mi ^-v & R55P7 BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIFT OF fH^nvQ W. Sage 1891 rC-l^y ,^ , ., ENGINEERING LiBR '"■"' : /^'^ QE 695.R3IP7 ImT"""^"' IIMl^ii«ffiI^^.,!?.?P°s"s of Britain. 3 1924 003 859 463 ,^100^ Date Due Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003859463 Pliocene Deposits of Britain. y\h p Showing the Distribution! of the Pl l^Ij.oc^nx-' rhip^>sth<, also lA.jnxt&rLi^ th^ 'AJI.Jivi ufrx of /i MEMOIRS OF THE GEOLOGICAL SURYEY UNITED KINGDOM. THE PLIOCEIVE DEPOSITS B R I T A I :N". CLEMENT RE ID, RL.'S., E.G.S. PWBIISHED BY OEDEB OE THE LOItDS COMMISSIONEEa 01 DEE HiJESXY'S TEEASUEY. LONDON : PRINTED EOH HER MAJESTY'S STATIONEUY OFEICK, BY EYRE AND SPOTXISWOODE, IBINTEES TO THE QUEEN'S MOST EXCELLENT MAJESTY. And to bo purohased, either directly or througli any Boaksoller, Trora BYItB AND SPOTTISWOODE, Ba3t Hakdin't Steeet, Fleet Stebkt, B.U. : ADAM and CHARLES BLACK, 6, North Beid&e, Edineukgh; or HODGES, FIGGIS, & Co., 104 Gkaptoh Street, D'jblih. 1890. Price Five Shillings and Sixpence. \ A30 False stratification and oblique bedding j are its constant characters - -J "/. Sand with numerous entire small shells and \ [. seams of comminuted shells - J e. Sands with numerous Bryozoa, often in the "| original position of growth, and some > 12 small shells and Echini - - J d. Com.minuted shells, large entire or double T shells, and bands of limestone in the i-15 upper part ■ - - - J c. Marly beds with numerous well-preserved "I and double shells, often in the position in y 10 which they lived - - - - J 6. Comminuted shells. Cetacean remains, "1 j Bryozoa - - - - - J ^a. Phosphatic nodules and mammalian remains 1 In a later paper a slight correction is made — " It is possible that the estimate for bed ' e' may be 2 feet, and for bed ' d' 5 feet, too thick, which would make the thickness of the lower division of the Coralline Crag about 40 instead of 47 feet." Under the heading " General Considerations " Prof. Prestwich gives an account of the history of the Older Pliocene strata, and of the physical changes which took place in the Anglo-Belgian basin during the Miocene and Pliocene periods. He then points to the varying conditions under which the different portions of the Coralline Crag were deposited, and traces the changes indicated by tlie beds overlying the Nodule Bed thus : " As the land subsided the coarser materials of the basement-bed were covered up by a bed of comminuted shells. This subsidence continuing, beds ' c ' and * d ' were deposited in comparatively deep and tranquil water. These beds are succeeded by the sands ' e,' abounding in Bryozoa, with small Echini, and a number of small bivalves, indicating apparently the greatest depth of sea (possibly of from 500 to 1,000 feet) attained during the Coralline- -Crag period. A change then took place, and a bed of comminuted * Quart. Journ. Geol. Soc, vol. xxvii. pp. 115-146, 24 CORALLINE CEAG. shells, with occasional oblique lamination, was spread over this deep-sea bed, indicating possibly a shallowing of the sea by a reverse movement of elevation, and the setting in of stronger currents with intervals of quiet deposition. Further elevation, exposing the sea-bed to the action of tides and currents, led to considerable wear and denudation of the lovrer beds and to the heaping up of the remains of Bryozoa and of MoUusca of beds 'f and ■' e ' in banks over portions of the sea-bed. Under such conditions the upper division ' _(/ ' of the Coralline Orag seems to have been generally formed ; at a few places only do some of the beds seem to have been formed tranquilly." " Bed ' h ' shows, in the finer state of comminution of the shells and Bryozoa, that the water probably continued to get shallower ; and finally a continuance of the same movement of elevation gradually raised the Coralline Crag above the sea, and exposed it to the denuding action which has removed so large a portion of it. Then, or during the Hed-Orag period immediately following, the Coralline Orag was broken up into detached islands and reefs, amongst which the Red Crag was deposited during a period of slow and small subsidence." To this paper is added a full list of the Coralline Crag mollusca, with the determinations revised by Gwyn Jeffreys. Comparisons are also made between the Coralline Crag fossils and the fossils of various continental Pliocene deposits, and also with the living faunas of different seas. The conclusion come to is that a much larger proportion of the Coralline Crag mollusca belongs to recent species than was allowed by Searles Wood, and that the Coralline Crag contains a good many northern forms not recognised by that author. Thus the fauna is made to appear more like that now inhabiting the British seas, and less like that of the Mediterranean, than had generally been thought. Next year (1872) Messrs. S. V. Wood, jun., and F. W. Harmer* gave a general description of the Coralline Crag, without entering into much detail of the sections. As the divisions adopted by them are somewhat different from those suggested by Prof. Prestwich, it will be desirable to quote their account, especially as it is founded on the life-long work of S. V. Wood, senr. After indicating the known extent of the deposit — which had scarcely been traced beyond the limits within which Mr. Charlesworth first described it in 1835 — they mention a trace "at Trimley, where it was observed in the digging of a ditch by the late Mr. ActOD." If this note is accurate it carries the OoralUne Crag 4 or 5 miles south of the furthest point to which it had previously been followed. Messrs. Wood and Harmer's general description of the Coralline Crag is as follows : " The Coralline Orag has long been known to consist of two main portions, and a third subordinate bed. The first and lowest of these consists of a series of calcareous * An Outline of the Geology of the Upper Tertiaries of East Anglia [with Map], iu the Supplement to the Crag Mollusca. Palceontographical Society. (1872.) CORALLINE CRAG. 26 sands, in some places more or less marly, which are rich in MoUuscan remains. The second consists of a solid bed formed of Molluscan remains, agglutinated with the fronds and fragments of various species of Polyzoa into a rock, so hard as to have been formerly quarried for building. The third and uppermost is a thin subsidiary bed, consisting of a few feet of the abraded material of the rock, reconstructed evidently in very shoal water, probably, indeed, between tide marks, as it is very obliquely bedded. " From the outliers at Tattingstone and Ramsholt this rock-bed is absent, but over the Sutton outlier a small cap of it remains Over the main mass, however, it spreads continuously, and either from a slight northerly dip of the whole formation, or else from a displacement of the underlying shelly sands, this rock-bed descends to the sea-level at the northern extremity of the mass." The authors then criticise the method by which an estimated thickness of between 80 and 90 feet had been bbtained for this formation, and consider that " the place to test the true thickness of the formation is clearly that where it is in the greatest state of pre- servation Estimated in this way, it will be ditficult to make out the thickness of the Coralline Crag as exceeding sixty feet." Messrs. Wood and Harmer object to Professor Prestwich's division of the lowest portion, the shelly sands, into constant and determinable horizons, characterized by special groups of fossils, and remark that " the author of the ' Crag MoUusca ' in his long researches has mainly confined himself to one pit at Sutton, afEord- ing a vertical range of but a very few feet, and yet from this spot he has obtained specimens of nearly the whole known species of the Coralline Crag, many of these being known to coUectoi's as occurring only at the pits near Orford. Not only this, but so inconstant is the Molluscan facies at any one place, that many species which once occurred at this spot (and some of them abundantly) have not been noticed there for many years. An attempt under such circumstances to group these shelly beds in any order of Molluscan succession would thus evidently be illusory." Prof. Prestwich had estimated the depth of water under which this Crag was accumulated at " possibly from 500 to 1,000 feet ;" but S. V. Wood, sen., " considers that nothing among the forms of MoUusca yet obtained from the Crag, points to the existence of any greater depth of water for their habitat than 35 or 40 fathoms, so that, coupling the physical difficulties with the exigencies of the molluscan evidence, we may, we think, regard the depth of the Coralline Crag sea of Suffolk as under 300 or even 250 feet, rather than as approaching 1,000." In the same year (1872) Messrs. A. and R. Bell gave some additional details of certain of the Coralline Crag sections, and a long catalogue of the fossils from the " Lower Crag," as the Coralline Crag is named in their papers.* * Ou the Englisti Crags and the Stratigraphical Divisions indicated by their Invertebrate Fauna. Proc. Geol. Assoc, vol. ii. No. 5, p. 185. Supplement by A. Bell, No. 6, p. 270, and The Succession of the Crags. Geol. Mag., vol. is. p. 209. 26 CORALLINE OKAG. S. V. Wood, sen., in his concludinji remarks at the end of the Supplement to the Crag MoUusca* (1874), criticises Jeffreys' identifications of many of the Coralline Crag species with recent, especially with arctic, forms, and maintains the accuracy of most of his own determinations. He observes that " it is obvious that this author's leanings are very marked, so as to group together allied Crag forms as varieties only of one species, and especially to make out a Crag shell to be either identical with a living species, or, at most, only a variety of it whenever the slightest presumption can be found for that course." Wood also points out that " another reason for not undervaluing even slight differences by which many of the Crag MoUusca are separable from their living analogues, and so reducing them to the inferior importance supposed to be possessed by the term ' variety,' exists in the discordance between the evidence presented by the Mol- luscan fauna when thus reduced, and that presented by the other organisms of the Crag period." He, therefore, is still of the opinion, held also by Forbes and Hanley, that the MoUuscan fauna of the Coralline Crag has its affinities chiefly with that of the Mediterranean. To this Monograph is added a Synoptical List of the Crag moUusca, in which is also given tiie geographical range of all the species which Wood recognizes as still living. In 1879 Wood published a second supplement to his Mono- graph, and in 1882, after his death, appeared the third supplement, edited by his son. To the third supplement S. V. Wood, jun., added some further notes on the physical conditions under which the Crag was deposited, and on the correlation with other deposits on the continent. During the years 1882-3 the maps of the Geological Surveyt appeared. These showed the boundaries of the formation more accurately than before ; but no fresh outliers had been discovered, though sunk rocks of Coralline Crag are noted as occurring off Thorpe and Sizewell, on the authority of Mr. C. P. Ogilvie. Mr. P. F. Kendall.t in 1883, drew attention to the fact that whilst the shells in a pit near Aldborough were, with one exception, of the kinds determined by Dr. Sorby to have their carbonate of lime in the calcite form, the many casts are, without exception, of the kinds in which the carbonate of lime is in the form of ara- gonite. Aragonite, though harder and of higher specific gravity than calcite, is a less stable substance, and is much more easily acted upon by carbonated water. He adds that " the consoli- dation of the Coralline Crag, and the dissolution of the aragonite shells, appears to have taken place previously to the deposition of the Red Crag, or at any rate of the middle pairt of it, as I have found a fragment of Coralline Crag with shells and casts in the coprolite diggings at Boy ton." During 1885 and 1886 were published the two Memoirs of the Geological Survey, in which Messrs. Whitaker and Dalton * Fdlceontographical Society. t Sheets 48 N.E. and N.W., 49 S.W., 50 S.E. t Geol. Mag., dec. ii., toI. x. p. 497. CORALLINE OEAG. 27 described the whole of the Coralline Crag district.* Most of their notes will be found incorporated in this chapter. The Coralline Crag, though occupying so small an area, is a formation of considerable importance to the geologist, owing to its extremely varied fauna and exceptional lithological character ; it must, therefore, be described more fully than will be necessary with some of the other divisions of the Pliocene series. As the Geological Survey, however, has been able to add little to our knowledge of this bed, and as many of the older observers saw sections now invisible, and in many cases had pits dug so that ^they might more thoroughly study the deposits, the following account of the sections in the Coralline Crag must be largely taken from the work of previous observers. Use therefore has been freely made of the published papers by Mr. Charlesworth, Lyell, Prof. Prestwich, and S. V. Wood, sen. and jun., especially where their notes refer to better sections than are now visible, but at the same 'time, that the student may not be led to search for pits long since overgrown, a note is added of the present state of the exposures. All the localities were re-examined by the writer of this Memoir in 1886 and 1889. Commencing at the northern extremity of the formation, the first indications of Coralline Crag are the sunk rocks oiF Sizewell and Thorpe. Two or three miles further south the Crag was formerly seen under the beach at Aldborough, but the sections are now sloped and built over, and this is the only place where the deposit has been found on the coast. Inland at Aldborough, near the Red House, there are pits on both sides of the high road. Another pit will be found about 100 yards north of Aldborough Hall, and from this was obtained the very perfect crab {Cancer fagurus) now in the Museum of Practical Geology. Further west, on the north bank of the River Aide, opposite Stanny Point, the Coralline Crag forms a low clifE of loose brashy rock. The pits near Aldborough are not good places for collecting, as the aragonite fossils are usually only in the state of casts, though bryozoa are often particularly well preserved. Crustacea also would seem to be exceptionally perfect, for besides the crab already mentioned. Prof. Prestwich speaks of a beautiful specimen, found by Mr. Norman Evans, probably referable, according to Dr. H. Woodward, to Gonoplax angulata. Leach. Prof. Prestwich thinks that near Aldborough the upper division of the Coralline Crag is alone exposed ; all the pits are certainly in rubbly limestone of the same character, and the base of the deposit is nowhere reached. On the south side of the River Aide, these beds reappear at a somewhat higher level, so that the upper part of the lower divi- sion skirts the marsh. At Iken Brickfield, about half a mile west-north-west of Calton Farm, Prof. Prestwich recordedf thirty * Ipswich, Hadleigh, and Felixstow (1885), and Aldborough, Framlingham, Or- ford, and Woodbridge" (1886). ■f Quart. Journ. Geol. Soc, vol. v. p. 347 (1849). 28 CORALLINE CRAG. feet of Coralline Crag underlying the Ked Crag. Only about eight feet could, however, be seen in 1886. The beds belong to the upper division with casts of shells, but the only section being in the middle of the pit, where the newer deposits have been entirely removed, the junction with the Red Crag cannot at present be examined. Mr. Dalton speaks of the beds near Redland's Covert as consisting of firm stony Crag, a mass of shells and casts, false- bedded at top and bottom, but not in the intermediate beds. Among the shells Mytili largely predominate, forming here and there the entire ' mass of considerable slabs. Near the top are concretionary masses, and a few Bryozoa. Bands of tufa occupy crevices and bedding-planes of open texture. Other sections of , Coralline Crag will be found at Calton Farm, and at a " Crag Pit " (marked on the map) half a mile to the west. The latter shows 10 feet of false-bedded rubbly limestone fuU of Bryozoa and broken Echinoderms. The rock-bed is, or has been, quarried at several points along the base of the Red Crag to the east- north-east of Sudbourn Church ; the sections are of no great interest, but the exact position of each will be found indicated on the maps of the Geo- logical Survey. At the cross-roads, four-fifths of a mile north- north-east of Sudbourn Church, is a large pit showing twenty feet of false-bedded buflE" Bryoaoan sand or soft limestone. Whole shells are rare in this pit, and in the upper part of the section they are only found in the state of casts. The pit close to Sudbourn Church (on the west side) shows a very good section of soft Bryozoan limestone, with Fascicula.ria near the top. Following next the road from Sudbourn Church to the Hall, a large pit will be found, exactly opposite the Park gates, in the angle of the roads to Chillesford and Snape. It is now not often worked, but shows extensive vertical faces of soft rock on which perfect Bryozoa weather out. Pecten opercularis is an abundant shell here ; other moUusca are not plentiful. While examining this section, I found a piece of drift-wood — too much decayed for microscopic examination — and a large splinter of mammalian bone, probably Cetacean. In Sudbourn Park old overgrown pits will be seen on each side of the road to the Hall. Several of these have been described by previous writers, but as the sections are not now visible, and they did not show anything exceptional, it is needless to repeat the details. One pit in the Park is still open, the " Crag Pit," marked on the map, on the low ground north-west of the Hall. This is a large shallow pit in loose calcareous sand or marl, which is still extensively dug for making paths. Unlike the beds met with further north, the sand is fuU of well-preserved moUusca. Large and perfect specimens of Cardita senilis and Cyprina islandica, often with the valves united, are abundant, and many fine specimens of Terebratula grandis have been found, though this last species is nowhere plentiful. A box of the sand was taken by me to London for more minute examination, but the results were somewhat disappointing, for the minuter forms COBALLINB CEAG. 29 of moUuBca were very scarce, though shells down to the size of the smaller species of Cardita and Astarte. occurred in large numbers. Scattered grains of glauconite were fairly numerous in the sand. Mr. Daltoii observes that in this pit the surfaces of the thin irregular bands of limestone are covered with delicate bryozoa, indicating probably the contemporaneous deposition and solidification of the stone. Following next the eastern margin of the Coralline Crag hill, the pit south of Ox House, above Sudbourn Marshes, is now used as a cattle yard. It shows vertical walls of soft false-bedded limestone, much overgrown by lichens. The rock-bed was also formerly quarried at Roydon Cottage and Roydon Hall Farm, but these pits have now been ploughed over. A large pit will be found close to Orford Castle, though here the rock-bed is reached beneath a considerable thickness of sand — probably Bed Crag — which slips and greatly obscures the section. South of Orford, in the stock-yard of Richmond Farm, there is a good section of false-bedded limestone, composed of comminuted shells ; the only perfect fossils observed were a few Anomias and a fish otolith. About half a mile further south, at High House and Low Farm, Gedgrave, there are three pits. The highest of these is in the rock-bed, but is now seldom worked. The middle one shows the base of the shell-limestone, seen at Richmond Farm, resting on an underlying shelly sand with perfect mollusca. The lowest pit is at the edge of the Marsh at Low Farm, and is worked down to the water-level. It shows false-bedded, white, cream-coloured, or buff calcareous sand, full of small shells and broken Bryozoa. The buif colour of the beds seems to be due to infiltration from above, for under inverted oyster-shells the sand is pure white. One or two phosphatic nodules were observed scattered through the Crag, but they are not abundant. This pit should be noted as probably the best now open, except that at Sutton, for the collection of the more minute shells, especially univalves. Small Scalaria and Rissoa of several species are plentiful ; among the bryozoa Salieornaria and Eschara monilifera are very abundant. The larger mollusca are here principally oysters and scallops. Between Gedgrave Marshes and Ferry Farm another pit has been opened in the same shelly beds, but the section is small and obscure. It shows four or five feet of false-bedded calcareous sand with thin bands of rubbly limestone. Small shells are abundant, including Cyprcea europaa and Odostomia. On the west side of the hill the two sections remaining to be described are perhaps the best known of any in the Coralline Crag. The most northerly of these is the " Broom Pit," near the Keeper's Lodge, and nearly a mile west of Orford. This pit is a good deal worked and. shows a clear vertical face of twenty feet, though none of the beds are hardened into limestone. S. V. Wood and S. P. Woodward both made, extensive collections here, and Prof. Prestwich described the section in his paper on the Coralline Crag.* The following sketch (Fig. 4) was made by me in 1886. * Quart. Journ, Geol. Sot., vol. xzvii. p. 122. (1871.) 30 COBALLINE OEAG. Fie. 4. Broom Pit, near the Keeper's Lodge, Gedgrave. Scale, 20 feet = 1 inch. 1. SoU. 2. Calcareous sands and mbbly limestone, crowded with Bryozoa, especially large masses of Faseieula/ria. A few perfect small shells. 3. Calcareous sands with scattered Fascicularia and other Uryozoa, and small shells. 4. False-bedded calcareous sand, with brbkea shells, mostly at the baae. Perfect valves of Psammabia — high np, lower down Ca^dium decorticatum, Pecten operculars, P. Gera/rdi, Nueula nvjileus, &c. 5. Similar sands; with a thin bed of hard marly limestone at the base. 6. Shell beds. Large shells abundant, especially in the lower part. Gyprma island/ica, G. rustica, Thraoia, ParwpcBa, PeetuncuhtB, Pecten masdm/UB, &o. Cetacean vertebra at point marked + . (This is the bed from which most of the shells are obtained.) Prof. Preatwich considers that the lower strata here belong; to his zone d, while the upper ones represent the lower part of zone e. As an example of the fauna from a single locality it may be interesting to give the following list of the moUusca obtained by S. P. Woodward in 1863 from the Broom Pit. He remarked that bivalves were abundant ; univalves, except Turritella incrassata, comparatively scarce. Adeorbfs striatus. Buccinum undatum. Caecum mammillatum. Oalyptraea chinensis. Cyprsea europaea. Emarginula fissura. Fissnrella graeca. Margarita trochoidea. Natica proxima. Kissoa crassistriata. Scalaria clathratula. subulata. Turritella incrassata. Trochns formosus. — ziziphinns. Anomia ephippium. • r striata. Astarte Basteroti. Burtini. gracilis (A. Galeotti). — mutabilis. ■ Omalii (abnndant). Broom Pit, Oedgrave. Cardita corbis. orbicularis. scalaris (abundant). senilis (abundant). Cardium decorticatum. - strigilliferum. Corbula nucleus (C. gibba). Crenella sericea. Cyprina islandica (abundant). rustica. Cytherea chione. — ; rudis. Diplodonta xotundata. Glycimeris angusta. Leda semistriata. Lima Loscombii. Limopsis aurita. Lucina borealis (abundant). ; — crenulata. Lucinopsis Lajonkalrii. Mactra arcuata. Mya truncata. Mytilus hesperianus. CORALLINE CKAG. 31 Nuoula nucleus. Ostrea edulis. Fanopsea Faujasii (abundant). Peoten Gerardi. maxim Qs. opercularis (abundant). pusio. tigrinus. Peotunculus glycimeris (abun- dant). Pinna pectinata. Psammobia ferroensis. Solen ensis. Tellina donacina. obliqna. Thracia inflata. ventricosa, Yenus casina (abundant). imbricata. ovata. Vertioordia cardiiformis. Lingula Dumortieri. Terebratula grandis (abundant). About three-quarters of a mile further south the Butley Eiver has cut into tlie Coralline Crag hill, so as to make a low cliff near Ferry Cottages. The section thus exposed is not good, though it shows shelly sands reaching to about 9 feet above the water- level. The well-known "Gomer Pit" lies in the field above, but the name does not appear in the 1-inch Ordnance Map. This pit is occasionally opened for the purpose of obtaining Coralline Crag fossils," which are perhaps here found more abundantly, better preserved, and of greater variety than in any other section of equal extenl. As the pit is only worked for the fossils, it is generally ploughed over in the summer time, and can very seldom be examined. The deposit consists of shelly sand, referred by Prof. Prestwich to his division d. Dr. S. P. Woodward, in 1863, spent a good de.il of time here, and the following list of fossils then collected has been communicated, like the last, by his son, Mr. H. B. Woodward, who assisted him. The pit is described as very rich in species, univalves and bivalves. 0