marble or marbly rocks. 
 The particular alterations mentioned appear to be due rather to 
 static metamorphism of the rocks. As has been mentioned, they 
 are apparently largely of the nature of granulation which has 
 more or less completely changed the original material and pro- 
 duced a tough rock from which fossils are extracted with much 
 difficulty. In some parts of the Champlain region rocks which 
 have thus been altered have also been changed further by dynamic 
 metamorphism and in such cases, of course, the earlier alteration 
 features are blended with those of later date or are quite concealed. 
 Gradations occur. In those rocks not much affected by dynamic 
 agencies the fossils retain their outlines more or less perfectly, 
 although crystallization may have destroyed details. In other rocks 
 
158 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 the features resulting from static metamorphism are very evident, 
 but other characters resuUing from shearing stress appear in the 
 shape of distortion of fossils and flowage or cleavage. In still 
 other rocks,, pressure has more completely obscured the older static 
 features with the destruction or almost complete obliteration of 
 fossil remains. 
 
 On Grand Isle the metamorphic characters of the Beekman- 
 town and Chazy rocks appear to be due chiefly, if not wholly, to 
 static changes. Absence of shearing, lack of distortion of fossils, 
 apparent absence of mass deformation by folding and other 
 features all point to such conclusion. If these rocks generally had 
 suffered any internal deformation they should give more evidence 
 of it, comparable with such as is found in other and similar rocks 
 of the region, some of which are clearly of similar age while 
 others probably are. Such deformation as these rocks may have 
 experienced probably involved extensive mass dislocation, rather 
 than what might be called internal adjustment, except as the 
 latter was locally developed at some places. 
 
 The static alteration features of these massive, granular 
 limestones give them an appearance of antiquity in contrast with 
 the rocks with which they are associated. In the Black River and 
 basal Trenton beds there is not present apparently the same de- 
 gree of alteration by granulation as the Beekmantown and Chazy 
 beds show. In these differences there is offered an indication 
 quite distinct from that which fossils show of a hiatus between 
 the Canadian and Mohawkian of the Champlain region. One is 
 tempted somewhat to speculate on what the conditions were which 
 led to the induration of the older rocks. 
 
 As was discussed in the first paper it has usually been as- 
 sumed that there has been no great amount of lateral disturbance 
 of any of the formations now found on Grand Isle, that the 
 various rocks, including the masive limestones of the Beekman- 
 town and Chazy formations, rest now substantially where they 
 were formed. Unfortunately, the conditions on the island at the 
 present time do not allow of positive determination of the relations 
 between the massive limestones and the younger rocks. It was 
 not possible to find any contacts of the former on the latter any- 
 where on the island. The idea that there has been displacement 
 of the rocks of the island rests upon the considerations that such 
 kind of deformation is widely prevalent in and characteristic of 
 the region and that the rocks of the island show the effects of 
 profound pressure. 
 
 It was first supposed that the shale formation of the whole 
 region had undergone more severe folding as a whole, than 
 now appears to have been the case, even in the eastern portion of 
 the basin where the pressures might reasonably be assumed to 
 have been more powerful. The comparatively small number of 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 159 
 
 exposures which it had been possible to inspect when such a view 
 was formulated seemed to indicate that the shales were usually 
 disposed in rather large close folds with o^^erturning and conse- 
 quent isoclinal structure. For places where the shales had clearly 
 been overridden by older rocks along thrust planes they were 
 discussed and pictured as having a prevaiHngly easterly dip, which 
 was attributed to overturning. The conditions noted in a more 
 extensive study of the region and from an examination of the 
 shale formation in widely separated localities contradict such a 
 view and have afforded data for a revision of ideas. 
 
 Any severe buckling or folding which the shales show now 
 seem to be more or less local corrugations which pass along the 
 strike into crush zones or fault fractures, or perhaps eventually 
 into relatively gentle flexures marked only by a profound cleavage. 
 Across the strike also these localized zones of severe folding, 
 fracturing and mashing will apparently pass into gently undulating 
 folds. Eastward toward the areas of the region marked by over- 
 thrust of older rocks on the shales the latter are more generally 
 crushed and tilted, but at some places not far from the present 
 margin of overthrust rocks they are notably flat, as indicated by 
 bedding and laminations, although when flat they are always 
 strongly sheared with the development of fracture cleavage. 
 
 What then are some of the conclusions to be drawn from 
 the flat position or, generally speaking, open folds which these 
 different rocks show, perhaps having Grand Isle principally in 
 mind at this point? These rocks have clearly been acted upon 
 by powerful compressive forces. This is shown on Grand Isle, 
 but more clearly at other places. In the absence of any folding 
 of large dimensions, or even universal close folding of small 
 dimensions, the inference is strong that these rocks yielded to 
 pressure chiefly through shearing of one kind or other. In this 
 particular the massive limestones behaved like the shales ; but 
 in the former the shearing did not always manifest itself as an 
 internal deformation with the development of fracture cleavage 
 or other pronounced internal structure attributable to pressure, 
 even when the associated shales often developed such structures 
 to a high degree. On Grand Isle the massive strata have clearly 
 effectively resisted any appreciable internal deformation for the 
 most part. If this is not the correct interpretation it is not only 
 difflcult to understand their own characters but also why the 
 much less massive, thinly-bedded, basal Trenton beds in west 
 part of the island have not been more severely deformed in all 
 ways. The massive beds have acted as a buffer for the younger 
 rocks. 
 
 What then has probably been the behavior of the massive 
 strata under pressure if they have not buckled or sheared with 
 any visible flow or fracture structures? They are probably to 
 be thought of as having moved as a great block or as blocks frag- 
 
160 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 mented from the main mass with which they were once joined. 
 They have resisted internal deformation in some places, as on 
 Grand Isle, without, however, being able to prevail completely 
 against the pressure. They were competent against such deforma- 
 tion as the shales exhibit, but not resistant enough to remain in 
 place. From a consideration of the very different primary char- 
 acters of the heavy limestones and the shales it is not difficult 
 to see how forces competent to crush the shales might leave the 
 massive limestones practically free of such features, but since it 
 is apparent that the shales could hardly have been so generally 
 crushed or sheared without diminishing their original breadth 
 from east to west to a marked extent, it naturally becomes a ques- 
 tion of how the massive rocks accommodated themselves to the 
 simultaneous action of the same forces. That accommodation 
 was reached in some places in the lake region by shearing even 
 in the massive limestones is shown in numerous cases, but on 
 Grand Isle it was effected chiefly by mass dislocation. 
 
 In the writer's first discussion of the probable structure of 
 Grand Isle (see first paper) some of the considerations developed 
 above were dwelt upon, but a good deal of stress was put upon 
 present conditions among similar rocks in other parts of the 
 Champlain region, particularly along the lake shore farther south. 
 In Shoreham and Orwell the present field relations leave no doubt 
 that older formations have ridden over the shales along thrust 
 planes, and while at many places the massive beds have been 
 somewhat folded and fractured and sometimes internally de- 
 formed, there are other places where the massive beds lie nearly 
 flat with little evidence of internal changes resulting from pres- 
 sure, although the rocks may be altered by other processes as is 
 the case on Grand Isle. The so-called "Potsdam" and "Beekman- 
 town" at Mt. Independence in Orwell and at Mutton Hill in Shore- 
 ham are cases in point. The conditions in other parts of the 
 Champlain basin also give support of very positive character to 
 the conclusion that massive Lower Ordovician beds similar to 
 those on Grand Isle have been moved by thrusts and are not now 
 in their original places. 
 
 In some studies which the writer made in the Hudson valley 
 region near Poughkeepsie, New York, among rocks which in spite 
 of their apparent remoteness from the Champlain basin have 
 much resemblance to certain strata of the basin, not only in re- 
 spect to age and general lithology, but in character of deforma- 
 tion as well, there seemed to be acceptable evidence for the con- 
 clusion that massive limestones of Lower Ordovician age had 
 been thrust through younger shales by reverse faulting, often 
 with a horizontal component powerful enough to drive the mas- 
 sive rocks in a lateral direction over the younger beds for a con- 
 siderable but usually indeterminable distance. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 161 
 
 While reverse faulting was recognized as probably playing a 
 part in the disturbance of the rocks of Grand Isle, so that they 
 are probably to be regarded as crowded somewhat by blocks 
 riding against other blocks, the view was rather favored (see first 
 paper) that the Beekmantown and Chazy beds, and some of the 
 younger rocks as well, had been moved along a "major" thrust 
 plane that had sheared beneath them after they had been broken 
 by earlier reverse faulting and had transported them, perhaps 
 for a long distance, from the east. They were thought of as 
 having ridden over the shales that form the eastern part of the 
 island, as well as others which intervene between the island and 
 the Vermont mainland. Largely on account of normal faulting 
 that probably occurred subsequent to the action of pressure on 
 these rocks it is not now possible to decide whether this view is 
 correct, or whether the massive rocks have simply broken through 
 the younger beds and perhaps have travelled only a short distance 
 over the shales which are now concealed beneath them. ' In this 
 connection it should perhaps be remembered that we are dealing 
 with an eroded and a sunken region. 
 
 From relations which are present in the Taconic hills of Sud- 
 bury and Orwell it was conjectured that a major thrust, like that 
 referred to above, might have cut in such way as to carry early 
 Cambrian strata at one place and early Ordovician at another over 
 the shale formation. The conjecture rested in part on the as- 
 sumption that early Ordovician beds lay unconformably upon 
 eroded Cambrian rocks. The conditions in the Taconic hills are 
 very puzzling and require further detailed study with reference 
 to this point, but there remains little doubt of the existence of 
 thrusting in the Taconic range. In the range the difficulty is 
 to account definitely for the remarkable present distribution and 
 contiguity of what appear to be Lower Cambrian terrigenous 
 rocks and certain limestones including probably lower and middle 
 Ordovician rocks. 
 
 The absence of large folds in the various rocks of the Cham- 
 plain basin does not seem to fall in with a view that these 
 formations were at any time elevated into mountain masses by 
 huge and extensive plications of the crust. But the absence of 
 large folds does not militate against an idea that there may well 
 have been a considerable elevation of the rocks at some time in 
 their history. That much elevation was possible seems to follow 
 from consideration of the result of integrating a large number 
 of thrusts of all dimensions, including those which now find ex- 
 pression in cleavage. The statement that there has not been ex- 
 tensive folding on a large scale is in accord with facts observed 
 in the field. Lack of such folds in the shales seems to have been 
 the direct result of failure to fold on the part of the massive beds 
 which underlay them. But if the latter were thrust into the shales 
 in varying degrees, sometimes into them, sometimes through them 
 
162 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 and sometimes even over them, the effect apparently would have 
 been to produce the crushed characters which they now show and 
 to give a prominent fracture cleavage, whether the shales re- 
 mained practically flat or were previously buckled into small folds 
 or jammed into crush zones. The massive rocks are in the posi- 
 tion of overthrust with reference to the shales that lie on one side 
 of them, and of underthrust with respect to shales that lie on 
 the other side and above them. Either relation seems sufficient 
 to account for crushing and shearing of the shales. 
 
 On Grand Isle then different masses of rocks are probably 
 to be thought of as now in more or less displaced relations with 
 respect to one another as the result of compression. But the 
 evidence on Grand Isle itself is inconclusive. Features elsewhere 
 in the region that show what the actual behavior has been and 
 what the tendency obviously was must be invoked and the prob- 
 able presence of a common plan of structure for the region must 
 be recognized in explaining the structure of Grand Isle. 
 
 It may as well be stated at this place as elsewhere that so 
 far as observations have gone on the Vermont side of Lake Cham- 
 plain, there is no evidence to show a thrust plane cutting beneath 
 all the rocks now exposed in the Champlain basin. If such plane 
 exists, perhaps evidence for it would hardly be sought on the 
 Vermont side. There may be such a plane cutting at c6nsiderable 
 but unknown depth and having its line of emergence in older 
 rocks on the New York side of the lake. On the Vermont side 
 the thrusts of various magnitudes which cut the rocks along the 
 general strike and which are repeated across it may be the surface 
 expression of a deep-seated shear, but the major thrusts on the 
 Vermont side cut above the weak shales of the region, and are 
 themselves apparently modified by antecedent faults and thrusts 
 of minor dimensions. 
 
 North Hero Township, 
 
 (Rouses Point topographic sheet.) 
 
 The township of North Hero comprises several small islands 
 of varying dimensions and two larger ones which are joined by 
 a narrow neck, a portion of which, known as the "carrying place." 
 is flooded at high water. These various insular areas are all of 
 low relief and are made up of the shale formation. As in the 
 case of Grand Isle the most satisfactory exposures are found 
 along shore. 
 
 While there are some minor variations in the bedded char- 
 acters of the rocks of the North Hero' islands they are prevail- 
 ingly black, limy shales with occasional firmer bands and much 
 like those of the northern end of Grand Isle, showing beds of 
 different thicknesses with the more muddy ones distinctly marked 
 by laminations, accentuated by weathering, vvliici* appear in rock? 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 163 
 
 that have been strongly sheared, as well as in those which have 
 not. The firmer beds are composed of tougher, more siliceous 
 material than the associated muds. On these low islands with 
 visibly limited vertical range of beds the firmer usually rusty beds 
 do not so frequently appear and are not such conspicuous members 
 as on the Vermont mainland, where they serve as useful features 
 for correlation. On North Hero, as elsewhere, these rocks are 
 of monotonous aspect, although with respect to the degree in 
 which they are now sheared and cut by cleavage they show con- 
 spicuous differences among their outcrops. 
 
 The rocks were examined primarily for their secondary struc- 
 tural characters. In their primary lithological features they form 
 a fairly homogeneous mass of deposits of apparently uninter- 
 rupted sequence. 
 
 Professor Perkins in his description of these islands has 
 given an accurate account of the distribution and other general 
 characters which it is hardly necessary to repeat, except as it may 
 be desirable to emphasize certain aspects that belong to a discus- 
 sion of the geology of the whole region. 
 
 The prominently argillaceous nature of the shale formation 
 comes out strongly from the manner in which its surface portions 
 have weathered. In many places the shale may be seen to grade 
 upward into clay which retains the primary laminated character 
 of the original rock. While the surface material of the islands 
 is apparently to a considerable extent of glacial origin, much of 
 the clay is purely residual material which has probably been 
 largely formed since the glaciation of the region. Such material 
 is apparently nowhere very thick. 
 
 While the shales have clearly buckled locally under pressure 
 and almost always show cleavage well developed, they are ap- 
 parently more commonly disposed in gentle swells of moderate 
 lateral extent and comparatively small vertical displacement so 
 that the bedding has low easterly or westerly dip and the axes of 
 the folds lie horizontally or more often have slight northerly or 
 southerly pitch. Such features are of interest with respect to the 
 deformational history of the region, particularly with reference to 
 the question of the extent of the region involved in the folding 
 which is supposed to have occurred at the close of Ordovician 
 time. 
 
 Studies made on North Hero seemed to show that the shales 
 are more severely jammed along certain north-south belts than 
 along others and that even shearing as expressed by fracture 
 cleavage shows similar geographical segregation and is more 
 marked in some places than at others even on the same meridians. 
 Fossils are not uncommon in parts least sheared, so far as fossils 
 are apparently present in these rocks ; but where shearing has 
 been severe, as might be expected, fossils are hard to find. 
 
164 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Some of the outcrops of the shore sections may now be 
 briefly described. 
 
 On the island that Hes just north of Grand Isle the rocks 
 along shore between Grand Isle bridge and City Bay lie generally 
 in a flattish position, from the bridge northward for a distance of 
 about two miles, pitching gently to the north and then changing 
 to an equally gentle southerly pitch. Whether the rock through- 
 out the distance mentioned all belongs to the eastern limb of a 
 common anticlinal fold is not certain. The dip is predominantly 
 easterly, but where the pitch changes to southerly, about a mile 
 south of City Bay, the rocks appear to be more broken by rough 
 compression "joints" and shearing planes than farther south. At 
 several places graptolites, probably G. quadrimucronatus, and 
 heads of T. becki were found. 
 
 Along the west shore of this island similar variations in direc- 
 tion of pitch were noted ; at Hazen Point the shales pitch south- 
 erly, less than a mile to the north they pitch in the opposite direc- 
 tion. In traversing the west shore one walks diagonally over 
 small, gentle anticlinal and synclinal folds. At Hazen Point the 
 dip is westerly, a mile north and nearly on the same meridian the 
 dip is easterly. Farther north, about midway of the shore, the dip 
 changes to westerly. Cleavage is usually well developed along the 
 west shore. It did not appear that one type of fold was more 
 marked in this regard than the other. In some places the folds are 
 quite symmetrical, but in others they are less so and sharper and 
 the beds are tilted to a high angle or even to a vertical position, 
 and are sometimes overturned. Mashing and fracturing of beds 
 are common in the sharper folds and most of the anticlinal buckles 
 show some modification from crushing. Usually these crush zones 
 are further marked by veinlets and streaks of calcite. Differences 
 with respect to the expression of shearing may be correlated 
 definitely with primary differences in the characters of the beds. 
 In both easterly and westerly dipping beds a sort of jointing 
 practically perpendicular to the bedding and parallel or diagonal 
 with the strike was occasionally noted, especially along the shore 
 of Pelot Point peninsula. This type of fracture is probably also 
 an expression of shearing strain. Plates XIX and XX serve to 
 convey ideas of the nature of some of the structures more clearly 
 than verbal descriptions could. It seems as though folding and 
 fracture sometimes preceded the formation of cleavage, as though 
 the latter were the final expression in such cases of the shearing 
 stress. Probably, however, these respective deformations were 
 sequential in the same episode. 
 
 If it were assumed that there was considerable lateral varia- 
 tion in the characters of the beds of this shale formation, it is 
 not difficult to understand that at some places along the same gen- 
 eral meridian the rocks were mashed or broken by faults of small 
 displacement and that at others sufficient relief came from frac- 
 
jrf^ 
 
 bJj.- 
 rtf> 
 
 
 tu o 
 
 el 
 
 =• o 
 o 
 
 oS 
 
 ■V 3 
 '3 O 
 
 
 
M Ctf W « 
 
 — 'i^ ^ li 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 165 
 
 ture cleavage or compression jointing. These different types of 
 deformation clearly belong to the same class or category and, 
 probably, to the same general episode of disturbance. 
 
 Along the west shore of the island in many places where the 
 rocks were not too badly sheared, graptolites and glabellas of 
 Triarthrus hecki were found. They were seen most abundantly 
 just north of Hazen Point and along the shore of Pelot Point 
 peninsula. Exceptionally low water in the season of 1921 allowed 
 an inspection of practically the entire west shore section. South 
 of Pelot Point the shales form bold cliffs which on foot are im- 
 passable except at low water. Possibly the rocks contain other 
 fossils, but such were not seen. 
 
 The shale formation continues from the island just described 
 to the one just north of it ; but on this northern island much of 
 the shore is very low and bowlder strewn, with no outcrops of the 
 shale now visible. Good outcrops occur along the east shore in 
 the southern part and on the west shore north of Blockhouse 
 Point. These sections show the same kinds of rocks and fossils 
 and the same structures as those found on the island just south. 
 
 Alburgh Peninsula. 
 
 (Rouses Point topographic sheet.) 
 
 The topographic and geologic features of Alburgh are quite 
 like those of the North Hero islands. The peninsula is everywhere 
 of low relief, only in two or three small areas rising above 200 feet. 
 Several swampy tracts occur and some of these probably mark 
 nearly or quite complete separation of the hard rock formation at 
 the present water-level, so that if the surface material which now 
 fills them were removed the peninsula would be resolved into 
 insular or smaller peninsular fragments of the shale formation. 
 
 The rocks of Alburgh were examined over the interior of 
 the peninsula at many places and for long distances where exposed 
 along shore, but on the shore and inland there are many stretches 
 and areas where the shales are not exposed. 
 
 Along the east shore bordering Alburgh Passage there is 
 an almost continuous outcrop of the shale. At many places be- 
 tween Wagner Point and Point of the Tongue the shales dip 
 easterly at low angle with easterly dipping cleavage. On the 
 west shore of the Point of the Tongue the rocks are much dis- 
 turbed, like those on the west shore of Pelot Point farther south 
 on North Hero. Near the point the rocks are folded into a fairly 
 sharp anticline. Northward the beds of the western limb stand 
 at a high angle of dip and still farther north are overturned with 
 high easterly dip, with shearing in the direction of the bedding. 
 
 After a stretch of sandy beach the rocks outcrop again at 
 Coon Point, whence, with a slight interruption at Palmer Cove, 
 they continue practically without break along the shore of Isle 
 
1C6 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 La Motte Passage, to within two-thirds of a mile of the toll 
 bridge. 
 
 At the western end of "Sand Beach," at Coon Point, the 
 shales form a gentle open syncline. This is followed westward 
 by a smaller, unsymmetrical anticlinal fold and this by a small, 
 irregular synclinal flexure, which is succeeded by a broader anti- 
 clinal swell and this in turn by a broken syncline whose western 
 limb is crushed against an anticlinal buckle. All the deformational 
 features appear to have been the result of compression. Some 
 portions of the rock had apparently become wedged between 
 others and 'confined, so that under continued compression there 
 occurred some differential movement and offsetting giving a 
 structure simulating step faulting as produced by gravitational 
 tensional stress. The beds are not distinguished by strong 
 cleavage. 
 
 At Coon Point, in fact, the rocks for the most part do not 
 show pronounced shearing and the locality is an excellent col- 
 lecting ground for fossils, particularly fragments of the trilobite, 
 Triarthrns becki, which were seen here in abundance. Graptolites 
 were also found. 
 
 In the section along the west shore north of Coon Point 
 there are no especially noteworthy structures different from those 
 which have been described. About two miles north of the point 
 the rocks show prevailingly low westerly dip and carry fossils 
 like those at Coon Point; a series of vertical joints with strike 
 N. about 52 degrees east cuts the shales at this place. 
 
 Just north of the Alburgh end of the Isle La Motte toll 
 bridge is a high cliff in the shales and the shore road cuts through 
 these rocks. At this place the rocks are severely jammed and 
 the laminated beds much distorted and broken, showing great dis- 
 order. The rocks are filled with veins and bunches of calcite. 
 North of these outcrops the shore is low and bowlder strewn with 
 few outcrops as far as Windmill Point. Between Windmill 
 Point and Rouses Point ferry landing the shales carry graptolites 
 and fragments of trilobites and dip westerly at a low angle with- 
 out conspicuous cleavage. 
 
 Ruedemann^ reports a list of fossils from alternating black, 
 calcareous shales and black to dark gray impure limestone out- 
 cropping along the lake shore one and a half miles east of Wind- 
 mill Point which leaves "no doubt of the Trenton age" of the 
 beds. 
 
 1 Twelfth Report of Vt. State. Geol., p. 97. 
 

 A 
 
 ^ 
 
 S 
 
 
 CB 
 
 i-^ 
 
 
 6J3 
 
 
 
 cS 
 
 ^ 
 
 
 C 
 
 tw 
 
 
 o 
 
 O 
 
 
 
 
 
 c 
 
 ^ 
 
 
 OJ 
 
 
 
 ^ 
 
 3 
 
 
 H 
 
 O 
 to 
 
 
 >> 
 
 ^ 
 
 
 
 OJ 
 
 
 ^ 
 
 
 
 o 
 
 o 
 
 a; 
 to 
 
 '*~t 
 
 
 
 a 
 
 rf 
 
 ■;:; 
 
 
 
 > 
 
 %-i 
 
 1-H 
 
 
 o 
 m 
 
 (P 
 
 0) 
 
 'O 
 
 ^^ 
 
 o 
 
 <0 
 J2. 
 
 O 
 
 § 
 
 ^ 
 
 
 d 
 
 c 
 
 <0 
 
 u 
 o 
 
 k1 
 
 ID 
 
 
 
 
 s 
 
 to 
 
 CO 
 
 M 
 
 
 COt(-i 
 
 c 
 
 d 
 
 O 
 
 o 
 
 H 
 
 
 " g3 
 
 m ^ M 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 167 
 
 Along the road that crosses the peninsula one and a half 
 miles north of Isle La Motte station and again along the shore 
 road and the shore near Dillenbeck Bay the shales yielded only 
 graptolites and T. becki. The same fossils were found at East 
 Alburgh and at Alburgh Springs along shore and also in some 
 outcrops along the road between Alburgh Springs and Alburgh, 
 west of Mud Creek. 
 
 The prevailing rocks now exposed over the Alburgh penin- 
 sula are the black, laminated shales and the conspicuous fossils 
 are graptolites, probably G. quadrimucronatus and fragments of 
 Triarthrus becki. 
 
 Isle La Motte. 
 
 (Rouses Point topographic sheet.) 
 
 In its main topographic outlines Isle La Motte bears much 
 resemblance to Grand Isle, of which it is also to a large extent 
 the geologic counterpart. In its general low relief it is like the 
 other islands of the lake and portions of the Vermont main- 
 land. Its rocks were noted very early in the history of geological 
 exploration of the lake region and have been more recently de- 
 scribed and mapped by Brainerd and Seely and by Perkins. In 
 the published descriptions of the rocks their outstanding deforma- 
 tional characters have been mentioned, but no definite attempt has 
 been made to account for the secondary relations which the 
 formations have to one another, nor to correlate the conditions 
 found on the island with those found in other parts of the region. 
 
 Several days were spent in a careful inspection of the island 
 and the following brief review of the formations, as well as the 
 more particular account and discussion of the secondary features 
 are based upon personal acquaintance with the rocks. 
 
 The formations on Isle La Motte include a small area of the 
 uppermost part of Brainerd and Seely's Beekmantown, exposed 
 chiefly along shore in the southern part of the island, a large area 
 of Chazy, including parts at least of all three divisions as defined 
 by Brainerd and Seely and having a combined thickness as meas- 
 ured by these observers of about 500 feet^ a small patch of Black 
 River of roughly determined stratigraphic boundaries, a con- 
 siderable area of Trenton limestone, and three relatively small 
 exposures of the so-called "Utica" shale. In some of their struc- 
 tural characters and in their geographic arrangement many of 
 the rocks have strong resemblance to similar rocks on Grand Isle. 
 
 The Beekmantown of the main island (Cloak Island will be 
 described beyond) is confined to the southern end known as "The 
 Head." Its surface extent is relatively small, although its shore 
 section is nearly a mile long. The top of the formation was 
 
168 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 drawn by Seely and Perkins at a dark, compact layer about 30 
 inches thick which carries Isochilina and which is further char- 
 acterized by breaking into large cubical blocks. The rest of the 
 formation, as exposed to the limit of low water, consists of firm 
 and shaly beds, varying in thickness from 6 to 30 inches. The 
 rocks pitch in a general northerly direction at a low angle of 
 about 5 degrees and are overlain by the lower Chazy. The gen- 
 erally flattish position of the Beekmantown beds and their lack 
 of any shearing deformation are noteworthy features. Their 
 primary characters have been sufficiently described by other 
 observers. 
 
 The Chazy strata, which succeed the Beekmantown, have a 
 similar flattish position, dipping at a low angle in a general north- 
 erly direction. Their present surface outcrops have a somewhat 
 sinuous strike across the island. The vertical variations both 
 among and within the lower Chazy beds are noteworthy, and 
 there are horizontal variations shown in the rocks along shore, 
 which are often accentuated by weathering, but which it is not 
 possible to trace for any considerable distance inland. As a 
 whole, the Chazy formation is impressive because of the massive- 
 ness of its beds. This massiveness appears to be at its maximum 
 in the limestone members of the Middle Chazy. The portion of 
 the Chazy regarded as forming the lower division, or Group A of 
 Brainerd and Seely, seems to have a larger visible extent on the 
 island than any other portion of the Chazy. The so-called Middle 
 Chazy is, however, widely exposed. Outcrops of the upper por- 
 tion are confined to a relatively small area on the east side of the 
 island about midway of its length. The beds of this upper por- 
 tion appear to pass westward beneath surface material, but out- 
 crops are lacking to show how far it may extend. 
 
 About midway of its length the island is divided by a low, 
 swampy tract of land, south of which except for a small strip of 
 shale along the east shore, the visible rock all belongs to the 
 Beekmantown or Chazy. North of this swampy land much of 
 the island is under clay or drift which conceals the hard rock 
 and in these areas the interesting features are the old marine 
 clays, the sea beaches with their fossils and the drift. The 
 drift may be partly an outwash from a readvance of the ice. In 
 it occur numerous shallow depressions, now often pools of water, 
 which suggest "kettles" formed by stranded blocks of ice. The 
 Pleistocene deposits present a problem by themselves which the 
 writer has made no effort to work out. 
 
 Over the eastern part of the northern half of the island the 
 hard rock outcrops in many places and apparently belongs chiefly 
 to the basal Trenton of the region. How far the members of this 
 formation may extend beneath the surface covering to the west 
 and north is a matter for conjecture. The Trenton rocks may be 
 traced by their outcrops over an area about one and a half miles 
 
PLATE XXII 
 
 Contact along a fairly regular and nearly vertical plane 
 of faulting between basal Chazy with subjacent Beek- 
 mantown beds and strongly brecciated middle Chazy 
 limestone, at the southwestern end of Cloak (Hill's) 
 island, Isle La Motte. View looking north. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 169 
 
 long and a mile wide. They reach the east shore in a few places, 
 but are usually separated from the lake by narrow bands of shale 
 or by the Black River. The Trenton rocks are rich in fossils and 
 in this particular and other features are much like those in the 
 western part of Grand Isle. 
 
 At the southeast, north of Clarks Bay, the Trenton beds are 
 separated from the lake shore by a small band of Black River. 
 There is nothing to suggest that the Black River ever had on 
 Isle La Motte a much greater extension in its secondary relation 
 to the other rocks with which it is now associated than it has at 
 the present time. As a whole the Black River and the Trenton 
 beds lie in a fiattish position and are not extremely deformed. 
 
 The Black River and Trenton beds seem to show with respect 
 to alteration differences from the Chazy similar to those which 
 have been mentioned for Grand Isle. The rocks of Isle La Motte 
 are clearly part and parcel of the series to which those of Grand 
 Isle belong. 
 
 Structure. The various expressions now to be seen of 
 the noteworty deformations of the rocks on Isle La Motte are 
 to be found chiefly along or near the eastern shore. Description 
 will begin with rocks at the southeastern end of the island. 
 
 The gentle northerly dip shown by the beds at "The Head" 
 continues around the southeast shore, nearly to the small point 
 south of Waite Bay. After an interval of about 100 feet of sandy 
 beach there is shown an abrupt change of structure. The rocks 
 at the point are greatly disturbed and brecciated. There seems 
 to be an easterly dip, but from the clear indications present of 
 severe compression this dip was interpreted as that of a rough 
 jointing due to shearing and not as that of bedding. The age af 
 the rocks is uncertain, but they are probably some part of the 
 Chazy. 
 
 South-southwest of Waite Bay is Cloak Island. Although 
 only a few acres in extent it possesses some very remarkable 
 structural features. A mere inspection would leave no doubt 
 of the fact that its rocks have been under severe compression. 
 
 The rocks are apparently mostly of Chazy age. A few fos- 
 sils were found, including Lingula limitaris Seely, and a some- 
 what plicated brachiopod shell showing both valves with their 
 markings. In the latter, although the beak was gone, other char- 
 acters were well preserved. These with the decidedly gibbous 
 outline strongly suggested Camerotoechia plena. Maclurea has 
 been reported from the west side of the island, but was not seen 
 by the writer. There may be present a small portion of the 
 Beekmantown whose relations will be described presently. 
 
 In the eastern part of the island are massive beds which 
 have clearly been folded and which at some places show westerly 
 dip and clear N.-S. strike. But this mass deformation is masked 
 by severe brecciation. The fragments of this badly crushed rock 
 
170 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 vary in size from small bits to pieces two, three or more feet 
 through. About midway of the island, east and west, and near 
 the south shore, a huge block of house-like dimensions rests 
 against the westward extension of the brecciated mass just de- 
 scribed. In this block the beds stand on end with E.-W. strike. 
 In them was found the plicated shell referred to above. This 
 block or mass is followed westward by more brecciated rock and 
 then occurs a somewhat detached mass of beds showing no ap- 
 parent brecciation or shearing. This mass is perhaps 10 or 12 rods 
 long from east to west and 5 rods wide from south to north. The 
 beds in this mass all dip northerly at an angle of about 20 degrees. 
 On the north they are cut off abruptly by a fault and rest along a 
 more or less regular and nearly vertical plane (see Plate 
 XXII) against coarsely brecciated rock similar in this respect to 
 the rock described for the eastern end of the island. The lower 
 members are much like some of the Beekmantown at "The Head" 
 on the main island ; they are rather thickly-bedded and often 
 weather to a rusty color. Above these are other beds, perhaps in 
 all about 15 feet thick, with some thin, almost shaly members. At 
 the base of this upper portion in some sandy layers were found 
 a number of fragments of Lingula limitaris Seely, which is 
 thought to mark the base of the Chazy in the Champlain region. 
 The northwestern and northern parts of the island are wooded 
 and outcrops are not satisfactory for study. Along shore in 
 these parts of the island the rocks usually form steep cliffs. On 
 the west shore the rocks give the impression of big blocks jumbled 
 together, but they are usually brecciated on a smaller scale as 
 well. There are indistinct traces of folding and indications that 
 in some places the beds stand on end. 
 
 The rather regular surface along which the conformable 
 northerly dipping beds of the southwestern part of the island 
 rest against the coarsely brecciated rock clearly marks a fault. It 
 seems probable that the brecciated rocks are the younger ; but what 
 was the mode of deformation that brought these rocks into their 
 present relations is far from clear. There seemed to be no in- 
 dications of drag on any of the exposed edges of the conformable 
 beds. The rocks of Cloak Island and those at the point just 
 south of Waite Bay on the east shore of the main island give 
 every indication of having been under severe compression. 
 
 Between the point described above and Waite Bay on the 
 main island are some rocks that are apparently not much de- 
 formed. Then along shore is a short, sandy stretch which is 
 succeeded northward by a beach of bowlders. Beyond this beach 
 the hard rock outcrops along shore and continues to Holcomb 
 Point. At some places friable layers have been cut by wave 
 action so as to leave more massive layers overhanging. At other 
 places the massive layers form the shore. South of Holcomb 
 Point the rocks are probably all Lower Chazy. The layers are 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 171 
 
 not appreciably cieformed. Similar rock occurs along part of 
 the shore of the bay north of Holcomb Point and is succeeded 
 by beds whose age was not determined, although they are probably 
 part of the Chazy. 
 
 About 40 or 50 rods south of Jordan Point a small bay shows 
 a narrow band of the shale formation, perhaps 300 yards long. 
 The rock is laminated like that on the Alburgh shore to the east. 
 The dip of the beds, as shown by the laminations, is prevailingly 
 westerly, but the rocks are crushed. North and south along shore 
 the shale gives place to limestone, and often the limestone forms 
 the higher part of a bank which lower down is composed of the 
 laminated shale. Search was made for a contact between the 
 limestone and the shale and what appeared to be one was exposed 
 by digging, but the relation was not decisive on account of the 
 weathered condition of the shale. Along the shore where this 
 band of shale occurs blocks of limestone have fallen down the 
 bank apparently from the action of the waves upon the soft 
 shale ; but it is not necessary to suppose that the limestone lay on 
 the shale. 
 
 The rock in the wooded pasture above the bank carries faint 
 coils of Madurea magna, and appears to be somewhat but not 
 severely sheared. North of the bay along shore is massive Chazy 
 carrying M. magna and Girvanella. These Chazy beds form a 
 gentle sag pitching northerly just north of the bay and southerly 
 near Jordan Point. The dip in general is westerly. But along 
 this part of the shore the bedding often loses distinctness or is 
 practically obliterated and the rock often appears as a crushed 
 mass with fragments varying in size from small, angular pieces 
 to big chunks. At other places instead of brecciation a shearing 
 structure is developed across the bedding, giving an impression 
 of easterly dip. The brecciated rock occurs at the southern end 
 of the band of shale mentioned above and again north of it, south 
 of Jordan Point. Its outcrops are not extensive, perhaps 75 feet 
 in the southern exposure mentioned and 200 feet south of Jordan 
 Point. This brecciated rock may be seen in contact with regularly 
 bedded layers of some of which it may be a part that has been 
 crushed. There has been some differential movement and disloca- 
 tion, but how extensive it is difficult to make out. Perkins re- 
 ported Illaenus and Madurea from two separate fragments in the 
 breccia. It is interpreted by the writer as an autoclastic rock. 
 The undeformed beds with which the breccia is in contact seems 
 to be Middle Chazy. 
 
 The low swampy tract extending from Clarks Bay just north 
 of Jordan Point, westward across the island probably is a zone of 
 fracture. 
 
 Just north of the eastern end of this swampy tract Black 
 River beds form a band along shore, perhaps 125 rods long and 
 10 or 12 rods wide. The beds of this formation form a gentle 
 
172 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 anticline at Hill's quarry, dipping westerly on one side at an angle 
 of about 5 degrees and easterly on the other limb at an angle of 
 about 12 degrees. Near the shore just east of Hill's quarry the 
 surface of the rock shows many coils and opercula of a Maclurea, 
 perhaps M. logani, and many small patches of sections of shells. 
 Except for the Maclurea, which was not seen by the writer in 
 the Black River elsewhere in the lake region, the rock closely re- 
 sembles that which in many parts of western Vermont has been 
 identified as belonging to this terrane. 
 
 For the most part the Black River beds are not marked by 
 ,severe internal deformation; but at the northern end of the strip, 
 at a small point a few rods south of William Hill's landing and 
 perhaps 5 rods north of undisturbed easterly dipping beds, the 
 rock is crushed with development of shearing (see Plate XXI). 
 This structure may be best seen on the north side of the point just 
 mentioned, where the thick layers of the Black River may be seen 
 to form a subordinate anticline in which the roughly jointed, 
 brecciated structure is particularly well shown. The bedding is 
 obscured, but is still visible. 
 
 North of the crushed Black River beds the low bank and 
 shelving shore are for a short distance in front of the William 
 Hill place formed by Trenton beds. About 50 paces north of 
 Hill's landing along shore are low ledges of a sheared, blackish 
 rock which a few steps northward forms a sharp headland in 
 which the lamination bands of the shale are clearly shown. The 
 laminations dip at a high angle westerly, or are greatly broken 
 and fragmented. The shale continues northward from the head- 
 land with the dip changing direction in the way so often observed 
 on the islands lying to the east. If not mashed the rock is 
 strongly sheared into a more or less fissile condition, and is often 
 veined with secondary calcite. 
 
 Perhaps one-third of a mile north of Hill's landing the shale 
 is interrupted along shore by a beach and then occurs a small 
 mass of Trenton limestone which continues for about 200 feet. 
 After another interval of beach the shale again forms the shore 
 and continues along it for perhaps one-half a mile. Then the 
 Trenton limestone outcrops again and extends to Cooper Point. 
 
 In all its exposure the shale forms only narrow strips on the 
 shore, but in the most northern one the rock may be frequently 
 seen in the bank and at one place it reaches across the shore road. 
 
 South of Cooper Point the limestone carrying Trenton fossils 
 is at one place folded, overturned and broken and a part of the 
 rock has overridden another part. At other places the rock shows 
 westerly dip and at others lies nearly flat. North of Cooper 
 Point the Trenton beds disappear under the shingle along shore. 
 Around Cooper Point Prasopora is abundant, but much altered. 
 Strong compression is manifest. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 173 
 
 West of the outcrops that have been briefly described for 
 the east, shore, between the swampy tract and Cooper Point, the 
 rocks exposed in the higher portions of the shore slopes, except 
 for some Black River that has been mentioned, is all Trenton and 
 the Trenton beds extend westward with numerous exposures 
 through the fields to the main island road running through the 
 village. 
 
 Away from the shore the Trenton beds exhibit less and less 
 evidence of internal deformation and show a gentle northeasterly 
 dip and northeast strike. The present topography of the pasture 
 land between the shore and the main island road clearly displays 
 the dip and strike of the beds as the land rises by terraces to the 
 west. 
 
 In ascending from the shore to the higher ledges lying west 
 of the camps along the shore road fossils appear, but there is an 
 appreciable difference between these eastern outcrops and those 
 that lie farther west with respect to the degree of deformation 
 and alteration of the rock. At the east the beds show clearly more 
 evidence of shearing strain, with subordinate mashing, although 
 the westerly dip is usually discernible ; the fossils are not well 
 preserved. 
 
 The fossils in these Trenton beds west of the camps include 
 the forms that distinguish the basal Trenton beds in the ridge 
 half a mile east of the west shore on Grand Isle and the rocks 
 themselves are counterparts. 
 
 To one who examines this island after a survey of the island 
 of North Hero and the peninsula of Alburgh the scant occurrence 
 of the shale formation on Isle La Motte is impressive. To one 
 w^ho may have been inclined to the view that the preservation at 
 the present surface of broad areas of the weak shale formation, not 
 only on the islands of the lake but also on the mainland, is perhaps 
 due to a covering until rather recent times of a more durable 
 formation which has been removed, the absence of any traces of 
 rock that might have served for such protection anywhere on 
 North Hero or Alburgh is also impressive. That such a covering 
 does exist and probably has existed in some places in the lake 
 region may be shown ; but that all the shales had precisely similar 
 thrust relations with massive limestones does not seem to have 
 been the case. 
 
 But as has already been discussed for Grand Isle and for 
 other parts of the Champlain basin the region is one eminently 
 characterized by upthrust of older into younger formations. This 
 mode of mass disturbance is widely prevalent and conspicuous, 
 and dominates all others. 
 
 It has also been indicated that good evidence exists to show 
 that subsequent to the great dislocations that piled the rocks 
 against one another, normal faulting occurred by which the rocks 
 were again fractured and displaced. It does not appear possible 
 
174 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 in many cases of displacement, both along and across the strike, 
 to say whether the dislocation was the result of compression or 
 normal tension faulting. In the case of massive and highly 
 elastic limestone strata it is possible to conceive that under com- 
 pression the conditions might have been such as to permit a frac- 
 ture across the strike that would produce relations simulating 
 those that would result from normal faulting. In the absence 
 of any positive criteria by which the exact nature of the differen- 
 tial movements between masses now clearly lying in displaced 
 relations to one another may be determined, the explanation of 
 such relations must rest upon probability. 
 
 The conditions on Isle La Motte are in so many respects 
 comparable with those on Grand Isle that it seems that an ex- 
 planation which would fit one would also fit the other, and the 
 conditions that exist in other parts of the region are such that 
 any interpretation which fits these two islands may probably be 
 applied to the relations involving similar rocks at other places, 
 with certain modifications. 
 
 The absence, so far as could be determined, of any traces of 
 older limestones at the present time on the shales of North Hero 
 and Alburgh stands against the view that these shales were ever 
 covered by such rocks and that the massive limestones of Grand 
 Isle and Isle La Motte represent downfaulted blocks of a much 
 more extended mass of such rocks that was thrust over the shale 
 and which has now largely disappeared by erosion. This dis- 
 tinctly does not mean that such limestones do not now an'd never 
 did rest on the shales at perhaps many places in the lake region, 
 or that shales may not underlie the massive rocks on Isle La Motte 
 and Grand Isle. It further does not mean that" the visible shales 
 of the northern islands of the lake never lay at some depth be- 
 neath overthrust masses. The discussion applies to the relations 
 among the visible rocks of these islands. 
 
 The field relations in the northern part of the lake region 
 have not after careful inspection seemed to favor the idea of 
 down-faulting of the shales among the older limestones through 
 gravitational stress. The field evidence everywhere rather sug- 
 gests that the present relations shown between massive limestones 
 and shales, where the latter, as indicated by their younger age, 
 occupy the downthrow side of a displacement, are the results of 
 compression, in spite of the probability of normal 'faulting in the 
 region and the lack of positive proof of thrust contacts. It is 
 proper further to weigh the question as to whether the massive 
 limestones of Grand Isle and Isle La Motte could have been thrust 
 into and perhaps over shales and whether the field relations and 
 various kinds of deformation lend themselves to such a view. 
 
 On the islands under discussion, there have not been found 
 any positive surface traces of overlap of older on younger rocks. 
 Some of the basal Trenton and associated Black River beds that 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 175 
 
 occur at the northern end of the ridge that runs east of the west 
 shore in the lower western half of Grand Isle are older than the 
 rocks along shore to the west of them and if normal faulting is 
 ruled out the topographic position and attitude of the beds of the 
 former fall in with idea of overthrust. Contacts are, however, 
 lacking. The lake waters conceal the hard rock that lies to the 
 west of the western shores of Grand Isle and Isle La Motte and 
 whether the shales come to the surface beneath the lake is not 
 known. Farther south in Shoreham and Orwell the margin of 
 thrust overlap of the heavy Hmestones on the shale may be fol- 
 lowed at the present surface, the shales lying to the west of the 
 margin above the lake water level. 
 
 On Grand Isle, as has been described, the massive older rocks 
 are more or less mashed and veined with calcite along their east- 
 ern margin. It is noteworthy that the more crushed and sheared 
 condition of the massive rocks, both on Grand Isle and Isle La 
 Motte, occurs along their irregular eastern margins. 
 
 A very similar condition has been noted and described by 
 the writer for certain rocks in the Hudson valley.^ Near Pough- 
 keepsie, N. Y., massive dolomites and limestones have field rela- 
 tions to slates very similar to the relations shown in the lake 
 region and which are plainly the results of the older rocks having 
 been thrust into the younger slates. The older beds have broken 
 both across and along the strike and in their eastern portions 
 often show slickensiding and brecciation near their contacts with 
 the slates.* In the Poughkeepsie region, along their western mar- 
 gins, the older rocks may often be seen in contact with the slates 
 into or over which they have been thrust. It is apparent from 
 the generally flattish attitude of some of these overthrust rocks 
 and the lack of deformation within them away from the brec- 
 ciated zone along their eastern margins that they underwent 
 little folding and essentially form great blocks that have been 
 broken from an extensive formation lying at depth and driven 
 upward. Although not equally manifest at all places a distinct 
 horizontal component may usually be recognized in these dis- 
 placements. Moreover, what sometimes appear now as reverse 
 faults are probably eroded thrusts. 
 
 Taking the apparent absence of any traces of the massive 
 Beekmantown, Chazy and Black River beds anywhere on Alburgh 
 and North Hero at its face value, it is not reasonable to assume 
 that the shales in these areas were overridden by a mass of the 
 older rocks and that the older limestones of Isle La Motte rep- 
 resent a detached block of such an overthrust mass preserved 
 by downfaulting. From the strong similarities which the second- 
 ary structural features in the northern part of the lake basin 
 have to those of the Hudson valley near Poughkeepsie, it may 
 not be unreasonable to suppose for each of these regions a similar 
 
 ^New York State Bull. 148, 1911. 
 
176 ' REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 deformational history. The Beekmantown, Chazy, Black River 
 and basal Trenton beds of Isle La Motte were broken from the re- 
 spective masses to which they belonged and which lay beneath the 
 shales and have under compression, through failure in any notable 
 degree to accommodate through close shearing, moved up into the 
 shale formation. By such deformation some portions of the 
 shale would in some measure probably have been overthrust and 
 other portions might be spoken of as underthrust. In both cases 
 the shale would occupy the downthrow side. Along the plane of 
 underthrust movement the relations produced might sometimes 
 suggest normal faulting; but it is clear that displacement due to 
 pressure would have involved differential movement between 
 masses that were both under compression. The shales accom- 
 modated through cleavage and minor deformation, but the lime- 
 stones refusing to do so moved as massive blocks. 
 
 If this interpretation is given to the relations of the lime- 
 stones of Isle La Motte to the shales, it may be thought surpris- 
 ing that the limestones are not more generally present at the 
 surface in nearby areas. But it is not necessary to suppose that 
 such upthrust masses had in all cases the same amount of dis- 
 placement with respect to the shales. Probably at depth the 
 massive beds of Lower Ordovician rocks, and probably older 
 rocks underlying them, have been variously broken and disturbed. 
 The various kinds of deformation now to be seen on the eastern 
 shore of Isle La Motte and along what was called the plane of 
 underthrust bear out the idea that it was the massive beds which 
 did the moving, so to speak. As is so frequently to be understood 
 in application to faulting and thrusting, a plane is not to be thought 
 of as a mathematical plane but rather as a zone of disturbance. 
 
 At some places it appears that the limestones along the under- 
 thrust side slid under the shales at a relatively low angle and at 
 Others ascended more nearly vertically. The massive rocks were 
 all the while crowded against the shales and the crushed condi- 
 tion of the latter is in such wise not difficult to explain. 
 
 The thought has occurred that possibly the crushed condi- 
 tion of the rocks as described for the eastern shore of Isle La 
 Motte and for Cloak Island was a character acquired within these 
 rocks at depth before actual rupture and extensive bodily move- 
 ment of ruptured masses. It certainly seems less likely that this 
 condition was acquired during simple upward movement into the 
 shales after rupture from the main mass at depth. The gradual 
 transition westward from strongly deformed beds along the east 
 shore of the island through those showing less and less strain to 
 undeformed beds seems to indicate that differential internal 
 deformation was followed by mass dislocation. 
 
 The relations and conditions on Grand Isle are in many par- 
 ticulars comparable with those on Isle La Motte and it seems 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 177 
 
 probable that the massive rocks of Grand Isle should be inter- 
 preted as upthrusts into the shale formation. 
 
 FRANKLIN COUNTY. 
 Highgate Township. 
 
 (St. Albans topographic sheet.) 
 
 General. The rocks of Highgate have long been known from 
 the investigations of Logan, who worked out some of their im- 
 portant structural relations. While there have been some modi- 
 fications with advancing knowledge of the age relations assigned 
 to some of the rocks, the general conclusions of this able geologist 
 have not been materially changed and jus map, so far as it went, 
 is accurate in detail of distribution and structure. The rocks of 
 the township have been much disturbed and altered. Contacts 
 are concealed and some relations much obscured by the mantle of 
 surface material. 
 
 In Highgate rocks are found extending south from the 
 Canada line along the lake shore and just to the east of it which 
 are more or less similar to those of the areas just described or to 
 some that occur near the lake farther south in Vermont, but some 
 of these rocks are greatly altered. East of a narrow and some- 
 what irregular strip of such rocks are others whose counterparts 
 have a great extension southward through western Vermont. 
 Occurring among the latter are still other rocks which show 
 features different from any of the others and present much diffi- 
 culty in the definition of their age, in their dorrelation and in the 
 explanation of their structural relationships to the rocks with 
 which they are associated. 
 
 Betzveen Missisquoi Bay and Rock River. Description will 
 begin with rocks along or near the shore of the lake, south of the 
 Canadian line. 
 
 Just south of the little bay at the village of Philipsburg, 
 Province of Quebec, the shore is formed of black, slaty rocks 
 carrying graptolites. These slates form a narrow, wave-cut plat- 
 form and low cliffs for about a mile south of Philipsburg. Ex- 
 cept for their greater alteration and more pronounced cleavage 
 and disturbance these rocks are much like those of Alburgh and 
 North Hero. They carry firm, siliceous bands, weathering rusty 
 brown, which from their fragmented condition and scattered 
 arrangement among the more shaly layers bear testimony to the 
 severe crushing which these rocks have suffered. In their de- 
 formational features these rocks are much like those which will 
 be described for the lake shore south of St. Albans Bay. 
 
 These slaty rocks are interrupted and replaced at places along 
 the shore of the bay by great cHffs of massive-appearing lime- 
 stones which often reach to the water's edge and are impassable 
 
178 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 except by boat. At the bases of many of these diffs are great 
 blocks which have broken from them and over which one may 
 sometimes scramble for considerable distances without, however, 
 coming upon the slates. Working southward along the tops of 
 these cliffs one comes to a small bay, a little way south of the 
 national boundary, in which the slate outcrops. Slate was observed 
 in the bank not more than 10 feet below the massive limestone 
 which caps it, but the actual contact is concealed. South of the 
 bay the limestone reaches the water and continues for many rods. 
 Its margin then recedes somewhat eastward and clay or shingle 
 forms the shore with the slates peeking through at places. Finally 
 the slates pass from sight towards Rock River Bay. 
 
 The surfaces of the massive limestones which have been 
 mentioned, in the extension of these rocks east from the shore 
 through woods and pastures to the Highgate-Philipsburg road, 
 were examined for fossils, but nothing definite was found. In 
 these rocks, which are greatly altered, fossils have apparently 
 largely been destroyed. In the shore cliffs these limestones 
 usually appear very massive, but at some places beds of not very 
 great thickness were observed. Sometimes a massive appearance 
 seems to be due to a sort of welding of beds by shearing. Where 
 bedding was observed it showed easterly dip at a low angle. 
 
 The calcareous beds exposed along and near the shore are 
 largely gray, dolomitic limestones distinctly siliceous and often 
 carrying chert, but away from shore these rocks pass upward into 
 white, more or less marbly limestones whose weathered surfaces 
 are often covered with a tracery of fine siliceous lines of lace-like 
 patterns standing out in low relief. These whitish limestones 
 outcrop along the Philipsburg-Highgate road from the national 
 boundary to and across Rock River and form numerous expo- 
 sures west of the road in the pastures and woods. East of Rock 
 River Bay, both north and south of the stream, the white lime- 
 stones were found in close association with the gray dolomites 
 and a similar association was noted east of Highgate Springs; 
 but at the latter place there is suggestion of dislocation and at 
 one place of westerly dip which is a variation from, the rather 
 uniform easterly dip shown by the rocks south of the Canadian 
 Hne, between the lake shore and the valley of Rock River. 
 
 A mile east of the shore near the Province line are indications 
 of synclinal structure which becomes well-marked two-thirds of 
 a mile north of the line. About one-fourth of a mile south- 
 southwest of St. Armand station and one-eighth of a mile west 
 of the railroad track, massive bluish-gray and yellow weathering 
 beds dip at an angle of about 18 degrees to the northwest. These 
 are succeeded westward and upward by massive-appearing rock 
 carrying fossils, some of which resemble Lituites. This massive- 
 appearing rock may be seen to be composed of relatively thin 
 layers which have been welded into a thick stratum, as it now 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 179 
 
 appears. Some of the rock shows a striped appearance in which 
 feature it looks much Hke similar rocks, which have been thought 
 to belong to the Chazy, farther south in Vermont. A half mile 
 north of these outcrops along the road from Moore's Corners to 
 Philipsburg the striped rock shows southeasterly dip and west- 
 ward is underlain by the bluish-gray and yellow weathering beds. 
 The rocks in the western limb of this syncline are plainly sheared 
 across the bedding, with the easterly dip of the induced cleavage 
 at a higher angle than the bedding. There was observed at some 
 places what was interpreted as a mashed structure as evidenced 
 by blocks of the yellow weathering beds involved with the dove- 
 colored or bluish rock. Westward towards the shore are found 
 rocks like those which have been described as making up most of 
 the surface between the lake shore and Rock River south of the 
 Province line, and a generally low easterly dip is maintained in 
 these rocks to their western margin. West from the axis of the 
 syncline just mentioned, the succession across the strike in the 
 limestones is probably from younger to older and older rocks. 
 
 These various rocks were regarded by Logan as parts of his 
 Quebec Group, a name that now has hardly more than historic 
 significance. There is still a field for careful work among these 
 rocks with regard to their exact age and correlation and the details 
 of their structure. 
 
 Brainerd and Seely seemed to recognize in the Philipsburg 
 series of Logan most of the members of their Calciferous (Beek- 
 mantown) of Vermont with some beds that may be Chazy. The 
 identification was largely on a lithological basis. 
 
 These rocks have not undergone extensive deformation by 
 folding. They have suffered considerable shearing and great 
 alteration from pressure and their relations to the slates along 
 shore, than which they are unquestionably much older, is that of 
 thrust which probably involved considerable lateral movement. 
 
 Along Rock River valley, south of the Province line, the 
 rocks did not give much hint as to the extent to which they may 
 have been brecciated along their eastern margins ; nor was it 
 possible to determine if transverse and longitudinal fractures are 
 present among these massive limestones between the lake shore 
 and Rock River valley. 
 
 In their lithological features and massive character these 
 dolomites and limestones show more resemblance to the similar 
 rocks of Benson and Orwell, which the writer has described in 
 relations to younger rocks quite like those shown by the rocks of 
 Highgate, than to any other rocks which he has seen. The gen- 
 eral resemblance is very strong and seems to point to a wide- 
 spread substratum of similar rock which was broken here and 
 there and thrust through and over younger beds, in which rela- 
 tions they are now exposed. 
 
180 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Highgatc Springs and vicinity. About one-half a mile south- 
 southwest of the mouth of Rock River is Limekiln Point. The 
 rock at this place is a grayish limestone which has been quarried. 
 It is unlike the rock that occurs along shore north of Rock River 
 Bay, and that to the east, north of Carman Brook. 
 
 Limekiln Point is separated by Phelps' Bay from a blunt 
 promontory lying to the southwest of the Point. This promontory 
 is the site of a former picnic ground. Over most of its western 
 portion the rock is a sheared, impure, shaly limestone which 
 forms low cliffs along the edge of the lake. These impure lime- 
 stones yielded somewhat distorted fossils, among which some 
 were sufficiently well preserved to warrant the following tentative 
 references : 
 
 Rafinesquina incrassata (Hall) ; compare Leptaena plicifera Hall, 
 fig. la, pi. 4 bis, Pal. N. Y. 1847. 
 
 R. incrassata, but larger than preceding, showing convex? valve 
 with narrow and fairly deep depression extending from beak to margin, 
 widening somewhat towards margin. 
 
 R. fasciata. comparable in size with fig. 3c and in detail with figs. 
 3a and 3d, pi. 4 bis, loc. cit. 
 
 The smaller specimen compared with R. incrassata has some re- 
 semblance to certain illustrations of the dorsal valve of Plectambonites 
 sericeus (Sowerby), but differs in proportions, being shorter along the 
 hinge line. The striae are also coarser, fewer in number, and of uni- 
 form size, with intermediate ones appearing near the margin. The 
 specimen referred to R. fasciata is comparable with R. alternata, 
 (Emmons). A gastropod of EccuUomphalus type was also seen. The 
 specimen was badly worn, but in spite of excoriation seemed to show, 
 particularly near the tip, low, annular ridges. There was no visible 
 angulation. 
 
 These fossils suggest that the shaly limestone may be of Upper 
 Chazy, or possibly Trenton age. These limestones are flanked on 
 the east by certain less sheared calcareous rocks that are in turn 
 overlain by beds that resemble the Black River. Portions of the 
 shaly limestones are less sheared than others, but most of these 
 rocks under the hammer break into irregular pieces whose surfaces 
 are suggestive of slight movements in the rock. In fact, the condi- 
 tion of most of these shaly rocks is substantially that of irregular 
 cleavage or crushing. 
 
 The shaly limestones just described occur on the east side of 
 the road running north from the Franklin House to the wharf on 
 the second promontory southwest of Phelps' Bay, and about a 
 half mile north of the hotel. In spite of shearing an easterly dip 
 is apparent. These rocks are succeeded westward, on the west 
 side of the road, by interbedded gray limestones and buff-weather- 
 ing dolomites which are well shown at the end of the promontory. 
 Flanking these limestones and dolomites on the west and ap- 
 parently conformable with them are purplish or greenish-gray 
 quartzitic sandstones in beds from 2 to 12 inches thick standing 
 on end. The quartzitic sandstones are perhaps a hundred feet 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 181 
 
 thick. South and west they give place to younger rocks, from 
 which they are probably separated by a dislocation. The sand- 
 stones form the western limb of a broken anticline. It is not 
 clear just what the relation of the shaly limestones is to the inter- 
 bedded gray and buff- weathering beds that lie west of them ; they 
 apparently lie above them. 
 
 The promontory bounded on the west by the sandstones is 
 separated by a slight embayment of the shore from a small point 
 at which occurs a series of very dark gray or blackish, thinly- 
 bedded limestones which gave good Trenton fossils. In fossils 
 and general lithology these Trenton rocks are comparable with 
 the basal Trenton beds as seen on the islands to the southwest. 
 They are folded and sheared. They grade into more shaly rocks 
 which outcrop in the bank and along the beach below the camps 
 southward until lost under the swampy land. Eastward above 
 the bank in the fields among the summer cottages the Trenton 
 beds are associated and folded with dense, black limestones of 
 probably Black River age. These rocks continue southward, 
 forming a ridge to the west of the Highgate-Swanton road. 
 About one-fifth of a mile south of the hotel they form an un- 
 symmetrical anticline with the Black River, forming the eroded 
 crest and the Trenton beds the eastern and western limbs. On 
 the east limb a reading gave the strike as N. 28° E. and the dip 
 about 25° to the east. The Trenton rocks yielded typical fossils. 
 On the west limb the beds dip at a high angle to the west or are 
 overturned. About a half mile south of these outcrops and about 
 on the same meridian a small ridge in the field west of the road 
 shows the western limb of an anticline with the Trenton and 
 Black River beds in inverted position. The Black River beds are 
 from 2 to 3 feet thick and filled with small calcite veins, which, 
 it may be noted, are frequent in all the beds of this formation 
 around Highgate Springs as they are in many other places in 
 western Vermont. The Trenton beds follow the Black River con- 
 formably on th^ west and dip at the same high angle easterly. 
 The Trenton beds yielded crinoid stems and fragments of other 
 fossils. Southward these rocks pass under surface material ; 
 the most southerly outcrop noted in Highgate occurs where the 
 Highgate-Swanton road crosses the railroad track. 
 
 Directly east from the Franklin House, across the track near 
 the mineral spring, beds carrying Trenton fossils (Cryptolithus) 
 dip to the east. These outcrops are separated by a stretch of 
 low, flat land about one-fourth of a mile wide from the massive 
 limestones in the quarries of the Missisquoi Lime Works. To the 
 south and southeast is an extensive sand plain under which the 
 hard rocks are largely concealed. _ Just north of the Swanton 
 line and a mile northeast of Swanton village, the road from Swan- 
 ton to Highgate Center crosses a low ridge of dove-colored lime- 
 
182 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Stone carrying patches of buff-weathering rock. These beds seem 
 to be Hke those at the promontory at Highgate Springs. 
 
 Structural Features at Highgate Springs. In conformity 
 with their less massive characters the various rocks around High- 
 gate Springs have been much more deformed by folding than 
 have the heavy dolomites and limestones that lie north and east 
 of them. The folding is distinguished by a tendency to over- 
 turning on the western limbs and actual inversion of beds in 
 some cases. Although now seen to be disposed for the most 
 part in folds the relations in some places indicate dislocations. 
 The Chazy rocks have ridden on the Trenton and 'the latter has 
 probably been thrust against younger slates. Shearing structure 
 in the form of brecciation or cleavage is to be seen in many of 
 the rocks. The more massive rocks show fewer distinct marks 
 of internal deformation. 
 
 Between the rocks at Limekiln Point and Highgate Springs 
 and those lying to the east, north of Carman Brook, as well as 
 those lying practically on the same meridian with the latter in 
 the westernmost quarry of the Missisquoi Lime Works, there is 
 an interval of surface material so that it is not possible to state 
 what are the contact relations between the rocks lying at the east 
 and those nearer the lake. But there can be no doubt that the 
 massive rocks along the lake north of Highgate Springs rest on 
 the slates by thrust and it is probable that the rocks at Limekiln 
 Point and Highgate Springs are separated from the altered 
 massive rocks to the east of them by a plane of thrust, and that 
 the present sinuous western marginal outcrop of the rocks lying 
 east of Highgate Springs and north of Carman Brook is essen- 
 tially a continuation of the obvious margin of overlap of the 
 similar rocks on the slates north of Rock River Bay. 
 
 According to this view, the folded, overturned and broken 
 strata at Highgate Springs and those of Limekiln Point probably 
 represent an aborted thrust which developed only to the point of 
 release of other rocks by rupture. These other jocks might not 
 be those which now form the surface east of the margin of over- 
 lap discussed above, but might be other rocks that are now covered 
 by these thrusted rocks. Such a view depends upon the idea of 
 repeated minor thrusts or reverse faults preceding other thrusts. 
 Exposure of rocks younger than the massive limestones has not 
 been accomplished east of the margin of overlap of the latter in 
 this part of Vermont and all sections east of this margin gives a 
 succession from younger to older formations, at least as far east 
 as the eastern valley of Rock River. 
 
 An alternative explanation seems to be that the rocks at 
 Highgate Springs and Limekiln Point may have ridden forward 
 on the same major shear with the more altered rocks lying to the 
 east and that the present trace of this shear at Highgate Springs 
 is on the west of the rocks at this place. This, however, assumes 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 183 
 
 that a major shear cut minor thrusts and faults at depth and 
 drove the truncated portions forward together. It is, of course, 
 not possible to decide the point. 
 
 In every case where a marked dislocation occurred it is to be 
 attributed to the more or less massive character of the rock and 
 its reluctant behavior under powerful compression. The rocks 
 behaved according to the elements of their primary structure. 
 The heavy members moved as masses ; the less massive accom- 
 modated by folding, crushing and shearing on a minor scale. 
 
 Northeast, east and southeast of Highgate Springs. Rock 
 River has a roundabout course from its source to Lake Cham- 
 plain. Its upper eastern portion flows northerly in a course 
 roughly parallel with the shore of Missisquoi Bay and about three 
 miles distant from it. The river crosses the Province line and 
 about two miles north of it turns west across the structural axes 
 of the hard rocks and then bends to a southwesterly direction to 
 enter the lake. 
 
 Part of the rocks to be described under the above heading 
 lie between the northward and southward courses of the river as 
 it touches Vermont and the rest are found in the territory that 
 extends southward and southwestward toward the Highgate- 
 Swanton line. 
 
 Along the eastern margin of the valley of the lower (west- 
 ern) portion of Rock River is a modified escarpment in a series 
 of interbedded, usually massive, siliceous dolomites, and quartzites 
 or quartzitic sandstones, which belong to so-called Red Sandrock 
 series, as this formation was named by the early geologists of 
 Vermont. The western outcrop of these rocks, beginning at the 
 Canada line, follows rather closely for a distance of about three 
 miles the road that runs from St. Armand, P. Q. southward past 
 Saxe monument to Swanton. For the rest of its course through 
 Highgate the western margin is much less distinct and usually 
 may be only approximately located from a few isolated outcrops 
 emerging through the sand plain. . The most western outcrop 
 noted in Highgate was in a bed of quartzite at Kelly Brook, 
 where this stream is crossed by a road one mile east of the 
 Central Vermont railroad track. 
 
 Over the higher land north, east and south of Saxe monu- 
 ment the members of this series are well displayed. Outcrops are 
 abundant along the roads and in the fields nearly to the eastern 
 valley of Rock River, and the series was traced southward along 
 the eastern edge of the sand plain through Carter Hill to a point 
 just north of the St. Johnsbury and Champlain railroad and 
 about a mile west of Highgate Center. 
 
 The members of the Red Sandrock series in Plighgate form 
 only a small portion of a great band of more or less similar rocks 
 that extends for a long distance southward in Vermont. Even 
 in rather widely separated areas in the northern part of the state 
 
184 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 there is close resemblance in sequence and thickness of beds of 
 this formation and in their colors, but in other places in Vermont 
 the members of the Sandrock series, are seemingly represented by 
 rocks which are apparently so unlike them that their common 
 membership in the same formation is easily overlooked. Even 
 within short distances, however, the members of the typical Sand- 
 rock series show appreciable horizontal and vertical variations in 
 lithological characters and thickness of beds which come out in 
 tracing the formation from place to place. At many places these 
 rocks show much confusion on account of disturbances which 
 have brought them into abnormal relations with other rocks ; but 
 leaving out dislocations it would not be possible to describe any 
 vertical section which would hold in detail for any great distance 
 away from the locality selected. 
 
 It seems probable from studies that have now been made in 
 various parts of western Vermont, reckoning with the principle 
 of lateral variation among rocks of the same general age, that 
 ideas about the age relations of some rocks will have to be revised. 
 It seems likely too, in view of deformations of the rocks, that 
 estimates of the thicknesses of some of them will have to be 
 modified. When the general similarity in field relations shown 
 by very different looking rocks is appreciated even the absence 
 of fossils in some of them may not stand in the way of recogni- 
 tion of the existence of a formational unit whose depositional 
 and deformational histories have been much the same throughout. 
 
 In Highgate the members of the Sandrock formation require 
 only brief description. It would require long and patient work 
 to catalogue all the minor variations, which when done would 
 largely represent wasted effort from our point of view. How- 
 ever, when the depositional history of the Lower Cambrian in 
 Vermont is written it will mean that much attention will have 
 been given to details of such kind. 
 
 South and east of Saxe monument are more or less massive 
 quartzites, often weathering to a rusty color, apparently passing 
 along the strike into reddish quartzites, and eastward across the 
 strike, towards Saxe Brook, into whitish quartzites, all more or 
 less regularly interbedded with gray, siliceous dolomites. The 
 quartzites are all more or less calcareous or dolomitic. 
 
 North of Saxe monument are gray, dolomitic quartzites and 
 siliceous dolomites passing eastward into flaggy quartzites. A 
 gray, rusty-weathering, impure quartzite east of the St. Armand 
 road and about 100 rods northeast of the monument gave recog- 
 nizable fragments of the glabella, cheeks and pygidium of 
 Olenoides marcoui. These were the only fossils found by the 
 writer. In these rocks fossils come out only when the rock has 
 weathered ; but as experience will show not all weathered rock 
 gives fossils, although it is probable that these are very common 
 in the rocks. 
 
. REPORT OF THE VERMONT STATE GEOLOGIST. lyS 
 
 Southeastward toward Highgate Center are brownish-gra}^ 
 quartzites and gray dolomites interbedded with flaggy quartzites. 
 
 In almost all the outcrops noted the dip is at a moderate angle 
 to the east. * 
 
 As a whole, these rocks probably make up a considerable, but 
 as yet undetermined, thickness of Lower Cambrian beds, showing 
 a rather uniform easterly dip and hardly any evidence of folding. 
 The topography gives an occasional hint of dislocation ; about one 
 mile east of Saxe monument, east of Saxe Brook, a prominent 
 scarp in massive quartzite probably marks a fault. 
 
 The rocks of the Sandrock series are unquestionably older 
 than the massive limestones that lie west of them along and east 
 of the shore of Missisquoi Bay. The only reasonable explana- 
 tion of their structural relations is that which Logan advanced 
 long ago; the Sandrock has been thrust against the limestones. 
 Whether the thrust carried the Lower Cambrian any considerable 
 distance over the massive limestones cannot be determined from 
 the relations in Highgate. No contacts were found, but about a 
 mile southwest of Saxe monument a quartzite bed of the Sand- 
 rock series is in close proximity to rocks of the lake shore series. 
 Outcrops that were seen in the sand plain southeast of Highgate 
 Springs show the margin of the Sandrock to be farther west 
 than it is at the north. 
 
 In their deformation the Lower Cambrian beds behaved 
 like the massive limestones to the west of them. While they 
 probably suffered subordinate dislocations which are not now 
 generally recognizable, they did not fold much but rather moved 
 as a mass. 
 
 In their lack of folding the members of the Sandrock series 
 in Highgate are in contrast to some of the similar rocks found 
 farther south in Vermont, which are, however, when folded, in 
 thinner beds. In their lack of this kind of deformation they are 
 in accord with similar heavy beds elsewhere. The rocks behaved 
 under pressure according to the elements of their primary struc- 
 ture. 
 
 In Highgate the Lower Cambrian series is nowhere in visible 
 contact with the shale formation as it is farther south on the 
 lake shore. But what the relations may be beneath the sand 
 plain that intervenes between Highgate Springs and Swanton the 
 surface covering effectually hides. 
 
 Eastern valley of Rock River. Along the eastern valley of 
 Rock River, or low on the eastern flanks of the hills of inter- 
 bedded quartzites and dolomites that have just been described, 
 occur outcrops of rocks very different from the members of the 
 Lower Cambrian series that bounds them on the west and from 
 rocks that lie immediately to the east. These rocks show inter- 
 esting differences among themselves from place to place and in 
 the same outcrop, but have a general resemblance to each other 
 
186 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 throughout and appear to make up a formational unit. They 
 form the northern extension of the formation which includes the 
 so-called "intraformational conglomerate," described by Edson 
 for the towns of Swanton and St. Albans, and which he was 
 inclined to view as of Middle Cambrian age. Logan showed 
 these rocks on his map (Atlas accompanying Geology of Canada, 
 1863) as a band extending northward from Highgate Center 
 across the Province line and as joining at the surface with his 
 Quebec rocks in southern Stanbridge. Along Rock River these 
 rocks as now exposed seem to hold to a fairly uniform width and 
 band-like distribution, usually less than a mile in breadth across 
 the strike and sometimes very narrow. Their representatives 
 farther south are often more scattered and irregular in distribu- 
 tion. 
 
 This formation was traced to within a half mile of the 
 Canadian line. At an exposure near the junction of the roads 
 about a mile and a half east-northeast of Proper Pond are thinly- 
 bedded, bluish limestones, whose outcropping edges along their 
 strike appear as wavy bands on the weathered surface of the 
 ledge. The limestone is associated with siliceous beds which lie 
 on it and appear to be conformable, as though interbedded. Con- 
 glomeratic structure is not prominent, being confined to a patch 
 about four feet square. However, the field was not exhaustively 
 examined at this locality. 
 
 The valley of Rock River is more or less filled with drift 
 and outcrops are intermittent. The next outcrops noted are one- 
 third of a mile to the south, west of the road running parallel to 
 the river. At this place the thinly-bedded, bluish limestone is 
 intermingled with slaty rocks. 
 
 About a mile farther south, near the junction of three roads, 
 are outcrops of sheared, bluish limestone, weathering to a dull 
 gray. The rock is splintered and at places shows small disloca- 
 tions which have completely severed the thin beds at numerous 
 places. 
 
 Southward where the road crosses the river, in the bed of 
 the stream, are sheared limestones now practically limy slates. 
 The bedding is largely obliterated by the cleavage which dips 
 easterly. The exposure of these rocks in the river bed may be 
 50 yards in breadth. 
 
 Above the river bank, southeastward, in a field east of the 
 road, is a curious mixture of rocks which in general aspect are 
 very like those making up several exposures in the towns of Swan- 
 ton and St. Albans, to be described later. In fact the rocks at 
 these several separated localities are counterparts, so far as litho- 
 logical features go. The most conspicuous member is the con- 
 glomerate whose fragments range in size from small pieces to 
 considerable blocks and are imbedded in a calcareo-siliceous 
 matrix. The conglomerate portions are intermingled with other 
 rocks, some of which are calcareous sandstones much like the 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 187 
 
 matrix of the conglomerate, and which sometimes weather to a 
 reddish bluff, and others are slaty rocks like those in the river bed 
 nearby. The fragments of the conglomerate are frequently 
 bluish limestone and often sharply angular in section. There is 
 much confusion and anything like orderly sequence was not dis- 
 cernible. There is visible shearing structure in some of the rocks. 
 
 A half mile farther south, where the road crosses the river, 
 near Johnson's farm, is a gorge worn by the stream in dark, 
 bluish-gray, finely granular limestone which yielded obscure fos- 
 sils, too fragmentary for positive determination, including a tiny 
 orthis-like form and several pieces of trilobites, all very small. 
 The rock shows folding and shearing and some brecciation.^ 
 
 Twenty-five rods southwest of the bridge at the last-named 
 locality and west of the road, at a small ridge, are excellent ex- 
 posures of the thinly-bedded, bluish limestones like those de- 
 scribed for the outcrops farther north. The edges of the beds 
 show a very conspicuous wavy arrangement and the layers show 
 all stages of fragmentation or dislocation from incipient parting 
 to rupture with varying degrees of displacement of broken parts. 
 According to the writer's view, these are distinctly secondary com- 
 pression effects, belonging in the category of brecciation, and not 
 to be confused with conglomeratic structure which parts of this 
 formation show. The angular character of the conglomerate frag- 
 ments often gives a distinctly brecciated appearance to that rock 
 in many of its outcrops and the fragments themselves often sug- 
 gest broken-up, thin, limestone layers ; but the principal structure 
 of the conglomerate proper seems really to be primary, although 
 the way it was produced remains a mystery. The conglomerate 
 itself may show secondary shearing effects like some of those in 
 the rocks associated with it. 
 
 Blue limestones like those in the ridge just mentioned con- 
 tinue southward on the strike and outcrop on the road going west, 
 along which road after an interval of drift they are succeeded 
 by the Cambrian dolomites and quartzites. 
 
 Highgafe Center. In a cut of the St. Johnsbury and Lake 
 Champlain R. R. one-fourth of a mile northwest of the village of 
 Highgate Center is exposed a laminated bluish limestone dipping 
 easterly at a moderate angle and cut by rough shearing joints 
 which dip in the same direction at a high angle. The rock has 
 weathered enough to bring out the essentially shaly character of 
 the rock by the laminations bands which it shows. 
 
 The field south of the cut, above the bank, gives numerous 
 exposures of the thin, blue limestones noted along the valley of 
 Rock River. The beds sometimes stand at a high angle of dip 
 and present the same wavy arrangement in the surface of the 
 ledge. The limestones are intermingled with ledges of gray 
 slates. All the rocks are greatly altered and without fossils. 
 
 ^ See supplementary note at the end of this paper. 
 
188 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Highgate Falls. At Highgate Falls the Missisquoi River 
 flows through a narrow post-glacial channel which the stream has 
 cut in a mass of jumbled rocks now exposed in its bed and banks. 
 The section from the bridge to the final outcrops at the base of 
 the falls is perhaps one-fifth of a mile long and practically cuts 
 the rocks from east to west across their strike. The gorge lies 
 about one-half mile south of the laminated, dark blue limestone 
 and thin, lighter blue limestones and intermingled slates, described 
 above for the locality just northwest of Highgate Center village, 
 and about two miles north-northwest of the northern exposures 
 in Swanton township of the thin limestones, shales and con- 
 glomerate which outcrop along the Highgate-St. Albans road. 
 
 In the upper part of the northern wall of the gorge just below 
 the bridge is a massive looking stratum of dark, fine-grained, 
 siliceous rock, twenty or more feet thick as now exposed, which 
 may be seen to have suffered some shearing, and which as a 
 whole shows little evidence of bedding. In the lower portion of 
 this stratum is a curious "breccia" of small blocks of slaty rock, 
 angular in section and imbedded in a matrix of dark, fine-grained 
 material. About 75 feet below the bridge, in the base of the 
 massive stratum, is included a large block of somewhat banded, 
 coarse-textured slate in a piece of which were found two ill-pre- 
 served specimens of graptolites, tentatively identified by the writer 
 as Dictyonema, probably flabelliforme, and Staiirograptus dicho- 
 tomus Emmons. 
 
 The occurrence of these bryograptoid forms at this locality is 
 worthy of note. The specimens were submitted to Dr. Ruede- 
 mann of Albany. While recognizing their poor state of preserva- 
 tion, Dr. Ruedemann felt sufficiently sure of the general affinities 
 of these fossils to write : "Even lacking a correct specific de- 
 termination of the forms, it is safe to say that they belong either 
 to the Schaghticoke or Deep Kill shales (Hudson valley forma- 
 tions) for the higher graptolite shales of the slate belt do not 
 afford similar species." In specific reference to the opinion of 
 the writer as to the forms to which these fossils might be referred, 
 or with which they might at least be compared, Dr. Ruedemann 
 wrote : "The fossil which you compare with Staiirograptus 
 dichotomus has indeed the general aspect and outline of that 
 species. On closer inspection, however, it appears to be rather a 
 young Dictyonema, flattened out in a vertical instead of a lateral 
 direction. This conclusion is suggested both by the Dictyoncma- 
 like appearance of the thecae and the apparent presence of dis- 
 sepiments connecting the branches. The fossil marked (2) is a 
 fragment of Dictyonema, possibly of the flabelUforme-group, but 
 also comparable to D. rectilineatum of the Deep Kill shale." 
 
 Dr. Ruedemann had no knowledge of the specific locality at 
 which these fossils were found. His properly guarded and yet 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 189 
 
 reasonably confident judgment that they probably represent a 
 Beekmantown horizon is of interest. 
 
 The question would at once be raised as to the probable ex- 
 tent at Highgate of the formation to which these fossiliferous 
 slates belong. This it would be difficult to state. In the gorge 
 the rocks change in lithological character within short distances. 
 The particular block yielding the fossils seems to be somewhat 
 isolated, although similar rock appears to form part of the river 
 bed adjoining the wall of the gorge. The rock carrying the fossils 
 gives place rather abruptly westward to the brecciated rock de- 
 scribed above as forming the basal portion of the massive stratum 
 and which also forms part of the river bed adjoining the wall. 
 
 The section passes vertically downward from the "breccia" 
 into a mass of jumbled grayish-black, or sometimes bluish-black 
 slates carrying firmer bands of yellow-weathering rock. The 
 slates are strongly sheared and the included firmer bands are 
 usually twisted or broken so that large detached, more or less 
 rectangular blocks, as the}?^ appear on the surface, now lie in 
 helter-skelter fashion among the slates, often oriented across the 
 strike at various angles. The disturbances which the slates have 
 suffered interfere with any reading of the dip of the bedding and 
 the thickness exposed remained undetermined. Close inspection 
 of the surface- of the slate at many places reveals the presence 
 of small fragments of slate very similar to their matrix, the whole 
 so thoroughly compacted that the broken up condition is hardly 
 visible except at close range. 
 
 Downstream the slates pass into a "brecciated" or conglom- 
 eratic layer 8 or 10 feet thick. This is followed by a succession 
 of alternating, thin bluish and more massive grayish-buff layers 
 dipping easterly about 18°, with a bed of the grayish-buff about 
 5 feet thick at the base, all distinctly sheared. This stratum may 
 be repeated for it is followed by a similar series which is suc- 
 ceeded by a "brecciated" stratum about 30 feet thick. 
 
 The rocks which form the bank of the river at the lower, 
 western end of the gorge were only casually inspected at the end 
 of a day's work. No fossils were found in them. 
 
 Though a diligent search was made in its upper part, no 
 fossils other than those mentioned were found in the gorge. 
 
 The section at Highgate Falls shows that the rocks forming 
 the gorge have been under great compression and that some of 
 them have been greatly crushed and sheared. It is not clear that 
 the "brecciation" shown by the various rocks is all of similar 
 origin. The fragmental basal portion of the massive stratum in 
 the upper part of the northern wall visibly grades into the over- 
 lying rock in such manner as to make it extremely difficult to 
 imagine just how it could be explained as due to friction or mash- 
 ing during movement. While there seems to be some indication 
 that the massive stratum has ridden over the beds below it, the 
 
190 REPORT OP THE VERMONT' STATE GEOLOGIST. 
 
 now thoroughly compacted "breccia" appears to be so related to 
 the main mass of the massive stratum that if thrusting did occur 
 the "breccia" could readily be imagined to have attained its pres- 
 ent condition prior to movement. 
 
 The evidence of differential movement between the massive 
 stratum, as it has been designated, and the black slates below it 
 consists not so much in the identification of any distinct thrust 
 plane between the two as in the contrast shown with respect to 
 primary bedding characters and internal deformation. The crush- 
 ing of the slates has been intense. It seems to suggest that they 
 were crowded by a heavy mass above them which has partly been 
 eroded. Perhaps they were also crowded from beneath. Data 
 were not found to determine whether masses of very different 
 age are involved. It is possible that most of the rocks belong 
 to a conformable or disconformable series which behaved accord- 
 ing to the nature of their primary structure. The block of slate 
 in which the fossils were found has much the aspect of an inclu- 
 sion caught up during thrusting. 
 
 Hungerford Brook. The road from Highgate Falls to St. 
 Albans crosses Hungerford Brook a mile south of Highgate vil- 
 lage. At the bridge and along and in the bed of the stream east 
 and west of the bridge are blackish slates. According to Dr. 
 Howell of Princeton, who has collected fossils from these rocks, 
 but who wishes to study his specimens with care before an- 
 nouncing his final conclusion, these slates may be of Upper or 
 late Middle Cambrian age. Dr. Howell bases his opinion in part 
 on the reported discovery by the Canadian Survey many years 
 ago of Agnostus orion at Hungerford Brook.^ 
 
 Eastern Highgate. The rocks lying to the east of the blue 
 limestones, slates and conglomerates along the eastern valley of 
 Rock River were only casually inspected along the low ridge near 
 the South Gore School and the road running from the school to 
 Highgate Center. The rocks are slates of very similar and mon- 
 otonous aspect and gave no fossils. They are associated with 
 conglomerate at some places. It would require further study to 
 reach any tentative opinion of the age of these rocks and their 
 relations to the rocks lying to the west of them. Thej were 
 mapped as "Georgia Slates" by the Vermont Survey. 
 
 Swanton Township. 
 
 (St. Albans topographic sheet.) 
 
 General. Swanton township is bordered by the lake on the 
 west. It includes Hog Island, an essentially insular area joined 
 to the mainland by the delta of the Missisquoi River. The town- 
 ship is bounded by Highgate on the north, by Sheldon and Fair- 
 field on the east and by St. Albans on the south. 
 
 'Personal communication. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. Igl 
 
 Hog Island. Hog Island, so-called, is the western extremity 
 of a peninsula jutting into Lake Champlain. The designation of 
 island is probably wholly correct with respect to the relation of 
 the hard rock portion of the peninsula to that of the Vermont 
 mainland ; but the island and mainland are now joined by modified 
 delta and flood plain deposits of the Missisquoi River which oc- 
 cupy a strip from two and a half to three miles wide, extending 
 from Maquam Bay at the south to the eastern portion of Missis- 
 quoi Bay at the north. Over this delta surface the Missisquoi 
 River now courses northward, in which direction it is extend- 
 ing its delta into Missisquoi Bay. The river enters the bay by 
 three short distributaries. Three sluggish water channels, known 
 respectively as Dead, Maquam and Charcoal Creeks, probably 
 mark former distributary outlets of the river. 
 
 The hard rock is exposed along shore and in many low-lying 
 ledges inland and apparently all belongs to the shale formation of 
 the region. The rocks are everywhere so similar in lithology and 
 structural features to those of Alburgh and North Hero that de- 
 scription would be largely repetition. Easterly and westerly dip- 
 ping beds were noted and both were observed to be cut by east- 
 erly-dipping cleavage. 
 
 Northivest, zuest and southwest of Swanton village. The 
 slates of Hog Island undoubtedly pass under the delta deposits of 
 the Missisquoi River and the low sand plain west of the village of 
 Swanton. There are few if any outcrops in the sand plain, but 
 at some places along the roads the surface soil contains abundant 
 chips of slate showing that the hard rock often lies close to the 
 surface. The Missisquoi from Swanton village northward rarely 
 cuts the slate above the surface of the river, as may be readily 
 seen in passing along the road that closely follows the southwest 
 bank of the stream ; a comsiderable ledge was noted on the north 
 bank of the stream about a mile north of Swanton Falls. 
 
 The slate outcrops at Swanton Falls in the western part of 
 the village. The rock has the usual characters shown by the 
 formation in its outcrops along meridians farther west, consist- 
 ing of slates with firmer bands, the former highly cleaved and 
 the latter bent or broken with small offsets. The slates are often 
 graphitic and carry graptolites, which have retained their form 
 but have largely lost their thecal structures. They seem to be 
 G. qiiadrifnucronatus. 
 
 The Missisquoi River makes a prominent bend to the south 
 just south of Swanton village. Southwest and south of this bend 
 is a wide expanse of lowland lying between the lake shore and a 
 meridian passing just east of the village. The slate formation 
 probably underlies this lowland throughout its breadth of three 
 and a half miles to the St. Albans line. Away from the lake the 
 slates are found only infrequently over the flat, sandy plain ; 
 but along the lake shore they are exposed from Hotel Cham- 
 
1P2 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 plain southward. They are laminated mud rocks with firmer 
 bands, marked by crushing and cleavage, and abundant calcite 
 veining. The shore section gives the same lithological and struc- 
 tural features found in the rocks of North Hero three miles to 
 the west. 
 
 Between Swanton village and the Missisquoi River. Swan- 
 ton village is situated largely on a sand plain. The only outcrops, 
 except those at Swanton Falls, occur south of the main village 
 between the road running from Swanton to St. Albans and the 
 Missisquoi River. 
 
 The rock in the western quarry of John P. Rich (Swanton 
 Lime Works) is a greatly altered, grayish- white, often somewhat 
 marbly limestone and as exposed in the face of the quarry gives 
 little evidence of bedding. In the southwestern part of the quarry, 
 as exposed in the summer of 1921, the gray limestone was seen 
 resting on black, graphitic, Hmy slate which is strongly sheared 
 and filled with small veins of secondary calcite and quartz. In 
 the slate a considerable hole had been dug apparently to see to 
 what depth the slate extended. The photograph shows the gen- 
 eral relations. See Plate XXIII. The slate is exposed over a small 
 space in the floor of the quarry. Its presence served to drive 
 quarrying operations in a horizontal direction eastward. 
 
 In an older quarry that lies to the southeast the rock is 
 similar to that just described, but shows bedding more distinctly, 
 with easterly dip. The gray limestone outcrops abundantly in the 
 fields near the quarries. It is everywhere crystalline and barren 
 of fossils. It extends eastward to the bank of the river, forming 
 conspicuous ledges at the highway bridge. Southeastward and 
 southward the rock either is not present or lies under the sand 
 plain along the river. The whole mass of this limestone south of 
 Swanton village as now exposed is about two-thirds of a mile in 
 extent from west to east and two-fifths of a mile from north to 
 south. It is now separated from all similar rock in the immediate 
 vicinity by surface material. The nearest outcrop northward and 
 the only one noted between this mass and similar rock east of 
 Highgate Springs is about a mile east-northeast of Swanton village 
 along the road to Highgate Center. At this place emerging from 
 the sand plain is a low ridge of gray hmestone associated with 
 patches of buff- or chamois-colored rock which are probably 
 parts of eroded layers. 
 
 The gray limestone ends rather abruptly west of Rich's 
 quarry. The extent to which it overlaps the slate westward was 
 not determined. It is probable that the slate passes round to 
 the south of the limestone mass under the surface covering ;_ for 
 although not observed in the immediate neighborhood of the lime- 
 stone, or along the river, about three-fourths of a mile to the 
 southeast, slate like that in the floor of Rich's quarry has relation 
 to gray limestone quite similar to that shown in the quarry. This 
 
>>^ 
 
 +-) 
 
 
 01 
 
 3 
 
 CO 
 
 o 
 
 'o 
 
 hn 
 
 <K 
 
 G 
 
 
 
 m 
 
 ,« 
 
 13 
 
 o 
 
 Sh 
 
 o 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 193 
 
 outcrop of the slate carries it to a meridian one-third of a mile 
 east of the eastern edge of the limestone mass south of Swanton 
 village, and about one mile east of the exposed slate at Rich's 
 quarry. 
 
 Rocks south of Szvanton village, bordering the eastern margin 
 of the lowland. The slate at the last-mentioned locality is per- 
 haps 20 rods east of the Central Vermont railroad track and a 
 few rods south of the road which after skirting the southwestern 
 bank of the Missisquoi passes eastward to join the Swanton-St. 
 Albans road. The rock occurs in a shallow pit that has ap- 
 parently been excavated for road material. Just east of the slate, 
 gray limestone with some darker beds near the base and irregu- 
 larly distributed yellow-weathering beds in the higher portions 
 forms a hill just east of the slate. The slate and calcareous 
 rocks were not seen in actual contact, but the space separating 
 the two is small and there is no doubt that the limestone lies 
 against the slate. Some of the limestone carries indistinct fossil 
 markings ; the rocks dip easterly and extend eastward to within 
 about 250 yards of the Swanton-St. Albans road. 
 
 It was not possible to determine the horizon of the slate 
 either at Rich's quarry or at the last-named locality ; but there 
 seems little doubt that it represents the slate formation of the 
 lake region and that it is younger than the limestones with which 
 it is associated. That there has been simple inversion of rocks 
 due to folding and overturning seems extremely improbable, for 
 it would then seem that other rocks should intervene between 
 the slates and limestones, which is not the case. The reasonable 
 inference is that the limestones rest by thrust overlap on the slates 
 in both cases. The relations conform to the regional type of 
 dislocation. 
 
 The limestones at both of the localities just described are 
 probably of Lower Ordovician and possibly of Chazy age. This 
 has hardly been proved by fossils, but is made probable by com- 
 parison with similar rocks in similar relations which will be de- 
 scribed beyond. 
 
 About 50 rods south-southwest of the outcrops last described, 
 west of the main line track of the Central Vermont R. R., in the 
 angle formed by it and the Alburgh branch, is a low hill composed 
 mostly of a schistose quartzite or quartzitic slate, apparently with- 
 out fossils. Associated with this quartzite are somewhat isolated 
 patches of bluish limestone in uncertain structural relations with 
 the quartzite. In its thinly-bedded character and litholog}^ the 
 limestone has resemblance to certain rocks of Trenton age. It 
 appears to be fossiliferous, but it is so altered that nothing distinct 
 was obtained. Calcite veining is frequent. The limestone shows 
 its bedding better at some places than at others and occasionally 
 presents a wavy arrangement in the outcropping edges of the beds. 
 It appears to have been caught up by the quartzite. The distribu- 
 
194 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 tion of the limestone in the quartzite is pecuHar. A conspicuous 
 exposure occurs just west of the track. This is followed west- 
 ward by quartzite and then occurs another somewhat band-like 
 strip of the limestone which seems to be lar*gely surrounded by 
 the slaty quartzite. The dip of both rocks is easterly. It is sus- 
 pected that the quartzite is repeated and that the limestone may 
 also be. The distribution and visible structure thus gives a rough 
 suggestion of interbedding-, which however does not seem prob- 
 able. The whole width of this hill from east to west is perhaps 
 200 or 250 yards. The rocks to the west of it are concealed. 
 
 About 100 yards south of this hill, and just west of the main 
 line track a small outcrop of the schistose quartzite emerges from 
 the surface covering in the low ground and just south of this is a 
 small exposure of thinly-bedded, bluish limestone. 
 
 A third of a mile to the south of these last-mentioned out- 
 crops, just north of Swanton Junction and west of the track, is 
 another hill which shows a very dififerent kind of rock. It belongs 
 to the quartzite-dolomite or Red Sandrock series lying to the east, 
 presently to be described. On the east side of the hill the bedding 
 dips easterly at a moderate angle for the most part, but at the 
 northeastern end near a small quarry, beds which dip easterly at 
 a high angle lie against others with varying westerly dip. This 
 hill shows a prominent scarp on the west, perhaps 60 or 75 feet 
 high, with the beds apparently dipping westerly at a high angle. 
 At the west the descent is everywhere abrupt to the surface of 
 the low ground that lies to the west. No contacts with the rocks 
 that lie beneath the plain were found. 
 
 South of this hill a private road runs westward across the 
 plain to two farm houses about one-half mile west of the Junc- 
 tion. The houses stand on a low ridge, on the east side of which 
 is a considerable thickness of rather heavily-bedded limestone, 
 some of which is striped exactly like many exposures of the so- 
 called Middle Chazy in other parts of the lake region. The beds 
 of this series dip easterly at a high angle and have a sinuous 
 strike with probable offsets. M. magna was not found, but a 
 ledge just north of the barn gave numerous specimens of the 
 characteristic Girvanella ocellata (Seely). These rocks are suc- 
 ceeded westward by beds of grayish-black limestone weathering 
 to a lighter gray than the Chazy and possessing all the lithological 
 characters of the Black River. They dip easterly like the Chazy 
 beds and are full of small calcite veins. Fossils were not found. 
 West of these, also dipping easterly, and apparently conformable 
 with the Black River beds, are thinly-bedded, blue limestones of 
 probable Trenton age. Crinoid stems, weathered section of shells 
 and a much worn brachiopod were found with other indistinct 
 fossils. The terrane is only partly represented. 
 
 These apparently conformable beds are thus seen to be over- 
 turned, probably on the western limb of an anticlinal fold, but pos- 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 195 
 
 sibly on the eastern limb of a syncline. The rocks in the plain, 
 both east and west are concealed. The writer's notes record no 
 siliceous beds in the Chazy at this place. The Black River seemed 
 to be in conformable contact with the Middle Chazy limestone. 
 This is a common association farther south in Vermont ; but it 
 will. appear from later discussions that there are differences in 
 the ways in which these associated formations are deformed at 
 various places. The field relations at this place did not suggest 
 any marked dislocations among the dift"erent members. As a 
 Avhole, however, they are thought of as resting by thrust against 
 younger rocks at the west. 
 
 A half mile to the south-southeast is the large mass in which 
 the Fonda quarry is excavated. It forms a hill just west of the 
 railroad track. The quarry has been sunk in the western slope 
 of a massive, crystalline, gray limestone which forms much of the 
 higher portion of the hill. Except for some blackish layers at 
 one place in the floor of the quarry the rock has much the same 
 appearance throughout and shows bedding imperfectly preserved, 
 with easterly dip. The rock is very much like that south of 
 Swanton village. South of the quarry on top of the ridge is a 
 sort of "hog-back" of altered calcareous sandstone or quartzite, 
 perhaps 200 yards long and 50 to 75 feet wide, which does not 
 appear in the quarry and seems to be surrounded by limestone. 
 East of this quartzitic rock is gray limestone associated with 
 layers weathering to a pinkish buff, which approach close to the 
 railroad track. East of the track is the Red Sandrock. 
 
 The ridge in which the quarry is located descends westward 
 by irregular surface to the plain that extends towards the lake. 
 The various rocks outcropping on the intermediate level west of 
 the ridge have a confused arrangement. At the west are beds 
 which are apparently to be correlated with the Chazy. The strike 
 of these beds at some places changes as much as 90° within a 
 few feet. They are associated with rocks having the markings 
 of the Black River and veined with white calcite. Numerous 
 outcrops of thin, blue limestones were noted in no very regular 
 relation to the other rocks. The latter carry obscure fossils and 
 seem to be of Trenton age. 
 
 The various rocks about Eonda's quarry have been much dis- 
 turbed. They have probably been broken by thrusts. All are 
 more or less crystalline, but this condition is most apparent in the 
 massive, gray limestone and associated beds forming the eastern 
 portion of the mass. The massive beds in the eastern portion of 
 the hill have probably been broken within themselves and have 
 also moved against the rocks now forming the lower western part 
 of the hill and all of them are probably in thrust relations to 
 younger rocks lying beneath the plain at the west. A certain 
 amount of flowage and crystallization serving to integrate and 
 weld layers into massive rocks, accompanied by a certain amount 
 
196 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 of folding and fracture, were the apparent modes of deformation 
 of the rocks prior to a bodily thrust of all the rocks to the west, 
 over the slates. 
 
 Thrusting may produce an apparent inversion of strata, but in 
 such cases usually very thick and massive rocks are involved. The 
 rocks in the eastern portion of the hill at Fonda's quarry dip 
 easterly and pass beneath a series of beds with very similar dip, 
 but which are unquestionably much older. The two series of 
 rocks have the guise of conformability, but one may hardly be 
 deceived thereby. It is hardly conceivable that the inversion has 
 been produced by overturning of these massive formations during 
 folding. The older rocks have their position by thrust. 
 
 It should not be understood that inversion of beds has never 
 occurred by folding, even among somewhat massive rocks ; but 
 rather that rupture and dislocation were more characteristic modes 
 of deformation among all the rocks, on one scale or other, in 
 western Vermont and largely on account of the presence of very 
 massive and exceedingly competent strata among them. Even 
 among rocks that folded the end result was often, if not usually,, 
 fracture and faulting. 
 
 South-southwest of Fonda's quarry are two old, dismantled 
 quarries, formerly known as Rich's Lime Works. The rocks at 
 both these places are like the gray, marbly limestone and asso- 
 ciated yellowish-weathering beds at Fonda's. In the fields nearby 
 are ledges of calcareous quartzitic sandstone. The rocks at and 
 near these old quarries form low ridges or discontinuous out- 
 crops and suggest that similar rocks may underlie some of the 
 surface deposits of part of the lowland roundabout. There is 
 nothing especially striking in the structural features at these 
 localities. The dip is at a low angle to the east. The southern 
 quarry is practically on the St. Albans line. 
 
 The Red Sandrock series of dolomites, quartsites and slates, 
 zvith associated limestones, in S want on township. The rocks which 
 will be described under this heading probably do not include all 
 the rocks belonging to the Lower Cambrian in Swanton. Some 
 other rocks that probably belong in this terrane, or to some other 
 part of the Cambrian, will be mentioned beyond. 
 
 No outcrops of the Red Sandrock series were found in Swan- 
 ton north of the Missisquoi River. The western margin of these 
 rocks at the north begins just south of the river and about one- 
 half mile east of the gray limestone at Swanton bridge. From 
 this point the visible margin then runs southward for a short 
 distance to the east of the Swanton- St. Albans road and then 
 west of and roughly parallel with it to the St. Albans line, where 
 it bends southwesterly in the direction of St. Albans Bay._ 
 
 By comparison later with conditions farther south it will 
 appear that the present western margin of these rocks is probably, 
 at least to some extent, an erosion trace in the course of the re- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 197 
 
 cession of this formation eastward and that it is essentially an 
 escarpment softened by erosion. 
 
 In Swanton the members of this Sandrock formation are not 
 in contact with the younger rocks that lie west of them. The 
 nearest approach to visible contact is southeast of Fonda's quarry 
 where the eastern outcrops of the mass at Fonda's quarry are 
 Avithin about 100 yards of dolomite beds of the Sandrock series. 
 As in Highgate and other parts of Vermont the extent of present 
 and former overlap remains uncertain because a surface section 
 does not expose the younger rocks beneath the Sandrock, east of 
 its present western margin (see, however, Ferrisburg township 
 described beyond). North of Swanton Junction the margin 
 swings west of the railroad track and the older rocks lie there on 
 a meridian occupied farther north by outcrops of the younger 
 gray limestone. This relation is, of course, only a suggestion 
 of appreciable overlap ; but at pjaces farther south definite con- 
 tact relations support the idea that the Cambrian beds moved over 
 the younger rocks. 
 
 Only the chief variations among the members of the Sand- 
 rock series may be noted. The history of these rocks with respect 
 to the conditions under which they were deposited is a chapter by 
 itself. 
 
 At Barney's quarry a mile east of Swanton village and on 
 the western margin of the Sandrock south of the Missisquoi River, 
 the rock has been removed for marble. The marble is a mottled 
 red and white siliceous dolomite of "brecciated" appearance. 
 Similar rock appears at other places in Swanton and in the town- 
 ships to the south and its various outcrops often appear to mark 
 approximately the same horizon, although it seems possible that 
 its pecuHar features are repeated in different beds. Bowlders of 
 this rock are common on the islands of the lake and on the main- 
 land. So far as it may be distinguished by color markings, the 
 mottling is a variable feature and in the same bed the mottled 
 rock appears to pass laterally into other rock of more homo- 
 geneous color and texture. While in a great many of its outcrops 
 this mottled rock is certainly not far above the supposed plane 
 of shear of the series of which it is a member, the rock itself does 
 not seem to give convincing evidence that its apparently brecciated 
 character was acquired from crushing during thrusting. If the 
 apparent brecciation is an effect of internal deformation it would 
 seem that unusual primary conditions must have existed, such, 
 perhaps, as an alternation of thin beds of sandy and magnesian 
 deposits. It is possible to imagine that such beds under pressure 
 could be broken and crushed with subsequent welding of the 
 whole into the massive condition which the rock now shows. On 
 the other hand, if these rocks were accumulated in shallow water, 
 which seems probable, it is possible to imagine that minor disturb- 
 ances during deposition might have produced the confusion and 
 
198 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 that the compacted condition was effected by consoHdation under 
 burial, or by dynamic pressure, or both. The gray and red rocks 
 into which the mottled variety seems to grade many times do not 
 seem to show appreciable shearing deformation. 
 
 The rock yields few if any fossils. Obscure markings that 
 might be interpreted in different ways are found in the more 
 homogeneous beds above and below the mottled rocks. Probably 
 some of these represent filled mud cracks or other purely physical 
 features of shallow water deposits. 
 
 The generally massive, siliceous dolomites, including the mot- 
 tled marble, pass eastward at the surface into rusty-weathering, 
 sandy shales or shaly sandstones, often "flaggy." The latter 
 outcrop frequently in the pasture along the road from Barney's 
 quarry eastward toward Donaldson's farm. These rocks carry 
 fragments of trilobites and in their lithological features are much 
 like the shales at "Parker's ledge" in Georgia township. 
 
 In the woods north of the pasture road just mentioned, and 
 perhaps one-fifth of a mile from it, is a small ledge of limestone, 
 apparently interbedded in the Sandrock formation, from which 
 were collected several specimens of a fossil identified as Kutorgina 
 lahradorica, var. sivantonensis. The writer was guided to this 
 locality by Mr. Donaldson and Mr. Bluett of Waterbury, Conn. 
 This fossiliferous rock was not found elsewhere by the writer. 
 
 East of Donaldson's farm, between it and a road running 
 north and also east of the road, are numerous ledges of rusty- 
 weathering, sandy shales which were regarded as the eastward 
 extension of those described above and as probably of Lower 
 Cambrian age. 
 
 Except for the limestone member the series as just described, 
 from sections made across it at different places, was observed to 
 form a broad band occupying nearly the whole width between the 
 Swanton-St. Albans road on the west and the Highgate-St. Albans 
 road on the east, and extending practically from the northern 
 boundary of Swanton township into St. Albans at the south. The 
 dip is usually easterly at a low angle. About a mile east of 
 Donaldson's and about one-fifth of a mile west of the Highgate 
 road a westerly dip was noted. 
 
 East of Donaldson's the shales seem to be more conspicuously 
 sheared than farther west and some of them are on meridians 
 occupied farther south by ledges of gray dolomite. It was not 
 clear whether shales passed laterally into dolomite ; but at other 
 places yet to be described, the field relations are not inconsistent 
 with such a view, although probable disturbances among the 
 rocks must always be kept in mind. 
 
 The so-called "Intrafonnational Conglomerate" and asso- 
 ciated rocks along the Highgate-St. Albans road and at other out- 
 crops in Swanton. South of Hunger ford Brook in Highgate, and 
 just north of the Swanton line, begins a series of outcrops of 
 
O o 
 +-1 
 
 ^« 
 
 aim 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 199 
 
 various rocks which from their field relations all seem clearly to 
 belong to the same formation. The principal exposures are along 
 or near the Highgate-St. Albans road which these rocks rather 
 closely follow southward for a distance of about four miles. 
 Outcrops become more intermittent towards the south. At the 
 south in Swanton, scattered outcrops in the drift extend the 
 geographical range of these rocks east of the Missisquoi Branch 
 of the C. V. R. R. to the base of the quartzite hills in the south- 
 eastern part of the township, and apparently show that this forma- 
 tion was once more widely represented over the surface than now. 
 However, as now preserved, these rocks form for the most part a 
 rather narrow belt on the east of the broader band of quartzite, 
 dolomites and shales described above. 
 
 The most conspicuous member of this series is a coarse con- 
 glomerate whose fragments vary in size from small pieces to 
 huge slabs or blocks weighing tons. With the conglomerate and 
 forming its paste or matrix is a finely-granular (arenaceous), 
 calcareous sandstone, which at some places forms a stratum on 
 which the conglomerate rests, apparently conformably. The 
 characters of the conglomerate and its associated sandstone are 
 well shown north of Skeels Corners, to the west of the road. At 
 this place the sandstone, which is coarsely bedded, forms an 
 irregular stratum beneath the conglomerate about 30 or 40 feet 
 thick. The rock is prominently siliceous and carries many small 
 veins of quartz which have weathered out in relief against the 
 body of the rock. The accompanying photograph shows the 
 surface of the conglomerate at this locality. See Plate XXIV. The 
 larger fragments of the conglomerate are often large slabs of 
 grayish or bluish limestone and these are mingled with many 
 smaller pieces of all sizes. 
 
 In the conglomerate the matrix is not always distinct from 
 the included fragments when the latter are small. The material 
 surrounding the coarser blocks is itself a conglomerate-breccia, 
 showing many small fragments on a broken surface. 
 
 North of Skeels Comers the conglomerate and its associated 
 rocks continue northward as a low ridge west of the road, and 
 by intermittent outcrops along the road, nearly to Hungerford 
 Brook. One-fourth of a mile north of the Swanton line an expo- 
 sure on the west side of the road gives unbroken thin beds of 
 bluish limestone, perhaps 2 or 3 inches thick, dipping westerly 
 and passing upward into broken and dislocated layers. 
 
 East of the road, north of the latitude of Skeels Corners, the 
 surface west and east of Hungerford Brook is flat, with the hard 
 rock mostly concealed. Along the road by Webster School are 
 low-lying ledges of slate like that in eastern Highgate, to the east 
 of Rock River. So far as surveyed over this fiat land east of 
 Skeels Corners, no conglomerate or limestone was observed. 
 
200 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 South of Skeels Corners, along the road or in the fields, the 
 members of this conglomerate-limestone formation outcrop at in- 
 tervals to within a mile of the St. Albans line. To the east the 
 hard rock that outcrops here and there through the extensive 
 surface material is largely slate; but south of the road to Greens 
 Corners in a pasture and on the bank of Hungerford Brook is a 
 ledge of calcareous rock that probably is a part of the formation 
 to which the conglomerate belongs, and a mile and a fourth south- 
 west of Greens Corners, one-third of a mile east of the railroad 
 track are inconspicuous ledges of bluish limestones like those 
 seen along the Highgate-St. Albans road and farther north. 
 
 Various fossils have been reported from this conglomerate 
 formation at its outcrops in Swanton, and those occuring in St. 
 Albans which wall be mentioned later, and these have been thought 
 to indicate a Middle Cambrian age ; but much uncertainty exists 
 as to what forms should be referred to the matrix and what to 
 the fragments. In Swanton the beds near Skeels Corners yielded 
 a few fragments of linguloid brachiopod shells whose characters 
 are too obscure for precise determination. In size and shape they 
 resemble as closely as any illustrated forms, Lingula ric'miformis 
 Hall, or Glossina trentonensis Conrad; but it would be going 
 altogether too far to claim that they are referable to either of 
 these species. It was not clear whether the fossils were in the 
 matrix or not. 
 
 Southeastern part of Sivanton tozvnship. In the southeast- 
 ern part of the township and in adjoining parts of Fairfield the 
 surface rises, forming hilly land. As inspected near the track 
 of the Missisquoi branch and along the road running parallel 
 with it on the southeast the rocks at the base of this high 
 land consist of quartzites and dolomites much like those found 
 along the base of the Green Mountains farther south in Vermont 
 and are tentatively regarded as of Lower Cambrian age. The 
 slates which underlie the flat land west of these hills, between 
 them and Hungerford Brook, may be and probably are of Cam- 
 brian age, but their exact horizon is not known. 
 
 St« Albans Township. 
 
 (St. Albans topographic sheet.) 
 
 Location. St. Albans township lies just south of Swanton. 
 
 The lake region. The broad area of low, flat land which 
 forms the western portion of the township of Swanton continues 
 with practically undiminished breadth into St. Albans. In St. 
 Albans as in Swanton the rock of this lowland belongs chiefly to 
 the Ordovician shale formation of the region. The shore of the 
 lake gives an almost continuous section in these rocks which have 
 the same general characters which have been described for them 
 on previous pages. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 201 
 
 Away from shore the hard rocks are mostly concealed, but 
 outcrops are found on knolls and low ridges along- the roads and 
 in the fields. Along the road from the lake shore to St. Albans, 
 past School No. 10 and the Tuller School, the slates were traced 
 by scattered ledges eastward to within one-third of a mile of 
 Stephens Brook. A half mile west of School No. 10 some riisty, 
 sandy shales yielded large numbers of graptolites, which were 
 identified as probably Diplograptus foliaceous, var. 
 
 In its southern portion the lowland forms a peninsula known 
 as St. Albans Point, which is separated from the mainland by 
 St. Albans Bay. 
 
 Among the shales, or slates as they might fittingly be called in 
 most cases, which probably make up most of the lowland, there 
 occur at several places other rocks which are very doubtfully 
 members of the shale formation. In spite of somewhat scanty 
 representation at the present time, these rocks may possibly have 
 some structural significance. 
 
 In the first place these rocks may be described as appearing 
 to have a stranded position among the shales and as foreign to 
 them. They have not been seen elsewhere in the region in such 
 relations nor in any other relations to the shales. In all their 
 outcrops these rocks now form dense, very much altered quartz- 
 ites, weathering white, but on fresh surfaces appearing blackened 
 as though at one time they had been in a very hot fire. They are 
 extremely tough and break reluctantly under the hammer. Be- 
 cause of the way in which they weather, their outcrops are con- 
 spicuous when close at hand, although they do not form large ex- 
 posures nor high elevations. In the course of a general survey of 
 the lowland along the roads and in adjacent fields the outcrops of 
 these rocks were sufficiently conspicuous and different from the 
 shales to call for a special examination. With the possibility 
 always in mind that on the islands of the lake or over the lowland 
 bordering its shore there might somewhere be found some rem- 
 nants of overthrust rocks that once lay on the shales but which 
 have now largely disappeared by erosion, these rocks were at first 
 hailed as possibly affording an example of what had so persistently 
 been sought. Since their outcrops are all low and topographically 
 merge with the surrounding slates, it is possible that they are more 
 extensive than is apparent and possibly there are other visible 
 ledges which were not seen. 
 
 The possible significance of these rocks seems to lie partly in 
 their geographical situation and relations and partly in the fact 
 that they have not been seen at any place as forming a part of 
 the shale formation. 
 
 The northernmost outcrops which were seen lie between the 
 lake shore and Jewett Brook, about a mile and a half north-north- 
 west of the Point School. At this place the rock has the greatest 
 surface extent of any of the exposures seen. It forms three low 
 
202 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 knolls in a north-south line and smaller patches west of them. 
 Roundabout are ledges of other rock more like the shale-slate 
 formation, but not always of well-defined character. Typical 
 shale, however, outcrops to the north on a meridian slightly to 
 the east, and also westward. 
 
 A mile south-southwest on the road running from the lake 
 shore to St. Albans Bay and one mile northwest of the Point 
 School are other outcrops, along and near the road. In a low 
 ridge just east of the road the bedding is distinct and there is a 
 small fold overturned to the west. 
 
 Other outcrops occur practically on the same meridian with 
 the last mentioned in the southern portion of St. Albans Point. 
 About two-thirds of a mile north of Hathaway Point, at the 
 summer place of Mr. Morton of St. Albans, shales may be seen 
 to form a high cliff along shore. Above the bank in the yard 
 near the highway occurs a small exposure of dense, white- 
 weathering quartzite which appears to be in place. At the ex- 
 tremity of Hathaway Point the quartzitic rock appears to lie on 
 greatly sheared and disturbed slate and the two are much involved. 
 The relations strongly suggest a thrust contact. Along the road 
 from Hathaway Point to "Kamp Kill-Kare" and in the fields 
 west of this road are other outcrops of the quartzite, which west- 
 ward gives place to typical shale. 
 
 The quartzite gives little or no hint as to its age. It lies on 
 meridians which farther south on the mainland in Georgia town- 
 ship, south of St. Albans, are occupied by shales and overthrust 
 limestones and members of the Red Sandrock series. It seemed 
 to the writer not unlikely that the small areas of quartzite just 
 described may be residuary fragments of a formerly much more 
 extensive mass of such rocks, or of others structurally related tO' 
 them, which once lay on the slates. The imagination must be 
 exercised in such a view, but the suggestion is not without sup- 
 port from other field relations in nearby areas. East of Stephens 
 Brook, north of the village of St. Albans Bay, are physiographic 
 outliers of altered limestones, presently to be discussed, which 
 are now nearly a mile removed from the erosion margin of similar 
 rocks which outcrop from beneath the massive quartzites and 
 dolomites of the Lower Cambrian Red Sandrock series. These 
 limestone masses are quite clearly eroded thrust-inliers in the 
 shale formation. 
 
 Equal in interest to the evidence of remarkable thrust phe- 
 nomena which the region shows are the indications of the great 
 amount of erosion which apparently must have occurred in pro- 
 ducing the present relations among the rocks. 
 
 Limestones east of Stephens Brook in St. Albans. Leaving 
 the main road that connects the village of St. Albans Bay and 
 the city of St. Albans, about two-thirds of a mile from the lake 
 shore, is a road running northward towards the Tuller School. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 203 
 
 Along its southern portion this road is bordered on both sides by 
 marbly gray or dove-colored limestone, but northward this rock 
 occurs mostly on the east side of the road where it forms the 
 lower portion of a scarp-slope that is capped by the Red Sand- 
 rock. About a mile north of the St. Albans road, west of the one 
 running northward, are low outcrops of bluish limestone which 
 may be of Trenton age. The gray limestone is intermingled with 
 some sandstone and carries yellow-weathering layers. Without 
 much doubt these rocks are the same as those at Rich's old 
 quarry and at Fonda's quarry farther north. With some inter- 
 ruptions these rocks continue northward to within about a mile 
 of the Tuller School. The dip is prevailingly to the east. 
 
 North of the village of St. Albans Bay and three-fourths of 
 a mile west of the road just described as running northward, are 
 two hills composed of gray limestone which has in its striped 
 appearance at places much resemblance to certain rocks which 
 the writer has elsewhere identified with the Chazy. The rock is 
 altered and massive in general appearance, with obscure dip and 
 strike. Faint markings were noted, but no distinct fossils were 
 found. These two hills are probably joined beneath the surface 
 material, but taken together they are isolated from the rocks 
 forming the scarp to the east and are probably surrounded by 
 slates. The slates are largely concealed roundabout, but outcrop 
 to the west of the larger western hill. 
 
 In and south of St. Albans Bay village. East of the village 
 of St. Albans Bay the escarpment formed by the gray limestone, 
 with its associated rocks and the Red Sandrock formation and 
 which in general borders the lowland on the east, is broken by an 
 embayment along which ascends the road from St. Albans Bay to 
 the city. This embayment marks a surface interruption in the 
 band of limestone and an eastward curve in the margin of the 
 Red Sandrock. South of the road the margin of the Cambrian 
 rocks swings westward and in the eastern part of the village of 
 St. Albans Bay the Sandrock is again in proximity to the gray 
 limestone south of the brook. To the west of the dove-gray 
 limestone occur other limestones which are much sheared and 
 altered. Some of it appears like the dense, black limestone found 
 with the Trenton at Highgate Springs and possibly represents 
 the Black River. Southwest of the Catholic church and in other 
 outcrops nearby are ledges of bluish limestone, weathering gray, 
 which are sheared and veined with calcite. This rock shows 
 fragments of fossils on the weathered surface and a small bowlder 
 gave a worn brachiopod shell like Strophomena. The rock is 
 probably Trenton and resembles other rock correlated with Tren- 
 ton at localities to the north. 
 
 South of the village, to the east of the shore road, is gray 
 limestone with some chamois-colored rock, associated with dense, 
 blackish limestone carrying demilunar traces of fossils which are 
 
204 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 like the markings which so frequently occur in the Black River. 
 Bluish, so-called Trenton limestone, is scantily represented. All 
 the rocks are sheared and veined with calcite. West of the shore 
 road the grass land is flattish, with no outcrops. The shale 
 formation probably underlies the surface material near the lake 
 shore. 
 
 The Red Sandrock series in St. Albans tozvnship. The 
 Lower Cambrian quartzite-dolomite series of Swanton continues 
 southward across the St. Albans line. Along their western 
 margin the Cambrian rocks cap the gray limestones as described 
 above and may be seen in actual contact at two places, at least. 
 With the limestone the Cambrian rocks form an escarpment 
 which faces the lowland and lake to the west. In St. Albans the 
 Cambrian massive dolomites and quartzites are most prominently 
 exposed along a ridge about one mile wide just east of the escarp- 
 ment. A section made across the strike due west of St. Albans 
 city showed essentially the same sequence of massive reddish, 
 gray and mottled rocks as found in the western portion of the 
 band of Cambrian rocks as described for Swanton. A reading 
 on a bed of the mottled "Swanton marble" gave the strike as 
 N. 10° E. and the dip as 8° easterly. The sequence is practically 
 duplicated at the Georgia line with approximately the same dip 
 and strike. 
 
 East of the ridge, along the valleys of Stephens and Rugg 
 Brooks, respectively northwest and southwest of St. Albans city, 
 the surface is lower and the rocks are extensively covered ; but 
 apparently Lower Cambrian rocks underlie most of the surface 
 in the area between the western marginal scarp and the main road 
 that runs from Georgia through St. Albans city to Highgate. In 
 the western outskirts of the city of St. Albans, north of the road 
 to St. Albans Bay, scattered ledges of sheared quartzite outcrop 
 only short distances from small ledges of conglomerate and slate 
 which will be mentioned again beyond, and well-bedded quartzite. 
 not notably sheared, forms low but prominent ledges on and near 
 the main road from St. Albans city to Georgia, about a mile south 
 of the center of the city. 
 
 Aldis Hill. Aldis Hill, to the northeast of the city, is ap- 
 parently composed chiefly of gray quartzite. At the northern end 
 of the hill the beds may be plainly seen dipping at a moderate 
 angle in a direction a little to the north of west. On the north- 
 east slope of the hill the edges of the beds are well exposed and 
 many of them may be seen to be only from 2 to 3 inches thick. 
 They carry frequent thin veins of quartz and are somewhat but 
 not severelv sheared. 
 
 St. Albans Hill. This hill lies partly in St. Albans and partly 
 in Georgia township. It is a prominent eminence lying just east 
 of the St. Albans-Georgia road. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 205 
 
 A private road leaves the main road about two miles south 
 of the center of the city, and passes round the northwestern end 
 of the hill. Along and near this road, perhaps 30 or 40 rods 
 west of the main road, are low-lying ledges of blue limestone 
 carrying some conglomerate. The topography suggests that there 
 is a fault at the northern end of the hill and that this limestone is 
 on the downthrow side. On the supposedly upthrow side is 
 massive quartzite. This apparent displacement is seemingly trace- 
 able in a southeast direction on the east side of the hill, passing to 
 the west of the farm house. Over the hill to the west and south 
 the rocks are quartzite, sheared quartzite or phyllite, and dolomite, 
 in such arrangement as to suggest that possibly that there was 
 lateral variation in the different beds and that some of the rocks 
 were sheared more than others ; also that there may have been 
 some faulting and offsetting so as to bring different rocks along 
 the same line of strike. The western slopes are generally steep. 
 On the southwestern side (in Georgia) are precipitous scarps 
 which mark dislocations. 
 
 Southeastern part of St. Albans toivnship and adjoining parts 
 of Fairfield and Fairfax. East of St. Albans Hill the boundaries 
 of the townships of St. Albans, Fairfield and Fairfax meet at a 
 common point. East of this point, at the southwestern end of 
 Bellevue Hill, are interbedded quartzite, dolomite and mottled 
 rocks practically on end, dipping at a high angle to the west or 
 east. At the base of the series is a stratum of dolomite which 
 looks as though it had been crushed. It breaks into fragments 
 which usually have small unaltered cores surrounded by rusty, 
 decomposed rock. These various rocks lie about a mile east of 
 St. Albans Hill. They are regarded as forming the eastward 
 continuation of the rocks of the hill, or a's possibly lying strati- 
 graphically just below them ; but in either case as members of the 
 Lower Cambrian series. North of these rocks quartzite forms 
 the western base of Bellevue Hill. 
 
 Bellevue Hill. The rocks on the northwestern slope of Belle- 
 vue Hill vary somewhat in character and are prevailingly sheared 
 into foliated rocks. Apparently depending upon their original 
 texture they are now sometimes phyllitic, sometimes schistose or 
 gneissoid. In one place a conglomerate was noted, sheared into 
 a coarse gneiss in which the squeezed pebbles could be plainly 
 seen. Distinct small folds may be observed in some places, par- 
 ticularly on weathered joint planes cutting across the strike. The 
 prevailingly easterly dip, as viewed on the surface, is then seen 
 to be that of an induced structure. The colors are greenish, gray 
 and sometimes purplish. The rocks are all prominently siliceous 
 in composition and in general strongly suggest the basal portion, 
 of some overlapping formation. Well-defined bedding, repeated, 
 small, sometimes overturned folds, variations in the purity of the 
 material and in the texture, all seem to accord best with the idea 
 
206 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 that these rocks are later than pre-Cambrian. They are possibly 
 altered derivatives of older rocks, not now exposed, and have 
 been sheared into schists and gneisses whose surface exposures 
 are deceptive. 
 
 The topography suggests that Bellevue Hill is part of an up- 
 thrust mass of rocks. The western slope is steep and is really a' 
 softened scarp. A banking of bowlder drift and a heavy cover- 
 ing of trees conceals the really precipitous character which the 
 slope now has at some places. In the recognition of the upthrust 
 relation of this hilly land at the east one finds the clue to the 
 clearly disturbed condition of the rocks described for the south- 
 western end of Bellevue Hill and for the westerly dip at Aldis 
 Hill. The beds were folded and sometimes tilted to a high angle 
 or overturned before rupture occurred. Over the higher por- 
 tions of the hilly land the dolomites have disappeared by erosion. 
 East of the supposed plane of thrust the rocks have usually been 
 strongly sheared. 
 
 East of St. Albans city. East of the city a road leads east- 
 ward over the rugged, hilly land to the French School. The 
 rocks along this road were carefully inspected. As exposed at 
 the surface they vary from slaty phyllites through coarser, darker 
 colored schistose or gneissoid quartzites to gray, granular quartz- 
 ites in no regular order. Slaty phyllites are more abundant east- 
 ward. 
 
 The limestone conglomerate and associated rocks in St. Al- 
 bans. Mention has already been made of the small outcrops 'at 
 the northern end of St. Albans Hill and in the western outskirts 
 of the city. The latter locality, commonly known as "Adam's 
 pasture," is one that has been visited by many geologists in their 
 studies of the stratigraphy of the region. Logan was one of the 
 first to report upon the rocks at this place (Geology of Canada, 
 p. 858) and described them as part of a band that was traceable 
 for about one-fourth of a mile north of the road before it disap- 
 peared. Logan also described another band of conglomerate 
 about one-fourth of a mile to the west at the base of a mass of 
 whitish sandstone. Both conglomerates were described as carry- 
 ing fragments of pure gray limestone. Immediately beneath the 
 base of the western strip "occurs a band of dark gray, slightly 
 micaceous slate, with Obolella cingulata." 
 
 The writer's observations at Adam's pasture showed that 
 what is present of this conglomerate formation is partly sur- 
 rounded by not very distant outcrops of sheared quartzite, and 
 afforded nothing definite as to the primary or secondary struc- 
 tural relations of the various rocks. 
 
 In the conglomerate the fragments of gray limestone are 
 imbedded in a matrix of calcareo-siliceous material like that found 
 in the conglomerates of Swanton and Highgate. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 207 
 
 West of the Central Vermont R. R. track, a half mile north 
 of the Georgia line, is another prominent exposure of the conglom- 
 erate formation, perhaps two acres in extent. With unimpor- 
 tant variations the rocks are like those at Skeels Corners. The 
 conglomeratic portion shows large and small fragments of bluish 
 or grayish limestones, with some sheared, marbly limestone, in a 
 calcareo-siliceous matrix which weathers to a yellowish gray. In 
 association with the conglomerate are distinctly bedded ledges of 
 arenaceous rock much like the conglomerate matrix. At this 
 locality none of the thinly-bedded, bluish limestone was seen, but 
 at the northern end of the exposure is a substantial thickness of 
 blackish slates which seem to lie beneath the conglomerate and 
 which have some resemblance to those found in association with 
 the blue limestone at Highgate Center. The formation including 
 the conglomerate, of which outcrops at various places in High- 
 gate, Swanton and St. Albans have now been described, has 
 yielded fossils to various investigators, but its age has not been 
 completely determined nor its relations positively elucidated from 
 such fossils as have been found. From its apparent relations to 
 other Cambrian rocks and from such fossils as have been dis- 
 covered the formation has been called Middle Cambrian. Dr. 
 Walcott thought that the fossils collected by himself and by G. E. 
 Edson indicated such an age. He listed thirteen species as found 
 in the various members of this formation, among which Para- 
 doxides, which was reported from the "argillite," seemed to argue 
 very strongly for a Middle Cambrian age for the formation. 
 
 The distribution and characters of the various rocks which 
 seemingly are to be regarded as together making up this singular 
 formation may be susceptible of another interpretation, in spite 
 of the apparent nature of the fossils. There is little doubt from 
 what observation the writer has made that the removal of the 
 surface covering would disclose a wider extent of these various 
 rocks than their present outcrops show. 
 
 Georg-ia Township. 
 
 (St. Albans and Milton topographic sheets.) 
 
 Location. This township which lies just south of St. Albans 
 is also bordered on the west by the lake. It is bounded by Fair- 
 fax on the east and by Milton on the south. 
 
 The slates and gray limestone along and near the lake shore 
 in Georgia. The gray limestone and associated rocks found lying 
 to the west of the margin of the Lower Cambrian Red Sandrock 
 series in St. Albans continue southward into Georgia, forming in- 
 termittent exposures between the lake shore and the margin of 
 the . Red Sandrock series. The limestone seldom reaches the 
 shore, but is separated from it by the slate formation with which 
 it is in intimate field association at several places. The outcrops 
 
208 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 of the gray limestone and its companion rocks in Georgia may be 
 briefly described. 
 
 East of the shore road running south from St. Albans Bay 
 village, and a half mile south of the St. Albans line, on "Shore 
 Acres farm," the gray limestone with interbedded, yellow- 
 weathering layers, in some places may be seen dipping easterly at 
 a high angle. The rock is. however, generally much sheared with 
 partial obliteration of the bedding. The gray rock is associated 
 at this locality with beds carrying markings that indicate a Black 
 River age. The structural relations are obscure. Above the lime- 
 stone to the east are the Lower Cambrian gray and mottled dolo- 
 mites dipping easterly at a low angle. 
 
 Just west of the shore road, south of "Shore Acres farm" 
 and between it and Mill River, are outcrops of sandstone with the 
 beds dipping easterly at a high angle. Just west of the sandstone 
 is bluish limestone which looks very much like the Trenton. The 
 dip is again easterly at a high angle and the sandstone and lime- 
 stone appear as though interbedded. 
 
 South of these outcrops is Mill River. In the bed and along 
 the sides of the river, above and below the bridge, is exposed a 
 gray sometimes obscurely striped limestone. Above the bridge 
 the dip is not clear, but below it the bedding may be seen to dip 
 easterly at a high angle, measured at one place as 53°. 
 
 About 200 paces west of the bridge the gray rock is succeeded 
 westward by apparently conformable sandstone and shaly lime- 
 stone which continue west for about 60 paces and are then fol- 
 lowed by shaly limestones and shales. In the river section no 
 beds were noted which had any resemblance to Black River rocks. 
 
 Gray limestone outcrops in the angle of the roads just south 
 of the Everett School and one- fourth of a mile farther south on 
 the east and west sides of the shore road. At Lime Rock Point 
 the gray limestone reaches the water's edge, while south of the 
 point the bank of the lake is formed of slate like that of the 
 St. Albans lowland and the islands lying to the west, but inde- 
 scribably crushed and jammed so that its included firmer bands 
 of rusty, siliceous rock are squeezed and faulted out almost to 
 obliteration. 
 
 East of the road on the farm of Mr. Wilcox the gray lime- 
 stone is clearly much disturbed and greatly sheared. Just south 
 of Wilcox's house black slate outcrops in the road and a fourth 
 of a mile farther south the shale-slate formation may again be 
 seen forming the shore clifif where the road closely hugs the shore 
 just north of Melville Landing. 
 
 The slate forms the shore from the small point south of 
 Melville Landing to the Milton line. Throughout this distance 
 the margin of the Red Sandrock series is one-fifth a mile or less 
 from the lake shore. The Cambrian rocks form the summit of a 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 209 
 
 sharp slope against which is usually piled a large amount of drift. 
 Through this covering the hard rocks outcrop at intervals. 
 
 South of Melville Landing near the top of the slope lie great 
 blocks spread about "like ruins." Some of these are quartzite 
 and others are composed of bluish-gray and chamois-colored 
 limestone with a "brecciated" texture not unlike that of the mot- 
 tled Swanton marble. Southward along the intermediate levels 
 of the slope at several places the soil indicates that the slate 
 formation is close to the surface and at one place about two miles 
 south of Melville Landing the black slate was found outcropping 
 Avell up the slope. A half mile farther south the gray limestone 
 with abundant calcite veins appears from beneath the Cambrian 
 dolomites and forms a conspicuous hill at the western base of 
 which the black slate outcrops. 
 
 About two and a half miles north of Camp Rich the shore 
 road turns abruptly eastward away from the bank of the lake 
 which it closely follows to this turn. Slate outcrops where the road 
 turns again southward. East and south of this slate outcrop is 
 gray, often sparry limestone of uncertain correlation. One-half 
 mile farther south, east of the road, sparry limestone has about 
 the same dip as the Cambrian dolomite that clearly lies above and 
 on it. West of the road is other limestone which continues nearly 
 to the slate along shore. 
 
 As indicated above, the lake is formed of the shale-slate 
 from the St. Albans to the Milton line, except at the Lime Rock 
 Point. It thus appears that along the Georgia shore the same 
 general relations prevail among the slates, gray limestones and 
 Cambrian dolomites as in Highgate, Swanton and St. Albans. 
 In Georgia it seems probable that at some places the Cambrian 
 rocks rest directly upon the slates, as will be conclusively shown 
 to be the case farther south, and as may be the case at certain 
 places north of Georgia ; but in Georgia and places north of it 
 the surface covering leaves some doubt. 
 
 There can be no doubt, however, that the relations among 
 the rocks along the lake shore in Georgia clearly mark thrusting 
 and dislocations and show that older rocks have moved over 
 younger ones. There was probably involved at least one great 
 low-angle thrust by which the Cambrian rocks were moved to 
 the Avest. Whether the gray limestone and its companion rocks 
 were secondarily involved in the thrust that drove the Cambrian 
 westward and were carried along with the latter, or whether they 
 are rocks that were independently driven on the slates on which 
 they now rest and were overridden by a later major thrust of the 
 Cambrian it is not possible to tell. Either history seems possible. 
 
 The escarpment formed by the margin of the Lower Cam- 
 brian Red Sandrock and the various limestones that lie beneath it 
 in southwestern Georgia is over a mile to the west of the meridian 
 on which are located the fragmentary outcrops of quartzite which 
 
210 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 were described for St. Albans Point. It seems likely that the 
 present margin of overthrust rocks north of Georgia is an erosion 
 trace of a mass of older rocks that once had an extension to the 
 west of the present western limit of these rocks and that the frag- 
 ments of quartzite now isolated within the slate formation on the 
 St. Albans lowland may be really remnants of resistant members 
 of such a mass. This seems probable, even though it must be 
 recognized that the thrust of the older rocks on the slates may not 
 have carried them so far west in higher latitudes as it did in 
 Georgia and farther south, for which idea one finds some support 
 in the present northeasterly trend of the margin of these rocks in 
 northwestern Vermont and in their extension northward into 
 Canada. 
 
 The Lower Cambrian Red Sandrock series of quartsites and 
 dolomites and associated shales in Georgia. The massive gray, 
 red, and mottled members of the Red Sandrock series near the 
 lake in Georgia are indistinguishable from the similar rocks in 
 the townships to the north. They do not appear to have suffered 
 any notable internal deformation and plainly dip at a low angle to 
 the east. Away frofn the lake the hard rock is more extensively 
 covered by surface material and emerges as knolls, hills and 
 ridges of varying dimensions. Around Georgia Plains and north- 
 ward along the headwaters of Mill River the underlying rock had 
 clearly been somewhat dissected before the surface covering was 
 spread over the region. 
 
 About a mile and a half north of Georgia Plains and about 
 the same distance east of the lake is a hill known to residents as 
 "Parker's Ledge." This locality has long been celebrated for the 
 Lower Cambrian fossils which have at various times been found 
 there. The farm of which the hill forms a part is now owned by 
 Mr. Montcalm. The prevailing rocks at the "Ledge" are dense 
 black or sandy, often micaceous, rusty-weathering shales, which 
 after diligent search may now afford fragments of OleneUus, 
 Olenoidcs, Microdiscus and other fossils. These shales have great 
 similarity to the rocks of Swanton which lie to the east of the 
 gray and mottled dolomites of that town and like the shales of 
 Swanton have some dolomite associated with them. Some of the 
 dolomites at the "Ledge" are of gray color and others are rusty- 
 weathering, siliceous rocks. The rocks at the "Ledge" have for 
 the most part a flattish position or dip to the east at a low angle. 
 
 A half mile south of the "Ledge" on the farm of Mr. Sart- 
 well quartzitic shales are interbedded with dolomite, but west- 
 ward on the Densmore farm the shaly members occur in greater 
 force and have much similiarity to those at the "Ledge." These 
 shales carry "fucoidal" markings, which are probably trails, but 
 did not yield other fossils. They give place westward at the 
 surface to the gray and mottled members of the Red Sandrock 
 series. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 211 
 
 The gray and mottled rocks near the lake in Georgia township 
 are thus seen to pass eastward at the surface into somewhat dif- 
 ferent rocks with which they may be conformable. The general 
 surface sequence and the dips of the various rocks suggest a con- 
 tinuous stratigraphical series, but it is not certain that the apparent 
 conformity is everywhere real and that dislocations do not inter- 
 vene among these various rocks that seem with more or less 
 definiteness to be of Lower Cambrian age. 
 
 In the northern part of the township the dolomites are suc- 
 ceeded eastward at the surface along the road crossing Mill River, 
 which passes School No. 7, by sheared quartzite, which also out- 
 crops frequently along the main highway from Georgia Center 
 to St. Albans, to the west of St. Albans Hill. Similar rock out- 
 crops around Georgia Center ; but west and southwest of Georgia 
 Center the quartzite is intermingled with areas of limestone con- 
 glomerate presently to be described. 
 
 The road running directly east from Georgia Center ascends 
 a slope over sheared quartzite. There is then an interval along 
 the road of a little less than a mile with no outcrops. Near the 
 junction of this road with one running south past School No. 11 
 are numerous ledges of massive gray and mottled dolomite clearly 
 dipping westerly. A reading gave the dip as Z7° and the strike 
 as N. 10° E. These rocks may be followed northward and south- 
 ward along their strike. Southward, about a mile and a half 
 from the junction of the roads just mentioned, massive dolomite 
 was noted dipping westerly, and northward, a mile north of Oak- 
 land, are similar rocks also dipping westerly. The latter outcrops 
 are two-thirds of a mile southwest of Bellevue Hill, described 
 above. Dolomite outcrops along the road on the lower western 
 slope of Cushman Hill, but is succeeded farther up the slope by 
 ■quartzite. 
 
 Taking into account the low easterly dip of the members of 
 the Red Sandrock series at their western margin and the sugges- 
 tion of their possible extension in that attitude eastward beneath 
 the surface the westerly dips of the rocks just described might 
 seem to show that the beds in question form a broad, shallow 
 syncline over most of Georgia township west of the C. V. R. R. 
 track. It is possible that they do and that the higher dips at the 
 east represent a pushing up of the eastern limb, with crushing 
 at some places (Bellevue Hill). The massive beds ruptured 
 instead of folding, the rocks east of the railroad track now oc- 
 cupying the upthrow side of a reverse fault-thrust. But as men- 
 tioned above it is not certain that dislocations do not intervene 
 between the western margin and the railroad track, so that it can- 
 not be positively stated that Georgia shales are conformably above 
 the dolomite series near the lake, although they seem to be. 
 
 The limestone conglomerate jormation in Georgia. In 
 Georgia the most conspicuous outcrops of the conglomerate, or of 
 
212 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 liriiestone that is apparently to be correlated with it, occur west 
 of Georgia Center and east and southeast of Georgia Plains. On 
 account of surface covering the outcrops are intermittent and of 
 variable extent in present surface exposure. West of Georgia 
 Center the conglomerate has all the essential features of the rock 
 in St. Albans and Swanton. It carries abundant limestone frag- 
 ments of dilterent sizes in a matrix of strongly siliceous material 
 which has enough calcareous matter to effervesce freely with acid. 
 
 Dr. Walcott in his early account of the Georgia section de- 
 scribed the conglomerate as apparently forming a great lenticular 
 mass of limestone, with intercalated beds of argillaceous shales, 
 and more rarely with arenaceous layers imbedded in the argil- 
 laceous shales. The fauna was described as Cambrian in char- 
 acter, and, in the absence of Olenellus and other typical Lower 
 (then called Middle) Cambrian fossils, as approaching the Upper 
 Cambrian.^ In his diagram of the Georgia section, Walcott 
 shows the conglomerate formation as an interbedded member of 
 the Georgia series. In referring to the vertical distribution of 
 the fossils (loc. cit., p. 20) he remarks that one species of the 
 typical Georgia fauna. Ptychoparia adamsi, "is represented in the 
 great 'lentile' of the Georgia section," but he drew the provisional 
 upper line of the Georgia Formation at the base of the lentile, as 
 it is at this horizon that there occurs a decided change in fauna 
 and that the deposit changes markedly from that below. 
 
 Several years later,^ after the recognition of the Lower 
 Cambrian age of the Georgia shales (the fauna of these shales 
 having been regarded by Walcott in his earlier studies [1886] as 
 Middle Cambrian) Dr. Walcott reproduced his early diagram 
 of the Georgia section, showing the conglomerate as an inter- 
 bedded member of the Georgia series and stated that it contains 
 a fauna that may jDrove to be of Middle, or possibly Upper Cam- 
 brian age. 
 
 In commenting on the Georgia section as late as 1911,^ Ulrich 
 said : "The base of the section is here unknown. As worked out 
 by Walcott, the lowest exposed formation is a limestone 1,000 
 feet thick. This is succeeded by 200 feet of 'Georgia shale,' and 
 over this comes 3,500 feet of shale and thin limestone. A quartz- 
 ite 50 feet thick follows and is in turn overlain by 1,700 feet of 
 limestone and shale, and this by 3,500 feet of shale. I have seen 
 only the upper part of this section, namely, the heavy bed of 
 shale last mentioned, which, together with all the underlying beds 
 has been referred to the Lower Cambrian by Walcott. Regarding 
 the upper shale I am strongly inclined to view it as of Canadian 
 age rather than Cambrian. There is some question in my mind, 
 also, concerning the age of the limestone supposed to belong to 
 the 1,700-foot bed. It contains small bivalved phyllopods {e. g., 
 
 1 Bull. U. S. G. S. No. 30, 1886, p. 17. 
 
 'Tenth Annual Rept., Director U. S. G. S., 1890, pp. 553-554. 
 
 3 Revision of the Paleozoic Systems, Bull. G. S. A. No. 22, 1911, p. 617. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 213 
 
 Indiana dcnnatoides (Walcott), /. pyriformis Matth., /. secunda 
 M., Bradoria scrutata, M.) which are characteristic of Lower 
 Acadian zones in New Brunswick and Newfoundland. As it is 
 not yet decided whether the Protolenus zone is late Lower Cam- 
 brian or early Middle Cambrian, the exact age of the Vermont bed 
 mentioned also remains uncertain." He then comments on the 
 complicated structure of Vermont rocks and of those of the 
 Taconic area in particular. 
 
 In the writer's studies of the structural relations of these 
 rocks it was not possible to show that the conglomerate is inter- 
 bedded in the shale series, or that it could not be interpreted as 
 resting unconformably upon eroded rocks. , The field relations 
 leave much uncertainty as to the stratigraphic relations of the 
 conglomerate to the rocks with which it is associated in Georgia. 
 If the conglomerate lies in a broad, open syncline of Lower Cam- 
 brian rocks it might be interpreted structurally as belonging to 
 any formation later than Lower Cambrian, and if its fossils are 
 truly Middle or still later Cambrian they might be regarded as 
 forming a primary fauna, or as secondarily included in a later 
 terrane by erosion of Middle or later Cambrian rocks. 
 
 Fairfax Township. 
 
 (St. Albans and Milton topographic sheets.) 
 
 This township bounds Georgia on the east. 
 
 Near the summit of Cushman Hill, about two-thirds of a 
 mile north of Silver Lake and just east of the Georgia line, the 
 present surface apparently marks erosion into the lower portions 
 of an overlapping formation. At numerous outcrops the rock, 
 which may be a rusty, impure quartzite or a greenish-gray, schist- 
 ose quartzite, carries scattered large grains qr rounded pebbles of 
 grayish-white quartz. In dimensions these pebbles range from 
 the size of a marble to that of an Q.gg. The pebbles are apparently 
 not sheared, but the rock in which they are included is sometimes 
 schistose. 
 
 The significance of this imperfectly developed conglomerate 
 and the obvious impurity of its matrix in places seems to be that 
 the rocks of this higher land are not a great way above or distant 
 from the old sea-floor on which the series of which they are a 
 part was deposited ; but no unconformable contacts nor any recog- 
 nizable older rocks were seen. The conglomerate is not purely 
 local, for similar rock was observed three miles farther east in 
 Fairfax, near Buck Hollow, and five miles to the north in St. 
 Albans, and also at the northern end of Bellevue Hill. The con- 
 glomerate is, however, everywhere local in the sense that it grades 
 laterally into impure quartzite, or derivatives of impure sands. 
 It is, therefore, intraf ormational in this sense ; it is basal only in 
 the same general sense. It indicates particular local conditions of 
 
214 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 deposition and perhaps minor oscillations. It can hardly be 
 interpreted as forming residuary parts of a formation that rested 
 unconformably upon the other rocks with which it is now asso- 
 ciated. 
 
 At the northern end of Georgia Mountain, in the southeastern 
 part of the township, along the hill road running east, south of 
 the Lamoille River, are outcrops of gneissic-looking rocks with 
 foliations dipping easterly at a high angle. On their weathered 
 surfaces, and on vertical joint or fracture planes across the strike, 
 these rocks give somewhat the appearance of squeezed conglo- 
 merates with the foliations bending gently around squeezed frag- 
 ments ; but the latter, on close inspection, have little appearance 
 of pebbles distinct from a matrix, and when the rock is broken 
 it looks much like somewhat impure quartzite. On the whole the 
 rock most suggests a sheared and welded quartzite, whose resist- 
 ance to deformation resulted first in shearing and brecciation. 
 The rock was then healed and compacted into a gneiss. The rocks 
 are succeeded eastward by outcrops of granular quartzite. 
 
 CHITTEJfDEN COUNTY. 
 
 Milton Township. 
 
 (Milton topographic sheet.) 
 
 Location. Milton, another lake shore township, lies just 
 south of Georgia. The southern boundary of Georgia forms the 
 northern boundary of Milton, throughout its extent. Westford 
 lies to the east and Colchester borders it on the south. 
 
 The lake border in Milton tozvnship. The escarpment, 
 capped by the massive beds of gray, red and mottled dolomites, 
 which closely follows the lake shore in Georgia and part of St. 
 Albans continues southward into Milton. In Milton, as in 
 Georgia, younger gray limestones and slate or outcrops of slate 
 alone intervene between the margin of the Red Sandrock series 
 and the lake shore. 
 
 North of Camp Rich, gray limestone occurs between out- 
 crops of slate in the shore road and the margin of the Red Sand- 
 rock series. South of the camp, towards Camp Watson, the 
 margin of the Cambrian rocks more closely approaches the shore 
 and outcrops of gray limestone are fewer. The shore road from 
 Camp Rich to Camp Watson is nearly all the way on the slates 
 which continue south to Eagle Mt. Camp at the mouth of Stone 
 Bridge Brook. 
 
 South of the mouth of Stone Bridge Brook, Eagle Mt. rises 
 to a height of 500 feet. It is composed of the massive dolomites 
 of the Red Sandrock series and has a steep scarp on the west 
 which was estimated in some places to be 200 or more feet high. 
 The Cambrian rocks continue southward with somewhat dimin- 
 ished but still conspicuous scarp to the vicinity of Camp Martin 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 215 
 
 (generally known as Camp Milton). Between Eagle Mt. Camp 
 and Camp Milton the margin of the Canibrian rocks is perhaps 
 300 feet from the lake and the slope between is steeper than is 
 usual farther north, apparently largely on account of large talus 
 blocks which have fallen from the scarp and which are now partly 
 covered with drift. Between Eagle Mt. Camp and Camp Milton 
 the slate formation shows continuous outcrop along shore and 
 throughout this distance gray limestone was not noted between 
 the shore and the scarp, except just north of Camp Milton. 
 
 East of Camp Milton is an erosion gap in the margin of the 
 Red Sandrock series. Trout Brook flows along the southern 
 margin of this gap to enter the lake. 
 
 The indication is strong that between Eagle Mt. Camp and 
 Camp Milton the Red Sandrock series frequently, if not usually, 
 rests on the slates. Just north of the mouth of Stone Bridge 
 Brook the slates form isolated shore cliffs 50 feet high without 
 any traces of overthrust rock resting on them. Just south of the 
 mouth of the brook the massive dolomite of the Red Sandrock 
 formation reaches close to the water edge with only a high water 
 or storm beach of slate shingle between it and the shore, no out- 
 crops of slate or other rock being visible. The topography and 
 geology suggest a fault along the gap mentioned above, the rocks 
 at the north occupying the upthrow side. The dolomite continues 
 south along the eastern edge of the swampy delta of the Lamoille 
 River to the delta portion of the Sandbar Bridge road, showing 
 as a low cliff of varying height, to the east of which the surface 
 ascends over the eroded edges of other members of the Red 
 Sandrock series. South of the delta road the erosion margin of 
 the overthrust dolomite series is less easily followed to the bank 
 of the Lamoille River. 
 
 Between Trout Brook and the Lamoille the dolomite prob- 
 ably rests on the slates just^as it does at Red Rock Point near 
 Malletts Bay in Colchester. 
 
 The steep western face of Eagle Mt. gives suggestion of 
 what the faded scarp all along the margin of the Cambrian Red 
 Sandrock formation may once have been. It seems quite likely 
 that the erosion modification of these resistant rocks along their 
 present trace was subsequent to the formation of the lowland in 
 the weaker shales and limestones in what is now the lake region. 
 It is, however, not apparent from the present relations of these 
 various rocks how far the Red Sandrock may have extended to 
 the west of its present erosion trace. It is interesting to note that 
 in some places the Cambrian rocks rest by thrust on limestone and 
 at other places on shales or slates that are younger than the lime- 
 stone. Such relations should have something to say about the 
 mode of deformation by which the present relations could have 
 been produced. 
 
216 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Just east of the road that runs from Camp Milton eastward, 
 about half a mile from the lake shore, a ledge of brick-red 
 quartzite-dolomite displays a texture which differs strikingly 
 from that which the mottled "Swanton marble" member of the 
 Red Sandrock series shows. The rock as a whole forms a mass- 
 ive bed in which may be clearly seen many angular fragments of 
 different sizes, including blocks of rectangular shape as seen in 
 section which bear strong resemblance to similarly shaped frag- 
 ments seen in the limestone conglomerate formation. Moreover, 
 the angular pieces are mingled with other larger, irregularly 
 shaped chunks, giving an assemblage like that in much of 
 the limestone conglomerate. The fragments are, however, of 
 much the same color as the rest of the rock and apparently are 
 composed of a material similar to the matrix in which they lie. 
 From the conditions it is not possible to tell whether the frag- 
 mented rock is an intra forma^ional conglomerate or a peculiar 
 form of brecciation. A similar fragmental rock of gray dolomite 
 occurs west of Checkerberry village and will be mentioned beyond. 
 
 The west-central portion of Milton township. East of the 
 escarpment that borders the lake the surface over the west-central 
 portion of Milton is largely formed of sand plains through which 
 the hard rock emerges as dwarf exposures which are often frag- 
 mentary and unsatisfactory for study. Arrowhead Mt., Cobble 
 Hill and the gorge of the Lamoille River give more extensive out- 
 crops. 
 
 From the escarpment near the lake the massive beds of the 
 Red Sandrock series extend eastward with low easterly dip, form- 
 ing in the western part of the township a fairly well defined band 
 of varying breadth from the Georgia line to the Lamoille River. 
 East of this band the members of the series lose distinctness as 
 one passes into the areas of more scattered outcrops of the west- 
 central part. Between the western band just mentioned and an- 
 other strip to the east that includes Arrowhead Mt., the village 
 of Milton and Cobble Hill, the exposures are prevailingly gray 
 dolomitic rock, rather sparingly associated, so far as the rocks are 
 visible, with a more quartzitic rock, without any very clear struc- 
 tural relations between the two. Some of the outcrops may now 
 be mentioned. 
 
 North of the Lamoille River, to the east and west of Streeter 
 Brook, are numerous outcrops of gray dolomite which give way 
 at places along the strike to quartzite. The relations suggest either 
 that dolomite grades laterally into quartzite, or that different but 
 conformable beds are exposed in different outcrops. Either inter- 
 pretation seems possible, if, as seems likely, the rocks are to be 
 correlated in a general way with the members of the series along 
 the lake. By such correlation is not meant precise stratigraphic 
 equivalence, but membership in a common formation which gives 
 good indications that horizontal variation in its different beds 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 217 
 
 was a common if not a usual condition and that dolomites and 
 more siliceous beds succeeded one another in a more or less 
 regular fashion within the formation. 
 
 From Milton village to the lake the Lamoille, in sinking its 
 channel since glacial times, has cut through hard rock at many 
 places, producing a considerable fall near Milton village and 
 minor ones farther west. The rocks which the river has thus cut 
 through show some interesting differences. 
 
 At West Milton the river cuts massive gray dolomite, which 
 outcrops in both banks and in midstream. A mile above this 
 village the rock is more notably siliceous. These rocks appear to 
 be the southward continuation of those lying west of Streeter 
 Brook, to the north. Farther up stream, from the point where 
 Streeter Brook enters the Lamoille to the abutments of the old 
 stage road bridge near the Milton Town Farm, the rock along the 
 stream is a slate, with easterly dipping cleavage. Where worn by 
 the water the rocks often show pseudolaminations probably cor- 
 responding with the cleavage. At places above the high-water 
 mark the rock is often a dense slate. The river cascades approx- 
 imately along the strike over these slates beloM^ the old bridge site, 
 forming what are frequently called by the residents the "minor 
 falls." The slates continue upstream towards Milton village and 
 seem to pass beneath other rocks forming the upper falls at the 
 mill of the International Paper Company. The slates near the 
 upper falls have been jammed and sheared with obliteration of 
 bedding and folded structure. Folding was seen at only one 
 place. Induration is the rule. The rock which apparently over- 
 lies the slate at the upper falls is a somewhat indeterminate mass 
 of gray dolomite and quartzite. At some places the rock shows 
 a texture precisely like the "Swanton marble," but without the 
 conspicuous variegated coloration. For the most part the rocks 
 resemble the members of the Cambrian series near the lake. 
 They are generally massive in present appearance, although there 
 are observable planes of separation which may represent bedding 
 or jointing. At the falls the massive rocks are cut by a dike 4 
 to 8 inches wide running across the strike. A dike of similar 
 rock, with apophyses, cuts the slates just west of the mouth of 
 Streeter Brook. The rock that makes the falls continues as a 
 scarp into the woods north of the falls. The general relations- 
 suggest that the dolomites have been pushed over the slates that 
 lie under and west of them. 
 
 Upstream above the falls, well shown both above and below 
 the bridge and sparingly along the streets in the village near the 
 bridge, is indurated quartzite. 
 
 Southwest and west of Milton village, south of the Lamoille. 
 is a broad, flat, sand plain with no outcrops except at its western 
 edge, west of Checkerberry village. A half mile northwest of 
 this hamlet, low ledges of dolomite show the peculiar conglom- 
 
218 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 erate or "brecciated" texture noted in previous pages as occur- 
 ring in a reddish bed of the Sandrock series near the lake, in the 
 Hmestone conglomerate and in the gorge at Highgate Falls. 
 
 North of the Colchester line and east of the road from 
 Checkerberry village to School No. 9, is gray dolomite dipping 
 easterly. This rock continues easterly across the road that runs 
 west of Cobble Hill, but on the western slope of the hill the 
 dolomite is marked by frequent inclusions of chert and lies at 
 the base of a modified but still notable scarp in the schistose 
 quartzite that makes up the principal portion of Cobble Hill and 
 that outcrops north of it and along the road that skirts it on the 
 east. 
 
 North of Milton village the Lamoille is deflected to a south- 
 ward course by the mass of Arrowhead Mt. which rises to a 
 height of 947 feet and forms a conspicuous feature of the town- 
 ship. The eastern slope of this mass shows gray dolomite and 
 quartzite, often sheared, but at places showing clearly defined 
 westerly dip. The westerly dip is conspicuous at the southern 
 end of the mountain proper. West of Arrow Mt., along the 
 road at the western base, are black, fine-grained, siliceous slates. 
 
 South of Arrowhead Mt., and about a mile north of 
 Milton village, quartzite forms bold, massive ledges west of the 
 Georgia road. The quartzite beds have been sheared so as 
 to give a more massive appearance than they really possess, a 
 feature common among these rocks in which shearing has welded 
 not always especially heavy beds into very massive looking rocks. 
 The quartzite just mentioned joins southward with that above the 
 falls in the village. 
 
 A broad surface section from the river in Milton village east- 
 ward along the road to School No. 6, shows that the quartzite at 
 the river is succeeded eastward by gray dolomite and quartzite 
 which form a low ridge just east of the railroad track. The rocks 
 are sheared but at places show a westerly dip. As one ascends 
 the hilly land east of the village, dolomite and quartzite roughly 
 alternate across the strike on the lower portion of the slope ; but 
 higher up the slope dolomite is absent and much of the rock, 
 while apparently originally a quartzite, shows a gneissoid struc- 
 ture like that which has been described for the northern end of 
 Georgia Mt. The rock sometimes shows the bedding across 
 which the gneissoid structure has been developed. The gneissoid 
 rock is succeeded eastward by ledges of not severely sheared 
 quartzite, which may be seen in the vicinity of School No. 6. 
 At some places the quartzite, including that which has been 
 sheared into a gneiss, is disposed in gentle folds. 
 
 The gneissoid rock might be regarded by some observers 
 as something dififerent from the quartzite with which it is asso- 
 ciated, but there are no contacts nor other field relations suggest- 
 ing that the rocks are members of different formations. The 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 219 
 
 possibility that older rocks might have been thrust into the quartz- 
 ite formation must be recognized ; but when the gneissoid struc- 
 ture appears in a bedded quartzite and when the quartzitic char- 
 acter of other gneissoid rock is so obvious and no valid distinctions 
 may be made among numerous exposures over large open fields, 
 the membership of these different rocks in a common formation 
 seems the ready and reasonable interpretation and the differences 
 seem to be explainable as due to various degrees of shearing and 
 primary difTerences in composition. 
 
 The quartzite and its gneissoid associate continue south from 
 the road to School No. 6 towards Colchester, along the higher 
 portions of the western slope of the hilly land ; but on the lower 
 portions of the slope the rock is quartzite. 
 
 A section was made along the road that runs from School 
 No. 10 to Bowmans Corner in Westford. The quartzite at the 
 western base of the hilly land continues to the bend in the road 
 two miles west of Bowmans Corner. The rock is sheared, with 
 strong cleavage dipping easterly. South of the road, at the bend 
 mentioned, white quartzite is associated with brick- or cherry- 
 red quartzite in such relations as to indicate that the two rocks 
 are lateral color variants of each other. Eastward along and 
 south of the road to Bowmans Corner are frequent ledges of gray 
 siliceous dolomite which is more or less intermingled over large 
 areas with quartzite and this quartzite-dolomite series extends 
 eastward nearly to the corner. 
 
 From the descriptions which have been given it will be seen 
 that much the same kinds of rocks and structures occur in Milton 
 as in Georgia. Near the lake the members of the Red Sandrock 
 series dip easterly at a low angle. Farther east are dolomites 
 and quartzites in scattered outcrops which apparently belong to 
 the same formation. Along meridians passing through and east 
 of Milton similar rocks show westerly dip at many places or are 
 apparently broken and thrust on rocks lying west of them. Most 
 of the rocks so far mentioned probably belong to the same general 
 formation in which there are differences among the beds due to 
 primary horizontal and vertical variations and to secondary shear- 
 ing effects. It appears that the underlying hard rock away from 
 the lake shore in Milton is probably essentially a Lower Cambrian 
 surface as is the case in Georgia. There are, however, among 
 these rocks some others which are not easily correlated with them, 
 such as the slates found along the course of the Lamoille River, 
 west of Milton. 
 
 Certain rocks in Westford tozvnship, adjoining Milton on the 
 east. At Bowmans Corner and along the road towards Essex 
 Junction is greenish slate or phyllite which over long distances is 
 more or less interchangeable with quartzite. The greenish slate 
 shows coppery-colored phyllitic and schistose variants and all have 
 
220 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 a good deal of similarity to similarly associated rocks at some 
 places in the Taconic hills many miles to the south. 
 
 A section along the road from Milton village by the Hard- 
 scrabble School to Westford gives quartzite at the western base 
 of the hilly land, then farther up the hill the gneissoid quartzite, 
 then a wide band of greenish slate, which is the northern exten- 
 sion of that near Bowmans Corner and then around Westford 
 village quartzitic schist which was followed over the high land 
 southwest of Westford village along the road to Essex Center by 
 the Beecher School. At the east the quartzitic schist frequently 
 carries segregated quartz and as a mass strongly resembles similar 
 rocks found in the Sudbury Hills. • 
 
 The limestone conglomerate formation in Milton. The ex- 
 tensive sand plains in Milton probably conceal some of this 
 formation. South of the hamlet of West Georgia, but south of 
 the Georgia line, are a few scattered ledges of rock, some of 
 which bear such close resemblance to thinly-bedded limestone 
 members of the conglomerate formation in Highgate and St. 
 Albans that there is little doubt as to their correlation with each 
 other. The exposures are few and were the only ones seen in 
 Milton except some fragmentary rocks found seven miles to the 
 southeast, near School No. 3, about a mile north of the Colchester 
 line. At the latter place, east of Malletts Creek and the railroad 
 track, are a few ledges of limestone, some of which resemble those 
 found to the north. No conglomerate was seen. 
 
 Colchester Township. 
 
 (Plattsburg, Milton and Burlington topographic sheets.) 
 
 Location. This township is bounded on the north by Milton, 
 on the east by Essex, and on the south by Burlington and South 
 Burlington. 
 
 The rocks along and near the lake shore in Colchester. In 
 Colchester township along what is now the border of the lake, 
 pre-glacial erosive processes had breached the massive dolomites 
 of the Red Sandrock series, producing a considerable basin which 
 is now flooded by the lake waters and is known as Malletts Bay. 
 
 North of Malletts Bay, between it and the Lamoille River, 
 various knolls and ridges give extensive outcrops of the members 
 of the Sandrock series which have been traced from St. Albans 
 along the margin of the lake. The erosion margin of these rocks 
 may be followed south from the Lamoille, east of Camp Winnis- 
 quam, to Red Rock Point, where the formation dips into the lake. 
 North of Red Rock Point the slates show in cliffs and low out- 
 crops along shore and at Clay Point form a pinnacle capped by 
 Champlain clays. About 200 rods north of Red Rock Point, 
 massive dolomite may be seen in contact with the slates. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 221 
 
 Around the bays and headlands of the serrated north shore 
 of the Bay and nearly to its eastern limit are perpendicular or 
 rugged clififs of gray or mottled dolomite much like that at Red 
 Rock Point. Similar rock outcrops along the road from Camp 
 Winnisquam to the Colchester-Grand Isle road. The dip is 
 easterly. 
 
 In a minor indentation at the northeastern portion of the bay 
 is a beach of sand at the edge of a swamp that marks the southern 
 end of a small valley. In the western wall of this valley the 
 rocks are massive but apparently in somewhat thinner beds than 
 those farther west and display the reddish and pinkish colors 
 characteristic of the Sandrock series farther north. On the 
 east side of the valley the rocks are prevailingly quartzitic and in 
 thinner beds, which weather white, gray and rusty brown. Fos- 
 sils were sought in the rusty layers, but without success. In some 
 of these rocks around Malletts Bay the late Mr. Griffin of the 
 Survey had found Olenellus and other fossils, but unfortunately, 
 his localities have not all been described in print. A low scarp 
 which bounds these quartzite beds on the west continues south- 
 ward along the eastern edge of the swampy land and along the 
 eastern shore of the lake north of the mouth of Aliens Brook. 
 Along this scarp may be seen lateral variations in l:he colors and 
 thicknesses of the beds. The quartzite continues south of Aliens 
 Brook to the sandy beach that borders the bay on the southeast 
 and south. 
 
 West of the sandy beach on the southern side of the bay a 
 peninsula known as Coates Island juts into the bay. West of the 
 'Tsland" and separated from it by a small bay is a peninsula 
 known as Malletts Head which projects northward to within 
 about one-half mile of Red Rock Point and somewhat to the west 
 of it. The. head forms a remnant of an old erosion margin of 
 the Red Sandrock which was breached to form the bay. On the 
 western shore of the Head the Ordovician slates underlie the 
 dolomite which forms the surface rock of most of the peninsula. 
 The relations at the head are entirely similar to those north of 
 Red Rock Point, and there is little doubt that slate lies beneath 
 the portion of the lake forming the inlet to the bay; but whether 
 slate underlies any considerable part of the bay as the hard rock 
 surface may only be conjectured. 
 
 The Red Sandrock lying on the slate on the western side of 
 Malletts Head is two-thirds of a mile west of that at Red Rock 
 Point, and unless there is a fault between, this fact points to a 
 former more westerly extension of the dolomites farther north, 
 confirming in a measure the suspicion that the margin of the 
 Sandrock at least for some of its course north of Malletts Bay is 
 a recession border. 
 
 The rocks of Colchester peninsula, west of the meridian of 
 Malletts Head, to the north of the Winooski River, were not 
 
222 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 inspected by the writer. The map of the Vermont Report shows 
 most of the peninsula as underlain by "Utica" or "Hudson River" 
 slates and, therefore, as not having any of the Sandrock on it 
 much to the west of the meridian of Malletts Head. 
 
 The Sandrock of Malletts Head and Coates Island is sepa- 
 rated from other exposures of this formation lying south of them 
 by a sand plain, the extension of which eastward and southward 
 forms a wide, sandy, partly swampy tract stretching from the 
 sandy beach that makes the southern border of Malletts Bay to 
 the Winooski River. Along the eastern border of this tract, 
 around the Colchester Town Farm, are outcrops of the Sandrock 
 formation which are the southward continuation of the beds 
 forming the east shore of Malletts Bay. 
 
 The altogether remarkable vertical variations shown by the 
 quartzite-dolomite series known in this region collectively as the 
 ■Red Sandrock has been described by Professor Perkins from his 
 own detailed studies and those of his assistant, the late Dan 
 Griffin.^ Differences in composition, thickness and color appear 
 in irregular but frequent succession between and within the dif- 
 ferent beds along different sections through the formation. 
 Lateral variations with respect to composition and color may also 
 be seen when the beds of this formation are followed along their 
 strike. Impure sands, fairly pure sands and sandy muds seem to 
 have been contemporaneous with each other and often at places 
 not very far removed from one another during the deposition of 
 these rocks. Many of the beds give clear evidence of shallow 
 water accumulations, probably on a slowly-subsiding sea-bottom 
 and one which underwent intermittent oscillation of level. Red- 
 dish shades of color, probably due to oxidation under atmos- 
 pheric exposure, frequent cross bedding, and many markings that 
 seemingly could have been produced only in relatively shallow 
 waters, or on exposed flats, all bear testimony to the nature of 
 the conditions under which these rocks were laid down. 
 
 There seems to be good reason for thinking that large areas 
 of this Red Sandrock formation once formed a surface of ero- 
 sion and unconformity on which other strata were deposited ; 
 but it is extremely doubtful if any considerable portion of such 
 surface is anywhere now preserved over the region where this 
 formation makes the outcropping rock. With the facts in mind 
 that the color variations which are assumed to be due to some 
 degree of oxidation of the material of the rock are repeated 
 throughout considerable vertical distances in this Red Sandrock 
 series and that lateral variations occur within continuous beds; 
 that large exposures of this formation at the present surface hold 
 to a faiVly uniformly gray color which is presumably a primary 
 feature ; and that thrusting has doubtless tended at least to pro- 
 duce an imbricating rather than a conformable series in the forma- 
 
 1 Sixth Rept. of the State Geol., pp. 227 et seq. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 223 
 
 tion, as a whole it is difficult to attribute the red color, where this 
 may be shown to be an ancient character of the rock, as due to 
 atmospheric changes following the elevation and erosion of the 
 rocks subsequent to their deposition as a series. The possible 
 explanation of the "brecciation" shown by the mottled members 
 of this formation as a primary feature has been discussed above. 
 All the noteworthy features of the Red Sandrock series are well 
 shown in the vicinity of Malletts Bay. 
 
 The age of this primarily conformable series has definitely 
 been made out by the discovery of Olenellus and Ptychoparia 
 adamsi in some of the beds near the bay.^ 
 
 East of the lake in Colchester. East of the lake much of 
 present surface is formed of sand. Gray dolomite or rusty, flaggy 
 quartzite outcrop here and there along meridians in the central 
 part of the township and dolomite and schistose quartzite which 
 appear to be interbedded give numerous outcrops along the east 
 road from Colchester village to Milton. The schistose quartzite 
 grades laterally into more massive quartzite. The prevailing dip 
 is easterly ; a westerly dip was not noted. 
 
 Two miles east of the Town Farm, ledges of gray siliceous 
 dolomite carry bunches of segregated quartz and some lace-like 
 tracings of silica on the weathered surface. These features give 
 the rock an appearance somewhat like that shown by some of the 
 rocks in Highgate just south of the Canada line, which probably 
 belong to a Beekmantown horizon; but such features are clearly 
 altogether too indefinite for purposes of correlation and while 
 the markings referred to were not noted in the rocks near the 
 lake, they may well be present there and in any event might readily 
 have been produced by agents of hydrothermal metamorphism in 
 such siliceous rocks. There seems no good reason for regarding 
 these particular rocks as other than Lower Cambrian. 
 
 A. mile east of the Town Farm a quarry opened for road 
 metal shows beds of gray dolomite dipping very gently to the 
 east. Uniformity of color gives at first sight a somewhat massive 
 appearance, but close inspection shows beds of moderate but 
 variable thickness. Sections of the bedding planes, as seen in the 
 face of the quarry which was opened along the strike, usually 
 show as ammonoid-suture-like lines, often of brownish (limonitic) 
 color. The bedding surface shows that these lines are traces of 
 partings between irregular pittings or hollows on the surface of 
 one bed into which project small cones from the under surface of 
 the overlying bed. Separation of the 4a-yers may sometimes be 
 complete along the pitted surface of the beds, but again will be 
 accompanied by horizontal fracture across the little cones when 
 there will appear small gray patches surrounded by irregular 
 brown lines. The irregular surfaces seemed to indicate shallow 
 rather than deep water deposits. These rocks are a half mile 
 
 1 Sixth Report, p. 229. 
 
224 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 or SO east of the Red Sandrock ledges near the Town Farm. 
 They are probably part of the same formation. 
 
 In the western part of Colchester village are low ledges of 
 gray dolomite. These rocks are on the meridian of those in the 
 quarry mentioned above. On the same meridian farther north, 
 south and east of Munson Flat, are excellent exposures of rusty, 
 flaggy quartzite which carries obscure fossil markings, but which 
 yielded nothing definite. 
 
 The rocks of Colchester, so far as seen by the writer, seem 
 to belong to a common formation and to be of Lower Cambrian 
 age. No rocks were noted in this township which could be cor- 
 related with the limestone conglomerate, or with other rocks which 
 have been noted in northern townships that seemingly were not 
 so easily placed in the Lower Cambrian formation ; but the ap- 
 parent or actual absence of such rocks may be a circumstance due 
 to covering, or erosion, or to the particular nature of the second- 
 ary structures of the rocks of this area. 
 
 Essex Township. 
 (Milton and Burlington topographic sheets.) 
 
 Location. This township adjoins Colchester on the east. 
 It is bounded on the north by Westford, on the east by Jericho, 
 and on the south by Williston and part of South Burlington. 
 
 General description. The rocks of Essex are the eastward 
 continuation of those of Colchester and the southward continua- 
 tion of those in Milton and Westford. 
 
 In western Essex, north of Essex Junction and east of the 
 road from the Junction to Colchester village, quartzite and dolo- 
 mite, apparently interbedded, form the western slope of hilly land 
 over which ascends the road from School No. 2 to Butlers Cor- 
 ners. The rocks dip easterly and are entirely similar to the rocks 
 of eastern Colchester. The quartzite is often somewhat mashed 
 and veined with quartz. These rocks are succeeded along the 
 road to Butlers Corners by greenish slate or phyllite. Slate was 
 traced to a half mile east of Essex Center. 
 
 In the eastern part of the township the rock is prevailingly 
 a quartzitic schist, carrying segregated quartz, and is the con- 
 tinuation of similar rock south of Westford village. On account 
 of shearing, the primary structural features of the rocks in the 
 eastern part of the township are obscure. 
 
 Black quartzitic schist outcrops in Essex Junction. 
 
 At the bridge across the Winooski, beneath the dam above 
 and below the bridge, is gray siliceous limestone or dolomite, 
 often much crushed and strongly crystalline. It holds to a rather 
 uniform color and character throughout the considerable mass 
 exposed. At one place at its western edge, below the bridge, the 
 jammed limestone can be seen resting on crumpled blackish slate 
 
REPORT OP THE VERMONT STATE GEOLOGIST 225 
 
 on which it has apparently been thrust. The ages of these rocks 
 are problematical. The limestone has been tentatively called 
 Beekmantown. It is part of the band called the Eolian Limestone 
 in the Vermont Report. The descriptions of the members of this 
 band have not differentiated among the different kinds of rock 
 found in it. As will appear in later discussions there is much 
 variation and probably rocks of very different ages are associated. 
 The structural relations are everywhere very obscure. 
 
 Burlington Township. 
 
 (Plattsburg, Milton and Burlington topographic sheets.) 
 
 Location. Burlington lies just south of Colchester. The 
 lake forms its western boundary and it is bordered on the east 
 and south by South Burlington. 
 
 The lake shore and vicinity. The northwestern part of the 
 township forms a part of what may be called the Colchester- 
 Burlington peninsula. In this part the land is low like that of 
 the adjoining part of Colchester, from which it is separated by 
 the Winooski River. East of this lowland is higher land marking 
 the southward extension of the Red Sandrock of Colchester. 
 Northwest of Burlington, at a promontory variously known as 
 Sharp Shins, Spht Rock Point, Lone Rock Point, or simply as 
 Rock Point, the Sandrock reaches the shore. At this place it is 
 often a yellowish magnesian sandstone, as weathered. On the 
 south side of the point it rises abruptly from the water, but north- 
 ward on the west it rests by thrust on crumpled Ordovician slates. 
 This locality gives the finest thrust contact of the Red Sandrock 
 on the slates anywhere to be seen and has been frequently fully 
 described. The slickensided under surface of the Cambrian rock 
 is most impressive. 
 
 From Rock Point southward, west and southwest of Bur- 
 lington, a low sandy beach extends for a distance of over three 
 miles, nearly to the blunt promontory marked at its southwestern 
 extremity by Redrock Point. This point should not be confused 
 with the one bearing the name Red Rock Point at Malletts Bay. 
 
 From outcrops near Lakeside Park to Queen City Park, the 
 rock along the water edge is the variegated Sandrock, but in 
 general is distinguished by red or reddish colors. Northward the 
 ledges are low and permit one to walk close to the water, but 
 near and at Redrock Point are bold, precipitous cliffs. Ripple 
 marks and mud crack patterns are frequent in these rocks as at 
 other places near Burlington. The beds dip to the east. These 
 red rocks may be traced at the surface eastward through Red- 
 rocks Park. No massive gray dolomite was noted in association 
 with them. 
 
 The rocks at Redrock Point undoubtedly extend eastward 
 beneath the surface deposits to join with those at Willard's Ledge, 
 
226 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 now commonly known as Phelps' quarry, a locality in the south- 
 ern outskirts of Burlington, to the east of the main road from 
 Burlington to Shelburne. In the quarry one has fine opportunity 
 to observe the variations in thickness and shades of color from 
 bed to bed and to see various forms of markings due to their 
 shallow water origin. The series is cut by dikes of igneous rock. 
 
 About a mile to the east-northeast of Phelps' quarry, along 
 the road from Shelburne Falls to Burlington, are low ledges of 
 gray sandy dolomite, dipping gently to the east, which presumably 
 lie stratigraphically above the beds of the quarry. This sandy 
 dolomite is on the meridian of gray dolomite lying on the red 
 beds at Winooski lower falls, which will presently be mentioned. 
 
 Within the city of Burlington, outcrops of the Sandrock are 
 few, but drilled wells in the western part of the city are described 
 as penetrating this formation and there is no doubt that the city 
 is underlain by it. 
 
 Gorge of the Winooski. The Winooski, like the Lamoille, 
 has cut post-glacial gorges along its course and the rocks so ex- 
 posed, with some that occur in Winooski village and to the east 
 of it, may be conveniently described at this point. 
 
 At the falls in Winooski village are red beds much like those 
 on the east shore of Malletts Bay and south of Burlington. Above 
 these red beds in midstream and in the south wall of the gorge, 
 below the bridge, is more or less massive-looking but obviously 
 bedded, grayish dolomite. The reddish beds below the gray rock- 
 are prevailingly thin, of various shades of red color, often brick- 
 red, and carry here and there ripple marks, mud cracks and some 
 cross-bedding. The beds thin out and thicken laterally and have 
 all the marks of shallow water deposits. 
 
 Gray dolomite outcrops in Winooski village in the railroad 
 cuts, on the line of strike of the similar rock in the river bank 
 below the bridge. On the south side of the river, in Burlington, 
 east of the Greenmount Cemetery and west of Grove Street, are 
 typical variegated beds of this formation dipping gently easterly. 
 
 It will thus be seen that along and near the lake in Burling- 
 ton the Red Sandrock shows the same general characters and 
 dip that it has farther north along the lake shore. 
 
 About, a mile east of Winooski village the river has cut a 
 winding gorge. At the hydroelectric power plant the wall of the 
 gorge is made of gray siliceous rock which eastward appears to 
 pass beneath other rock that is more calcareous and which in fact 
 at the lime-kilns is a marbly limestone which is quarried for 
 lime. No sharp line of separation was found between the two 
 kinds of rock. In the old and new quarries at the lime-kilns the 
 rock is strongly crystalline, remarkably uniform in appearance 
 and without distinct bedding. A similar lack of bedding appears 
 in the massive, weathered rock as it outcrops near the quarry in 
 the wall of the gorge just below the bridge. West of the new 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 227 
 
 quarry, south of the river, surface exposures in the fields show 
 bluish-gray, marbly limestone puddled with yellowish-gray rock. 
 The latter as eroded most often appears as patches and streaks on 
 the marbly rock. The white-weatheriijg, marbly rock occurs 
 north of the river and the railroad track, to the west of the high- 
 way bridge, and passes westward at the surface into gray, siliceous 
 rock. 
 
 No fossils were obtained from any of these rocks and their 
 structural relations are problems not yet solved. In notable 
 particulars the limestone in the quarries and adjacent fields has 
 very strong resemblance to the similar rocks east of Highgate 
 Springs and south of Swanton village. 
 
 Professor Perkins has told the writer that fossils were found 
 by Griffin in Colchester, north of the lime-kilns, which seem to 
 be of Beekmantown age (Rhaphistoma canadense Bill, and Cryp- 
 tosoon wingi Seely). 
 
 East of the lime-kilns the Winooski winds through a sand 
 plain to the falls at the bridge south of Essex Junction. 
 
 South Burlington. 
 
 (Burlington topographic sheet.) 
 
 Location. This township bounds Burlington on the east and 
 south. For a mile and a half south of Redrock Point the shore 
 of Shelburne Bay forms its western boundary. Williston lies to 
 the east and Shelburne to the south. 
 
 General description. The red beds of the Sandrock forma- 
 tion pass beneath the surface covering near Queen City Park, and 
 the shore southward to the southern boundary of the township 
 shows no outcrops. East of the shore, sand is plentiful ; the 
 eastward extension of the red beds in South Burlington may only 
 be conjectured. Sand plains extend to the northwestern part of 
 the township, to the bank of the Winooski River. 
 
 About two and a half miles southeast of Burlington a road 
 from the Williston turnpike crosses Potash Brook. At this place 
 is white, marbly rock like that at the lime-kilns two miles to the 
 north. 
 
 Southeast of these outcrops and again southward along the 
 road from Williston turnpike to Hinesburg and between the road 
 and Muddy Brook are numerous ledges of limestone. Some of 
 these are composed of thinly-bedded, bluish rock, of which the 
 bedded characters are somewhat better shown in outcrops a little 
 to the east in Williston, and other ledges are more massive looking 
 rocks of somewhat striped appearance as though thin layers had 
 been welded by shearing into more compact and thicker beds. 
 This massive, striped rock is particularly well shown at the school- 
 house about two and a half miles south of the Williston turn- 
 pike. The rocks were searched for fossils without success. They 
 
228 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 lie on meridians a little east of those occupied by the marbly 
 limestone and its associates at the lime-kilns east of Winooski. 
 There is some resemblance between certain members of the lime- 
 stones near the Winooski gorge and those in the southeastern 
 part of South Burlington. The rocks at these two places are 
 much more readily correlated with each other than either are with 
 the gray, sandy dolomite (siliceous limestone) found in associa- 
 tion with the red beds of the Sandrock formation at the west 
 and that with which they or similar rocks are rather intimately 
 intermingled a little farther south in St. George and Hinesburg. 
 In Hinesburg a4id Charlotte and townships south of them, 
 marbly limestone is often in intimate field association with rocks of 
 very different character and which may be correlated without much 
 hesitation with the Lower Cambrian ; but these latter rocks are 
 quite similar in all essential features to rocks which more distantly 
 surround the white, marbly or bluish limestones of South Bur- 
 lington and Williston. In other words, there is a rather close 
 correspondence between various rocks in South Burlington and 
 Williston and others in the townships to the south of them ; but 
 the field intimacy among these rocks that are apparently of very 
 different age is much more pronounced in some areas than in 
 others. 
 
 Williston Township. 
 
 (Burlington topographic sheet.) 
 
 Location. Williston lies east of South Burlington. It is 
 bounded 'on the north by Essex, on the east by Jericho and Rich- 
 mond and on the south by St. George and a part of Hinesburg. 
 
 General description. In Williston, along and west of the 
 road running south from Essex Junction to Hinesburg, about one 
 and one-fourth miles from the outcrops in the river at the bridge 
 south of Essex Junction, Allen Brook cuts through gray, siliceous 
 limestone or dolomite much like that at the bridge. 
 
 The Hinesburg road crosses the Williston turnpike. One- 
 third of a mile south of the turnpike, east of the road to Hines- 
 burg, black, gray- weathering slate, with easterly dipping cleavage, 
 is associated with mashed limestone or dolomite, bluish-gray on 
 fresh surfaces, but weathering gray, which is very close to the 
 slate. Contact is concealed. The limestone showed no discern- 
 ible dip. The relations are very similar to those below the bridge 
 south of Essex Junction, described above. 
 
 About a mile east of these outcrops, just south of the Willis- 
 ton turnpike, conspicuous knolls give a surface succession from 
 west to east of siliceous dolomite, fissile, blackish and lighter 
 colored phyllites, and quartzite. Gray dolomite outcrops a mile 
 to the northeast, north of Allen Brook ; but eastward the prevail- 
 ing rock is quartzitic schist, often carrying segregated quartz. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 229 
 
 South of Williston turnpike, east of the road running from 
 Essex Junction to Hinesburg, except for the outcrops mentioned 
 above, the prevaiHng rock is the quartzitic schist, which forms 
 rolHng, hilly land extending eastward into Richmond and south- 
 ward into St. George and Hinesburg. This schist gives place at 
 the surface westward, north of Brownell Mt. and Sucker Brook, 
 to bluish limestone with which the schist is intermingled at 
 places in no regular way. The arrangement gives the impression 
 that the limestone lies on the schist. Westward toward Muddy 
 Brook the limestone thickens and becomes more massive looking, 
 as described above for the eastern part of South Burlington, and 
 outcrops of schist are lacking. 
 
 At the foot of the steep western slope of Brownell Mt., 
 near the road skirting the mountain on the west, is crushed bluish- 
 black slate with cleavage dipping easterly and at some places 
 clearly brecciated. The schist making up the mass of Brownell 
 Mt. has apparently ridden by thrust over the slate. West- 
 ward the slate is succeeded by striped, bluish limestone like that 
 described above. 
 
 Although no conglomerate was noted in .the limestones south 
 of the Winooski there is much resemblance between the striped, 
 bluish members of them and similar rocks found farther north in 
 the conglomerate formation. There is, moreover, a close corre- 
 spondence in the associations with other rocks and in structural 
 relations. At the north the rocks as has been shown are often no 
 more conglomeratic than are the limestones of South Burlington 
 and Williston. 
 
 Shelburne and St. George Townships. 
 
 (Willsboro and Burlington topographic sheets.) 
 
 Location. Shelburne lies south of South Burlington and 
 borders the lake. The northeastern part of the township adjoins 
 the southwestern part of Williston. St. George on the east is 
 like a small strip cut off from the eastern end of Shelburne. On 
 the south are Charlotte and Hinesburg. A long tongue of land 
 belonging to Shelburne extends northward into the lake and 
 separates the main body of Lake Champlain from Shelburne Bay. 
 
 General description. Most of the peninsula just mentioned 
 is formed of the shale formation which extends from Shelburne 
 Point southward on both shores, on the east nearly to the southern 
 limit of the bay and on the west to join the shale of the mainland 
 along which it continues with some interruptions along shore to 
 the southern boundary of the township. Outcrops are frequent 
 on the peninsula between its shores, but southward away from 
 the lake the shales are mostly covered and are succeeded eastward 
 by the red and gray rocks of the Sandrock series. 
 
230 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 On Shelburne peninsula the shales, or slates, carry the firmer, 
 rusty-weathering bands so characteristic of this formation all 
 along the lake shore north of Burlington and in general lithological 
 features are like the members of the formation on the islands 
 and the mainland in the northern part of the lake region. 
 
 It seems probable that the lake bottom in Burlington and 
 Shelburne Bays is underlain by the slates, in which these indenta- 
 tions of the shore have been excavated, probably in some cases 
 after a covering of overthrust rock belonging to older limestones 
 or to the Sandrock series had been eroded. The general field re- 
 lations all about suggest such a history and further give some 
 support to the view that in Shelburne and other places where 
 these friable mud rocks have been preserved they owe their pres- 
 ervation to a covering of more resistant rock that was removed 
 at a relatively recent date. Juniper and White Islands are in- 
 sular outcrops of the shale to the west of the peninsula. 
 
 The slates on Shelburne peninsula are cut by numerous dikes 
 which have been described by Kemp.^ 
 
 The Sandrock forms headlands on the southwest shore of 
 Shelburne Bay and gives numerous outcrops between the bay and 
 the village of Shelburne. The red beds are conspicuous along 
 the Shelburne-Burlington road just north of the LaPlatte River 
 and these and other members outcrop west and southwest of 
 Shelburne village. The dip is at a low angle to the east. 
 
 East of Shelburne Falls, to Shelburne Pond, the rocks are 
 gray, siliceous dolomites not distinguishable from the similar beds 
 around Shelburne village. The rocks just east of Shelburne Falls 
 are on the meridian of those in the eastern part of Burlington. 
 
 East of Shelburne Pond, between it and the main road from 
 Burlington to Hinesburg, the prevailing rocks are marbly or 
 bluish limestones, forming the southward continuation of those 
 in the southwestern part of Williston and the southeastern part 
 of South Burlington. Near the Hinesburg road these limestones 
 give place to gray, siliceous dolomite which continues over the 
 western boundary of St. George township. East of the dolomite 
 in St. George the hilly land is made of quartzitic schist which 
 joins that of Williston and Hinesburg. 
 
 A generalized surface section from west to east across the 
 areas south of the Winooski River, which have so far been de- 
 scribed, gives the Ordovician shale formation at the west, then 
 the Red Sandrock series of red and gray quartzites and dolomites, 
 then a very different kind of rock that is a metamorphosed lime- 
 stone, and finally quartzitic schist with some gray dolomite on 
 the same meridians with the schist both of which belong to the 
 same general formation. The types of rock and the sequence are 
 the same as in the townships north of the Winooski. The varia- 
 
 'Bull. U. S. G. S.. No. 107, 1893. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 231 
 
 « 
 
 tions are perhaps less significant than the similarities, from a 
 structural viewpoint. 
 
 Charlotte Township. 
 
 (Willsboro and Burlington topographic sheets.) 
 
 Location. Charlotte lies south of Shelburne and borders the 
 lake. It is bordered by Monkton on the east and by Monkton and 
 Ferrisburg on the south. 
 
 The rocks along and near the lake in Charlotte. From the 
 Shelburne line to the latitude of Wing's Point the lowland along 
 the lake is made of clay, with few outcrop's of the shales along 
 shore. 
 
 On the road running from Charlotte village westward to the 
 lake shore and McNeil's ferry, about a mile east of the shore, 
 Black River limestone, carrying the markings so familiar in this 
 formation in the lake region, dips westerly at a low angle and is 
 underlain apparently by Upper Chazy with similar westerly dip. 
 Nearer the lake are Trenton beds, also dipping westerly at a low 
 angle or lying nearly flat. At the water edge just south of the 
 ferry the dark blue Trenton rocks are full of well-preserved and 
 characteristic basal Trenton fossils. After a surface interruption 
 along the shore of the bay south of the ferry the Trenton beds 
 appear on the north shore of Cedar Beach promontory and con- 
 tinue around its border to McNeil Bay. At Cedar Beach prom- 
 ontory the dip changes to southeast or east. These Trenton 
 rocks are nowhere severely altered. They are in fact like the 
 Trenton rocks of Grand Isle and Isle La Motte. In respect to 
 certain features of alteration they dififer from the Chazy just as do 
 the beds on the islands mentioned. 
 
 On the west shore of a small promontory that juts into 
 McNeil Bay are beds that were correlated with part of Brainerd 
 and Seely's Beekmantown. A third of a mile farther east are 
 magnesian rocks of doubtful correlation, but probably also Beek- 
 mantown. These are followed eastward by ledges of Chazy lime- 
 stone, dipping easterly, and carrying Girvanella ocellata Seely. 
 There seems to be exposed a small patch of Black River to the 
 east of these Chazy rocks. 
 
 The road on Thompson's Point crosses diagonally a series 
 of beds that appear to belong to the Beekmantown by comparison 
 with the Shoreham section. The beds dip at a low angle to the 
 southeast. 
 
 On the southeast shore of the bay, south of Thompson's Point 
 near the Ferrisburg line, are Chazy beds dipping to the southeast. 
 
 The various massive beds described as probably Beekman- 
 town or recognizable as Chazy, are not folded, but as shown by 
 changes in strike from place to place and by visible geographic 
 offsets are twisted, and broken across the strike and probably 
 
232 REPORT OP THE VERMONT STATE GEXDLOGIST. 
 
 along it. On the whole the rocks do not show pronounced in- 
 dications of internal deformation. There is nothing to show their 
 relations to the slates that probably lie north of them under the 
 clay-covered lowland. The writer's field map indicates that shale 
 lies on a meridian to the east of these massive, basal Ordovician 
 rocks ; outcrops were noted a mile north of Charlotte station and 
 also a few rods west of Ferrisburg station in the adjoining town 
 of Ferrisburg. These various rocks in southwestern Charlotte 
 belong to the lake region proper, as defined in the early part of this 
 paper. The probable relations among them may be judged from 
 those shown by other rocks in townships farther south. 
 
 East of the Rutland railroad track in Charlotte. South of 
 Charlotte station is a considerable mass of igneous rock forming 
 Barber Hill. The rock has been described as Bostonite (a soda- 
 rich, acid, dike-forming rock). Similar rock forms dikes on 
 Shelburne Point and in North Ferrisburg village. 
 
 East of the railroad track in Charlotte township by far the 
 largest part of the visible rock emerging through the drift belongs 
 to the Sandrock series. East of Charlotte village the reddish 
 members of this formation form Pease Mt. Along the road that 
 runs southward, east of Pease Mt., similar rocks dip easterly and 
 join with the red beds of Mt. Philo. The rocks of these two 
 mountains are on meridians which are occupied farther north by 
 the Sandrock formation in Shelburne, but which to the south in 
 Ferrisburg are occupied by comparatively unaltered shales, thinly- 
 bedded, dark blue, basal Trenton limestone and Chazy rocks 
 which belong to the lake series and are in fact the eastward ex- 
 tension of the rocks along the lake in Ferrisburg. 
 
 East of Pease Mt., around East Charlotte, exposed at sev- 
 eral places along or near the road running in a north-south 
 direction through the village, are outcrops of beds of siliceous 
 dolomite, dipping easterly at a low angle. On this road, about a 
 mile and a fourth north of the village, is marbly limestone ; but a 
 mile farther north the gray dolomite outcrops again and continues 
 towards Shelburne Falls. 
 
 Around Prindle Corners, two miles southeast of East Char- 
 lotte, interbedded quartzite and dolomite show a series much like 
 that found around Middlebury and Brandon to the south. The 
 rocks in southeastern Charlotte and adjacent portions of Hinesburg 
 indeed mark a transition in the Lower Cambrian formation from 
 the generally more massive, interbedded, siliceous and magnesian 
 rocks of the Sandrock series in the northern townships and the 
 recognizably thinner beds of what has been called by the writer 
 in earlier papers the "interbedded series" of the Lower Cambrian 
 in the Vermont valley. 
 
 As a consequence of their more thinly-bedded character, the 
 rocks around Prindle Corners and neighboring parts of Hines- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 233 
 
 burg are frequently jammed into close folds so that the beds 
 stand at high angle of dip or even on end. 
 
 Northeast of Prindle Corners along the road and in the 
 fields the Cambrian quartzites and dolomites are intermingled 
 with marbly rock, but the field relations as usual give no definite 
 clues as to the structural relations. 
 
 Hinesburg- Township. 
 
 (Burlington topographic sheet.) 
 
 Location. Hinesburg lies east of Charlotte. 
 
 General description. In the southwestern part of Hinesburg 
 are interbedded quartzites and dolomites which join with those 
 around Prindle Corners in southeastern Charlotte. The beds are 
 usually sharply folded with high easterly or westerly dips, but 
 along the meridians of such closely folded rocks, at other places 
 the folding was not always so severe. The interbedded rocks 
 east of Prindle Corners continue southward into Monkton and 
 northward in western Hinesburg, but in northwestern Hinesburg 
 are considerable exposures of marbly limestone, which, so far as 
 the hard rock is now visible, seem more or less definitely to be 
 surrounded by gray, siliceous dolomites. 
 
 West of Mechanicsville, along and west and east of the 
 Hinesburg road, the gray dolomite is abundant and forms a con- 
 spicuous ledge known as High Rock on the east side of the road. 
 Massive, gray dolomite occurs between Mechanicsville and Hines- 
 burg and in numerous massive and prominent ledges southeast of 
 Hinesburg on the east side of the road to Starksboro, continuing 
 southward nearly to the township boundary. The extension of the 
 dolomite east of the main road is irregular, being most marked in 
 hollows around Mechanicsville and Hinesburg. East of the main 
 road the land is mostly hilly and made of quartzitic schist. 
 Dolomite and schist at different places occupy the same meridians 
 and the field relations show that the two rocks are members of a 
 common formation and that the preservation of the dolomite 
 along the western margin of the hilly land is due to certain favor- 
 able structural relations resulting from the deformation of the 
 rocks. 
 
 It will thus be seen that from the lake shore eastward through 
 Charlotte and Hinesburg a broad surface section gives near the 
 lake the shales and comparatively unaltered limestones of clearly 
 recognizable Lower and Middle Ordovician ages, then an abrupt 
 transition to the Red Sandrock of Pease Mt. and Mt. Philo 
 which are succeeded eastward by gray dolomites and interbedded 
 dolomites and quartzites more or less intimately intermingled in 
 their present .surf ace outcrops with marbly limestone, and finally 
 the massive, gray dolomite and quartzitic schist of the hilly land 
 at the east. A field inspection is essential in order to appreciate 
 
234 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 fully the similarity which such a section has in rock types, 
 sequence and general field relations with the sections in northern 
 townships which have been described, and its correspondence in all 
 essential particulars with areas farther south. These resem- 
 blances are clearly due to what may be called strict homology, to 
 borrow a biological term, in the secondary structural features and 
 in certain primary relations which obtained among the various 
 rocks, although all of the rocks may not be of precisely similar 
 age. 
 
 The Lower Cambrian formation is seen to show from west 
 to east and from north to south many variations of thickness, 
 color and sequence in the vertical arrangement of its beds, cor- 
 respondifig with lateral variations in the original character of the 
 material and variations in the conditions under which the material 
 was deposited from time to time. North of Weybridge the more 
 purely terrigenous rocks of this formation are found in the hilly 
 land by which the Champlain lowland is joined to the mountains 
 farther east, but such rocks also form the present surface rock 
 over portions of the eastern edge of the lowland. South of Wey- 
 bridge the terrigenous rocks are extensively preserved in the 
 Taconic hills. 
 
 ADDISON COUNTY. 
 
 Ferrisbnrg and Vergennes. 
 
 (Willsboro, Burlington, Port Henry and Middlebury topographic 
 
 sheets.) 
 
 Location. The township of Ferrisburg and the city of Ver- 
 gennes are conveniently discussed together. Ferrisburg is on the 
 lake shore south of Charlotte. On the east it adjoins Monkton 
 and part of New Haven and on the south is bounded by part of 
 New Haven, Waltham, Vergennes and Panton. Vergennes forms 
 an area two miles square which is bounded by Ferrisburg on the 
 north, by Ferrisburg and Waltham on the east, by Waltham and 
 Panton on the south and by Panton and Ferrisburg on the west. 
 
 General description. Ferrisburg is a large township and 
 includes a variety of rocks, all of which ma:y be correlated with 
 others which have been described in previous pages, but some of 
 which show field relations of great interest in relation to the 
 general structure of the region. Description will begin with the 
 western and central portions. 
 
 Around Camp Meeting Point, north of the mouth of Lewis 
 Creek, fossiliferous Chazy limestone forms a low, anticlinal fold. 
 Between the point and the railroad track are low outcrops of 
 shales which are undoubtedly younger than the rock at the point. 
 
 Near Bluff Point, west of the Little Otter, much of the 
 rock is apparently of Chazy age. Specimens of Maclurea magna 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 235 
 
 were found near the road from Kingsland Bay to Ferrisburg, at 
 the bend in the road, about two-thirds of a mile east of the bay. 
 The beds dip gently eastward. East of this place outcrops are 
 largely concealed along the sluggish creek. 
 
 Limestone outcrops at intervals along the road that runs 
 south from Kingsland Bay. Just south of the junction of this 
 road with the one that runs from it to Fort Cassin Point are 
 extensive outcrops of probably Chazy limestone, dipping easterly ; 
 but about one-fourth of a mile from the main road along the one 
 to Fort Cassin Point, graptolitic shales were noted. At Fort 
 Cassin Point, which is probably really an island surrounded partly 
 by water and partly by the delta and levee deposits of Otter 
 Creek, are limestones which were assigned by Brainerd and Seely 
 to division D of their Beekmantown formation. Bedding is dis- 
 tinct and the layers have a flattish position. The rocks are more 
 or less indurated but fossiliferous. Although great numbers of 
 different species have been found at this locality, particularly in 
 the weathered rock, fossils are now found only after dihgent 
 search in the firm, unweathered rock. Seely states that the Fort 
 Cassin rocks were assigned to division D by Brainerd after care- 
 ful stratigraphic study of the region. The fauna of these rocks 
 is in need of further careful study in order to be sure of its exact 
 horizon. The apparent separation at the surface by shales of the 
 rocks at Fort Cassin from the Chazy beds mentioned as occurring 
 along the road to Kingsland Bay suggests that the succession 
 east from the lake is probably not a conformable one, but rather 
 that breaks, probably of the nature of thrusts, intervene. 
 
 East of the probable Chazy rocks on the Kingsland Bay road 
 the surface is all clay. The hard rock underlying the clay is 
 probably all shale. 
 
 West of Otter Creek and south of Kellogg Bay, are outcrops 
 of fossiliferous Chazy which lie on a meridian slightly to the west 
 of the Fort Cassin beds a mile to the north. With some inter- 
 ruptions the Chazy beds, dipping everywhere to the east, form 
 the shore and slopes adjacent to it from Summer Point at Kellogg 
 Bay southward past Basin Harbor to Button Bay. At many 
 places, notably at Basin Harbor and between it and Button Bay, 
 the beds afforded excellent specimens of M. magna and Girvanella. 
 Near Kellogg Bay perhaps not all the rock belongs to the Middle 
 Chazy ; at Summer Point the beds may belong to a lower division 
 of this formation or to Upper Beekmantown. 
 
 Eastward again between the outcrops along shore and Otter 
 and Dead Creeks, presumably the underlying rock is shale, which 
 is found in scanty, low outcrops along the road from Basin 
 Harbor to Panton ; but sand plains along the Otter and elsewhere 
 clay conceal the rock to within a mile and a half of the city of 
 Vergennes. 
 
236 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 The Chazy rocks that form the point which projects towards 
 Button Island, near Button Bay, pass eastward beneath clay 
 which forms most of the shore of Button Bay. Along the shore 
 south of the bay the shales outcrop for a distance of about two- 
 thirds of a mile north of the Panton line. Fossils collected from 
 these shales and those along the Panton shore southward by 
 Gould and Ruedemann were assigned by Ruedemann to three 
 different horizons in the Canajoharie shale of Trenton age. 
 
 About one and a half miles west of Vergennes, north of the 
 Otter and between it and the road running from Vergennes to 
 Fort Cassin and Kingsland Bay is a hill of badly crushed, magne- 
 sian limestone, without fossils or distinct structure. A mile to 
 the east, north of the road, and just west of the playgrounds of 
 the Industrial School are excellent outcrops of massive Chazy 
 beds, dipping gently to the east and carrying numerous coils and 
 opercula of M. magna and abundant specimens of Girvanella. 
 East of the playgrounds and north of the city, similar beds with 
 similar fossils dip to the west at an angle of 34° and strike N. 
 40° E. East of these outcrops, west of the railroad track, is a 
 road running north to Ferrisburg. East of this road, respectively 
 a half mile and a mile north of the westerly-dipping Chazy beds 
 just mentioned, are other Chazy beds dipping easterly. The 
 structure thus shown by the Chazy northwest and north of Ver- 
 gennes shows the formation to be disposed in gentle anticlinal and 
 synclinal swells. More altered rocks of probably Chazy age at 
 Marsh Hill and south of it, to the northeast of the city, form a 
 gentle, anticlinal fold. 
 
 At Vergennes falls the river tumbles over massive, grayish, 
 magnesian limestone which apparently dips easterly. Close in- 
 spection shows it to be crushed and brecciated, but now healed 
 into a compact rock. Seely called this rock Beekmantown. 
 
 Below the falls, near the boat landing on the Industrial School 
 grounds, shales carrying numerous graptolites, identified as G. 
 quadrimucronatus, outcrop in the low bank of the stream. Be- 
 tween the falls and the westerly-dipping Chazy beds north of the 
 city, described above, shales or argillaceous limestones, usually 
 much sheared and slickensided and filled with small veins of 
 calcite, outcrop along the road, apparently exposed from beneath 
 a mass of overthrust Chazy. 
 
 About two miles northeast of Vergennes, west and east of 
 the main road from Vergennes to Ferrisburg, east of the railroad 
 track, are Trenton beds somewhat sheared, but carrying hosts of 
 recognizable basal, Trenton fossils, including Calymene scnaria, 
 Cryptolithus tesselatus, linguloid forms and bryozoa. These 
 rocks are particularly well exposed on the land of Carl Fields. 
 The Trenton rocks form a ridge between the main road and the 
 one running from it to the west of Shellhouse Mt. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 237 
 
 A half mile northeast of this ridge of fossiliferotis Trenton, 
 southeast and east of Ferrisbiirg village, are outcrops of Chazy 
 limestone which are on meridians on which lie the rocks at Marsh 
 Hill and south of it, as mentioned above. Rocks of apparently 
 Chazy age continue northward, east and west of the road on the 
 west of Shellhouse Mt. North of the mountain the road ascends 
 over blue, Trenton rocks, which as outcropping in the road gave 
 Trenton fossils, including C. tesselatus. Towards Mt. Fuller 
 these Trenton beds are associated with more massive, dense lime- 
 stones, weathering a light gray, now shattered and filled with 
 calcite veins and which strongly suggest the Black River, and are 
 in fact much like recognizable Black River rocks found farther 
 south in Waltham and Addison townships. Sheared limestone, 
 probably of Trenton age, continues northward along the cross 
 road west of Mt. Fuller nearly to the North Ferrisburg-Monkton 
 road. At one place along this cross road, sheared limestone is 
 in contact with quartzite and probably overlain by it. One-third 
 of a mile to the east is a scarp in the quartzite that makes Mt. 
 Fuller. 
 
 At North Ferrisburg village, Lewis Creek has cut down into 
 crumpled, black shales or shaly limestones which are exposed in 
 the bed and banks of the stream at many points in the village and 
 west of it towards the lake. Northward on the meridians of 
 these shales in the creek is the Red Sandrock of Mt. Philo. These 
 shales have been called "Utica"; they are without much doubt 
 younger than the rocks that form the hilly land south and south- 
 east of them. 
 
 The rocks that apparently belong to the Chazy formation 
 and form the surface just west of Shellhouse Mt. give place 
 in the steep western face of the mountain to white quartzite 
 which is notably jammed. The quartzite extends eastward, giving 
 place near the township boundary to interbedded dolomites and 
 quartzites, all, including the quartzite at Shellhouse Mt., dip- 
 ping easterly at a low angle. The interbedded rocks form a 
 band along the eastern edge of the township and southward join 
 with similar rocks in New Haven. South of Shellhouse Mt. 
 the Cambrian rocks pass under drift and between the band 
 of interbedded rocks at the east and the limestone of Marsh Hill 
 and neighboring exposures is an area of low, flat land, with no 
 outcrops ; but directly north of the mountain, as has been shown, 
 are limestones and shales of the lake series which occupy the 
 meridians of the quartzite of the mountain and the interbedded, 
 Lower Cambrian rocks that lie east of it. 
 
 The Trenton and Black River limestones southeast of North 
 Ferrisburg village and the shales in Lewis Creek are visibly 
 sheared or shattered rocks and somewhat metamorphosed, but 
 are readily recognized and traced as the eastward extension of 
 the rocks near the lake. They are notably less crystalline and 
 
238 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 marbly than the calcareous rocks found among the Lower Cam- 
 brian rocks on meridians farther east. The occurrence of the 
 Lower Cambrian rocks north and south of North Ferrisburg 
 village on the same meridians with the little altered lake rocks 
 near the village and the extension of the present margin of the 
 former at Pease Mt. in Charlotte to a meridian over a mile west 
 of that passing through North Ferrisburg village, point to thrusts 
 by which the older rocks rode over the younger. It is also 
 probable that the massive limestones of the lake series rode over 
 younger shales, either by independent thrusts or during the trans- 
 lation of the Cambrian beds. 
 
 The field relations near Vergennes certainly suggest that the 
 older limestones of the lake series have ridden over the younger 
 limestones and shales. The latter are sometimes sheared and 
 crushed. At Vergennes falls the dolomite is brecciated ; but the 
 Chazy beds northwest, north and northeast of the city are not 
 folded much. They are most sheared and altered in their eastern 
 outcrops ; but even then may sometimes lie flat, as may be seen 
 near the cemetery east of Ferrisburg village. 
 
 The conditions around Vergennes seem to show what was 
 argued to be the probable structure on the islands in the northern 
 part of the lake. They also give support to the idea that a great, 
 low-angle thrust carried the 'Lower Cambrian beds over the rocks 
 of the lake region and that to some extent, at least, the present 
 western margin of the former is an erosion trace of an overthrust 
 mass of which some portions have disappeared. 
 
 Monkton Township. 
 
 (Burlington and Middlebury topographic sheets.) 
 
 Location. Monkton lies east of Ferrisburg and is bounded 
 by Charlotte and Hinesburg on the north, by Starksboro on the 
 east, and by Bristol and part of New Haven on the south. 
 
 General description. This township includes a prominent 
 physiographic outlier of the Green Mountain plateau, generally 
 known as "Monkton ridge," which enters Monkton from Bristol 
 at the south and extends through the central portion nearly across 
 the township. To the east of Monkton ridge, and separated from 
 it by a valley of irregular surface, another prominent ridge, 
 known as Hogback Mt., and which is also an outlier of the main 
 range, enters from Bristol and extends northward just west of 
 the eastern boundary to within about a mile of the northern town- 
 ship line. 
 
 These prominent physiographic features are fundamentally of 
 structural origin. They are interpreted as primarily thrusted 
 masses which were later modified by normal faulting. The de- 
 pression which now separates Monkton ridge from Hogback and 
 that which separates the latter from the main range is in each case 
 
REPORT OF THE VERMONT STATE GEOLOGIST, 239 
 
 a more or less perfectly developed grahen and on a small scale 
 illustrates the structural character of the famous Vermont valley, 
 which beginning farther south near Brandon extends to Pownal 
 between the Green Mountain plateau and the Taconic range. The 
 structural and physiographic features in the eastern part of Monk- 
 ton and adjoining parts of Starksboro have their counterparts at 
 other places along the western edge of the Green Mountain 
 plateau. 
 
 Into the northwestern part of Monkton township the reddish 
 beds of the Sandrock series extend from the southeastern part of 
 Charlotte and give conspicuous outcrops on the low hillsides at 
 many places. East of the road from Monkton to East Charlotte, 
 northeast of Mt. Fuller, the red beds are interbedded with some 
 dolomite and the dip is gently to the west. 
 
 At Mt. Fuller and southward along the road to Barnumtown, 
 beds of cherry-red quartzite form conspicuous outcrops and dip 
 to the east at a low angle. A low scarp bounds Mt. Fuller on the 
 west. It is interpreted, as in some degree a recession scarp, for 
 one-third of a mile to the west of it a fragmentary patch of 
 quartzite rests against sheared, probably Trenton limestone, as 
 noted above. 
 
 South of Mt. Fuller the surface falls off to slightly lower 
 levels and apparently the purple quartzites pass under somewhat 
 higher members of the Sandrock series ; but whether this is 
 actually the case or whether the interbedded quartzites and dolo- 
 mites forming the surface rocks southward represent lateral 
 variations of the beds at the north may not be easily decided. 
 
 Near Barnumtown the interbedded series appears in force 
 and at places shows most severe effects of compression, being 
 not only jammed into close folds, but twisted along the strike and 
 otherwise deformed. The interbedded rocks continue south from 
 Barnumtown over Cronkhite Hill and along the road to New 
 Haven Junction. At some places the members of this series lie 
 in flat attitude, but within short distances such beds pass ap- 
 parently both along and across the strike into others that are 
 highly inclined and greatly jammed. These features have much 
 resemblance to others which have been described for quite similar 
 rocks around Brandon (see first paper) and have their counter- 
 parts in other localities yet to be described. 
 
 In the northern part of th'e township, along the road from 
 North Ferrisburg to the village of Monkton Ridge, are low-lying 
 outcrops of closely- folded, interbedded quartzites and dolomites 
 which are the southward extension of those in southwestern 
 Hinesburg and near Prindle Corners in Charlotte. 
 
 Two miles farther south, just west of Monkton village 
 (Monkton Borough), similar rocks with cherry-red quartzite mem- 
 bers form the hill known as Mt. Florence and show numerous 
 outcrops in the fields directly north of the hills. In the hill red 
 
240 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 quartzites apparently dip gently to the west, while directly east of 
 the hill the members of the interbedded series are jammed into 
 close folds and are sheared and crushed. 
 
 From Monkton Borough, over the ridge to East Monkton, the 
 rock is mainly quartzite or quartzitic schist, apparently for the 
 most part dipping easterly. Just north of East Monkton village 
 rather thinly-bedded, quartzite beds stand on end or by apparent 
 overturn now dip easterly at a high angle. These rocks are sheared 
 and slickensided and give every indication of having been jammed 
 against the beds that lie west of them. 
 
 Distinct scarps, irregularly disposed and overlapping more 
 or less along the general strike of the rocks, are distinctly visible 
 features along the eastern face of the ridge north of East Monk- 
 ton village. These scarps probably mark planes of faulting by 
 which the rocks that lie in the valley of Pond Brook have been 
 left at lower levels. Quartzite forms the eastern slopes and 
 scarps of Monkton ridge from East Monkton to Monkton Ridge 
 village. South of the latter village, east of Monkton Pond, the 
 gray and white quartzite is distinctly sheared so that the dip is 
 obscure. 
 
 For a mile and a half east of Monkton Ridge village the 
 rocks are distinctly bedded, gray dolomites, lying flat or dipping 
 westerly, but just west of the northern end of Hogback Mt. * 
 the dip of the dolomite changes to easterly and this rock gives 
 place eastward to quartzitic schist, or sheared quartzite, with 
 some members of pure white, granular quartzite. Eastward 
 towards the road that runs from Hinesburg to Starksboro the 
 quartzite gives place to gray, siliceous dolomite, usually of massive 
 appearance, but carrying some thin beds. 
 
 In Monkton township, just as in Hinesburg at the north, as 
 one goes east from the western margin of the Cambrian rocks 
 towards the hilly land, the interbedded rocks are seen to give 
 place at the surface to dolomite or quartzite, apparently accord- 
 ing to the manner in which displacements have altered the primary 
 relations among the rocks. These relations are quite like those 
 to be noted farther south in Bristol and Middlebury, and those 
 which the writer has described for the Brandon region. 
 
 The southern portion of Monkton ridge, south and southeast 
 of East Monkton village, is largely composed of sheared quartzite ; 
 but, as will be mentioned again later, in the northwestern part of 
 Bristol the quartzite apparently passes beneath massive, gray, 
 siliceous dolomite which lies to the east of interbedded dolomites 
 and quartzites in the northeastern part of New Haven township. 
 
 The outcropping rock along the road that runs through the 
 valley of Pond Brook is quartzite ; but probably this quartzite was 
 once overlain by dolomite like that which occurs at the northern 
 end of the vallev, to the east of Monkton Ridge village, as noted 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 241 
 
 above, and presumably the softer rock has been largely eroded 
 over what is now the floor of the valley. 
 
 The western face of Hogback Mt. is steep and marked 
 by prominent scarps. 
 
 No marbly limestone was noted among the Cambrian rocks 
 just described for Monkton. Its absence seems to be correlated 
 with the relatively higher topographic levels of the members of 
 the Lower Cambrian series in this township. The marble ap- 
 pears to the south and southwest in New Haven. 
 
 Stai'ksboro Township. 
 
 (Burlington and Middlebury topographic sheets.) 
 
 Location. Starksboro lies east of Monkton and the north- 
 eastern part of Bristol. 
 
 General description. Lewis Creek has its source in the hills 
 of Starksboro. The stream from the junction of its headwater 
 tributaries flows north across the township through a valley that 
 separates Hogback Mt. from the main range. The floor of 
 the valley is dotted with hills. As noted above, it is a structural 
 basin secondarily modified by the erosion of much of the rela- 
 tively soft rock. The hills over its floor are formed of either 
 quartzite or dolomite whose beds during the period of their com- 
 pression were folded and sheared and now often stand on end. 
 
 Some of the special features of the Starksboro area have been 
 described by N. C. Dale.^ 
 
 The western wall of the valley is formed by the eastern face 
 of Hogback and is marked by numerous scarps. The mountain 
 is broken by transverse faults along which erosion has worked to 
 give a serrated skyline to the ridge. Less prominent scarps occur 
 to the east. 
 
 A feature to be noted is the apparent absence of the so-called 
 interbedded series, which is a condition apparently to be correlated 
 with thrust displacements which elevated older rocks against 
 younger ones and not necessarily with the original absence of 
 these beds over the area in question. 
 
 The rocks forming the hills to the east of the Starksboro 
 road were not inspected in Starksboro township, except in a small 
 area around South Starksboro village, which will be more con- 
 veniently described in connection with Bristol township. 
 
 Fanton Township. 
 
 (Port Henry topographic sheet.) 
 
 Location. Panton borders the lake and lies between Ferris- 
 burg on the north and Addison on the south. Its eastern bound- 
 ary is formed by a portion of Otter Creek which separates it 
 from the town of Waltham. 
 
 1 Twelfth Report of the State Geologist, p. 43. 
 
242 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 General description. In Panton the hard rocks are exten- 
 sively concealed by surface material, and wholly so over the 
 central portion of the township west and east of Dead Creek. In 
 the western part, outcrops are confined to the lake shore and to 
 a low ridge that lies between it and the road running from north 
 to south across the township, through Panton village, and in the 
 eastern part to scattered exposures to the west of Otter Creek. 
 
 The shore section beginning in Ferrisburg, two-thirds of a 
 mile north of the Panton line, shows black shales pitching north- 
 erly which yielded scattered graptolites and brachiopods. These 
 shales southward pass conformably into others with more numer- 
 ous limestone bands and these are underlain conformably by 
 thinly-bedded limestones full of characteristic Trenton species. 
 The pitch of these various beds is in a general northerly direction. 
 Southward is thickly-bedded, more massive limestone which re- 
 sembles the Black River. The so-called Black River beds are 
 somewhat folded so as to give at some places a westerly dip and 
 an unusually massive appearance when viewed from the west. 
 Southward are other massive limestone beds of different lithology 
 and strongly brecciated. These rocks gave two small Maclurea- 
 like coils on the weathered surface and it is thought that some 
 Chazy rocks are at this place involved in the shore section. The 
 brecciated limestone southward lies against black shales which are 
 somewhat crushed. The contact is a short distance north of 
 Arnold Bay. From this contact the black shales continue south- 
 ward for a short distance with southerly pitch, and then, with 
 change of pitch to north, to and around Arnold Bay, where they 
 form the small promontory on its southern side. 
 
 The structural relation of the brecciated limestone to the 
 shale, north of Arnold Bay, is far from clear. There is no doubt 
 that the limestone is much older than the shale. The crushing of 
 the latter near the contact seems slight, but if taken with the other 
 disturbance shown by the southward tilting of the shale beds, it 
 is possible to reconcile the conditions with the idea of an upward 
 movement of the older rock into the shales which was probably 
 preceded by brecciation of the limestone at depth. The folding 
 shown by the somewhat massive, so-called Black River beds north 
 of the brecciated limestone indicates that the rocks have been 
 under compression and that, therefore, the contact in question is 
 probably one of thrust. 
 
 East of Arnold Bay and the shore road is a low ridge. Just 
 east of the shore road and south of the one running from Arnold 
 Bay to Panton village are low ledges of what appeared to be 
 Black River beds dipping easterly. Farther south along this 
 ridge are numerous outcrops of what appeared to be Chazy beds 
 and still farther south, others which appear to be part of the 
 Beekmantown. Eastward to the west of and sometimes along the 
 road running south from Panton village the Chazy rocks form an 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 243 
 
 almost continuous outcrop for over two miles and extend into 
 Panton village. In the village, rocks that appeared to be of Black 
 River age lie on the east side of the road, north and south of the 
 one running to Vergennes. Columnaria was found in bowlders, 
 but not in place. 
 
 From the meridian of Panton village eastward the surface 
 is formed of clay and outcrops are lacking as far east as the low 
 ridge about two miles east of Dead Creek. 
 
 In the southwestern part of Vergennes at a road metal 
 quarry is dark gray, magnesian limestone which is conspicuously 
 brecciated at some places. The rock is like that at the falls in 
 the city and is probably a part of the Beekmantown by compari- 
 son with rocks in the Shoreham section. Farther south along a 
 road running west of this quarry are outcrops of gray, magnesian 
 rock and quartzite which resemble as much as anything in the 
 region the rocks of Mt. Independence in Orwell, and seemed to 
 the writer, without much doubt, to represent the lower, part of 
 Brainerd and Seely's Beekmantown and their so-called "Pots- 
 dam" as found in Shoreham. The outcrops of these rocks are, 
 however, few and of small extent and the correlation is tentative. 
 
 For the rest, little may apparently be learned of the hard 
 rock underlying this township. 
 
 If, as seems likely, the rocks in the eastern part of the town- 
 ship are Lower Beekmantown and those to the west beneath the 
 clay are shales, the former have probably ridden over the latter 
 by thrust much as they have north of Highgate Springs and 
 also to the south in Shoreham and Orwell. The massive rocks in 
 the western part of the township probably represent an independ- 
 ent upthrust into the younger shales. 
 
 Waltham Township. 
 
 (Port Henry and Middlebury topographic sheets.) 
 
 Location. Waltham is separated on the west from Panton 
 and the northeastern part of Addison, which lies south of Panton, 
 by Otter Creek. On the north it is bounded by Vergennes and 
 part of Ferrisburg and on the east and south by New Haven. 
 
 General description. Waltham is distinguished topograph- 
 ically by the considerable elevation known as Buck Mt. De- 
 scription may conveniently begin with the rocks lying between 
 Otter Creek and the mountain. 
 
 A road to Weybridge runs directly south from Vergennes on 
 the west side of Buck Mt. About a mile south of Vergennes, 
 between the road just mentioned and another running east of 
 the mountain to New Haven Junction, is strongly sheared, blue 
 limestone of probably Trenton age. Fossils have largely been 
 destroyed. A half mile farther south along the same meridian 
 and east of the Weybridge road is very much mashed limestone 
 
244 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 having the Hthological characters of the Chazy and often carry- 
 ing numerous small indistinguishable fossils and recognizable 
 specimens of Girvanella. The rocks have been sheared, but a 
 general easterly dip may be discerned. Along the strike of the 
 beds the dip changes from a high to a moderate angle. East of 
 these Chazy rocks are outcrops of Trenton limestone beds also 
 dipping easterly. 
 
 Eastward towards the road running from Vergennes to 
 New Haven Junction, beds of limestone form an anticline along 
 meridians which are occupied farther south by the Red Sandrock 
 of Buck Mt. The limestone is not like the Trenton beds just 
 west of it, but in its general characters more closely resembles 
 the dove-gray beds carrying yellow-weathering or chamois-colored 
 layers and patches which are intermingled with interbedded 
 quartzites and dolomites in the areas farther east. It lies on the 
 meridians of the Chazy limestone at Marsh Hill, east of the city 
 of Vergennes. It was apparently regarded as Trenton by Seely 
 and is apparently so shown on his "Geological Map of Addison 
 County" (see Seventh Report of the State Geologist), but this 
 map fails to depict in any detailed or accurate manner the various 
 rock outcrops in Waltham, 
 
 North of Buck Mt. a cross road joins the Weybridge and 
 New Haven roads. South of this cross road, along the one 
 to Weybridge, Chazy limestone, dipping easterly and carrying M. 
 magna and Girvanella forms numerous outcrops. South of these 
 Chazy beds on the west side of the road, opposite the school house, 
 is somewhat sheared, Trenton limestone with many surface mark- 
 ings of fossils. Prasopora was found at this locality. The beds 
 dip easterly and are filled with many small veins of calcite. A 
 mile to the south on both sides of the road, beds of Chazy lime- 
 stone, dipping easterly, form conspicuous ledges. On the east 
 side of the road the rock is visibly sheared, but its fossils are 
 distinct and included distorted specimens of M. magna and many 
 specimens of Girvanella. East of these beds are much altered 
 Black River rocks, full of small veins of calcite, but still showing 
 the characteristic surface markings of the Black River beds of 
 the lake region. The Black River beds dip easterly. Some of 
 the soil-covered spaces which now separate the Chazy and Tren- 
 ton outcrops may be underlain by Black River rocks. 
 
 The various rocks along the Weybridge road just described 
 belong to the lake series. They are the southward extension of 
 similar rocks around the city of Vergennes and those which lie 
 north of the city in Ferrisburg. All the various kinds of rocks 
 are visibly sheared at some places and show other effects of com- 
 pression On the southwestern side of Buck Mt., massive Chazy 
 beds may be followed a half mile east of the Weybridge road and 
 seem to be repeated across the strike as though piled on each 
 other by successive thrusting, but in the presence of such ap- 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 245 
 
 parent repetition of beds in this region it is not always easy to 
 decide whether the conditions are due to thrusting or normal 
 faulting, even when there can be no doubt that as a whole the 
 rocks involved have been disturbed b}' thrusts. 
 
 The rocks along the Weybridge road are on meridians to 
 the east of those occupied by the brecciated, gray, magnesian lime- 
 stones at Vergennes falls and the similar rocks south of the city. 
 From the fact that north of Vergennes the Chazy, with easterly 
 dip, extends to meridians west of the falls makes it difficult to 
 visualize the relations of these various massive rocks to each 
 other. It seems probable that in a good many cases, massive 
 Lower Ordovician strata broke at depth and were shoved upward 
 into younger rocks in such way that the younger beds on one 
 side were underthrust and on the other overthrust. The hori- 
 zontal component varied. The brecciated condition of the rock 
 at Vergennes falls and south of the city may be the expression of 
 internal deformation within the Beekmantown rocks on either the 
 underthrust or overthrust border of the ruptured mass. The 
 rocks in eastern Panton which have been described and regarded 
 as probably representing the Lower Beekmantown may have 
 underthrust the rocks along the Weybridge road, in a general 
 sense, and have overthrust the shales which are thought to lie 
 to the west of' them. 
 
 It is interesting to note that the calcareous rocks in eastern 
 Panton and the western part of Waltham are on meridians oc- 
 cupied by the Red Sandrock formation of Snake Mt. in western 
 Weybridge and the southeastern part of Addison. 
 
 East of the Weybridge road passing west of Buck Mt., 
 the calcareous rocks above described in general lie at the base of 
 a series of scarps that bound the mountain on the west. The 
 drift that has been piled against these scarps conceals contacts 
 between the limestone and the Sandrock. The scarps mark planes 
 of faulting; but it is not clear whether the present structural 
 relations of the rocks involved are due to reverse faulting and 
 modifications simply from erosion, or whether primary thrusts 
 have been modified by tension faulting as well as by erosion. 
 
 East of the scarps the surface of the mountain slopes grad- 
 ually eastward across the eroded edges of red quartzite beds 
 which dip gently to the east. East of the mountain, in the 
 western part of New Haven township, the surface is generally 
 covered with drift, but there are some exposures of red quartzites 
 along the direct road from New Haven Junction to Vergennes. 
 
 In the southeastern corner of Waltham are interbedded mem- 
 bers of the Lower Cambrian series which are probably to be 
 thought of as stratigraphically above the red quartzite forming 
 the eastern slope of Buck Mt. For the most part these mem- 
 bers of the interbedded series, which carries some red quartzite, 
 dip to the east, but on their western margin a slight westerly dip 
 
246 RETORT OF THE VERMONT STATE GEOLOGIST. 
 
 was noted indicatinj^ a small amount of flexure in these rocks. 
 These interbedded dolomites and quartzites join southward with 
 others in New Haven township which will be described beyond, 
 and the red quartzite of Buck Mt. also extends southward with 
 reduced elevation into New Haven at the south. 
 
 New Haven Township. 
 
 (Middlebury topographic sheet.) 
 
 Location. This township is one of irregular boundaries. 
 In general it is bounded by Waltham on the west, by Ferrisburg 
 and Monkton on the north, by Bristol on the east and by Middle- 
 bury and Weybridge on the south. 
 
 General description. In a small jog in the very northwest- 
 ern part of the town are outcrops of Chazy limestone which are 
 the southward continuation of the Chazy beds along the Wey- 
 bridge road in the southern part of Waltham. The rocks carry 
 Middle Chazy fossils and dip to the east. 
 
 A mile to the south of these rocks is an assemblage of dove- 
 colored limestones, with buff-gray layers which now frequently 
 appear as patches among their associated dove-colored beds. 
 These rocks are not like the Chazy beds just north of them ; but 
 are somewhat like the calcareous rocks lying north of Buck 
 Mt. and very much like other rocks found on meridians farther 
 east, more or less intermingled at the present surface with Lower 
 Cambrian rocks and which are very abundant over large areas in 
 the townships of Weybridge and Middlebury. In northwestern 
 New Haven these beds are usually much disturbed, but at some 
 places may be seen to have easterly dip. In their various litho- 
 logical features these rocks are not easily correlated with any of 
 the members of lake series proper; fossils are absent or obscure 
 and their age has been much of a puzzle to all students of the 
 region. 
 
 A few rods north of the junction of the road from Addison 
 village to New Haven Junction, and the one from Vergennes to 
 Weybridge passing west of Buck Mt., members of this forma- 
 tion of dove and gray rocks rest on crushed and .sheared, bluish- 
 black, shaly limestone that has strong resemblance to the Trenton. 
 The contact may be plainly seen on the eastern side of the Ver- 
 gennes road. It seems to be a thrust contact. About a half mile 
 to the west on the north side of the Addison road are graptolite 
 shales with members of the dove and gray series forming the 
 surface above the shales which are exposed in a cut in the bank 
 of the road. East of the dove and gray beds is red quartzite 
 which extends south from Buck Mt. Farther to the east and 
 southward the hard rock passes under clay or drift. 
 
 About a mile and a half east of Otter Creek and the out- 
 crops just described is a low ridge formed by the interbedded 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 247 
 
 rocks of the Cambrian, which are the direct southward extension 
 of the similar rocks in the southeastern part of Waltham and 
 which still hold to a gentle easterly dip. Traced southward these 
 interbedded rocks pass under drift for a short distance. Then 
 along the same meridian are scattered outcrops of gray, siliceous 
 dolomite which continue to within a mile and a half of Wey- 
 bridge village. 
 
 Northeast and east of Weybridge village, to the west of and 
 along the railroad track, are numerous exposures of the dove- 
 colored rock and its bufif-gray associate. In their outcrops about 
 a mile southwest of Spring Grove Camp Ground, these rocks fre- 
 quently stand on end and show evidence of extreme compression. 
 Similar rocks occur southwest of New Haven Junction, where 
 they show the same evidence of compression and are strongly 
 sheared. 
 
 East of the Rutland R. R. track at numerous places, over a 
 strip about a mile and a half wide extending from the northern 
 to the southern boundary of the township, are exposures of more 
 or less striped or marbly limestone. Two miles north- northeast 
 of New Haven Junction, near the Ferrisburg line, outcrops of 
 gray, siliceous dolomite or interbedded dolomite and quartzite at 
 places roughly alternate across the strike with outcrops of striped 
 blue or marbly limestone. The structural relations are very 
 obscure, but at places there seems to be suggestion that the marble 
 lies on the dolomite and at others that the interbedded rocks have 
 been thrust over the marble. 
 
 The surface of the hill just east of the quarry of the "Green 
 Mountain Lime Works," gives massive, striped bluish and gray 
 rocks interbedded with some siliceous layers and others that 
 weather to a grayish-buff. The gray rock carries obscure coils, 
 but a careful scrutiny of weathered surfaces did not give anything 
 definite. In the quarry of the lime works the rock is generally 
 more or less massive and crystalline and is practically a marble. 
 Planes of stratification are visible, but the beds are much de- 
 formed and dip and twist in various directions. In the fields 
 near the quarry, in what appear to be surface exposures of rocks 
 like those in the quarry, are rocks quite similar to those just de- 
 scribed for the hill east of the quarry. 
 
 Northward across the road from the quarry, white, marbly 
 limestone is intermingled with gray dolomite. Still farther north, 
 along the so-called "Plank road" in the southwestern corner of 
 Ferrisburg, white, marbly limestone lies south of the road, just 
 west of a mass of gray, siliceous dolomite showing bedding well 
 marked, and on the north side of the road, on the same meridian 
 with the marble, is a low ridge composed of interbedded quartzite 
 and dolomite, at this place largely quartzite, showing a gentle 
 anticlinal buckle pitching gently to the north. A fourth of a mile 
 to the west is gray dolomite dipping at a low angle to the east ; 
 
248 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 and about the same distance to the east is gray dolomite again, 
 which northward along the same meridian gives place to inter- 
 bedded rocks lying nearly flat. 
 
 The field relations in the absence of definite contacts do not 
 permit positive statement of structure ; but at the time of inspec- 
 tion it appeared that the primary relation was that of marble 
 resting on Cambrian rocks and that the latter had been thrust 
 against and sometimes over the former. It will appear from 
 later discussions that the primary relation of the marble probably 
 was that just indicated and that in several cases the rocks, whether 
 massive dolomite or interbedded dolomite and quartzite on which 
 the marble lay, were broken and thrust over the marble. 
 
 Eastward towards Bristol, along the "Plank road," in the ex- 
 treme southwestern corner of Monkton, but practically on the 
 New Haven line, are ledges of massive dolomite forming the low, 
 southern portion of Monkton ridge. Southward these rocks dis- 
 appear beneath Cedar Swamp ; but south of the swamp, on the 
 same meridian, and just south of the Bristol R. R. track, begins a 
 ridge of the interbedded series. Near the crossing of the New 
 Haven-Bristol road and the railroad track are beds of red quartz- 
 ite which dip gently to the west. Slightly to the southeast is a 
 distinct scarp on the western side of a considerable hill of inter- 
 bedded dolomites and quartzites. Two-thirds of a mile east, 
 across a low area, is another hill or ridge of the interbedded rocks, 
 which on the western side are terribly jammed and puddled. 
 Eastward the beds undulate and stand at various angles of dip, 
 but at the summit of the eastern slope they may be seen to dip 
 gently to the west. The eastern slope of the hill from these beds 
 down to the road that runs from New Haven Mills northward 
 towards Monkton is drift covered ; but southward, northeast of 
 New Haven Mills, is whitish, granular quartzite apparently 
 overlain by gray dolomite. The quartzite outcrops on both sides 
 of the dolomite and dips to the east; the dolomite is sheared so 
 that its bedding is obscured ; but at places it seems to be standing 
 on end. 
 
 South-southwest of New Haven Mills, south of the river, on 
 the meridian of the quartzites and dolomites north-northwest of 
 the village, is another ridge of the interbedded rocks. On the 
 west of this ridge the rocks dip westerly, but on the eastern slope 
 they form the distorted, pushed-up eastern limb of an anticlinal 
 fold. The effects of compression at this place beggar descrip- 
 tion. The often somewhat massive quartzite beds are jammed 
 into Z-shaped folds and strongly sheared withal and wave back 
 and forth along the strike. The structure is identical with that 
 shown by similar rocks east of Brandon, as elsewhere described, 
 except that the jamming is more severe. The interbedded rocks 
 may be followed along this ridge southward to the Middlebury 
 line and have anticlinal structure throughout. Near the southern 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 249 
 
 boundary of the township these rocks are only a mile from the 
 quartzite scarp along the edge of the plateau, from which they 
 are separated by the ledges of massive, gray dolomite forming 
 the hill known as the "Cobble." 
 
 North of New Haven Mills, partly in Bristol, are several 
 low, detached hills of gray dolomite, some of which show scarps 
 on the west. Sheared, gray, siliceous dolomite forms the bed and 
 banks of the river at New Haven Mills. 
 
 The interbedded rocks forming the hill with the prominent 
 scarp southeast of New Haven village join at the surface with 
 similar rocks along the road that runs directly south from the 
 village along which they outcrop through a distance of two miles. 
 One-half mile west of the road and about a mile south-southwest 
 of New Haven village are outcrops of bluish-white marble, 
 flanked on the west by striped bluish limestone with spots of 
 Tnarbly rock, all dipping easterly and all marked by strong flow- 
 shearing. The striped rock has much superficial resemblance 
 to some Middle Chazy of the lake series. No fossils have sur- 
 vived the severe deformation of the rock. About a half mile 
 west of these outcrops are others of similar rock on the east side 
 of the road from Spring Grove Camp Ground to New Haven 
 village, and south of the latter are still other outcrops of bluish 
 limestone somewhat involved with bui¥-weathering layers. 
 
 Two miles southeast of Spring Grove Camp Ground, in the 
 angle of the roads, are outcrops of bluish and marbly Hmestone 
 intermingled with fragmentary patches of the interbedded series. 
 Since these rocks lie on the meridians of the interbedded rocks 
 farther north it seemed likely that the marble had actually been 
 overridden by the Lower Cambrian rocks. The relations again 
 are similar to those among the interbedded rocks and the marble 
 around Brandon. 
 
 On the meridian of the rocks described in the last paragraph, 
 south of New Haven River and west of Muddy Brook, is a ridge 
 which extends southward into Middlebury township. Great con- 
 fusion prevails among the surface rocks along this ridge. At its 
 northern end, which is the portion included in New Haven, on the 
 east slope, gray dolomite is intermingled with striped blue lime- 
 stone. Westward over the summit the striped blue limestone is 
 intermingled with patches of interbedded dolomites and quartzites, 
 the latter often forming exposures of considerable size, with well- 
 defined bedding and dip. In some places the members of the in- 
 terbedded series lie flat, in others they dip to the west and in others 
 the structure may not be made out. A survey of the hill showed 
 that quartzites and dolomites are often involved with the lime- 
 stone in such a way as to give the appearance of being inter- 
 stratified. The surface is greatly broken by gullies and knolls 
 of various dimensions. In some places the striped blue rock 
 
250 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 shows in massive ledges ; in others the rock is apparently all gray, 
 siliceous dolomite. 
 
 The secondary structural features are very complicated ; but 
 the general field relations seemed to point to involved thrust rela- 
 tions like those which have been described for the region around 
 Brandon. Similar conditions will be described for Middlebury 
 in subsequent pages. 
 
 No fossils were found although it seemed as though they 
 should be and diligent search was made. 
 
 East of this ridge, near Muddy Brook and on the township 
 line, is a marble quarry, known as "marble ledge." Marble also 
 outcrops to the north of. the quarry, just south of New Haven 
 River. Gray dolomite forms the eastern wall of the quarry and 
 marks the surface along which the marble has been quarried. 
 Again, the conditions are precisely like those in some of the quar- 
 ries around Brandon. 
 
 Wing was reported by Dana^ to have found an Orthoceras, 
 resembling O. primigeniunt Hall (a Calciferous form), in rocks, 
 a little way south of the quarry, east of the brook, in Middlebury. 
 On the basis of this fossil the rocks were assigned to the Beek- 
 mantown by Dana and later by Seely. In fact all the various 
 rocks that have just been described for the southwestern part of 
 New Haven were called Beekmantown by Seely. A great deal 
 of the marbly and striped limestone in the writer's opinion has 
 more lithological resemblance to the Chazy and it is certain that 
 Lower Cambrian dolomites and interbedded rocks are involved 
 with the marbly limestone. The writer tried to find the spot which 
 Wing, Dana and Seely visited, following carefully the directions 
 given by Dana (loc. cit.) but failed to note the outcrop. 
 
 Dana further mentions discovery by Wing of other fossils- 
 a half mile northwest of the Orthoceras locality, and apparently 
 on the eastern slope of the ridge west of Muddy Brook. At thi^ 
 locality "and apparently in the same formation with the last, there 
 are specimens resembling Ophileta compacta; there was also found 
 here a large Maclurea." 
 
 "About a mile southwest of the Middlebury quarry and thirty 
 or forty rods west of Mr. E. Kirby's residence, in an old orchard, 
 several distinct convoluted shells were seen on a dark, siliceous 
 Hmestone dipping west. The beds are probably Calciferous." 
 
 North and south of Beldens, in the fields east of Otter Creek 
 and in the bed of the river itself, are extensive exposures of 
 usually distinctly bedded gray and buff-weathering rocks which 
 are different from the striped blue and marbly limestones that lie 
 east of them. These rocks have also been called Beekmantown. 
 They extend southward into Middlebury, where they present in- 
 teresting field relations yet to be described. The age of the rocks 
 is doubtful ; they may be part of the Beekmantown, but in the 
 
 3 A. J. S., vol. XIII, 1877, p. 406. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 251 
 
 writer's opinion, Beekmantown has been employed in much too 
 inclusive a way for the more or less altered rocks over the east- 
 ern portion of the Champlain lowland. 
 
 Bristol Township, including parts of Lincoln Township. 
 
 (Middlebury topographic sheet.) 
 
 Location. Bristol borders New Haven on the east. Lincoln 
 lies east and southeast of Bristol. 
 
 General description. The southern portion of Monkton ridge 
 extends into the northwestern portion of Bristol. Most of the 
 portion of the ridge included in Bristol is made of quartzite, but 
 massive, gray dolomite occurs at the southern end near the New 
 Haven line. South of this dolomite is Cedar Swamp, from which 
 at the south emerge the interbedded quartzites and dolomites of 
 the eastern part of New Haven. 
 
 A surface section southward from Monkton ridge into New 
 Haven thus gives with interruptions a succession from quartzite 
 through gray, massive dolomite to interbedded quartzites and 
 dolomites and suggests that this is the usual stratigraphic sequence. 
 
 The valley occupied by Pond Brook in Monkton extends 
 southward into Bristol, but its basin character gradually fades 
 southward towards Bristol village owing to the falling oft* in 
 elevation of the southern portion of Monkton ridge. 
 
 Bowlder drift topped by sand plains largely conceals the hard 
 rock around Bristol village west of Hogback Mt. Gray, siliceous 
 dolomite, dipping westerly, outcrops northwest of the village and 
 southwest of it, west of "Bristol Flats," other dolomite marks 
 the northward extension of the rocks at and north of New Haven 
 Mills. 
 
 South of Bristol village, to the east of Bristol Flats and 
 just east of the road that runs along the eastern edge of the Flats, 
 the rock is largely a gray or brownish-gray, granular quartzite, 
 dipping easterly; but eastward at places near the foot of South 
 Mt. the quartzite dips westerly. Southward, gray dolomite form- 
 ing the northern end of "Cobble" hill, conceals the quartzite. 
 
 In the township of Bristol, west of Hogback and South Mt., 
 the underlying rock is thus seen to be quartzite with overlying 
 dolomite which form a shallow, synclinal fold, suggesting that 
 the valley of Pond Brook is primarily a syncline which has been 
 modified by faulting. 
 
 In Bristol, as in Monkton, the western face of Hogback shows 
 a succession of scarps along the strike. The rock along these 
 scarps, which were inspected at many places, is essentially a 
 quartzite which is usually strongly sheared and much like some 
 of the rock that has been described for the hilly land east of St. 
 Albans and Milton. In spite of shearing the bedding is visible 
 
252 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 and dips to the east. The easterly dip is well shown on the 
 mountain at the ledge known locally as "Table Rock." 
 
 New Haven River enters the lowland through a gap between 
 Hogback and South Mt. Along this pass the quartzite may be 
 observed at many places dipping easterly and the southern end 
 of Hogback may clearly be seen to be bounded by a series of 
 scarps marking fault displacements across the strike. The river 
 has availed itself of these lines of weakness. 
 
 At Ackworth, ledges of quartzite are abundant. The dip is 
 easterly at a small angle and the rocks exhibit little or no internal 
 deformation. There is a slight northerly pitch. On the road 
 towards West Lincoln, about one-third of a mile east of Ack- 
 worth, the dip is westerly. 
 
 The valley of Beaver Brook and Baldwin Creek north of 
 Ackworth is the southward continuation of the valley of Lewis 
 Creek in Starksboro. It is primarily of synclinal structure, but 
 is modified by faulting. The eastern face of Hogback shows 
 scarps marking faults. A mile and a half north of Ackworth, 
 gray dolomite on the west side of the road dips westerly. 
 
 Quartzite continues north from Ackworth east of the Starks- 
 boro road. At the western end of the gorge of Baldwin Creek is 
 strongly sheared rock, much like that on the western side of Hog- 
 back. In the bed and banks of the stream a fourth of a mile 
 east is blackish phyllite which is probably a sheared muddy mem- 
 ber of the quartzite formation. Two-thirds of a mile farther 
 east, in the north bank of the gorge, are impure quartzitic and 
 calcareo-siliceous beds greatly sheared and crushed, which have 
 some resemblance to the interbedded series found in the lowland 
 to the west of the plateau. At South Starksboro the prevailing 
 rocks are impure, coarse schists which were interpreted as prob- 
 ably originally forming impure basal portions of the overlapping 
 Lower Cambrian series. 
 
 A mile southeast of South Starksboro, on the side of the 
 road near a school house, was seen a small exposure of inter- 
 bedded quartzite and calcareous rock. East of these beds in the 
 fields are others of quartzite lying nearly fiat. 
 
 The interbedded, impure quartzites and calcareous rocks west 
 and southeast of South Starksboro seem to resemble the inter- 
 bedded series of the lowland west of the plateau closely enough 
 to be regarded not as precise equivalents perhaps, but as related 
 members of a common formation. It would seem that in the 
 probess ofi overlap such rocks were carried eastward into what 
 is now the plateau, just as gray dolomite was also carried at some 
 places. 
 
 The quartzite exposed in the bed of New Haven River, south- 
 east of Ackworth. gives place southeast of West Lincoln to 
 gneissic rocks that are different from the sheared rocks that 
 seem more or less definitely to belong to a formation which 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 253 
 
 originally consisted of various kinds of sediments and which is 
 probably of Lower Cambrian age. Similar gneisses were noted 
 near the river at Lincoln Center and in South Lincoln and are 
 regarded as probably pre-Cambrian and as forming a part of 
 the floor of deposition of the quartzite-schist-dolomite formation. 
 
 Three and a half miles south of Bristol village the "little 
 notch road" leaves the lowland and climbs over the mountain to 
 South Lincoln. The western portion of the road cuts through 
 the southward extension of the quartzite of the western part of 
 South Mt. From places along the road, east of the front range 
 of hills, they may be seen to be bounded on the east by scarps, to 
 the east of which the surface is lower. The suggestion which the 
 topography gives of down-faulting on the east of the front range 
 is supported by the occurrence of considerable exposures of gray 
 dolomite along the road towards South Lincoln. The dolomite 
 is intermingled over large areas with micaceous, quartzitic schist, 
 which apparently weathers fairly easily, but it did not appear 
 from any outcrops which were noted that the schist is interbedded 
 with the dolomite. The gray dolomite is lithologically much like 
 that west of the plateau. In some of its outcrops it occurs in 
 undulating folds sheared across the bedding. This dolomite was 
 interpreted as the extension eastward into the plateau of the 
 dolomite that is found in what is now the lowland to the west of 
 it, and as part of the Lower Cambrian series. 
 
 Around South Lincoln in the beds of streams, foliated, 
 gneissic rocks not easily interpreted as sheared members of the 
 Cambrian formation were noted and at the time of their inspec- 
 tion seemed to be probably a portion of the pre-Cambrian forma- 
 tion of basal gneisses. No attempt was made to trace the quartz- 
 ite-dolomite-schist formation into the eastern part of Lincoln. 
 
 While some of the members of the formation, which is re- 
 garded as Lower Cambrian, in their occurrence in the mountains 
 are not very much deformed internally, others of them are and 
 in some places shearing or crushing is severe, and gneissoid or 
 schistose structure is common. The most severely sheared types 
 might be confused with other rocks and assigned a different age 
 and possibly to an older series, without careful discrimination; 
 but it seemed that any of the gneisses which could be interpreted 
 as probably older than Cambrian are sufficiently different from 
 sheared and altered younger rocks to be fairly easily distin- 
 guished, at least within the areas examined by the writer. Such 
 might not be the case farther east in the mountains. 
 
254 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Addison Township. 
 
 (Port Henry topographic sheet.) 
 
 Location. Addison township borders the lake and lies south 
 of Panton. It is bounded on the east by parts of Waltham and 
 Weybridge and on the south by Bridport. 
 
 General description. Like Panton, a large part of the west- 
 ern portion and most of the central portions are covered with 
 clay. Outcrops are, therefore, practically confined to the lake 
 shore and the somewhat hilly eastern part. 
 
 From the Bridport line northward along shore as far as 
 Chimney Point is clay. At Chimney Point are beautifully glaci- 
 ated ledges of Chazy with the beds dipping at a low angle to the 
 west. Similar beds with about the same dip occur to the north- 
 east, on the north bank of Hospital Creek. 
 
 North of Hospital Creek, to the west of the Chazy outcrops, 
 on the lake shore, are thinly-bedded limestones, weathering gray 
 but bluish on fresh surfaces, clearly derived from limy muds, 
 and full of characteristic basal Trenton fossils. The beds also 
 dip westerly and at an angle about like that of the neighboring 
 Chazy rocks at the east. They have apparently a slight northerly 
 pitch. 
 
 These Trenton rocks are succeeded along shore northward 
 by more or less regularly interbedded, blackish limestone and 
 shale. The limestone members contain Trenton fossils, including 
 Prasopora, and the series plainly marks a transition from the 
 "basal" Trenton beds into rocks that are more notably shaly and 
 which continue along shore to Potash Bay. The dip throughout 
 is gently to the west. Graptolites were found at numerous places 
 in the shales, but Triarthrus hecki, so common in the shales in 
 the northern part of the lake region, was not seen. The shore 
 section from Crane Point to Potash Bay is about three miles long. 
 The dip is so gentle that the rocks lie almost fiat. They seem to 
 be broken hardly any, if at all, by displacements and as a whole 
 give a considerable thickness of apparently conformable beds 
 ranging from the base of the Trenton well up into the shale 
 formation. 
 
 East of the shore section the hard rocks are usually beneath 
 clay ; some apparently Trenton rocks outcrop along the road north 
 of Hospital Creek. 
 
 In general the rocks along shore in Addison appear to form 
 the western limb of a gentle anticlinal fold. The apparent struc- 
 ture permits the interpretation that the basin of the lake west of 
 Addison was excavated in shales that conformably overlay the 
 rocks that lie along shore and that similar shales extend eastward 
 beneath the clay. In other words, along the Addison shore there 
 is little or no suggestion of overthrust of older rocks on the shales 
 such as is seen in many other places along or near the lake. If 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 255 
 
 the rocks around Chimney and Crane Points constitute a con- 
 formable series, Black River beds should intervene between the 
 Chazy and Trenton, by analogy with conditions at other places in 
 western Vermont. There are some outcrops on the road north 
 of Hospital Creek which indeed suggest the Black River, but if 
 these rocks are generally present they are for the most part con- 
 cealed. 
 
 The eastern boundary of Addison zigzags through the mass 
 of Snake Mt. which lies partly in this township and partly in 
 Weyb ridge. North of Snake Mt. the eastern boundary follows 
 Otter Creek to the Panton line. 
 
 The higher portions of the mountain are in Addison. The 
 rock is chiefly red quartzite, like that of Buck Mt. The surface 
 of the mountain falls off abruptly northward and gives place to 
 a clay-covered lowland. The western face of the mountain is 
 marked by scarps, against which at places rest banks of glacial 
 drift. 
 
 Along and near the road that runs just west of the moun- 
 tain are outcrops of limestone which may now be described. 
 
 From Addison village a road runs eastward to Weybridge, 
 passing north of Snake Mt. About a mile east of the village 
 another road runs southward just west of the mountain. East 
 of this road on the northwestern slope of the mountain are beds 
 of shaly limestone lying nearly flat but which have perceptible 
 easterly dip and are rather conspicuously sheared. These out- 
 crops yielded a few Trenton fossils. Perhaps 150 rods farther 
 south, along the roadside, are ledges of Chazy limestone also 
 dipping easterly and carrying characteristic fossils. The Chazy 
 continues southward for a fourth of a mile and is flanked on 
 the east by Black River beds. A mile to the south on the same 
 meridian with these rocks are shaly limestones which outcrop in- 
 termittently along the road to the Bridport line. 
 
 To the west of the road just followed is another parallel 
 with it which runs through Addison village. Sheared limestone 
 carrying Trenton fossils and dipping easterly outcrops one-half 
 mile north of the Bridport line and a mile farther north are 
 ledges of Chazy with easterly dip. 
 
 The calcareous rocks lying west of Snake Mt. apparently 
 form a monoclinal series dipping easterly, with the Chazy at 
 the base overlain by Black River and sheared Trenton limestone. 
 While the outcrops are scattered, the field relations among them 
 permit the interpretation just given and also the inference that 
 the beds are mainly conformable, although possibly displaced 
 somewhat with reference to each other. About six miles to the 
 west the same series dips in the opposite direction. It is not 
 easy to imagine that the rocks along the lake shore and those 
 west of Snake Mt. form the limbs of a common anticlinal arch, 
 for the dip is so low that in the wide interval between them there 
 
256 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 seemingly should occur other outcrops of the heavier members, 
 which does not seem to be the case. If there were several folds 
 over the interval that now separates these rocks there should be 
 intermediate ridges which do not occur. 
 
 Although along meridians, now occupied at the surface in 
 Addison by clay, Chazy rocks are exposed in Panton, this cir- 
 cumstance does not seem to justify the- inference that the clay in 
 Addison is directly underlain by Chazy limestone; for in Shore- 
 ham to the south these meridians show the shales as the surface 
 rock. As will be shown beyond, it is probable that the clay 
 over central Addison and Bridport is underlain by shales, and that 
 the older limestones are deeper down. The key to the structural 
 relations among the various rocks in Addison seems likely to be 
 found in the major kind of deformation which the region has 
 suffered. Snake Mt. is primarily an unlift of the older rocks 
 which have also been thrust to the west. The limestones west 
 of the mountain have probably suffered similar deformation. 
 The quartzite of Snake Mt. in Addison and the calcareous rocks 
 west of it are on meridians occupied by probable Beekmantown 
 farther north in Panton. 
 
 Weybridge Township. 
 
 (Port Henry and Middlebury topographic sheets.) 
 
 Location. Weybridge is bordered on the west by parts of 
 Addison and Bridport, on the north by parts of Addison and New 
 Haven, on the east by parts of New Haven and Middlebury, and 
 on the south by Cornwall. 
 
 General description. The eastern slope of Snake Mt. de- 
 scends into the western part of Weybridge. All the outcrops in- 
 spected west of the Lemon Fair are of Red Sandrock, which dips 
 to the east. 
 
 Clay forms the surface over much of the valley of the Fair, 
 and that of the Otter west of Weybridge village. 
 
 East of the Fair, at varying distances from it, the surface 
 rises to form Weybridge Hill, which is a ridge of much the same 
 pattern as that of Snake Mt., but of lower elevation. On the 
 west of the ridge are steep slopes and numerous softened scarps 
 from whose summits there extends eastward an irregular surface 
 which in general descends to the bed of Otter Creek. 
 
 Near the Cornwall line the steep western margin of the 
 ridge forms what is known as "The Ledge." It is marked by a 
 scarp which extends southward into Cornwall. At "The Ledge" 
 the rock is massive, gray limestone without well-defined structure 
 or dip. It yielded no fossils. The same rock continues north- 
 ward to within a half mile of Center, a small settlement two miles 
 south of Wevbridge village. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 257 
 
 Southwest of Center, along a road that descends diagonally 
 across the steep western slope, is black phyllite forming a distinct 
 s-carp, to the west and east of which lie calcareous rocks much 
 like those of "The Ledge." The phyllite forms the northern 
 termination of what was designated in the Vermont report and 
 by later observers as the "central belt of slate," and has been 
 regarded as of "Utica" or "Hudson River" age. In the writer's 
 opinion, the rock has little resemblance to the so-called "Utica" of 
 the lake region proper and does not suggest an altered derivative 
 of that formation. On the contrary it is entirely similar to phyl- 
 lite occurring in Cornwall at the south, which will be described 
 beyond, and which seems clearly to be the northward extension 
 of the phyllites of Whiting and Sudbury, which are regarded as 
 much older. The field relations southwest of Center might pos- 
 sibly suggest that the phyllite is interstratified with the limestone 
 that borders it on the west and east; but such relation is hardly 
 possible if the phyllite is what the writer conceives it to be. The 
 general relations point to displacements and it seems most likely 
 that the phyllite was thrust into the limestone. 
 
 North of Center towards Weybridge, east of the road, is 
 strongly sheared, calcareous rock of quite uncertain correlation 
 which lies to the west of numerous outcrops of somewhat marbly, 
 dove-gray limestone associated with chamois-gray patches which 
 are badly crumpled and mixed up. 
 
 Farther north, south of Weybridge village, what now appears 
 as massive, gray, dolomitic limestone forms scarps east of the 
 road to Center. The rock has been under compression but is 
 not conspicuously sheared. No fossils were found. In lithology 
 it resembles somewhat the rock at "The Ledge" near the Corn- 
 wall line and to some extent also the gray rock that is found at 
 the east in association with the quartzite. Similar rock forms 
 the falls and banks of the river at Weybridge village. The gray 
 dolomite at Weybridge village is on the meridians of that which 
 occurs two miles north of the village in New Haven and the 
 latter, as previously shown, with slight surface interruption joins 
 the interbedded dolomites and quartzites southeast of Buck Mt. 
 
 According to Dana, Wing found at Weybridge upper falls, 
 on the west side of the slate, presumably the northward continua- 
 tion of the phyllite found farther south, "Rhynchonella beds" 
 (called Chazy) lying beneath "Sparry limestone" (Trenton). 
 The "striped stratum" (Chazy) was described as full of fossils. 
 This locality was not seen by the writer, but became known to 
 him from subsequent reading of Mr. Wing's discoveries in Ver- 
 mont. 
 
 Southeast of Center, on the road towards Middlebury and 
 in adjacent fields, are ledges of striped limestone which suggest 
 the Chazy. Farther south towards Middlebury along the road, and 
 over the part of the township lying east and southeast of Center 
 
258 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 and west of Otter Creek, are abundant ledges of sheared, dark 
 bluish limestone resembling Trenton. These rocks apparently 
 occupy a broad band in eastern Weybridge, west of Otter Creek. 
 Fossils were not found in Weybridge. Later, on a trip made 
 over territory- southwest of Middlebury village in northeastern 
 Cornwall, Trenton fossils were found in similar sheared, dark 
 bluish limestones which lie on meridians practically marking the 
 western boundary of the similar rocks in Weybridge. 
 
 The Otter which flows north from Middlebury village forms 
 part of the eastern boundary of Weybridge and separates it from 
 Middlebury. On the Middlebury side the sheared, bluish, so- 
 called Trenton rocks give place to marbly, dull gray rocks with 
 associated yellowish or chamois-gray layers which form a broad 
 band in this part of Middlebury township and join at the north 
 with similar rocks in the southwestern part of New Haven, which 
 have been described. 
 
 From west to east across Weybridge the rocks, broadly speak- 
 ing, are not disposed in folds, but in an irregular sequence prob- 
 ably due to reverse fault displacements along the strike, with 
 probably some imbrication due to lateral thrust. The latter is 
 not clearly exhibited by a definite contact in Weybridge, but in 
 Middlebury village below the falls a good overthrust contact may 
 be seen, as will be later described. 
 
 Middlebury Township. 
 
 (Middlebury and Brandon topographic sheets.) 
 
 Location. On the west Middlebury is separated from Wey- 
 bridge by a portion of Otter Creek, and is further bounded by 
 a part of Cornwall. On the north it is bounded by New Haven 
 and a part of Bristol, on the east by Ripton, and on the south by 
 Salisbury. The eastern portion of the township includes a strip 
 along the western border of the Green Mountain plateau. 
 
 General description. The gray limestones and interbedded, 
 buff- or chamois-weathering layers which lie just east of the 
 Otter, north of Middlebury village, have already been mentioned. 
 They give prominent exposures on both sides of the railroad track 
 south of Beldens, and between the track and the river southward 
 towards Middlebury village. In the village below the falls they 
 are in juxtaposition with strongly sheared, limy shales and at 
 one place show a good thrust contact, with the shale which has 
 been pictured by Seely. Seely called the shale Trenton and the 
 overthrust rock Beekmantown. 
 
 South of the latitude of Beldens these rocks continue eastward 
 at the surface to the road running from Middlebury village to 
 New Haven Junction. Southward, west of Chipman Hill and 
 east of the railroad track, they largely pass under drift. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 259 
 
 North of Chipman Hill a cross road leaves the main road 
 Tjetween New Haven and Middlebury and runs one-third of a 
 mile due east and then bends southeastward. South of this road 
 at the northern end of Chipman Hill is sheared limestone which 
 corresponds closely with rock in Ferrisburg to the northeast of 
 the city of Vergennes and which near Vergennes by the fossils 
 in several places and by the lithology in others, was correlated 
 with the Chazy. East of the cross road, after it makes it bend 
 to the southeast, is altered, now somewhat crystalline limestone, 
 weathering to a light blue, which suggests the Trenton. It is 
 apparently without fossils at this place. This rock is on the 
 western margin of a ridge which extends from New Haven into 
 Middlebury, the rocks of which at its northern end in New Haven 
 have been described (page 249). In the Middlebury portion 
 of the ridge, west of the road that runs lengthwise along it, is 
 much the same assemblage of rocks found at the northern end. 
 Rocks identified as members of the interbedded series of dolomites 
 and quartzites are more or less intermingled with outcrops of 
 striped or gray limestone and some gray dolomite. East of the 
 road are abundant exposures of gray limestones associated with 
 somewhat yellowish-weathering rocks. These sometimes give 
 place to striped limestone which resembles the Chazy. 
 
 Eastward is Muddy Brook, west of which was seen quartzite 
 associated with some dolomite. These rocks lie on a meridian 
 west of the marble at "marble ledge" quarry near the New 
 Haven line. At the quarry the marble is associated with gray 
 dolomite which forms the eastern wall of the quarry. 
 
 East of Chipman Hill is a topographic break in the ridge 
 mentioned above. South of this break, a little north of east of 
 Middlebury village, is a hill of camel-hump shape which is 
 geologically a southward continuation of the ridge. This hill 
 presents relations of much interest. On the top of the hill are 
 interbedded quartzites and dirty, somewhat yellowish-weathering 
 dolomites, dipping westerly and not strongly sheared or folded, 
 which apparently lie on bluish-gray or dull gray limestone which 
 seems to be more deformed and altered. This hill seemed to 
 show the interbedded rocks of probably Lower Cambrian age 
 resting on probably younger (Chazy) limestone. 
 
 South of this hill a road runs from Middlebury village east- 
 ward towards the mountain. The road forks about a mile east 
 ■of the village, and near the fork gray dolomite is seen to form a 
 fold or "roll" very much like the structure seen at the old quarry 
 southeast of Leicester Junction and at the Norcross quarry south 
 of Dorset Mt. One-half mile east of the fork, on the north 
 side of the road running east, is the quarry of the Middlebury 
 Marble Co., now worked for lime. The marble is not a very 
 good commercial stone, but in all essential particulars is like the 
 marble in the quarries around Brandon. The marble continues 
 
260 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 eastward for a short distance at the surface and then gives place 
 to gray, siHceous dolomite and interbedded quartzite and dolomite, 
 the latter dipping easterly at a high angle. The dolomite and 
 interbedded rocks lie along meridians occupied both to the north 
 and south by similar rocks. Eastward is other gray dolomite 
 and then the scarps in the quartzite along the edge of the plateau. 
 
 About two miles south-southwest of Middlebury village are 
 ledges of dove-gray or bluish rock which were regarded as prob- 
 ably of Chazy age. The noteworthy structure is the strong 
 shearing. The dip is obscure ; in some places it seemed to be to 
 the west ; in other places the beds appeared to stand on end. 
 These outcrops are a mile east-northeast of other ledges in east- 
 ern Cornwall which carry Trenton fossils, including Prasopora. 
 
 Two miles directly east of the rocks called Chazy, which were 
 just mentioned, and south of the road from Middlebury village 
 to East Middlebury, are two short ridges composed chiefly of 
 dove-gray or bluish limestone carrying patches of yellowish-gray 
 rock. Similar rocks occur one and a half miles to the southwest, 
 just west of Otter Creek on the road from Farmingdale to 
 Cornwall. 
 
 At Farmingdale are outcrops of gray, siliceous dolomite like 
 that usually associated with the quartzite along the eastern border 
 of the lowland. This gray dolomite is intermingled with some 
 marbly limestone along the road running from Farmingdale east- 
 ward to within a fourth of a mile of the main road from Salis- 
 bury to Middlebury. West of East Middlebury village, near the 
 junction of the main roads, are interbedded dolomites and quartz- 
 ites forming a gentle anticline, the beds dipping westerly south 
 of the road from East Middlebury to Middlebury on one meri- 
 dian and easterly to the north of the roads on a meridian slightly 
 to the east of the other. 
 
 Along the road from East Middlebury to Bristol, a mile 
 northwest of East Middlebury village', is massive quartzite over- 
 lain by dolomite, the latter clearly dipping westerly. 
 
 In the bed of the river east of East Middlebury village, beds 
 of quartzite dip westerly. 
 
 South of East Middlebury is a hill composed of granular, 
 gray quartzite which is a dismembered part of the rock of the 
 plateau. 
 
 The geological relations and topographic features in the east- 
 ern part of Middlebury township are very similar to those found 
 at many places along the eastern edge of the lowland and in the 
 Vermont valley. They are in all cases apparently of similar 
 genesis. The rocks in the eastern part of the lowland are dis- 
 membered parts of the formations of the plateau. 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 261 
 
 Bridport Township. 
 
 (Port Henry and Ticonderoga topographic sheets.) 
 
 Location. Bridport borders the lake and Hes south of Addi- 
 son. It is bounded on the east by parts of Weybridge and Corn- 
 wall and on the south by Shoreham. 
 
 General description. Away from the lake shore in the west- 
 ern part and over the central portions of Bridport, clay usually 
 conceals the hard rock. Outcrops of shale yielding broken grap- 
 tolites outcrop intermittently along shore from a point near the 
 northern township line southward past Plumies Point to a con- 
 spicuous jog in the shore line about one and a half miles north of 
 Crown Point ferry landing. 
 
 Near the landing at West Bridport are what appear to be 
 Chazy and Black River beds. 
 
 Seely mentioned some exposures of so-called Beekmantown 
 rocks near the head of the West Branch of Dead Creek ; but on 
 his map showed such rocks at the head of the East Branch. The 
 writer did not see these rocks, but found flat, clay-covered land 
 around the head of the West Branch. Southward in .Shoreham, 
 shales outcrop on meridians occupied by the We'st Branch in 
 Bridport. 
 
 Shales outcrop north and south of Bridport village and at 
 places along the road which runs east from the main Bridport- 
 Addison road just north of the village. Along the second road 
 running east, north of the village, about two miles east of the 
 Addison road, and on the meridians of the Red Sandrock to the 
 north in Addison, are blackish shales which sometimes are strong- 
 ly folded and sometimes lie rather flat, all marked by well-de- 
 veloped cleavage. Southwestward these rocks give place at the 
 surface to sheared, shaly limestone and these in turn to some- 
 what m3.ssive, plainly bedded limestone, which is not severely 
 deformed internally and which has much the aspect of other rock 
 a mile to the southwest which is clearly older than the shale. The 
 shale is a mile slightly to the west of south of the southward ex- 
 tension of the Red Sandrock of Weybridge into the northeastern 
 part of Bridport. 
 
 South of Bridport village a road runs easterly, to the north 
 of Hemenway Hill. Along this road and south of it in the field 
 are blackish cleaved shales, which a mile east of the main Brid- 
 port-Shoreham road are succeeded along the road by thinly- 
 bedded, blue limestone with good Trenton fossils. East of these 
 Trenton beds a road runs southerly on the east side of Hemenway 
 Hill. West of this road and just south of the fossiliferous Tren- 
 ton outcrops are ledges of rock which nn its lithology suggests 
 part of the Beekmantown in Shoreham. Farther south on the 
 east slope of the hill are outcrops of rock of more decfded re- 
 semblance to some of the Beekmantown. The beds dip to the 
 
262 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 east and are on meridians occupied by beds correlated with the 
 Beekmantown at Mutton Hill in Shoreham. 
 
 The rocks outcropping on the east slope of Hemenway Hill 
 are separated by the flat land along the Lemon Fair River from 
 rocks forming a low ridge in western Cornwall and which appear 
 to be the northern continuation of the rocks of Cutting and Delano 
 Hills in Shoreham. which are considered to be of Beekmantown 
 age, as defined by Brainerd and Seely. 
 
 The conditions in the eastern part of Bridport certainly 
 strongly suggest upthrust of older rocks into younger ones, with 
 some overlap of the former. The older rocks are in some cases 
 members of the Red Sandrock series and in others probably of 
 the Beekmantown. Probably Chazy and Trenton beds have in 
 some cases been involved in thrust. 
 
 Cornwall Township. 
 
 (Port Henry, Ticonderoga, Middlebury and Brandon topographic 
 
 sheets.) 
 
 Location. Cornwall on the west adjoins the southeastern 
 part of Bridport and the northeastern part of Shoreham. It is 
 bounded on the north by Weybridge, on the east by parts of Mid- 
 dlebury and Salisbury, and on the south by Whiting. 
 
 General description. The red quartzite of the Red Sandrock 
 series of the Snake Mt. mass projects from Bridport and Wey- 
 bridge into the northwestern part of the township. 
 
 On the meridians of this quartzite, farther south along the 
 western border of the township, is a ridge falling off on the west 
 into the flat land along the Lemon Fair in southeastern Bridport, 
 and sloping more gradually eastward into more or less drift- 
 covered land. The rock in the ridge has been called Beekman- 
 town and certainly has resemblance to part of that formation as 
 described for Shoreham. The dip is apparently generally if not 
 always to the east. 
 
 East of Beaver Branch rises another ridge of somewhat 
 similar pattern which is the southward extension from Weybridge 
 into Cornwall of the ridge already described for its northern por- 
 tion in Weybridge. Its western margin begins at the north in a 
 precipitous scarp known as "The Ledge." The scarp continues 
 southward for a distance of two miles and merges with a more 
 gentle slope northwest of CQrnwall village. The beds dip east- 
 erly. The rock may be largely Beekmantown, but about a half 
 mile northwest of Cornwall village are beds of dove-gray rock 
 also dipping easterly and apparently stratigraphically above the 
 rocks to the northwest of them. These beds may be Chazy. 
 
 Outcrops of Chazy limestone, which in some places show 
 fossils, occur south of the village along the road towards Whiting. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 263 
 
 These rocks are succeeded southward by exposures of sheared 
 limestone of uncertain correlation. 
 
 The main road going north from Cornwall village forks 
 about a mile and a half north of the village. Along the west 
 branch, near the fork of the road, is black phyllite. Just east of 
 this rock are ledges of sheared limestone which gave good Tren- 
 ton fossils, as previously described (page 258). The Trenton 
 rocks continue southward to the east of the road through Corn- 
 wall village and are intermingled with black phyllite or schist 
 carrying some massive quartzite. 
 
 One-third of a mile north of the village a road runs easterly 
 towards Farmingdale in Middlebury. Two-thirds of a mile east 
 of the main road are ledges of quartzite with associated black 
 phyllite which are succeeded easterly by ledges of limestone re- 
 sembling the Trenton. Fossils were not found. Eastward are 
 beds of sheared rock resembling the Chazy. These presumably 
 Chazy beds form a short, low ridge along the western border of 
 the northern end of Cedar Swamp ; the beds dip easterly and carry 
 obscure fossils. 
 
 Near the Whiting line a road runs easterly from the main 
 Whiting-Cornwall road towards Salisbury station. Black phyl- 
 lite outcrops along this road and in the fields north of it, to the 
 west of Cedar Swamp. Observations showed that the black 
 phyllite or schist is frequent north of this road, between the 
 swamp and the Whiting-Cornwall road. It is associated with 
 sheared limestone of uncertain correlation. 
 
 Black phyllite was also found along the road running west 
 from Middlebury village, about two and a half miles west of the 
 village and a mile south of the Weybridge line. This phyllite 
 joins that of Cornwall with that of Weybridge. 
 
 The relations northeast, east and southeast of Cornwall 
 village are strikingly similar to those found at the northern end 
 of the Taconic range in Sudbury, except that in Cornwall there 
 is less quartzite exposed and more phyllite mingled with the cal- 
 careous rocks than is the case' in Sudbury, and that the calcareous 
 rocks carry obscure fossils in Cornwall and in other respects seem 
 to be more easily recognized. The phyllites of Cornwall join 
 through the similar rocks of Whiting with the quartzites and 
 schists of Sudbury. 
 
 In the early descriptions of the black and lighter colored 
 phyllites and the quartzites which extend north from Sudbury 
 through Whiting and Cornwall into Weybridge they were re- 
 garded as of "Utica" (Brainerd and Seely) or "Hudson River" 
 (Vermont Report, Wing and Dana) age. The principal reason 
 for such assignments seems to have been because they are asso- 
 ciated with rocks of Trenton age, which are intermingled with 
 them or border them. 
 
264 REPORT OF THE VERMONT' STATE GEOLOGIST. 
 
 The Vermont Report and Wing both recognized that the 
 "central belt of slate" in Weybridge, Cornwall and Whiting is the 
 northern continuation of the Taconic range; but apparently 
 neither considered the possibility that the rocks composing it may 
 be much older than they indicated. 
 
 It has already been remarked that the phyllite of Weybridge 
 bears little resemblance to the rocks near the lake. The quartzite 
 occurring with the phyllite in Cornwall and Whiting in such way 
 as to leave no doubt of the common membership of the two in 
 one formation seems to prohibit the inclusion of these rocks with 
 the Ordovician shale. On the other hand, the phyllite and quartz- 
 ite are so similar to rocks in the Taconic range and at some places 
 along the western margin of the plateau near Brandon that they 
 probably belong to the same formation and to one including the 
 granular quartzite, and are probably, therefore, of Lower Cam- 
 brian age. 
 
 There may also be said to be some doubt as to the inclusion 
 of all the gray, dolomitic limestone that occurs to the east of the 
 Red Sandrock of Snake Mt. in northern Cornwall, but particu- 
 larly in Weybridge, in the Lower Ordovician (Beekmantown). 
 On a lithological basis, which is often the only one that may be 
 employed, it would be hard to decide ; for some of the gray rock 
 is siliceous and has much the same appearance as the rock asso- 
 ciated with quartzite nearer the plateau. The matter is com- 
 plicated not only by undoubted deformations, but probably also 
 by unusual conditions of sedimentary overlap of Ordovician beds 
 on an eroded surface of Cambrian rocks which included siliceous 
 dolomite, as has been frequently shown. 
 
 Shoreham Township. 
 
 (Ticonderoga and Brandon topographic sheets.) 
 
 Location. Shoreham lies south of Bridport and is bordered 
 on the west by the lake, on the east by parts of Cornwall and 
 Whiting, and on the south by Orwell. 
 
 General description. In his first paper the writer briefly dis- 
 cussed certain features of the geology of this township, based 
 upon a personal review of the geological relations described by 
 Brainerd and Seely, and in connection with the geology of the 
 town of Orwell which adjoins Shoreham on the south. The east- 
 ern part of the township displays the type section of the so-called 
 Beekmantown of western Vermont. For a detailed description 
 of this section the reader is referred to Brainerd and Seely's 
 original account.^ 
 
 What underlies the flat land along the course of the Lemon 
 Fair River in southeastern Bridport may only be conjectured ; 
 but immediately east of this flat area in Cornwall and south of it 
 
 iBull. No. 3, Arner. Mus. Nat. Hist., 1890-91. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 265 
 
 in Shoreham are rocks which by comparison with those of the 
 East Shoreham section are apparently to be correlated with the 
 so-called Beekmantown. In the very northeastern part of the 
 township the Lemon Fair has trenched these rocks and low cliffs 
 appear in them on both sides of the stream. On the east side, 
 practically on the Cornwall line, and on the road running west 
 from West Cornwall village, a steep westerly dip was noted and 
 the beds are sheared across the bedding. From these ledges a 
 scarp runs southward along the western base of the hill and the 
 prevailing dip along it is apparently to the east. About two-thirds 
 of a mile south of the westerly-dipping beds some Chazy appears 
 to be present on the west side of the road. Southward along the 
 old "Amherst road" to Richville what appear to be Beekmantown 
 rocks may be followed by intermittent outcrops showing easterly 
 dip nearly to Richville. The rocks along this road are the north- 
 ern extension of those of Delano and Cutting Hills which are 
 included in Brainerd and Seely's Shoreham section of the 
 Beekmantown. 
 
 Observations show that the eastern half of Shoreham town- 
 ship is largely formed of Beekmantown which is associated with 
 some older rocks of so-called "Potsdam" age and younger beds 
 belonging to the Chazy and Trenton. Chazy and Trenton beds 
 border the Beekmantown on the east and are involved with it 
 just east of Shoreham village. As Brainerd and Seely clearly 
 showed, the massive rocks^ have been broken by thrust faults 
 along the general strike of the rocks at several places. By these 
 thrusts the older Beekmantown and underlying "Potsdam" have 
 been fractured so that older beds have moved into and over 
 younger rocks. Prior to or during thrusting, some folding oc- 
 curred ; but the major deformation was that of fracture accom- 
 panied by thrusting. 
 
 At Mutton Hill, two miles north of Shoreham village, massive 
 teds of quartzite of so-called "Potsdam" age dip easterly on the 
 west side of the hill and appear to pass conformably beneath 
 Beekmantown beds which also dip easterly. Southeast of Mutton 
 Hill quartzite and dolomitic limestone show the effect of great 
 pressure and at some places have easterly dip. 
 
 The "Potsdam" quartzitic sandstone and overlying Beek- 
 mantown may be followed south from Mutton Hill through 
 Shoreham village to Barnum Hill near the Orwell line and then 
 into Orwell, where the marginal trace of the overthrust rocks may 
 be seen north of Huff's Crossing. 
 
 West of Shoreham village, at Sisson Hill and west and north- 
 west of it, and along the road from Larrabee's Point to Cream 
 Tlill are abundant exposures of the black Ordovician shales, often 
 folded, but sometimes lying nearly flat, and always sheared. 
 These shales show practically the same structural features as 
 those which have been described in previous pages. It has be- 
 
266 REPORT OP THE VERMONT STATE GEX)LOGIST. 
 
 come evident that the shales hold throughout a long distance in 
 western Vermont to much the same structural features. Near 
 the margins of overthrust they are always excessively jammed 
 and sheared, but may nevertheless often retain a flattish attitude, 
 having undergone their chief deformation by shearing. 
 
 The shales outcrop at Fivemile Point and southward along 
 the lake shore, but in northwestern Shoreham the area inter- 
 vening between the shore and the road running north from Lar- 
 rabee's Point is covered by the ubiquitous clay. 
 
 East of Cream Hill is Cedar Swamp, which separates the 
 shales of Cream Hill from the "Potsdam" and Beekmantown of 
 Mutton Hill. Shales presumably underlie most of the area of 
 the swamp, which marks a zone of displacement. 
 
 Near Larrabee's Point, north of the boat landing, are Tren- 
 ton beds in association with shales and, south of the landing,. 
 Trenton beds are underlain by others of Black River age and 
 these by gray limestone of uncertain correlation. 
 
 In Shoreham the evidence for reverse faulting and thrust- 
 ing is clear and distinct. It is even more so in Orwell at the 
 south, as the writer has elsewhere shown. 
 
 Whiting Township. 
 
 (Brandon topographic sheet.) 
 
 Location. This township lies directly south of Cornwall. It 
 is bounded on the west by parts of Shoreham and Orwell, on the 
 east by parts of Salisbury and Leicester and on the south by Sud- 
 bury. 
 
 General description. For Whiting a brief description will 
 suffice. The hard rocks are concealed by surface material over 
 much of its area, particularly in the eastern portion to the west 
 of Otter Creek. As already mentioned, the phyllites extend 
 north from Sudbury through the central part of Whiting. In 
 the northwestern part, limestone of apparently Trenton age bor- 
 ders the band of phyllite on the west. In the southeastern part 
 along and near the road running from Whiting village to Leicester 
 Junction and also south of this road are more or less detached 
 exposures of limestone which seems to be the northern continua- 
 tion of sheared, marbly and bluish limestone carrying layers and 
 patches of yellowish-weathering rock which make up the con- 
 spicuous hills in the northeastern part of Sudbury. Eastward, 
 these rocks join with others that are similar in the western part 
 of Leicester. 
 
 Salisbury Township. 
 
 (Brandon topographic sheet.) 
 
 Location. The western boundary is formed by a portion of 
 Otter Creek, which separates the township from parts of Corn- 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 267 
 
 wall and Whiting. It is bounded on the north by Middlebury, 
 on the east by parts of the mountain towns of Ripton and Goshen, 
 and on the south by Leicester. 
 
 General description. The western portion between Otter 
 Creek and the railroad track is low, flat land and affords few out- 
 crops. West of Salisbury station, in the lowland that borders 
 Otter Creek, are a few island-like knolls of marbly or bluish 
 limestone with layers of chamois or pinkish-buff color. The 
 rocks frequently show thinly laminated structure. The whole 
 assemblage is much like that found southward in Leicester and 
 in the northeastern part of Sudbury and adjoining parts of 
 Whiting. 
 
 A road runs south from Salisbury station, just to the east 
 of the railroad track. East of this road and a few rods south of 
 the station, dove-blue or marbly limestone, often with thinly- 
 laminated structure that represents or simulates bedding, is asso- 
 ciated with chamois or pinkish-buff colored beds and the two give 
 an assemblage that is very much like that found in the hills in 
 the northeastern part of Sudbury. The structure is often much 
 like that found among the interbedded quartzites and dolomites 
 lying to the east; at places beds which have been closely folded 
 and now stands on end lie against others forming a gentle syncline. 
 Between such compressed zones and the less violently folded 
 rocks there apparently exists a displacement due to reverse fault- 
 ing. These rocks continue southward. A mile south of the 
 station, south of a cross road running east, in some outcrops of 
 westerly-dipping beds which appeared to be conformable, bluish, 
 marbly limestone is interbedded with chamois colored rock and 
 these are apparently underlain by interbedded marble, chamois- 
 gray limestone and quartzite, the latter usually in thin beds but 
 showing one about a foot thick. 
 
 Two-thirds of a mile to the southeast of these outcrops is a 
 hill in which the rock on the west slope and part of the summit is 
 marbly, dove-blue rocks showing extreme effects of pressure 
 which is expressed by conspicuous flow and fracture shearing. 
 At the summit of the east slope of this hill are patches of quartz- 
 ite which seemed either to rest on the sheared, marbly rocks or to 
 be involved with them by thrust. 
 
 On the meridian of these rocks, about a mile south of West 
 Salisbury village and east of the road running south from it, is 
 another hill on the northwestern side of which are many outcrops 
 of striped blue rock, strongly resembling the Chazy of the lake 
 region. The beds have prevailingly westerly dip, but are strongly 
 sheared with easterly dipping cleavage. No fossils were found. 
 A cross road skirts this hill on the south and runs easterly to 
 join the Farmingdale-Salisbury road. Along the cross road, to 
 the east of the hill, is gray, siliceous dolomite like that associated 
 with the quartzite along the eastern edge of the lowland. A few 
 
268 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 rods east of this dolomite is marble, then more gray dolomite 
 dipping easterly, then east of the Farmingdale road the inter- 
 bedded series of quartzite and dolomite which forms an anticline 
 between the Farmingdale road and the one that runs northward 
 from Salisbury village on the west of Sunset Hill. 
 
 From descriptions just given, it will be apparent, by reference 
 to the writer's first paper, that northwest of Salisbury village, 
 marble, gray dolomite and interbedded dolomites and quartzites 
 are involved in field relations quite like those which occur around 
 Brandon. 
 
 West and north of Lake Dunmore, quartzite. siliceous dolo- 
 mite and interbedded quartzites and dolomites have such field 
 relations to one another as to leave no doubt, even in their present 
 disturbed and eroded condition, of their common membership 
 in one formation. To what extent these different rocks may 
 grade laterally into one another the conditions in the eastern part 
 of Salisbury do not permit statement. As has been elsewhere 
 shown, at some places in the Vermont valley the vertical sequence 
 is more or less plainly from basal quartzite through gray dolomite 
 into interbedded quartzites and dolomites. 
 
 East of Lake Dunmore is a very prominent scarp of quartzite 
 forming the western edge of the plateau. Dolomite resting on 
 quartzite occurs above this scarp around Silvef Lake. It also 
 occurs at places around the shore of Lake Dunmore in such rela- 
 tions as to indicate that normally the dolomite rests on quartzite. 
 The rocks around Dunmore and north of it are in fact more or 
 less completely dismembered portions of the plateau. 
 
 A section from Lake Champlain eastward through Shore- 
 ham, Whiting and Salisbury to the Green Mountain plateau is 
 comparable with one farther south extending from the lake east- 
 ward through Orwell, Sudbury and Brandon. The essential 
 similarity is disguised but not obscured by differences in degree 
 of displacement of the rocks. The northern section is a down- 
 throw region in relation to the other, partly from flexure in the 
 direction of the strike and partly from faulting, due in part 
 probably to deformation subsequent to earlier thrust displace- 
 ments. It should again be noted, perhaps, that it will apparently 
 always be difficult to discriminate between displacements primarily 
 resulting from pressure and those which were caused by normal 
 faulting either along independent planes, or along those of earlier 
 thrusting. 
 
 In the northern section the younger rocks (Ordovician) are 
 more fully preserved and apparently show, in spite of deforma- 
 tion, an overlapping, probably disconformable, depositional series 
 ranging from the "Potsdam" (Ozarkian) through "Beekman- 
 town," Chazy and Trenton. Thrusting has partly restored the 
 ancient Cambrian surface on which these rocks were laid down. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 269 
 
 In the southern section the Cambrian is more fully shown (see 
 writer's first paper). 
 
 Leicester Township. 
 
 (Brandon topographic sheet.) 
 
 Location. Leicester lies south of Salisbury. It is separated 
 by a portion of Otter Creek from Whiting on the west and is 
 bounded on the south by Brandon and on the east by Goshen. 
 
 General description. The rocks of this township join those 
 of Salisbury with those of Brandon. They present practically 
 nothing that is essentially different in respect to rock type or 
 structure from the areas to the north and south. 
 
 The ledges in southern Salisbury are separated from out- 
 crops in southern Leicester by the wooded flats or swampy land 
 along Leicester River and its tributaries. 
 
 In the Huntley lime quarry, west of the Otter at Leicester 
 Junction and west of the main quarry at some smaller holes, 
 may be seen buff and pinkish colored beds of marble or crystal- 
 line limestone, usually standing at a high angle of dip. At the 
 big quarry these beds are jammed in with gray dolomite and all 
 show the effects of extreme compression; but none of the rocks 
 indicates much in any respect as to its age. 
 
 At the so-called Swinnington quarry, southeast of the Junc- 
 tion and east of the Otter, marbly limestone which has been quar- 
 ried is overlain by gray, magnesian rock which shows a remark- 
 able fold in the form of a recumbent, closely compressed anticline 
 which has been aptly called a "roll." This is pictured by the 
 State Geologist (Seventh Report, p. 352). The roll is inter- 
 preted by the writer as the portion of a mass now largely eroded 
 which was thrust over the marble on which it now rests. The 
 peculiarly folded structure was probably acquired by frictional 
 drag during thrust. Similar rolls have been mentioned in pre- 
 vious pages for other places ^ in western Vermont at which ap- 
 parently similar rocks were involved. 
 
 Two-thirds of a mile east of the Junction, north of the road 
 running east from the covered bridge, are ledges of dove-blue or 
 marbly limestone v/ith patches of chamois-gray. Eastward these 
 pass under drift; but about a mile to the east are ledges of 
 strongly sheared, striped, blue, crystalline limestone not very 
 distant from others of gray, siliceous dolomite like that which is 
 associated with the quartzite at the east. East of these are other 
 ledges of dove-blue limestone and its associated chamois-gray 
 rocks and farther east the interbedded dolomites and quartzites 
 which are much folded and form the southward continuation of 
 the similar rocks of Salisbury and the northern extension of those 
 in Brandon. The interbedded rocks extend in Leicester to the 
 east of Mt. Pleasant, which is bordered on the east by a distinct 
 scarp, at the base of which lies Mud Pond. 
 
270 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 Lake Dunmore lies in a structural basin perhaps primarily of 
 synclinal structure, but bounded on the west and east by faults. 
 Those on the east are the southern extension of those marking" 
 the western edge of the plateau in Salisbury. 
 
 In some particulars the interbedded rocks of Leicester form 
 a transition between those found farther south in the Vermont 
 valley and those occurring over the eastern portions of the low- 
 land in the northern townships. This transitional character is 
 shown by thicker beds and by reddish colors which are more 
 common at the north. 
 
 GENERAL SUMMARY. 
 
 Edward Hitchcock in his "Preliminary Report," a sort of 
 preface to the first volume of the Geology of Vermont, wrote in 
 substance that the rocks of Vermont were the most difficult ones 
 to understand of any with which he had ever attempted to grap- 
 ple. It does not appear in his remark whether he drew any 
 distinctions among the different rocks ; but apparently he recog- 
 nized that although the geology of some parts of the state is 
 easier to comprehend than that of other parts, the whole region 
 is one of great complexity. The efforts of many workers have 
 contributed only to a partial solution of the age relations and struc- 
 tural features of the various rocks. 
 
 In the lake region proper, as defined in this paper, fossils 
 were found many years ago and the ages of the different rocks 
 are now for the most part at least approximately known ; but their 
 structural relations have always been and are even now obscure. 
 While distinct progress has been made by Wing and others in 
 tracing the formations of the lake region into the eastern parts of 
 the Champlain lowland, the Vermont valley and the Taconic 
 range, it has not seemed altogether strange that Hitchcock was 
 confounded by the obscurity which prevails over the areas which 
 he mapped as "Eolian Limestones," in which, metamorphism and 
 deformation have introduced so much confusion. 
 
 It is not the purpose of this summary to point out in detail 
 how the writer's views differ from those of others ; but it seems 
 as though confusion has often resulted from failure to interpret 
 correctly the major structural features of the region. 
 
 For the sake of convenience of discussion, western Vermont 
 may again be broadly defined as that part of the state which in- 
 cludes the islands of the lake and the low areas along its borders, 
 herein called the lake region proper, the relatively low land lying 
 between the lake region and the Green Mountain plateau, the 
 western marginal portion of the plateau, the Vermont valley and 
 the Taconic range. These various divisions together form a fairly 
 broad region east of the New York boundary, reaching across the 
 state from north to south. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 271 
 
 The writer started out on the program of surveying this 
 whole region. The work has been accomphshed, after a fashion, 
 for the Vermont valley and the Champlain lowland and for parts 
 of the Taconic range and the western margin of the plateau. 
 The survey as made has hardly been exhaustive, but has been 
 carried out as carefully as possible in the time that has been avail- 
 able for the purpose. Experience has served to show how puz- 
 zling are the problems presented by the region and how elusive 
 is any final and definite solution of some of them. However, in 
 spite of the difficulties that stand in the way and the uncertainties 
 that exist, there seem to be manifest such similarities among 
 various rocks and in the field relations shown by them that some 
 generalizations may be ofifered which would hardly be warranted 
 without a survey of the region as a whole. 
 
 When the various outcrops that have been described in the 
 preceding pages have been plotted on the several topographic 
 sheets involved and these are placed in their proper positions with 
 respect to each other, certain features and field relations stand 
 out which now deserve examination and discussion. 
 
 In the first place it becomes very evident that the major 
 physiographic features and many of the minor ones as well are 
 primarily due to ancient deformations of the rocks which set the 
 stage for later structural changes and the action of erosive agents. 
 The various divisions which have been defined are all structurally 
 homologous areas, some more obviously than others, which are at 
 the present time largely separable only on geographic and physi- 
 ographic bases. This homology consists in the essentially identical 
 types of rocks found in each and the major structural relations 
 which these formations have to each other. While the writer's 
 studies in the Taconic range lack the measure of fullness of those 
 carried out in the lowland divisions, it seems most probable that 
 this division is only a special physiographic type whose principal 
 features are incident to the ways in which the forces which de- 
 formed the whole region acted in the portion of the region oc- 
 cupied by it at different phases of its history and to certain 
 primary variations among the various related rocks that were 
 laid down in what is now western Vermont. It seems probable 
 that distinctions among the various rocks of the region have often 
 been made on secondary features and that an essential unity in 
 rock type and structure has been overlooked. 
 
 A tendency to regard different portions of the region as 
 things more or less apart has appeared in one form or other 
 during and since the days of the early surveys, and it may be 
 said that by reason of the heterogeneity that exists over western 
 Vermont as a whole, on account of primary differences among 
 the rocks and metamorphism and deformation, it is not surprising 
 to find that what now appear to be subordinate or secondary 
 
272 REPORT OF the: VERMONT STATE GEOLOGIST. 
 
 features have been emphasized and that fundamental similarities 
 have been overlooked. 
 
 In the first place, it is well again to note that the lake with 
 its islands differs in no essential way from the mainland areas 
 which adjoin it; the clay or sand or bowlder drift that usually 
 conceals the hard rock on the mainland differs only in physical 
 properties from the water of the lake. In fact, as has already 
 been pointed out, in many places near the lake and within its 
 confines, clay instead of water may be said to inundate the land 
 where the surface of the hard rock is below the present water- 
 level. The areas of the hard rock now beneath the waters of the 
 lake, or beneath the deposits of one kind or other which take 
 their place, are probably primarily old stream denuded surfaces 
 which have been generally modified by glacial action and in cer- 
 tain portions after inundation by water also by the waves. The 
 topography of the lake region stands in contrast to the rest of 
 th^ Champlain lowland on account of the more vulnerable char- 
 acter of its rocks, whose presence at the surface is a circum- 
 stance consequent upon relations produced by ancient deforma- 
 tions which the region underwent. 
 
 If, as seems likely, there have not been any marked displace- 
 ments of the crust during or since the action of the erosive agents 
 which shaped the present surface, then the several physiographic 
 divisions of the region may be regarded as chiefly consequent 
 upon relations produced among the formations by crustal dis- 
 turbances. 
 
 The islands of the lake and also, without much doubt, the 
 hard rock surface beneath the water, as well as extensive areas of 
 the adjacent Vermont mainland over which the hard rock is 
 partly exposed and partly hidden, are dominated by rocks which, 
 although altered and deformed in varying degrees, are on the 
 whole less metamorphosed and less crystalline than are the various 
 formations of calcareous rocks found over the areas that lie to 
 the east of the lake region. Away from the lake along surface 
 sections from west to east at some latitudes the succession is often 
 marked by a sort of transition from comparatively little altered 
 rocks, through others in which fossils have been largely oblit- 
 erated to highly metamorphosed rocks with dim, uncertain traces 
 or else no suggestion of organic remains. Even along such sec- 
 tions it should be understood that the sequence is not one marked 
 simply by difference of metamorphism of the rock, but is an in- 
 terrupted one caused partly by deformations and partly by ero- 
 sion. In some sections, on account of displacements and thrusts 
 which have moved rocks from the east over those at the west, the 
 change from rocks whose geological age may be fairly readily ap- 
 parent, at least so far as the fossils are understood, to rocks 
 which have been profoundly altered is abrupt. 
 
REPORT OF THE VERMONT STATE GEOLOiGIST. 273 
 
 The rocks of the lake region, including the islands and much 
 of the adjacent mainland, as determined by their fossils, range in 
 age from lowest Ordovician (possibly Upper Cambrian), "Ozark- 
 ian," through various horizons of "Beekmantown." Chazy and 
 Trenton, possibly to horizons that are homotaxial with the 
 Utica as elsewhere known. The so-called Ozarkian is an in- 
 durated sandstone, in some places apparently lying conformably 
 beneath basal Beekmanto%\Ti magnesian limestone. In Xew 
 York, in the Mohawk valley and elsewhere, these two formations 
 are described as separated by an unconformity which it is claimed 
 has been traced into the Champlain and St. Lawrence valleys ; but 
 the unconformit}- in the lake region is not apparent from any 
 physical e^-idence. The fossils are scant\' and poorly preserv-ed. 
 
 The East Shoreham section appears to give the complete 
 series of the Beekmantown of the lake region, but elsev\-here 
 usually only parts of this formation are shown. The special 
 characters of the members of this formation will not be described 
 at this place. "WTien ail are present the thickness has been esti- 
 mated as about 1.800 feet. The Chazy succeeds the Beekman- 
 town, and at some places, as at Isle La Motte. the lowest beds of 
 the series show indications of shallow water or shore origin, sug- 
 gesting oscillations of the sea bottom and probably a discon- 
 formity. In a large number of places the Chazy rocks have a 
 considerable thickness, but usually this formation, like the Beek- 
 mantown. is apparently only partly represented, at least in surface 
 exposures. At numerous localities Chazy rocks, often clearly 
 belonging to the intermediate members of the series, or so-called 
 ]\Iiddle Chazy, are overlain by beds of dense, "black hmestone of 
 Black River age.. The Black River is suceeded by the basal 
 Trenton ( "Glens Falls'' j limestone, which is in turn followed by 
 a series of argillaceous limestones and shales, some of which 
 form a more or less distinctly transitional group with respect to 
 both litholog}^ and fossils between the basal Trenton limestone 
 and the mud rocks that make up the youngest Ordovician of the 
 lake region. These mud rocks are apparently of Trenton or of 
 Trenton-" L'tica"" age. 
 
 Without much doubt, the original primary sequence among 
 the various rocks now exposed to view in the immediate region 
 of the lake was as above given and may be summarized as follows : 
 
 1. "Ozarkian" sandstone. 
 
 2. Beekmantown siHceous and magnesian limestones. 
 
 3. Chazy limestone, including some sandstone at the base. 
 
 4. Black River limestone. 
 Trenton (basal or "Glens Falls'") Hmestone. 
 Transitional limestones and shales ( "Canajoharie."' Tren- 
 ton, Ruedemann). 
 
274 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 7. Later shales ("Stony Point," Trenton, Ruedemann), 
 some of which may be contemporaneous with Utica as elsewhere 
 known (New York). 
 
 Whether the different formations just enumerated are 
 separated from one another or are broken within themselves by 
 erosion intervals will not be discussed at len^h in this paper. 
 Apparently our present knowledge is insufficient to decide the 
 matter in many cases. From what is known of the relations 
 among apparently equivalent formations elsewhere, as in New 
 York for example, disconformities are probably present; but in 
 Vermont the conditions make it difficult or impossible to say 
 whether the partial representation of a formation at many places 
 is due to non-deposition or to displacements among the rocks. At 
 the present time there is no section which shows all these forma- 
 tions in their sequence. In some places a surface covering un- 
 doubtedly conceals portions of formations ; but at other places 
 parts are clearly absent, either as the result of non-deposition or 
 from other causes. 
 
 The various formations of the lake region have clearly been 
 disturbed and probably by more than one deformation. As a 
 whole they have been faulted down with reference to the crystal- 
 line rocks of the Adirondack region ; but in addition they show 
 unmistakable evidence of profound compression which finds ex- 
 pression in disturbed relations due to fracture and reverse fault- 
 ing within the various formations with varying degrees of actual 
 overthrust, which sometimes carried the older rocks on the 
 younger limestones and shales. The less resistant, more thinly- 
 bedded rocks have been somewhat broken and faulted as masses, 
 but have been more conspicuously sheared by fracture cleavage ; 
 the more massive formations were also internally deformed but 
 were more characteristically disturbed by mass dislocation. At 
 some places it is very evident that the rocks have been moved and 
 are now not in their original relations to other rocks with which 
 they are contiguous and at other places the presumption is often 
 very strong that displacements have occurred. It is not always 
 easy to decide whether a deformation which is clearly due to 
 compression is a case of relatively simple reverse faulting, or 
 whether considerable lateral movement with actual overthrust has 
 taken place. In the preceding pages the probabilities have al- 
 ready been discussed for various localities. 
 
 In the lake region the base or floor on which the series of 
 formations above enumerated were laid down is not exposed. 
 One would suppose that at some depth or other the oldest member 
 of the lake series which seems to be the so-called Ozarkian sand- 
 stone must rest on older rock ; but rocks older than this sandstone 
 which apparently could have formed the floor of the Ozarkian 
 sea are not certainly known in the Vermont portion of the lake 
 region, except the members of the Lower Cambrian formation 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 275 
 
 which have been brought to their present relative positions by 
 thrust. Furthermore, the Ozarkian sandstone at no place where 
 it is now exposed is, so far as the writer knows, in undisturbed 
 condition, but on the contrary occupies its present position by 
 thrust. On the west side of the lake the Potsdam sandstone is 
 often in faulted relations with the members of the lake series. 
 The Lower Cambrian rocks that lie to the east of the lake give 
 only a vague suggestion of what is at depth in the lake region 
 proper. Presumably these Lower Cambrian rocks extend beneath 
 the lake at some unknown depth ; but what immediately overlies 
 them is not known. 
 
 Why the various thrusts which may be shown to exist in the 
 immediate lake region have always cut through the Ozarkian or 
 some younger formation it is not easy to understand. If the lake 
 series rests on older rocks than the Ozarkian but younger than 
 the Lower Cambrian, one wonders why such rocks do not now 
 appear at the surface somewhere br other in the lake region. The 
 fact that they do not and that the members of the Lower Cam- 
 brian do not appear by upthrust west of their present margin 
 forms the basis of the conception, first clearly formulated by 
 Logan, that there was a great lateral thrust fault by which the 
 older masses at the east were driven over the rocks of the lake 
 region. But of the fact that the members of the lake series have 
 themselves in varying degrees participated in thrust movements 
 there is now no longer any doubt. 
 
 It is possible that there exists a deep-seated plane of major 
 thrust that cut through the roots of successive reverse faults and 
 that this plane is beneath any rocks now exposed in the lake 
 region and is concealed because of subsequent normal faulting 
 which dropped all the rocks that lie betweent the x\dirondack 
 mass and the Green Mountain plateau. If such a plane exists and 
 if it cut through pre-Cambrian rocks it might not be easy to recog- 
 nize and could hardly be detected on the Vermont side of the 
 lake. 
 
 On the New York side of the lake is a sandstone of Upper 
 Cambrian age which is not like the Ozarkian sandstone of the 
 lake series in Vermont. This sandstone has not been recognized 
 in Vermont, but has a wide distribution on the east and north of 
 the Adirondacks, where it apparently rests unconformably upon 
 pre-Cambrian rocks. One is confronted with a problem of great 
 complexity in trying to account for the deformations and primary 
 conditions which could have produced the present relations. 
 
 It seems probable that so far as thrusting is concerned the 
 situation involves some such history as follows : Possibly during 
 a time when overlying masses of rock which are now eroded were 
 present in the region, there occurred more or less extensive 
 thrusts by which older formations were driven through younger 
 ones. These great shears, as such, did not necessarily pass to the 
 
276 REPORT OF THE VERMONT STATE GEOLOGIST. 
 
 surface at the time they occurred, although if they did, they 
 seemingly must have had some expression there, probably as 
 folds. In any event the effect obviously was to bring older 
 against younger masses. This was not accomplished in any set 
 fashion, but by irregular displacements of varying degrees. There 
 was, however, produced a considerable regularity in the relations 
 which certain formations came to have to one another. One 
 may imagine that at certain places, notably in the lake region, on 
 account of diminishing pressure, older rocks were not driven 
 into overlying formations far enough to cause them to appear at 
 the surface during later erosion. It seems also probable that 
 during such deformation older rocks were often carried over 
 relatively unde formed younger formations and that the latter 
 were preserved until relatively recent times by a covering of more 
 resistant rock. The present preservation of relatively soft rock 
 was not due, however, simply to the service of a protecting cover- 
 ing, but was favored by crustal deformations due to normal fault- 
 ing which occurred after the period of thrusting and which 
 brought different areas of the region to a lower elevation with 
 reference to the base level of erosion. 
 
 It seems clear that all the different rocks were subjected 
 to a certain amount of compression, but that on account 
 of the massive character of many of the formations in- 
 volved, folding was subordinate and fracture with thrust became 
 the dominant type of displacement. 
 
 There are .good reasons for thinking that a thrust which was 
 initiated, perhaps as a reverse fault, in one formation often 
 sheared away from it into an overlying one and that from such 
 behavior either the older formation or the one overlying it was 
 driven over a still younger formation. Various modifications might 
 have been produced. By a series of reverse faults preceding the 
 development of a horizontal thrust the latter could be conceived 
 as cutting the planes of the faults at depth and as driving several 
 blocks on a common shear; If the several reverse faults were 
 of different degrees of throw the thrust might have cut through 
 younger rock at the west than at the east or have driven in dif- 
 ferent ways at dift'erent places, producing final effects not very 
 different from those resulting from the mode of behavior pos- 
 tulated in the first part of this paragraph. 
 
 The applications of the ideas as to possible or probable thrust 
 behavior which have just been given depend, however, not only 
 upon the recognition of thrusting as the dominant mode of 
 deformation of the region under compression and upon the present 
 apparent relations which the various formations have to each 
 other, but also upon the relations that existed among these forma- 
 tions prior to the action of pressure. The explanation of the con- 
 ditions which now exist requires, therefore, some examination of 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 277 
 
 the question of the probable primary relations of all the rocks to 
 each other. 
 
 For the lake region proper the probable, primary sequence of 
 the various formations now found within it has been given. On 
 the New York side of Lake Champlain, for the, areas that lie 
 along or at various distances away from the lake, apparently 
 studies yet remain to be carried out in detail with regard to ar- 
 rangements among the rocks with special reference to displace- 
 ments. In Vermont, as is evident from the descriptions that have 
 been given, the lake rocks have been disturbed by thrusts and 
 there may be recognized a more or less well defined zone of de- 
 markation at the present surface between the relatively unaltered 
 rocks of the lake region and others lying to the east which are 
 either visibly more altered or are notably different in age and 
 lithological character. This zone constitutes what has long been 
 known as "Logan's line." 
 
 Regarding this zone for convenience as a line, by which 
 symbol it would be portrayed on a map, it may be described for 
 purposes of summary as follows : Entering Vermont from 
 Canada in western Highgate it follows the present lake shore for 
 two or three miles, then extends through the south-central part 
 of Highgate into Swanton, then passes approximately through the 
 central parts of Swanton and St. Albans to St. Albans Bay. 
 From St. Albans Bay southward it extends roughly parallel with 
 and near the shore in the southwestern part of St. Albans, and on 
 through Georgia and Milton to Colchester, where it coincides 
 with the present shore north of and around Malletts Bay. It 
 cuts across Colchester peninsula to the shore north of Burlington 
 and southward across Burlington and Shelburne Bays. From 
 Shelburne Bay southward across the southwestern part of Shel- 
 burne, on through Charlotte, Ferrisburg, Waltham, the south- 
 eastern part of Addison, and the northeastern part of Bridport, 
 the surface relations usually permit fairly definite separation of 
 the older or metamorphosed rocks from the lake series, but drift 
 often more extensively separates outcrops and hides relations in 
 these townships and from Ferrisburg to Bridport the apparent 
 line of separation is a decidedly sinuous and irregular one with 
 encroachment eastward at some places of the members of the 
 lake series on meridians which to the north and south are occupied 
 by overthrust rocks. 
 
 From the Canadian boundary to Bridport the line that is be- 
 ing described marks for the most part an abrupt separation of 
 the youngest Ordovician rocks, which are generally shales with 
 some included siliceous bands, from more or less altered and 
 metamorphosed calcareous rocks, or from massive, interbedded 
 quartzites and dolomites that belong to the Cambrian system. 
 
 From northeastern Bridport southward through Shoreham 
 into the northern part of Orwell the Cambrian rocks are concealed 
 
278 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 and the zone of overthrusting is occupied by not very greatly 
 altered rocks belonging to the Ozarkian or Beekmantown forma- 
 tions of the lake series which take the place of the members of 
 the Red Sandrock formation or of much altered calcareous rock 
 which are prominent along the margin of overthrust for so many 
 miles in the northern townships. In the latitude of Shoreham 
 the rocks that apparently represent the Red Sandrock series 
 farther north are black phyllites with interbedded quartzite mem- 
 bers. These rocks lie farther east in Weybridge, Cornwall and 
 Whiting and emerge from beneath rnore or less altered calcareous 
 rocks that may in some cases be rather satisfactorily correlated 
 with members of the lake series. The phyllites of Whiting join 
 southward with those of Sudbury at the northern end of the 
 Taconic range. The phyllites and quartzites of Sudbury and 
 Hubbardton pass beneath the calcareous rocks of eastern Orwell 
 and northeastern Benson, which are of Chazy-Trenton age, and 
 rise in central Orwell and in Benson to form high hills which are 
 on meridians occupied by the Red Sandrock of Snake Mt. in 
 Addison township. 
 
 The phyllites and quartzites of the northern part of the 
 Taconic range are here and there overlain b|y Chazy and Trenton 
 limestones with which they are now involved through thrusting 
 and faulting. In the writer's first paper an attempt was made to 
 show that phyllites and quartzites, like those of the Taconic hills, 
 probably pass beneath the various calcareous rocks of the Ver- 
 mont valley and join with similar rocks of the Green Mountain 
 plateau, although attention was distinctly directed to the prob- 
 ability that both reverse and normal fault plane now separate the 
 rocks of the Taconic range from those of the plateau. 
 
 A broad acquaintance with the rocks of western Vermont 
 would, in the writer's opinion, serve to show that the fractures 
 and displacements constituting the zone which has just been traced 
 are only accentuated instances of many such displacements which 
 break the rocks along their strike in the lake region, in the eastern 
 parts of the Champlain lowland and along the western margin of 
 the plateau. Along Logan's line, so-called, it is easier to discern 
 the presence of thrust dislocations because of the wide difiference 
 in age and lithological characters of the rocks now in contact ; in 
 the lake region and particularly in the areas to the east the dif- 
 ferences between rocks that lie in displaced relations are not 
 always so readily seen. 
 
 The rocks east of Logan's line essentially form a Cambrian 
 surface. Different maps that have been published and different 
 descriptions of the region have recognized the presence of rocks 
 of later age than the Lower Cambrian here and there over this 
 surface. In some cases the rocks that with more or less definite- 
 ness may be distinguished from Lower Cambrian have a con- 
 siderable extent and continuity, but on the whole, they may be 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 279 
 
 said to be fragmentary in character, as now preserved, and more 
 or less intermingled with Lower Cambrian and possibly other 
 Cambrian rocks. 
 
 The rocks which in this paper are correlated with the Lower 
 Cambrian are far from being homogeneous throughout their 
 extent. In previous pages, frequent mention has been made of 
 the manner in which these rocks vary in lithological character in 
 a lateral direction, even within relatively short distances, and 
 vertically from bed to bed. Some types of rock found in the 
 terrane have a wide geographical extent in the region, but it is 
 not certain that at different places they belong to the same horizons. 
 Over the region as a whole, the terrane as now displayed is dis- 
 tinguished by notably different kinds of rocks, some of which are 
 extensive enough to be regarded as formations ; but such dif- 
 ferences, even though pronounced, seem to be explainable in part 
 as due to differences in respect to sources of supply of material 
 and to different conditions of deposition and in part to disturb- 
 ances and alteration which the rocks have experienced. Over a 
 large part of the region an ancient Cambrian surface has been 
 partially restored by processes of thrust; it is not a perfect 
 restoration, partly because of irregularity of thrust and partly 
 because of erosion. Within the areas which have been surveyed 
 the presumably younger rocks that are here and there intermin- 
 gled with the Cambrian in the lowland have not been found on 
 the higher land that borders the lowland on the east. 
 
 The rocks which in this paper are correlated with Lower 
 Cambrian include : 
 
 1. Apparently altered derivatives of older rocks of probably 
 pre-Cambrian age ; sheared quartzitic rocks, frequently gneissoid 
 or coarsely schistose, sometimes conglomeratic and sparingly 
 arkosic, found at numerous places along the western marginal 
 portion of the Green Mountain plateau and in the hilly land ad- 
 jacent to it. 
 
 2. Extensive areas of white and gray, granular quartzite, 
 frequently sheared but often without pronounced internal def- 
 ormation, occurring in heavy layers or as thick masses of rela- 
 tively thin beds. These rocks grade laterally and vertically into 
 flaggy quartzites, schists, phyllites and slates. These various 
 rocks are now found within the marginal portions of the plateau, 
 and along the eastern portion of the Champlain lowland and mixed 
 with graywacke quartzite are found in Weybridge, Cornwall and 
 Whiting and in the northern portion of the Tacoriic range. 
 
 3. Massive, gray, siliceous dolomites and dolomitic quartz- 
 ites grading laterally into one another and into quartzite and 
 downward into sheared or massive quartzite and perhaps laterally 
 and downward into schists or phyllites ; grading upward and per- 
 haps laterally into 
 
 4. More or less distinctly interbedded dolomites and quartz- 
 ites which vary in different parts of the region with respect to 
 thickness and color of the different members. 
 
280 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 Members of 3 are common along the margin of the plateau 
 and ill the eastern portion of the lowland in association with 
 dififerent members of 2 and with different phases of 4 occur over 
 much of the lowland, intermingled with quartzite or schist, or 
 with calcareous rocks of probably younger age. 
 
 These different rocks appear to be parts of the same general 
 formation. Ver}^ different kinds of rocks were probably essentially 
 contemporaneous and all together probably originally composed an 
 essentially conformable series. Published descriptions of the dif- 
 ferent geographical or more or less altered phases of this series 
 have differentiated them into Granular Quartz, Talcoid Slates 
 and Schists, Talcoid Conglomerate, Dolomite, Red Sandrock. etc. 
 and have recognized only in part what the writer believes to be 
 their essential contemporaneity. Into the nomenclature that has 
 at one time or other been employed to describe these rocks there 
 have crept some terms indicative of age which seem to be in many 
 cases distinctly misleading in their implication. 
 
 Topographic conditions-may be largely discounted. Present 
 geological relations must reckon with the evidence that the rocks 
 of western Vermont have been jammed, sheared, faulted and 
 driven over one another. Ancient effects due to compression and 
 normal displacements which apparently came later are sufficient 
 to account for most of the field relations, if the principle of 
 lateral variation, as discussed in preceding pages, be allowed. 
 
 Fossils have been found by different workers at various 
 places in western Vermont among the rocks enumerated above and 
 correlated with the Cambrian. Most of the fossils are regarded 
 as of Lower Cambrian age. 
 
 Some observers have assigned a different and much later age 
 to certain rocks which have not yielded fossils and which the 
 writer regards as probably parts of the Lower Cambrian. Such 
 assignment has apparently often been based on such features as 
 superposition with respect to rocks probably younger than Lower 
 Cambrian and intimate field association with such rocks. Such 
 relations might readily have been produced by thrusts and other 
 displacements, as has been elsewhere discussed. 
 
 Others have "hazarded" an opinion that at some places some 
 members of the series that is herein regarded as probably Lower 
 Cambrian may be of Middle Cambrian age ; but apparently such 
 opinion is based on the idea that the thickness which has been 
 assigned to the Lower Cambrian is too great along certain sec- 
 tions in which the rocks appear to be conformable. Again it 
 seems that sufficient account has not been taken of the deforma- 
 tions of the region and the probable existence of displacements in 
 an apparently conformable series. 
 
 It is recognized that fossils have been found, as has been 
 mentioned in this paper, which suggest a Middle or late Cam- 
 brian age for certain rocks now present in western Vermont. 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 281 
 
 The localities at which these fossils were found are in the north- 
 western part of the State. The rocks yielding them are in some 
 places slates, in others, a peculiarly fragmental rock which has 
 been referred to as an "intraformational conglomerate." 
 
 From the time when the Cambrian rocks of western Ver- 
 mont, which were first called Middle Cambrian, were recognized 
 as belonging to the lower part of the Cambrian system it has 
 usually been supposed because of failure to discover over any 
 considerable portion of the region, fossils that could positively be 
 called Middle or Upper Cambrian, that rocks belonging to those 
 horizons were never deposited in what is now western Vermont. 
 It cannot be affirmed to-day that such rocks were ever laid down 
 over any considerable part of it. But taking such fossils as have 
 been found at their face values, it would appear that Cambrian 
 j-ocks later than the Lower Cambrian were formed in some parts 
 of the region. 
 
 It apparently does not follow from failure to find Middle or 
 later Cambrian rocks preserved over the region as a whole, that 
 such were never present. It is clearly necessary to recognize 
 that such rocks may have been eroded. But if such rocks were 
 ever present and were later eroded it is reasonably clear from 
 present field relations that they were removed, at least for the 
 most part, prior to the deposition of th^various calcareous rocks 
 of presumably later date that are now intermingled with rocks 
 that apparently belong to the Lower Cambrian. 
 
 The present conditions in western Vermont seem to point to 
 some sort of disturbance of the region after the Lower Cambrian 
 rocks were laid down. This disturbance may have occurred so 
 early in the Cambrian that late Cambrian rocks were formed only 
 in a small part of the region or it may have occurred after Cam- 
 brian rocks younger than the Lower Cambrian were widely dis- 
 tributed. There seems to be no positive evidence to show which 
 condition was more probable. The apparent result was a de- 
 nuded Cambrian surface which, except as it has been more or 
 less deformed and eroded subsequent to deformation, is what 
 we see to-day. This eroded surface was submerged and on it were 
 laid down rocks of younger age than the Cambrian. 
 
 On account of the profound deformation of the whole region 
 after these later rocks were deposited, their original relations to 
 the denuded surface on which they were laid down are everywhere 
 greatly obscured. At no place which the writer has visited can 
 there be clearly identified at the present time an unconformable 
 sedimentary contact between the Cambrian and younger rocks, 
 while at the same time, apparently little doubt may be entertained 
 that most of the altered, calcareous rocks, with some of which the 
 members of the Cambrian are now associated or even contiguous, 
 are younger than the latter and separated from them by a great 
 unconformity. This seems to be the situation practically every- 
 
282 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 where, both in the lowland regions and in parts of the Taconic 
 range. It is conceivable that in some parts of the region late 
 Cambrian rocks were not completely eroded before the denuded 
 Cambrian land mass was submerged ; but if such is the case the 
 localities are apparently few in number. 
 
 Where later Cambrian rocks remained in place after general 
 denudation, it is not difficult to imagine that when these rocks 
 were washed by a transgressing sea fossils of Middle and pos- 
 sibly Upper Cambrian age could have been involved and pre- 
 served in the basal member of a transgressing series, which mem- 
 ber instead of being of Cambrian age would belong to a much 
 later date. Cambrian types might or might not have been inter- 
 mingled with other fossils. 
 
 The so-called "intraformational conglomerate" from its field 
 relations often appears to be a facies of the basal member of a . 
 younger formation that was deposited on an eroded Cambrian 
 surface. It was hoped that in Vermont, fossils might be found 
 in the matrix of the conglomerate that would confirm this idea ; 
 but up to the present time the writer has found nothing that is 
 conclusive. 
 
 The conglomerate formation in its Georgia occurrence was 
 described by Walcott as a great lenticle or lentile in the Cambrian 
 series ; its present distribution and relations in some places do not 
 seem to bear out this idea. 
 
 The conglomerate- may be traced from its outcrops in High- 
 gate southward through S wanton and St. Albans into Georgia, 
 but it occurs as detached areas and very apparently as a facies of 
 a formation which includes some calcareous sandstone, thinly- 
 bedded, blue limestones and shaly rocks. The conglomerate is 
 sometimes only slightly developed as a lateral variation of lime- 
 stone beds and then is usually fine grained. In other places it 
 is more extensive and composed of bowlders of all sizes, usually 
 with a matrix of calcareo-siliceous material and arenaceous tex- 
 ture. The formation is from all appearances represented at some 
 places in the northern townships by bluish limestones in which 
 the conglomeratic phase in present exposures is either not at all 
 or only sparingly present. South of Georgia, in Milton and Col- 
 chester, rocks which in a more or less satisfactory way may be 
 correlated with this formation are only sparingly present in sur- 
 face exposures. These have been mentioned in preceding pages. 
 In Williston township near Brownell Mt. and west of it, thinly- 
 bedded, bluish limestones were noted ; but south of the Winooski 
 River the calcareous rocks which are intermingled in surface 
 outcrops with quartzite, dolomite, or interbedded quartzite and 
 dolomite are striped, blue limestones and bluish or white, marbly 
 rocks in which conglomerate was not noted. 
 
 The usually distinctly crystalline and often highly metamor- 
 phosed, calcareous rocks that are intermingled with the Cambrian 
 
REPORT OF THE VERMONT STATE GEOLOGIST. 283 
 
 beds over the lowland region south of the Winooski River and 
 east of the western, marginal zone of overthrust of Cambrian 
 and other rocks on the lake series have been mentioned somewhat 
 in detail in preceding pages. Attention was frequently directed 
 to the resemblance which many of these rocks have to members 
 of the lake series. These rocks have not often yielded fossils. 
 In a few cases they have afforded obscure or recognizable mark- 
 ings of shells of gastropods or cephalopods on the basis of which 
 they have been called Beekmantown, Chazy and Trenton. 
 
 Published descriptions and maps of the eastern portion of 
 the lowland south of the Winooski River have certainly confused 
 Cambrian rocks with others. On account of the confusion which 
 exists it would not be easy to distinguish the various rocks from 
 one another on a map. It does not seem surprising that Hitch- 
 cock was puzzled by these rocks and that in the absence of any 
 means of separating them he embraced them all in one formation 
 called the "Eolian Limestone." Later observers have apparently 
 done what amounts to the same thing. 
 
 Since Hitchcock's time some progress has been made in 
 separating the members of his Eolian Limestone on the basis of 
 fossils ; but apparently if we are to understand the geology of the 
 areas of disturbed and altered rocks of the eastern part of the 
 lowland, the Vermont valley and the Taconic range, other criteria 
 will have to be used^ as well as fossils. 
 
 In the work of finding the fossils, Mr. Wing wrought with 
 great perseverance. Proceeding east from the lake region he 
 "identified" the Trenton east of the "central belt of slate" in 
 Leicester, Cornwall and Middlebury. He found the Chazy at 
 West Rutland, and Trenton rocks in the northern hills of the 
 Taconic range. The Chazy was described as affording fossils in 
 Leicester, Cornwall and Middlebury, while by, means of the 
 "striped stratum" the Chazy was traced into the western part of 
 Brandon, in the fields and quarries of that town, and from Bran- 
 don southward into Pittsford and northward into Salisbury. 
 Beekmantown (Calciferous) beds were also described as occur- 
 ring in Salisbury, Leicester and Brandon with their fossils. 
 
 In a section reproduced by Dana^ from Wing's notes and 
 intended to show the arrangement of the rocks from west to east, 
 beginning with the Red Sandrock in eastern Shoreham and ex- 
 tending to the quartzite east of the main belt of "Eohan Lime- 
 stone" in Leicester, beds are shown as Lower and Upper Cal- 
 ciferous which probably are interbedded dolomites and quartzites 
 belonging to the Lower Cambrian. 
 
 From the investigations of Wing and from the writer's 
 studies, it appears that Chazy and Trenton rocks are present in 
 the main belt of the "Eolian Limestone." The Beekmantown 
 may be present in the western part of this belt, but the data are 
 
 lAmer. Jour. Sci., Vol. XIII, May, 1877. 
 
284 REPORT OP THE VERMONT STATE GEOLOGIST. 
 
 not C(?nclusive. Some of the rock so described appears to be 
 Chazy and some of it is Cambrian. 
 
 From the evidence that has come in of various kinds, it now 
 appears that a broad region of denuded Cambrian rocks was 
 gradually submerged in Ordovician time and was transgressed hf 
 an Ordovician sea. The overlap probably began at the west, but 
 from present field relations it is not clear just how the transgres- 
 sion proceeded. The altered calcareous rocks now distributed 
 among the Cambrian rocks over the eastern portion of the Cham- 
 plain lowland and the Vermont valley and parts of the Taconic 
 range are probably largely the eastern representatives of members 
 of the lake series. By faulting and thrusting the younger rocks 
 have been much disturbed, together with the Cambrian floor on 
 which they originally lay. The Cambrian beds have in many 
 places been thrust into, through and over the younger limestones. 
 In the process the latter have been sheared and metamorphosed so 
 that they can be with difficulty identified with their representatives 
 farther west near the lake. 
 
 The character of the basin in which these younger rocks were 
 deposited is not now clear. It seems probable that there was in 
 general a sort of trough produced by a warping of the crust and 
 that there occurred a sort of periodic pivotal oscillation of land 
 and sea bottom, producing retreat and advance of the strand line. 
 One of these seems to have occurred at the close of the Middle 
 division of the Chazy and another at the close of the Upper 
 Chazy. Similar episodes may have occurred during the Cam- 
 brian. The older parts of the trough were, however, gradually 
 deepened and the positive areas were slowly submerged. The 
 Beekmantown apparently never reached far to the east, but part 
 of the Chazy encroached eastward as the trough widened. A 
 positive movement confined the Upper Chazy to the present lake 
 region, but a resubmergence brought in the Black River and Tren- 
 ton. Whether the later mud rocks ever lay over the disturbed 
 areas east of the lake it is hard to tell. How far east the lake 
 rocks may once have extended may only be conjectured. 
 
 There are reasons for thinking that the Cambrian rocks and 
 the younger rocks involved with them have in general moved 
 as a whole for a considerable but indeterminate distance west- 
 ward over the eastward extension of the lake rocks. In Ferris- 
 burg, along Lewis Creek, the Ordovician shales extend a con- 
 siderable distance to the east of the irregular margin of thrust 
 overlap of older rocks. These shales appear to be on the under 
 side of a great lateral thrust. At numerous places along the 
 present shore of the lake members of the Lower Cambrian or 
 limestones clearly older than the shales lie on the latter by thrust. 
 At some places also there are indications of remnants of 
 overthrust rocks isolated among the shales and now some distance 
 removed from the apparently recessional margin of older rocks 
 
REPORT OP THE VERMONT STATE GEOLOGIST. 285 
 
 lying to the east of them. It seems possible that isolated patches 
 of quartzite found among the shales in the flat land in the western 
 part of St. Albans township may be such remnants. The thought 
 occurred that these outcrops might be exposures of older rocks 
 that had been thrust through the shales, but such history seems 
 unlikely. That the quartzite belongs to a different formation 
 from the shales is apparent, for no such rock has anywhere been 
 found making up a part of the shale formation. 
 
 In Orwell there are detached masses of massive Beekman- 
 town limestone which are apparently surrounded by shale and 
 which may be thrust-erosion inliers of older rock. 
 
 SUPPLEMENTARY NOTE. 
 
 During the summer of 1923 the ledge in the bank of Rock River, 
 at the bridge near Johnson's farm, was revisited. A number of addi- 
 tional fossils were found, among which were well preserved valves of 
 Nisusia {OrtMsina) festinata {Billings) and the pygidia of Eodiseus 
 (Microdiscus) speciosus (Ford). These fossils were sent to Dr. Ruede- 
 mann of Albany for his inspection. Dr. Ruedemann confirmed the 
 writer's recognition of the trilobite and identified the brachiopod. 
 
 The ledge in which these fossil fragments were found is just north 
 of the west end of the bridge. The outcrop yielding fossils is small 
 and partly covered with soil, but the rock seemed to be in place. In 
 lithology it is not just like the banded limestone that lies in the bank 
 just beneath and which forms the bed of the stream above and below 
 the bridge. 
 
 The fossils are clearly of Lower Cambrian age; but it is not cer- 
 tain that all the limestone associated with the rock carrying the fossils 
 is of similar age. 
 
 nmu ¥39JQ38 z?.m % m 
 
PROGRESS OF STREAM GAGING IN VERMONT 
 
 During the Two- Year Period Ending September 30, 1922. 
 
 C. H. Pierce. 
 
 DEPARTMENT OF THE INTERIOR, 
 UNITED STATES GEOLOGICAL SURVEY. 
 
 WATER RESOURCES BRANCH 
 
 Boston, Novemer 20, 1922. 
 To THE Honorable, The Governor of Vermont, 
 
 State House, Montpelier, Vt. 
 Dear Sir: 
 
 During the biennial period of 1921-1922, the investigation of 
 water resources of Vermont has been carried on by the United 
 States Geological Survey in cooperation with the State of Ver- 
 mont, the cooperating state official being Mr. H. M. Mcintosh, 
 State Engineer, during 1921, and Mr. George A. Reed, State 
 Engineer, during 1922. 
 
 The work ' of measuring the flow of the rivers has been 
 continued during these two years, and the results of stream gaging 
 at ten stations are shown by the accompanying tables. Efforts 
 have been made to continue the records throughout the winter 
 periods, and this has been very successful, despite the fact that 
 very low temperatures are experienced at times. The mainte- 
 nance of the gaging stations during the winter and the making 
 of measurements under ice conditions are much more difificult 
 and expensive than the maintenance during the summer months, 
 but inasmuch as the lowest stages of the rivers in Vermont are as 
 likely to occur during February as any other month of the year, 
 it seems very essential to obtain information of the flow during 
 the winter periods. 
 
 In addition to the work of maintaining gaging stations men- 
 tioned above, we have also made a tabulation of the existing water 
 power developments and notes as to where additional power could 
 be obtained. Although the most obvious power sites have al- 
 ready been put into use, there still remain many opportunities for 
 additional power development. With the increasing difficulties 
 in obtaining fuel for steam power, it is apparent that more difficult 
 and expensive water power development will be made use of in 
 the near future. A study of the stream flow records will show 
 that a very large percentage of the total run-ofif from the rivers 
 goes to waste during the spring months and at other times when 
 
 IINIV. OF NASI GEOLOfiy UBRARY 
 
»v 
 
M 
 
 
 m 
 
 
 (Mmj^ 
 
 S^l 
 
 
 ^^MpM^ 
 
 fflH 
 
 ap?/;. 
 
 n^SwTr.Sr^