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 A- /irccr-J 6NGI,NEERfNG LIBRARY 
 
 A- Jir^^ jyi^i^M 
 
Cornell University Library 
 QE 264.G78A9 1869 
 
 Explanation of sheet ^Ayrshire; southwe 
 
 3 1924 004 098 673 
 
Cornell University 
 Library 
 
 The original of tiiis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924004098673 
 
SCOTLAND. 
 
 EXPLANATION OF SHEET 
 
 7. 
 
 AYRSHIRE: SOUTH-WESTERN DISTRICT. 
 
 EDINBURGH: 
 FEINTED BY MURRAY AND GIBB, 
 
 FOB HER MAJESTT's STATIONEKT OFFICE. 
 
 18 6 9. 
 
 Price Threepence. 
 
•g'gO^ X^ 7 
 
 to tke 
 
 GEOLOGICAL SURVEY MAP 
 
 SCOTLAND 
 
 JhiHUTud: ontheScaU/ofOne/iiuSiloaTml^ 
 
 ORKNEYS ^K/^ 
 
 —i PtiblisTied/ 
 
 Iny prepanxtioiv 
 v^ Merrwin pul/lished' 
 
SCOTLAND. 
 
 EXPLANATION OF SHEET 
 
 7. 
 
 AYRSHIRE: SOUTH-WESTERN DISTRICT. 
 
 EDINBURGH: 
 FEINTED BY MUEEAY AND GIBB, 
 
 FOB HER majesty's STATIONEKT OFFICE. 
 
 18 69. 
 
PEEFACE. 
 
 The present sheet of the Geological Survey Map of Scotland was 
 surveyed by Dr. John Young, Mr. James Geikie, Mr. B. N". Peach, 
 and myself ; Professor A. C. Ramsay being at the time Local Director 
 of the work under the Director-General, Sir Roderick Murchison. My 
 share of the mapping extends from the northern edge of the map south- 
 wards to a line drawn from the north flank of Pinbain Hill to Little 
 Letterpin. Dr. Young mapped the ground immediately to the south of 
 that line, as far as the Lendal "Water and the Banclaer Toll-bar. The 
 remainder of the map to the south was surveyed by Mr. James Geikie, 
 except the ground lying to the east of a line drawn from Dalreoch, 1-| 
 mile E. of Colmonell, southward by Liglea in Glen Tig, to Drumbowie 
 Rig, which was mapped by Mr. Peach. 
 
 The northern portion of the sheet, from BaUantrae to Girvan, forms 
 part of the area described by Sir Roderick Murchison in 1851, and of 
 which he pubhshed a Sketch-Map, in which this part of Scotland was' 
 first brought into general correlation with the Silurian rocks of Wales. 
 [Quart. Journ. Geol. Soc, vii. 139.) 
 
 Of the following Explanation, paragraphs 2, 4, 8-10, 17, 20, 25-28, 
 32, and 34, have been furnished by Mr. James Geikie, the rest have 
 been written by myself. The lists of fossils have been prepared by Mr. 
 Etheridge, Palaeontologist to the Survey, It is proper to add, that the 
 full details of the Survey of this district fall to be given in the Geologi- 
 cal Survey's Memoir on the Geology of Ayrshire, which is in preparation. 
 
 ARCH. GEIKIE, 
 Director. 
 
 GEOLOaiOAL SUKVEY OFFICE, 
 
 Edinbtjkgh, July 1869. 
 
EXPLANATION OF SHEET T. 
 
 I. AREA EMBRACED IN THE MAP. 
 
 1. This sheet of the Geological Survey Map of Scotland comprises the 
 south-western maritime tracts of the county of Ayr from near Girvan to 
 the mouth of Loch Ryan. Along the southern edge of the Map three 
 small portions of Wigtonshire project to the northward ; but, with these 
 exceptions, the whole area belongs to the old division of Ayrshire known 
 as Carrick. It includes the mouth of the Girvan Water, the valley of 
 the Stinchar as far up as the confluence of the Assel, Glen App, the 
 Water of Tig, and the upper streams which drain into the Water of 
 Luce. The area included in the Map is about 110 square miles. 
 
 II. FORM OF THE GROrND. 
 
 2. The physical features of this district present little variety. The 
 country is hilly throughout, the only comparatively level tracts being 
 the narrow strips which flank the principal streams. But although this 
 is the general character of the region, yet, if we take the line of the 
 River Stinchar, which flows south-west, we shall find that the ground to 
 the north of this river is somewhat more diversified than the more elevated 
 tract of hiUy land to the south. This latter may be described as an 
 undulating and sloping table-land, the axis of which runs N.E. and 
 S.W. through Beneraird (1435 feet over the sea). Near the northern 
 margin of the district, in the neighbourhood of Ballantrae, the ground 
 (300 feet or thereby above the sea-level) begins to ascend gently at 
 first for about a mile and a half, after which it rapidly slopes up from 
 400 or 500 feet to a ridge of hills (1200 feet) which overlooks the long 
 straight valley of Glen App. The highest point in this district is 
 reached in Beneraird, south of Glen App, from which point the ground 
 slopes away to the south in a series of soft undulations. Nearly all this 
 area is moor and pasture land, the cultivated tracts being almost exclu- 
 sively confined to a few narrow bands along the course of some of the 
 streams. The slopes of this undulating table-land seldom show any bare 
 rock, but are abundantly coated with peat and coarse grasses, which gives 
 a bleak and desolate aspect to the country. In the district north of the 
 River Stinchar the ground does not attain a greater height than about 
 860 feet ; but the surface generally wants the smooth undulation of the 
 more elevated tracts towards the south, many of the hills being precipitous 
 and abrupt, and showing numerous broken scaurs and crags of rock. 
 
 3. Two leading systems of valleys traverse the southern uplands of 
 Scotland, and both are exhibited on the present Map. The one runs 
 parallel with the general strike of the Silurian formations, that is, north- 
 east and south-west ; the other crosses the intervening ground transversely 
 
in a general north-west and south-east direction. The former, or longi- 
 tudinal series, is seen in the dominant valleys of the Girvan, Stinchar, and 
 Glen App ; to the latter, or transverse series, belong the numerous tribu- 
 taries which flow from either side into these streams, as well as those 
 which, rising on the table-land south of Glen App, flow down towards 
 the Bay of Luce. With one exception, no connection has been traced 
 between the direction of the valleys and the line of any faults among the 
 rocks. The longitudinal valleys run more or less along the strike of the 
 strata, but without adhering rigidly to one group of beds. The Stinchar, 
 for instance, w.inds to and fro over unaltered, metamorphosed, or crystal- 
 line rocks, while at the same time it sku-ts, flows along for a little way, 
 and then crosses lines of fault. The same features are exhibited by the 
 Girvan. There can be no doubt, however, that the strike of the rocks 
 has guided the course of these streams, and determined the parallehsm 
 of all the longitudinal valleys. The transverse valleys, on the other 
 hand, are much more sinuous and irregular, and, so far as can be 
 ascertained, bear little or no reference to the geological arrangement of 
 the rocks beneath them. They wind across the edges of the highly in- 
 cUned Silurian strata, very much as they would have done through any 
 other group of rocks. 
 
 4. The one singular exception to the want of relation between the 
 trend of the valleys and the line of the faults is furnished by Glen App. 
 That valley coincides with the line of a fracture which has been traced 
 from Finnart Bay for many miles inland. This dislocation everywhere 
 gives rise to a marked feature even when the hollow is not occupied by a 
 water-course. This is well seen in the present Map. From the head of 
 the Water of App the depression or hollow is easily traced across the 
 watershed into the Muck Burn. The peculiar straightness of the Glen 
 App valley is quite abnormal, and serves to distinguish this from the other 
 longitudinal valleys, where no connection can be traced with any fracture 
 of the rocks underneath. As in the district south of the Stinchar, so here, 
 agricultural operations are carried on chiefly in the valleys and along the 
 coast-hne, the remaining portions of the ground being in pasture land. 
 
 . The fertile fields, the fine banks of natural wood and other timber, and the 
 comfortable farm-houses of the Stinchar valley, contrast strongly with 
 the bleak stretches of moor and pasture land, and their lonely shepherds' 
 cottages, unmediately beyond. 
 
 5. The coast-line from the northern edge of the Map, southward to the 
 mouth of the Stinchar, presents a narrow flat selvage of ground between 
 the sea-margin and a steep bank which marks a former coast-line, and 
 sweeps up into the hilly ground of the interior. In one or two places, par- 
 ticularly at Bennane Head, this level platform is interrupted by the pro- 
 jection of a bold headland into the sea. In such cases, the coast road 
 which lies along the platform has to ascend and cross the interruption. 
 South of the Stinchar, a line of broken cUff descends abruptly upon the 
 sea all the way south into Loch Ryan, and the high road has therefore 
 been diverted inland so as to reach the shore again by the valley of Glen 
 App. 
 
 6. III. FORMATIONS AND GROUPS OF ROCK ENTERING 
 INTO THE STRUCTURE OF THE DISTRICT. 
 
 Aqueous. 
 ' Alluvium, Peat. 
 
 Recent and Post- 
 Tertiary. 
 
 Blown Sand. 
 Raised Beaches. 
 Glacial Drifts. 
 
Permian. Red Sandstone and Breccia. 
 
 stone^^M'd^ \[ ^^^ Sandstones and Conglomerates. 
 
 (Lower Llandovery. 
 Lower Silurian. ■< Caradoc. 
 (Llandeilo. 
 
 Metamoephic and Igneous. 
 
 Miocene (?) Dolerite dykes. 
 
 f Altered semi- crystalline strata, bedding still distinct 
 in some parts. 
 Felspathic and Porphyritic rocks. 
 Associated with Felstone. 
 Lower Silurian { Syenite, 
 rocks. Diorite. 
 
 Hypersthenite. 
 Diallage rock. 
 Serpentine. 
 
 IV. GEOLOGICAL STRUCTTTRE OF THE DISTRICTS 
 CONTAINED IN THE MAP. 
 
 7. With the exception of the two small patches of Old Red Sandstone 
 towards the north-eastern corner of the sheet, and the little Permian out- 
 lier at Ballantrae, all the ground represented by the Map is occupied by 
 rocks belonging to the Lower Silurian series. It will be seen that the 
 course of the River Stinchar very nearly coincides with a marked line of 
 division in this Silurian district. To the south the rocks are of the usual 
 character which prevails among the uplands of the south of Scotland. 
 But on the north side of the line these strata have been much meta- 
 morphosed, and they are pierced by intrusive masses of syenite, felstone, 
 and diorite. Each of these two areas falls to be described separately. 
 
 Lower Silurian, 
 a. District South of the Stinchar Valley. 
 
 8. A large fault, with downthrow to the north, which runs parallel 
 with the valley of the River Stinchar in a long sinuous line, from Brack- 
 ness Hole on the sea-coast to Pinmore on the Stinchar (i.e. N.E. and 
 S.W.), forms the northern boundary of this district. The strata consist 
 of greywacke, conglomerate, shale, and occasional bands and beds of 
 Lydian stone. They have not yet yielded fossils, except some obscure, 
 possibly fucoidal, markings, but they are probably referable to some part 
 of the great Llandeilo series.* Greywacke is by far the most abundant 
 kind of rock. It is commonly of a blue or bluish-grey colour, and varies 
 in texture from a fine-grained mudstone to coarse-grained grit, which 
 occasionally becomes pebbly and conglomeratic. These various kinds of 
 greywacke occur in thick beds and thinner bands, which are usually much 
 jointed; hence the rocks are not well adapted for building purposes. 
 Occasionally, however, the joints are less plentiful, and the greywacke 
 might be easily quarried ; but the want of good roads, and the distance 
 from railways, render these rocks, save for local purposes, practically 
 valueless. The greywackcs are interbedded with lines, partings, bands, 
 and beds of shale, usually hard, shattery, fine-grained, greyish-blue, 
 
 * At Cairn Eyan, whicli lies a little to the south-west, on the same line of strike, 
 Mr. J. Carrick Moore found Oraptolithus folium, G. pristis, G. tcenia, etc. See Quart. 
 Joum. Geol. 8oc., vol. v. p. 13; Murchison, Siluria, 4th ed. p. 155. 
 
8 
 
 grey, or green. In some places these show a rude cleavage, but 
 this is not common ; they are nowhere rendered suitable for roofing 
 purposes. Bands of coarse conglomerate occur here and there, and 
 one great mass occurs on the north side of the Glen App fault, 
 forming the hills of Auchencrosh and Smirton, Balragie Fells, etc. 
 Another mass of conglomerate, on the same strike, forms the bold 
 headlands between Corsewall Point and Milleur Point, in Wigtonshire. 
 The nature of the stones in these conglomerates, and their great size, 
 render this deposit sufficiently remarkable. The stones and boulders con- 
 sist principally of syenite, gneiss, granite, yarious porphyries, felstone, 
 quartz rock, quartz, greywacke, etc., and they vary in size from mere 
 pebbles up to blocks four and five feet in diameter. The general character 
 of the deposit is that of a coarse boulder conglomerate, in which some- 
 times all trace of bedding is lost. No metamorphic nor igneous rocks 
 from which the boulders in this conglomerate could have been derived, 
 exist in the neighbourhood ; nor indeed do such rocks of pre-LlandeUo 
 age occur nearer than the Laurentian rocks of the north-western High- 
 lands and islands of Scotland. Possibly the boulders may have come 
 from some ancient Atlantis ; and considering the great size of many of 
 the blocks, and the considerable distance they may have travelled, it is not 
 unreasonable to conjecture that ice may have had something to do with 
 their transport. No ice-markings, however, were observed upon any of 
 the stones ; nor, when we reflect upon the vast age of this deposit, could 
 these be expected to have resisted the long-continued action of percolating 
 waters. 
 
 9. The general strike of the rocks of the district is N.E. and S.W., and 
 the strata are almost always inclined at high angles. The beds have, on 
 the whole, a prevailing dip towards the south-east ; but immediately south 
 of Colmonell it will be seen, from the opposing dips indicated upon the 
 Map, that the strata are in fact arranged in synclinal and anticlinal 
 folds. Even when the dip is persistent for several miles towards the 
 south-east, this need not imply a vast thickness of strata, for the beds 
 may simply be thrown back upon each other in a series of rapid folds, 
 the tops of the arches or curves having been removed by denudation. 
 Thus the same beds may again and again appear. Some magnificent 
 examples of contorted strata occur in the bold sea-cMs between Downan 
 Point and Finnart Bay. In some places the greywackes are curiously 
 honeycombed with circular and oval cavities, the origin of which does 
 not appear evident. They may perhaps denote the former presence of 
 something organic. Ripple marks have been observed upon the surfaces 
 of some of the fine-grained greywackes, but they are not very common. 
 
 10. The Silurian strata of the district, as indicated on the Map, are 
 traversed by dykes or veins of intrusive rocks. These generally run 
 along the prevalent hne of strike, and present much the same petrographi- 
 cal characters as the similar intrusive rocks which are met with in the 
 Silurian uplands of the south of Scotland. The most common variety is 
 a pinkish, finely crystalline or compact felstone, porphyritic with crystals 
 of felspar, and sometimes containing clear quartz in globules scattered 
 through tlae matrix. Dykes of dark-coloured diorite also traverse the 
 Silurian strata in some places ; they coincide in direction with the felstone 
 dykes just described, and must be distinguished carefully from the later 
 set of dolerite dykes, to be afterwards referred to. 
 
 b. District North of the Stinchar Valley. 
 
 11. Between the two Silurian districts which are divided by the line of 
 the Stinchar vaUey, there is as much diversity in geological structure as 
 
9 
 
 there is in external outline. To the north of that valley the Silurian rocks 
 appear to belong almost entirely to the Caradoc group, though some por- 
 tions south of Girvan may perhaps be referable to the Lower Llandovery 
 group. The structure of the ground, however, is exceedingly complicated, 
 and cannot be adequately described, without taking in the district to the 
 east, which will be elucidated in the explanation to Sheet 8. Over and 
 above their foldings and fractures, the rocks have been to a large extent, 
 and over a considerable area, metamorphosed. 
 
 12. Where the metamorphism and the intruded crystalline rocks are 
 absent, the strata are found to consist of greywacke, shale, conglomerate, 
 and limestone. Of these the limestone is the most important member, 
 inasmuch as it contains fossils, from which the Caradoc horizon of the 
 strata is determined. It is a white or grey compact amorphous rock, 
 occurring in large lenticular masses, and usually associated with coarse 
 conglomerates, which sometimes both underlie and overlie it. It is well 
 exposed in the large quarries at Aldons ; smaller portions occur at Little 
 Letterpin and Pinmacher. East of these localities, it forms large masses 
 between the valleys of the Assel and Stinchar. In the metamorphic , 
 tracts also a number of exposures of limestone have been noted, as 
 shown upon the Map. Though surrounded now by more or less crystal- 
 line altered rocks, there can be no doubt that these latter areas of 
 limestone, as shown by their fossils, belong to the same series as the 
 limestones to the north-east. 
 
 13. Fossils from the LiTnestone at Aldons* 
 
 CytHeropsiS Aldensis. Turbo ? 
 
 , , sp. Murchisonia large sp. new. 
 
 Maclurea Logani. Holopea ? 
 
 ,, magna. Belleroplion. 
 Eaptistoma ? 
 
 14. The conglomerates form a very marked feature among the Caradoc 
 rocks of this region. They give rise to bold craggy hills, of which ex- 
 amples are furnished by the Dinvin HQl, Glendrissock Hill, and the Byne 
 Hill ; or, when in smaller mass, they stand out as a rough top to a smooth- 
 sloped eminence, — as in the Dow Hill, to the south of Girvan. Usually 
 they are very coarse in texture, their well-rounded stones consisting of 
 syenite, quartz, porphyry, felstone, greywacke, serpentine, etc. As a rule, 
 bedding is either absent, or can only be indistinctly made out. Where, 
 however, the stones are smaller in size, the conglomerates become distinctly 
 bedded, and pass off into mere pebbly grits. The matrix varies in colour 
 from a dirty brown to a dull green, the latter being the prevailing colour 
 to the east of the present Map. In texture the paste is sometimes 
 coarse and granular, sometimes fine-grained ; and occasionally so hard, 
 that, as in the Byne Hill, the smooth casts of the stones are preserved in 
 it long after the stones themselves have fallen out. 
 
 15. In the area embraced by the present Map, the only locahty where 
 a continuous intelUgible section can be followed for some distance, is along 
 the coast-Une between Girvan and Kennedy's Pass. On the beach at 
 Shalloch, beds of very coarse conglomerate, greywacke, and shale are 
 found dipping to N.E., or standing on edge, and much contorted. A Kttle 
 farther south, beyond these disturbed strata, a series of beds begins at 
 Shalloch Mill, and, striking south-westward nearly parallel with the coast- 
 line, extends as far as the foot of Pinbane Hill, where the metamorphosed 
 rocks commence. Along the beach from Shalloch Mill to Ardwell Bay, 
 the dip is at high angles to S.E. ; on the inland slopes behind Ard- 
 
 • See the list from the Craighead limestone, in Explanation of Sheet 14 of the 
 Geological Survey Map, par. 1 4. 
 
10 
 
 millan, and ttence along the shore to Kennedy's Pass, the dip is north- 
 westward. Hence it would appear that the rocks here are disposed in 
 a synclinal trough, the axis of which runs through Ardwell Bay. Along 
 the south-eastern edge of this trough, a massive conglomerate rises from 
 under the other beds, and stretches southwards until lost among the meta- 
 morphic rocks. Here and there, too, on the points of the farthest pro- 
 montories, we find coarse conglomerate and pebbly grits rising from under 
 the beds on the other side of the syncline. Above these lower strata there 
 are exposed on the beach, beds of hard greywacke, shale, and pebbly grit. 
 One zone of red and green shale is particularly observable. Throughout 
 these beds, courses of nodular impure Mmestone, or cement-stone, fre- 
 quently occur, and sometimes contain well-preserved fossils. The manner 
 in which the beds are broken and twisted by small faults, can be readily 
 examined on the beach, where also the numerous dolerite dykes, to be 
 afterwards referred to, are well displayed. The shore to the south-west 
 of Ardwell is occupied by a series of hard flagstones and flaggy shales, 
 which are either vertical, or inclined at steep angles to N.W. They are 
 frequently much twisted and broken, more particularly as they pass south- 
 westwards. They lie directly upon the conglomerate of Kennedy's Pass. 
 To the south of Ardmillan House, however, close to the northern margin 
 of the conglomerate, certain beds of shale and greywacke were detected 
 by the Geological Survey, from which a large suite of fossils was obtained. 
 
 16. Fossils Collected hy the Geological Survey at Ardmillan Brae. 
 
 Stenopora fibrosa. Modiolopsis or AmbonycHa. 
 
 Heliopora (Favosites). . Ortlionota. 
 
 Petraia elongata. 
 
 Holopella ? sp. 
 
 Illaenns Bowmanni. Holopea. 
 
 1ms gigas ? KapMstoma lenticularis. 
 
 Stygma latifrons. ,, sp. 
 
 StauroceplialTis globiceps. MurcHsouia. 
 
 Phacops Brogniarti. Maolurea. 
 
 „ Dalmanni. Cyclonema crebristria. 
 
 Bronteus Hibernicus. Opbileta compacta. 
 
 Orthis elegantnla. ** Connlaria elongata. 
 
 „ calligramma. Tbeca reversa. 
 „ „ var. virgata. „ triangularis. 
 
 „ sp. ,, vaginala. 
 
 Ebyiicbbnella (Eetzia) cuneata. ,, sp. 
 
 Leptaena teniiioincta. Ecculiomplialiis minor. 
 
 „ sericea.** „ sp. 
 
 ,, ? sp. ,, Scotious. 
 
 Strophomena grandis.** 
 
 ,, arenacea. Belleropbon acutus. 
 
 Disoina laevigata. ,, carinatus. 
 
 „ „ var. „ trilobatus. 
 
 Cuoullella or Area. Ortlioceras imbrioatum. 
 
 Ctenodonta. „ ibex. 
 
 Modiolopsis. ,, sp. 
 
 %* Species marked with asterisks are particularly abundant at this locality. 
 
 17. The metamorphic rocks of this district, although numerous and 
 varied in character, may yet be conveniently grouped into three classes 
 — Felspathic Rocks, Diorites, and Serpentines. These masses usually 
 occur in belts or bands, agreeing in general dip and strike with the 
 surrounding unaltered strata. The chief interest which is attached 
 to the altered strata of this district consists in the fact that they exhibit 
 certain arrested stages of metamorphic action, so that we can in many 
 instances begin with unaltered beds, and trace their gradual passage 
 
11 
 
 into crystalline rocks, which cannot be distinguished from those which 
 have had a true igneous origin. The Felspathic rochs are by far the 
 most abundant, and vary much in structure and aspect. A common 
 character among them is that of a dull, compact, sparingly por- 
 phyritic rock, and much resembling many of the true porphyrites of 
 the Old Red Sandstone. The more crystalline rocks belonging to this 
 division are indicated in the Map by a dark tiat, and lettered F — the 
 pale shade of carmine, lettered '^, representing those portions of the 
 strata which are less crystalline, and in which the original character of 
 the strata may not unfrequently be observed. The Diorites and Serpen- 
 tines have a more definite character than the last mentioned group of 
 rocks, and are often interbedded, or very closely associated. The former 
 (Diorites) are expressed in the Map by the dark shade of carmine, with , 
 white stippling, while the Serpentines are marked out by green wavy 
 lines on a pale carmine ground. A glance at the Map will show that all 
 these rocks stretch across the district in a series of alternate bands from 
 south-west to north-east, thus corresponding with the general strike of 
 the Silurian strata. Their northern boundary will also be seen to be 
 exceedingly irregular, portions of the crystalline masses stretching out 
 into the unaltered strata, while faults and overlaps of Old Red Sandstone 
 add still more to the confusion. The detailed structure of this interesting 
 region will be described in the Geological Survey's Memoir on the Geology 
 of Ayrshire. The following table of the more important rocks, and the 
 localities where they are best seen, may in the meantime be of service : — 
 
 a. Felspathic Rocks. 
 
 1. Amygdaloidal. Localities. 
 
 a. Granular strata, witli scat- Between Balcreuchan Port and Port Vad. 
 tared patches having a vesi- 
 cular structure. 
 
 6. Amorphous, dii-ty-green and Between Balcreuchan Port and Port Vad. 
 brown rocks, with homb- 
 like patches of amygdaloid. 
 
 c. Amygdaloid, with spherical Coast between Knockgowau HiU and the 
 cavities. mouth of the Stinchar ; also at many 
 
 points on the shore north of Bennane 
 Head. 
 
 2. Felspar Porphyry. Shore, foot of Balcreuchan Bum; Knock- 
 
 gowan HiU ; etc. 
 
 3. Brecciform Rocks. Shore near Bennane Head, Knockdolian 
 
 Many of these are altered ■^^• 
 conglomerates. 
 
 4. rinely-crystalhne Rocks. Various parts of shore north of Bennane 
 
 b. Dioritic Rocks. 
 
 1. Diorite. BalsaUoch, Carleton, Lendalfoot, Fell 
 
 HiU, etc. 
 
 2. Syenite. Byne Hill, Ailsa Craig. 
 
 3. Hypersthenite. Shore at Lendalfoot. 
 
 4. Diallage Rock. Shore at Lendalfoot. 
 
 c. Serpentine, etc. 
 
 1. Serpentine. Shore at Lendalfoot; Balhamie Hill; 
 
 hiUs from Lendalfoot to the Byne Hill. 
 
 2. Altered Limestone. Shore near Pinbane, LafSncleary ; Whilk ; 
 
 Often very serpentinous. irrddia^tiW^e™'" ""'^ '' 
 
12 
 
 18. Ailsa Craig is an OTal-shaped island, lying ten miles west from 
 Girvan. Its extreme height is 1113 feet, its longer (or IST. and S.) dia- 
 meter is about 1500 yards, and its shorter (or B. and W.) diameter, from 
 1000 to 1250 yards. It rises nearly vertically from the sea, on all sides 
 except the east. There a triangular patch of low shingly ground inter- 
 venes between the base of the steep eastern declivity of the island and the 
 waves. The Craig consists of a grey fine-grained syenite, which, on the 
 southern and western precipices, shows a system of close, parallel, vertical 
 joints, by which a columnar aspect is given to the rock. Though no 
 Silurian strata are visible here, there is every reason to' believe that this 
 syenitic mass rises among rocks of that age, resembling in this respect, 
 as well as to some extent also in petrographical character, some of the 
 crystalline rocks which rise through the Silurian strata of the south of 
 Ayrshire. Dykes of dolerite run in a north-westerly direction through 
 the syenite. These belong to the late series referred to in par. 21. One 
 of the most interesting features on Ailsa Craig is seen in its parallel lines 
 of shingle, marking successive stages in the advance of the coast. (See 
 par. 33.) 
 
 Old Bed Sandstone. 
 
 19. Two areas of red sandstone and conglomerate are marked upon 
 this Map. One of these is cut through by the lower reaches of the Girvan 
 Water, and forms a continuation of the Middle (?) Old Red Sandstones 
 which stretch northwards to near the Heads of Ayr, and eastwards to 
 Maybole and the Doon. These strata are more fully described in the 
 Explanations of Sheets 13 and 14. The second area lies as a small out- 
 lier in the valley of the Bynehill Burn, a little to the south of Girvan. 
 That this outHer belongs to the Middle (?) Old Red Sandstone series is 
 inferred both from its proximity to the members of that series, so well 
 seen on the hills to the south of the Girvan Valley, and thence northward 
 to near the mouth of the Doon, and from the similarity of its beds to those 
 of these adjoining tracts. As indicated on the Map, the existence of the 
 outlier has been largely determined by a series of faults, by which the 
 newer strata have been thrown in among the Silurian rocks. On the 
 southern margin of the outlier, however, we meet with its lowest beds, 
 lying unconformably upon and made up from the waste of the older 
 formation. These bottom strata dip, on the whole, in a more or less 
 northerly direction, and this continues to be the prevalent inclination 
 throughout the length of the outlier. The angle varies from 5° up to 60°, 
 or even to 90°. The strata consist chiefly of dark red sandstones, some- 
 times passing into a dirty -green tint. Along with these, there occur 
 several thick zones of conglomerate, which, in its higher beds, is reddish 
 in colour, and consists chiefly of different fragments of red greywacke. 
 Towards the base of the series, however, the tint becomes greenish ; and 
 as these conglomerates have been derived from the older Silurian con- 
 glomerates, they are sometimes hardly distinguishable from the latter, 
 more especially where they have been thrown into a vertical position. 
 In the stream between the two farms of Drumfairn and Cairntop, con- 
 glomerate is seen resting upon and made up of the green serpentine 
 rock of the metamorphic Lower Silurian series. The metamorphism, 
 therefore, is here older than a part of the Middle (?) Old Red Sandstone. 
 In the Byne Hill Burn, from the farm of Balkeachy to Byne Hill Bridge, 
 and also in several of its tributaries between these two points, excellent 
 sections of the sandstones and conglomerates are exposed. 
 
13 
 
 Permian. 
 
 20. To this formation is assigned a set of thin-bedded red sandstones, 
 only seen along the coast between Ballantrae and Bennane Head. These 
 strata frequently show ripple-marked surfaces, and rain-prints have been 
 observed upon them. At the pier, Ballantrae, they contain a red breccia. 
 From that point to where they cease, near Bennane Head, they have a 
 general northerly dip, with an average angle of from 8° to 15°. As their 
 beds must be truncated against the bank of older rocks, which rises in- 
 land from the coast-line, it is believed that they are faulted down in the 
 manner shown upon the Map. The Permian age of these strata is inferred 
 from their resemblance to the Permian sandstones which overlie the coal- 
 field of Ayrshii'e. They are cut through by dykes of dolerite, which may 
 be seen upon the beach. 
 
 Miocene (P). 
 
 21. Later than all the rocks described in the foregoing paragraphs 
 comes a series of dolerite dykes. These preserve a prevalent north- 
 westerly direction, with which they cross the older formations, irrespective 
 of strike, dip, joints, or even of faults. Good examples are shown on the 
 beach to the south-west of Girvan, where the dykes cut through highly 
 inclined Lower Silurian greywacke and shale. Farther south similar 
 dykes traverse the metamorphosed rocks, whUe near Ballantrae they rise 
 through the Permian sandstones. The rock of which these dykes consist 
 is usually a fine-grained dolerite, sometimes dull, earthy, and decomposing, 
 and sometimes with lines of vesicles running parallel with the sides of the 
 dyke. 
 
 22. These dykes are not confined to this district. They abound over 
 the south and west of Scotland, and are connected with the great doleritic 
 plateaux of Antrim and the Inner Hebrides. As the latter are undoubt- 
 edly of Miocene age, the dykes which diverge from them are referred to 
 the same date. (See Explanation of Sheet 14, par. 63, and references 
 there given.) 
 
 Faults. 
 
 23. All the large faults in the area embraced by the present Map run 
 from S.W. to N.E., which is likewise the prevalent direction of the greater 
 dislocations throughout the southern half of Scotland, as well as the chief 
 line of strike of the geological formations throughout Great Britain. The 
 parallelism of these fractures is shown on the Map. Thus, from the mouth 
 of Glen App a fault has been traced for many miles inland, with a singu- 
 larly unbending north-easterly trend. Farther north hes the fault already 
 referred to, which, by a downthrow to the north, brings down the higher 
 and metamorphosed parts of the Lower Silurian series against the Llan- 
 deilo rocks. This and another dislocation seem to come together near 
 Aldons, whence a marked fault extends in the same line for many miles 
 up the south side of the Stinchar Valley. The two chief faults which 
 bound the Old Red Sandstone outlier south of Girvan have approxi- 
 mately the same trend ; while a little farther north we find the south- 
 western extremity of a large fault which bounds the Silurian district 
 on the north-west. Numerous minor faults, as shown on the Map, diverge 
 from the main line of the great fractures. 
 
 Glacial Drifts. 
 
 24. Carrick, of which' the area embraced in the present Map forms the 
 south-western extremity, is the north-western part of the mountainous 
 
14 
 
 region which stretches from Nithsdale to Loch Ryan and Luce Bay. Its 
 hills and valleys diverge from high grounds which served as an inde- 
 pendent centre of dispersion for the ice of at least the later stages of the 
 glacial epoch. Hence the markings which have been left upon its rocks 
 bear witness to the movement of thick masses of ice from these high grounds 
 outwards into the Irish Channel. In the valleys they run along the hill- 
 sides, indicating that the valleys served formerly to drain off the ice as 
 they now drain off the water. But that the ice was in mass sufficient not 
 only to fill the valleys, but to mount over the intervening ridges, is well 
 shown on the range of hilly ground between the Stinchar and the Girvan. 
 There the striEe on the rocks look directly up to the great Galloway up- 
 lands. The knolls have still the characteristic forms of roches moutonnees, 
 even where the strise have been effaced by time. This is admirably seen 
 in the hollow of the ridge between the Fell and Byne Hills above 
 ArdmUlan House, where the well ice-worn hummocks of diorite still re- 
 tain in places their striae pointing to W. 5° N. Where the coast-line is 
 low, the strife on the rocks retain the direction with which they have ad- 
 vanced from the interior. This is well shown on the beach at Shalloch 
 Mill, where, under a recently removed covering of boulder clay, the fine 
 grey Silurian shales retain the ice-groovings which strike W. 5° N. 
 When, however, the ground rises more steeply from the sea, the trend of 
 the strise corresponds, on the whole, with that of the coast-line. Ex- 
 amples of this relation are seen on the flanks of Pinbane Hill, at Downan 
 Point, and a little south of the shore end of the Stinchar fault. From 
 these facts it appears that the low ground now covered by the Firth of 
 Clyde was filled with ice moving steadily southward, and that into this 
 main sheet there flowed thick masses which descended along the valleys 
 from the high lands of Carrick and Galloway. 
 
 25. The Drift of this hilly district presents many features of interest 
 which cannot properly be described without reference to the ground to 
 the east (Sheet 8). There are two boulder clays, a lower and an upper 
 deposit. The lower boulder clay, usually concealed below the overlying 
 drift, is for the most part only to be seen in stream cuttings when these 
 go deep enough. Its usual character is that of a stiff, tenacious, light- 
 brown, and sometimes greenish-grey clay, thickly set with numerous well 
 striated and polished stones. These have been exclusively derived from 
 the rocks of the district. Between this deposit and the upper boulder 
 clay, beds of earthy gravel and sand occasionally occur. The upper 
 boulder clay is generally of a dirty-brownish colour. The stones with 
 which it is charged, although often well scratched and smoothed, yet, as a 
 rule, are larger, more angular, and less pohshed than the corresponding 
 stones in the lower deposit. It is frequently rudely stratified, containing 
 gravel and sand, and ' guttapercha ' clays in places. Even where such 
 intercalated beds are absent, lines of stones can frequently be traced. 
 Many large boulders occur, in this drift, which often appear to pass into 
 a coarse shmgle and boulder gravel, closely resembling morame matter in 
 character. This latter kind of drift is abundantly scattered over the hUly 
 grounds south of the Stinchar valley, where it is occasionally heaped up 
 into mounds. It is in the valleys where the stratified character of the 
 upper drift is most apparent. A fine section of stratified upper boulder 
 drift is seen in the old sea cliffs near Bennane Head, where the sandy 
 beds have yielded comminuted fragments of shells. 
 
 26. Kames of sand and gravel have been observed a little north of 
 Knockdolian Hill ; mounds of coarse gravel and angular debris also occur 
 here and there along the northern flank of the Auchencrosh Hills. These 
 mounds, and probably the kames at Knockdolian also, appear to be con- 
 nected with the upper boulder clay. The drift generally lies thickest 
 
15 
 
 in the valleys, appearing only in a sparse and scattered manner upon 
 the hill-tops, where, however, it often attains a considerable thickness, 
 especially in the hilly region south of the Stinchar. 
 
 27. Erratic blocks are very numerous, and often attain a great size. 
 Several very large boulders of greywacke and other Silurian rocks occur 
 at Pyell Craig, on the north bank of the Stinchar between Ballantrae and 
 Colmonell. One of these, called the ' Cloven Craig ' (forming one of a 
 stream of boulders), is a great mass spht along the joints into three main 
 fragments. The largest fragment must contain upwards of 2500 cubic 
 feet, and the other two portions are not mneh smaller. Granite boulders 
 brought from the mountains round Loch Doon abound. They are par- 
 ticularly numerous in the valley of the Girvan, and on the beach north of 
 the mouth, of that stream. 
 
 Raised Beaches. 
 
 28. Traces of old coast-hnes at a higher level than the well-marked 
 25-feet raised beach are seen at Gu'van and Ballantrae ; at the latter place 
 two such higher terraces are seen, the lower being 50 feet, and the higher 
 75 feet above the sea. On the side of Downan Hill, at the mouth of the 
 Stinchar, several high-level ledges have been excavated on the slope ; but 
 these are only seen when looked at from some httle distance. The 
 highest of these ledges is about 300 feet above the sea. The rocks are, 
 however, so much broken up and weathered, that the terraces, on a closer 
 inspection, can hardly be traced. They are best seen from a point a 
 little way up the valley of the Stinchar. 
 
 29. On the north side of the Girvan, a little above its mouth, there are 
 traces of a terrace which may represent the 40-feet beach of the west of 
 Scotland. Fragments of whut seems to be the same terrace are found 
 farther south, near Shalloch Mill, and at Ardmillan. 
 
 30. The 25-feet raised beach forms one of the most marked features of 
 the coast scenery of this district. From Girvan to Ballantrae it runs 
 along the coast-line as a narrow strip of ilat meadow land, from the 
 inner margin of which, representing the former coast-hne, the hills rise 
 abruptly into the interior. This terrace has here usually been cut out 
 of boulder clay, as is well seen at Girvan, and thence southwards to 
 Kennedy's Pass, at Lendalfoot and Ballantrae; in other parts of its 
 course it has been excavated in sohd rock. At one or two places 
 between Girvan and Ballantrae the terrace is interrupted by the advance 
 of the high grounds into the sea. At Bennane Head, for example, an 
 interruption of this kind takes place, but the beach immediately recom- 
 mences on the other side. 
 
 Blown Sand, Shingle Beaches. 
 
 31. Patches of blown sand occur at Gu-van, Lendalfoot, and Ballantrae. 
 These have to some extent spread over and heightened the 25-feet raised 
 beach, as has likewise happened along the rest of the Ayrshire coast-line 
 to the north. They form mounds and ridges, which are covered over 
 with coarse grass, and eventually converted into pasture land. 
 
 32. At the mouth of the Stmchar no blown sand is formed, as the 
 whole flat there is liable to be flooded by the river after unusually heavy 
 rains. It may be mentioned here, that, since the pubhcation of the 
 Ordnance Survey Map, m 1859, the Stinchar has opened for itself a new 
 mouth through the high gravel bar which at this point stretches along 
 the coast, the old mouth being now closed. 
 
 33. On the east side of Ailsa Craig a low triangular piece of ground 
 hes at the base of the cliffs. This consists of coarse shingle, which has 
 
LIST OP PUBUCATIONS 
 
 OF THE 
 
 GEOLOGICAL SUEVEY OF SCOTLAND. 
 
 I.— Maps on One-inch Scale. 
 
 7. Ayrshire, South-Western Districts. 6s. 
 
 13. Ayrshire, Turnberry Point. 4s. 
 
 14. Ayrshire, Southern Districts. 6s. 
 24. Peeblesshire. 6s. 
 
 32. Edinburghshire and Linlithgowshire. 6s. 
 
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 41. Fife, East part. 6s. 
 
 n.— Maps on Six-inch Scale, illustrating the Coal-fields. 
 
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 Haddingtonshire. 
 
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 A Detailed Catalogue may he had gratis, on appKcation to the Geological Survey 
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 Agents appointed for the Side of the FublicationB of the Geological Survey. 
 
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