293
THE GEOLOGY OF THE CHARMOUTH CLIFFS, BEACH AND FORE-SHORE.
By W. D. LANG, M.A., F.G.S., F.Z.S.
CONTENTS. PAGE, INTRODUCTION 294 THE LIAS- I. COMPOSITION AND CONDITIONS OF DEPOSIT 296 I I. STRUCTURE. 299 Ill. FAULTS ., • 302 IV. THE GENERAL SEQUENCE- (a) Primary Divisions. (b) Stages. (c) Series. (d) Zones 3°4 V. THE DETAILED SEQUENCE- (a) Angulatus and Bucklandi zones. .• 308 (b) Tuberculatus zone. r , Subzone. of Arnioceras. 2. Sub zone of Mtcroderoceras birchi . 3II (c) Obtusus zone- r. Subzoue of A rietites brooki. 2. Subzone of Xtpheroce1'as planicosta. 3. Subzone of A stero ceras stellare 315 (d) Oxynotus zone • 320 eel Raricostatus zone 321 (I) Armatus zone . 322 (g) :Jamesoni zone. 324 (h) ibex zone. . 324 (i) Daorei zone 326 (j) Margarttatus zone 329 VI. HISTORICAL SUMMARY. 330
THE CRETACEOUS- I. GENERAL CONSIDERATIONS (a) The Cretaceous Overstep. 333 eb) The General Character of the Beds 333 II. STRATIGRAPHICAL SEQUENCE- (a) General sequence, (b) Detailed sequence. 334 III. SECTlONS- (a) General remarks, (b) Details of the Gault Sections. 338 IV. COMPARISON OF THE GAULT BEDS ON BLACK VEN, STONEBARROW AND GOLDEN CAP-":- (a) The Pebble Bed. (b) Beds 1-2. (c) Beds 3-10. 347 V. STRATIGRAPHICAL SUMMARY . 350
THE POST-CRETACEOUS DEPOSITS I. THE CHERT-BED REMAINS 35° II. THE PLATEAU DEPOSITS. 35r III. THE CHAR VALLEY DEPOSITS 352 I V. THE BEACH 353
BIBLIOGRAPHY- A LIST OF TITLES OF WORKS REFERRED TO IN THE PAPER AND CONCERNING THE GEOLOGY OF THE DISTRICT 354
CONCLUSION. 359 PROC. GEOL. Assoc.. VOL. XXV, PART 5, 1914.J 20 294 W. D . LA NG ON
INTRODUCT IO N . I SI T ORS to Charmouth and Lvme who come with the V intention of finding fossils are 'often disappointed at the results of their collecting. Those to whom the fossils appe al chiefly as specimens of form and shape, having heard much of Lyme as a collecting ground, seen in museums fossils f rom the neighbourhood in numbers and in fine preservati on, and read their descriptions in the works of De la Beche, Buckland, Sowerb y, and others, lea rn by experience that specimens such as they expect to find are commonest in the cottages of fishermen and in the shops of Lyme. Those, on the other hand, whom the evolutionary history and , consequently, the ord er of succes sion of the fossils interests, learn that for one specimen found in place in its bed, twenty are picked up loose on the cliff-slopes and on the beach. It is true that a large amount of time and labo ur are necessary, whether for obtaining fine specimens or a succession of forms whose exact horizon is known; and really to learn their evolutionary sequence it is essential eith er to live in the neighbourhood for some time or regularl y to revisit the locality for a great num ber of years. Thus it is 'that, although hundreds of species are known and described from the Lyme district, our knowledge of their exact horizons, so necessary for unravelling their evolution, is very small. And to help towards this end has been the chief motive of the work resultin g in these notes. The first requisite for collecting fossils in pl ace is to know the exact geological hori zon of the spot whence the fossil is being taken ; and for convenience in determining this, it is necessary to map the cliff and fore-shore in detail. H ence arose the maps.* In drawing them man y points of stratigraphical interest incidentall y were involved. And so it appears how intimately one asp ect of geology is connected with another. F or, sp ringing from a pa lreontological aim, the results appear at first sight main ly stratigraphical. The maps, record ing geological structure and stratigraphical sequence, are the outcome of an attempt to find fossils in place as a means towards unravelling their evolution. It would appear ungracious not to acknowl edge here the help received from various sources. First, from those who already have written on the geology of the district, references to whose works will be found scattered throughout the text of the se notes; particularly from the author of the two last Survey Memoirs dealing with this district, the late Mr. H. B. Woodward, who directed the excursi ons on both the former occasions when the Geologists' Association visited these parts, and, in the Memoirs, has given a detail ed account of the geology and a summary of what • Publisb ed as Par t 6 of thi s Volume of tb e P ROCEEDINGS. THE GEOLOGY OF THE CHAR:\IOUTH CLIFFS. 295 has been formerly written. With these authors must be remem bered the local collectors, fr om Miss AIming onwards, who so largely supplied the various authors with their fossil material. Secondly, acknowledgment must be made of help from many pr ofessional colleagues and friends, who by identifying speci mens and by advice in other technical points have rendered valuable assistance, especiall y Dr. A. S. Woodward, Dr. F. A. Bather, Mr. R. B. Newton, "Mr. G. C. Crick, Dr. C. W. Andrews, 1I1r. W. Campbell Smith, Mr. R. H. Rastall, Mr. L. F. Spath, Mr. S. S. Ruckman, 1I1r. D. ~. S. Wats on, Mr. C. D . Sherborn, 1\lr. H . L. Hawkins, :'dr. C. P. Chatwin, and others. Thirdly , help has been received from the Charmouth and Lyme residents, who, during frequent visits extending over a period of some fift een years, have always been ready with local information and advice. T o the late Miss Harriot Templer, of Charmouth, I am ind ebted for sketches that show" differences in the former physiography of the neighbourhood. Mr. Thomas Hunter, fisherman,· has imparted much information that is made use of in the following notes. Finally, my wife, by constant help in the field and at home, has rendered possible the work resulting in these notes, that otherwise would have remained unwritten. To und erstand rightly the salient features of Charmouth geology, ifis necessary to consider the three periods of denuda tion that from time to time ha ve influenced the district. The evidence of these periods is clearl y marked on the cliffs. The most casual observation will show that the cliffs consist of clays below and of sand above. The cla ys (with occasional lime stones), which extend f rom the base to more than half -way up the cliff, are of Liassic age, and are thrown int o gentl e folds, though , on the whole, they dip in an east-south-easterly direc tion. At the height of a little over 300 ft. a nearly hori zontal line" truncates these Liassic clays, and the cliff con tinues upwards in beds of loamy Cretaceous sands, with no appreciabl e dip, passing into the weathered remains of Chert beds, also Cretaceous in age, which in their turn are capped with Cretaceous and post- Cretaceous drift. The hor izontal line separating the Liassic clays below from the Cretaceous sands above marks a plane of denudation that was formed in late Jurassic and early Cretaceous times. t That is to say, when the visible geological history of Charmouth began, the whole of this area was und er the sea, and the Lias was being deposited as a more or less homogeneous, calcareous mud derived from the denudation of limestones (probably Carboniferous Limestone) t in some neighbouring land (possibly the Mendip
•Very clearly shown In the ske tches by Buckland (Buckland, 1822, PI. xiv), als o In tbe sections of the Survey Memoir (Wo odward and Ussher, 19 I1, p. 2 2 ). t De Ran ce. 1874. PP.248-9. ~ Possibly Devonian also. See II . B. Woodward, I88g. p , xxxv l, W . D . LANG ON
Hills). * The whole of the Lower Lias was thu s deposited, and on it, as sediments of various kind s, the rest of the Lias, the Lower and the Middle Oolites, and , prob ably, the lower pa rt of the Upper Oolites. The sea-bott om with all these sed iments was then elevated , and the resultant folding is shown in the und ula tions now seen in the Liassic beds of the Charmouth cliffs. As soon as the f ormer sea-bed became dr y land, denu dation began a nd proceeded dur ing la te Jurassic and early Cretaceous times, until , by the end of the Lower Cretaceous period, all the land in the Charmouth distr ict (fo rmed of Middle and Upper Lias and Oolite) had been worn away to sea-level, and , subsiding, had formed a new sea-bottom ready to receive the U ppe r Cretaceous deposits. This is the plane that is shown by the horizont al line on the cliffs between the Li as clays and Cretaceous sand, and it marks the end of the first period of denudation. During Upper Cretaceous times, the Gault, Upp er Green sand, and Chalk were deposited in the sea which had again occupied the Charmouth district ; and during the next period of elevation they suffered denudation, until, in this area, all the Chalk was removed, and again the land was reduced to sea level. Thus a second plane of marine denudation was form ed. This plane is shown by the flat -topped hills of the district, of which the Char mouth Cliffs, Black Ven, and Stonebarrow are sections. If the present valleys were filled in to the level of lines draw n fr om hill-top to hilI -top, a nearl y flat surface would result ; and thi s would be the plane of post-Cretaceous denudation. which, uplifted to its present level , and acted upon during a third period of denuda tion that is still in progress, has been to a great extent destroyed, and is repr esented only in isolated patches by the flattened hill-tops. The third denuding period is that prevailing at the present time. It has carved the existing valleys, and is the main cause of the present scenery. Its final stages are shown in the long stretches of reefs that emerge at low tide and mark the beginning of a third p lane of denudati on. It is thu s seen that the sediments of Charmouth were deposited during three periods that may now be considered in turn -the Liassic, the Cretaceous, and the post-Cretaceous periods .
THE LIAS.
I.-COMPOSITION AND CONDITIONS OF DEPOSIT. In addition to the cla ys with occasional limestones just mention ed as constituting the Li assic rocks of the Charmouth cliffs, th ere is sandy matter in some beds of the margaritatus zone. If th ese, however, be discounted, the description just given
• De la Beche, ,83 9. p. 233. THE GEOLOGY OF THE CHARMOUTH CLIFFS. 297 holds good. But, although it is generally true, yet, when the beds are examined in detail, the description is somewhat mis leading. It would be truer to describe the sequence as a series of blue-grey, more or less calcareous clays (marls), than as a series of sharply defined clays separated by equally distinct limestones. And of these marls, the more calcareous appear paler, never become truly shaly, but here and there are traversed by indurated bands or by numerous closely-set impure lime stones j the less calcareous are much darker in colour, often appearing as paper-shales with minute selenite crystals bet ween the larninse, and traversed here and there by impure limestones that are of two extreme types, nodular and tabular, both of which may occur in the same bed, though generally a given bed is definitely of one type or of the other. In the nodular lime stones the transition from the marly clay is more abrupt, while in the tabular limestones it is more gradual. Such a description at once suggests that the limestones were not deposited as such, but are the result of segregation of calcium carbonate after the formation of the beds. If this is so, the Charmouth Lias was deposited as a more or less homogeneous marl derived from pre-existing limestones and clays. Deposi tion took place not far from the shore line (lignite" is frequent, and Pterodactyls} occur) , at a fair rate (since the beds are not thin compared with the Lias of the same stages in other locali ties), and, on the whole, uniformly, so that bedding planes are hardIy, if at all visible, yet mar ked enough to determine the distribution of segregated material. Occasionally, however, there would be a pause in sedimentation, allowing some accumula tion of organic remains, visible now as fossil-beds.T Subse quently segregation of the calcium carbonate of the marl occurred in varying degrees. The view that all the limestones of the Lias in this district were formed by segregation was held as early as 1865 by Day, who says:~ "The Limestones (the' Blue Lias Stone' of com merce) are the best known portion of the Lias. Their origin, as well as that of the nodules of limestone that occur in the marls above, are alike attributable to segregation from an originally calcareous ooze, and not to an alternate deposition of calcareous and argillaceous sediments." But, though thus early recognised as concretionary, the tabular limestones have been treated bv later authors as sedirnentarv in origin j thus. H. B. -Woodward, in 1893, II admits only limestones with irregular surfaces and "the nodular limestones or cement-stones and septaria" as segregations j and the same
'" De la Beebe, r8.N, p. 23r. t Ibid, 1839, p. 230. t Ibid. 1839. pp. 2'S, .229. ~ Day. 186j. p. 519. H. B. Woodward, ,893, p. '9. W. D. LANGON author, apparently, admits no more in his report of the last excursion to Lyme.* Again, Jukes-Browne, speaking of the English Lias generally, says t" the dark grey shaly beds, .. . with the frequent interbedded layers of argillaceous limestone, are evidently deposits formed in the more central and deeper parts of the sea." The least altered beds of the Charmouth Lias are the Belem nite Marls, that consist of some 80 ft . of pale marl, in which here and there the calcium carbonate has segregated along the bedding planes, forming paler bands. These paler beds often fade imperceptibly into the less pale beds; but where they are more clearl y marked, the y are often harder along the middle line. T he next stage in segregation is shown in . Table Ledge (Plate 39, Fig. B), which , while pas sing gradually above and below into marls, is hard enough in the middle to be called a limestone. From such a bed as Table Ledge, the transition to a tabular limestone is easily seen. The frequency of tabular limestones below Grey Ledge suggests that there was more cal careous matter in the original deposit that formed them than in that which formed the beds between them and the Belemnite Marl s ; and that these beds represent a more advanced stage in alteration of an original deposit similar to th at of the Belemnite Marls. The B irchi Bed (P late 40, Figs. A and B), if the impersistent lime stone at the base of the Bro aki Clays is included with it , is an instance of a limestone now tabular, now nodul ar j while the S tellaris Nodules and the Lower Limestone of the Green Am monite Beds are cases where the calcium carbonat e has segre gated into nodules only. Occasionally nodules of limest one occur sporadically in the clays; and sometimes tabular limestones appear for a short distance only. It is important in describing a section to state whether a limestone is persistent or impersistent, and continuous or discontinuous. Much of the detailed descrip tion of the Survey Memoir is misleading owing to obscurity on this point. At some horizons calcium carbo nate is found in the form of tabular masses varying in thickness from a fraction of an inch up to a few inches, with a fibrous structure that gives to any piece a superficial resembl ance to a bit of I noeeramus shell. Such " beef " (of the Survey Memoir) is abunda nt in the S0 ft. or so of shal es beneath the Bire/ti Bed, and where that bed is nodul ar there is a shell of " beef " both above and below it. And it is generally to be noticed th at the strings of "beef," even the thinnest, are double, and, when present, a lenticle or nodule occurs between the two halves that, diverging, enwrap it. More over, the " beef" generally exhibits cone-in -cone structure (see Plate 40, Fig. A). Ammonites may be found repl aced by • H. B. W ood war d, ' 906, p, 327. See als o Cla yden, in W oodward, lac. cit., and ' 906, p , lI S· t A. J. [ukes-Browne, '9", p . 257, PL,HE 39. 1' I [Photo by W. D . Lang: [Photo by W . D . La ng: A.-BL UE LIAS LIM FSTONES. C HURCHC LIFFS, N ORT H. B.-BLUE LIA S LI MESTONES ( BEL OW) ,' AND BASE OF EAST OF LYME. BLACK MARLS (A BOVE), ABOUT HALF-WAY BETWEEN CHAR MOUTH ANI) LYM E. To fa ce page 298. TilE GEOLOGY OF TIlE CHARMOUTII CLIFFS. 299 "heef," in which case the ornament of the Ammonite appears on both sides of the slab. Certain horizons consist of paper shales. These are clays that split along the bedding-planes into thin laminre. If the surface of a lamina is examined, it is often seen to be sprinkled with very small selenite crystals. It is conceivable that in these cases the segregation of selenite in very small crystals along the hardly indicated bedding-planes caused the lamination and pro duced the paper shales. * II.-STRUCTVRE. Before the sequence is described, it will be necessary to consider the relations of the cliff sections to the dip of the beds. The direction of the true dip is indicated by the reefs that lie along the line of strike and are exposed at low tide. The true dip is then seen to be approximately east-south-east, as would be supposed from the outcrop of the Lias inland. Thus the true dip is seen in section only where the trend of the coast is east south-easterly, that is, cast of Charmouth. Immediately west of Charmouth the coast is running nearly east and west j and then, as the head of the bay is passed, south of west j and, finally, nearly in a south-south-westerly direction. This has the effect of lessening the apparent dip, which should be reduced to nothing, or even slightly reversed, as the coast curves more and more to the southward. This is what we should expect to find if the direction of the true dip were uniform. But instead of having a uniform east-south-easterly dip. the beds are thrown into gentle folds, of which the most important is a synclinal passing under Lyme. It is convenient to call this fold the Lyme syncline. The effect of this reversal of the dip is to give a slight south south-westerly apparent dip to the beds of the Church Cliffs] near Lyme Church, that otherwise would appear to be practically horizontal. The Lyme syncline is followed eastwards by a slight anti cline (the Church Cliffs anticline), the axis of which runs in a south-south-westerly direction 'along the reefs south-east of Lyme Church, and cuts the Church Cliffs some 500 yards north-east of the Church. This anticline gives place to a very slight syncline with an axis that runs scawards through the muddy foreshore marked "Cockpits" on the Ordnance Survey map j and, ohliquely, up on to Black Ven, This little fold rnav be called the Cockpits syncline. It is very clearly shown at low tide in * Clayden. 1906, p, IIO, considers that the laminatIon is due to strongly-marked bedding planes. and that each plane marks a II brief pause in deposition." t The tel m "Cihurch Cliffs," should, I believe, be applied only to the cliff Immediately under the Church. It is more convenient to extend it so as to include the whole of the low cliff formed Ify the Rlue Lias Limestones, in distinction to Black Ven, which is com posed of Lias above the Blue Lias series and of Cretaceous Beds; and it is in this extended sense that" Church Cliffs " is used in this paper. 30 0 W. D. LANG ON the reefs in Cockpits, and its western limb (the eastern limb of the Church Cliffs anticline) is marked by a steep dip in the limestones of the Blue Lias series. That these limestones should show steeper folding than the superposed clays is likely, since the more compressible mass of the clays would accommodate themselves to lateral pressure, and would express the result of this pressure in variations in thickness rather than in folds as steep as those of the limestones beneath them. The unaccom modating character of the limestones is also shown by small faults that here and there traverse them (at times only some of the limestones), but do not affect the clays above---e.g., where Second Bed comes down to the beach about 200 yards west of Cockpits, Table Ledge above is unfaulted, Grey Ledge, Glass Bottle, Top Quick and Verity in the middle are faulted, whilst Best and Second Bed below are not faulted (see Plate 39. Fig. B). If this is the true explanation of the faulting and greater dip of the limestones of the Blue Lias series, it dates their formation (on the supposition that they are entirely of the nature of segregations) to a time prior to the late Jurassie up heaval and first period of denudation mentioned above in the introduction. The Cockpits syncline is followed by a reversal on Black Yen-the Black Ven anticline-that leads the beds with a gentle east-south-easterly dip to the disturbance in the Char valley. The best guide to the Char valley disturbance is the Birchi Bed. It descends nearly to the beach before it is lost sight of a little west of the Coast Guard look-out (now abandoned by the Government), On the fore-shore, not many yards to the west of the look-out, is a small reef.. not marked on the Ordnance Survey map, called by the fishermen "Little Ledge" (see Map 2 and Fig. 23, Section A). This has a gentle east south-easterly dip and seems to belong to the undis turbed series of Raffey's Ledge and the other reefs to the west. Undisturbed beds could be traced (1914) a few yards east of Little Ledge. On the fore-shore, about the same distance to the cast of the Coast Guard look-out as Little Ledge is to the west of it, the Birc1ti Bed is seen as a reef with a stoep east-south-easterly dip, and Shales with Beef below Birchi occur with a similar dip some yards to the west of this Birchi reef. If the Birchi reef were carried westwards with this steep dip, it would about meet the Birchi Bed where that disappears on the cliff west of the Coast Guard look-out. It is, however, extremely improbable that there is here a steep bend in the bedding without a fault, and it is fairly safe to place a line of fault running sea wards from along the end of Lower Sea Lane (probably it here r:oincides with the old river-bank), between the disappearance of the Birchi Bed in the cliff and its reappearance on the fore-shore. But the actual downthrow of this fault would be very small, not E.", E. -7 ~W .N.w . ... o S£CTlON A. <'"} rUE v INE'VAl\.D . III re .....l",s(AL "N'l , I<. ~ ... "1"£. 'R. (H"" . ::; fIM(NT MILL . ~ r- "'~&LI.''' D Q.E. o :' :;:: Eo< ::Jo ... 0:: ...".-... • : . : ._-~ -,..-:. < :z: ~ ~W .N.W , u E.SE , ~ SeCTION .:B :z: ~U T Eo< 'RI D GE FAULT. .D OWNTW l\OW 100"' , ON r.. ot« :,. o o l'.tlGE W AT E1\ >-lo ~ o ~ :z: Eo< FIG. 23. A.-SECTI ON AT CIlAR~IO(;TH BEACH , PARALLEL WITH TH1-: COAST , SHO W II\G TI l}; CHAR V,\I.I ,EY DI S·llJ RIlAI\O:. B.-SECTION OF THE LOWE RI'ART OF TilE C LIFF m :T WEI'N RIDGE WATER A:'-1D T H E LAR GE R IDGF. FAI JLT, 5110\\ '1:'-1(; T H E TIlREE STEP Fi\IILT S TIlAT P RE CEDE THE LA I\GE FA ULT. AN/) TilE IJISTRIB l;TION ON THE C LI FF OF TilE lJIFfE R F.:-IT HORIZON SOF TilE BEI.ElIlNITE MARl,S. 3°2 W. D. LANG ON as much as the vertical distance between the Birchi Bed on the fore shore and the cliff base (where the Birchi Bed on the cliff would: arrive if continued eastwards from its disappearance until it was in a line with the Birchi Bed.on the reefs). This distance would not be more than about 10 ft., and not 50 ft., which is the down throw given in the Survey Memoir.* The steeply-dipping reef of Birchi just mentioned is at the western extremity of Mouth Rocks. These constitute a muddy' expanse of reefs, plentifully strewn with shingle from the steep beach above, consisting of the Birclzi Bed (see Plate 40, Fig. B) and the Brooki Shales thrown into violent folds, often vertical and even slightly overfolded. The Birchi Bed is seen in three sharp anticlines forming as many seaward-running reefs j and, further east, there were (1913) signs of the Lower Cement Bed, forming a slight reef on the fore-shore and in a line with a well-formed' ledge with a high easterly dip running across the river sea wards of the New Cut and continuing the New Cut's eastern bank. Contorted strata are seen on the river bank east of the Lower Cement Bed reef and continue eastwards for some twenty yards, after which they give place to undulations (Fig. 23, Section A). The dip on the whole, however, is westerly until, at about half-mile east of where Lower Sea Lane ends on Charmouth beach it reverses, and the beds take on an east-south-easterly dip, rather steep at first but flattening considerably after the first half-mile. t This arch may be called the Stonebarrow anticline, and it is seen to give way to the Ridge Water syncline as the beds are followed eastward to the waterfall of that name, situated nearly a quarter of a mile east of Westhay Water and just beyond the limits of Map 3. East of Ridge Water the beds turn up with rather a sharp westerly dip and are broken by three little step-faults with a down-throw of about 10-20 ft. to the east. The distance fallen, however, is recovered in each case before the next fault, owing to the steepness of the dip. Rather less than 300 yards east of Ridge Water the cliff ends abruptly in the big Ridge Fault which throws the beds down on the east about 100 ft. (See Fig. 23, Section B). III.-FAULTS. Most of the faults to be seen on the Charmouth cliffs have been mentioned incidentally in the last section. But it still remains to be considered how thev mav be classified. First may be taken those minor faults that affect 'a certain thickness only of beds in the Lias. These occur in the limestones, and probably >I' Woodward and Ussher, 19II, p. 27. following Day, 1863, p- 281. t See Lang, 1913, p. 403, for the dip from the western end of Fairy Dell to the Ridge Fault. THE GEOLOGY OF THE CHARMOUTH CLIFFS. 303 are due either to the breaking of the comparatively unyielding limestones during the pre-Cretaceous upheaval, when the folding of the Lias was induced, or to the recent slipping of pieces of the face of the cliff as the result of weathering. To the first class probably belongs the small fault already mentioned where Middle Quick reaches the beach on the north-eastern side of the Church Cliffs anticline (Plate 39, Fig. B); and another, in the same limb of the anticline, about two-hundred yards nearer Lyme, where Second Tape reaches the beach. In the former case the limestones from Gray Ledge down to Venty are thrown down a foot or so on the east, and in the latter case Third Quick, Top Tape, and Second Tape about the same amount on the west. Faults shown on the fore-shore at Black Ven Rocks, and probably affecting the beds as high as Table Ledge that are covered with talus at the cliff-foot opposite this. spot, may be classed here. A fourth instance occurs at the summit of the Black Ven anti cline where the Birchi Bed and Shales with Beef are let down some 10 ft. on the east; and, again, about 200 yards further east, the Birchi Bed is let down a few feet on the west. Again, the obtusus zone, from the Coinstone above to the Lower Cement Bed below, is faulted down on the east, where the last-named bed reaches the beach under Stonebarrow Cliff. The remaining faults in our area are the Ridge fault in St. Gabriel's valley, with the small step-faults that accompany it, and the assumed fault accompanying the Char valley disturbance. The fact that the first and last-mentioned lie in or near the valley bottoms suggests the likelihood that their presence deter mined the direction of drainage when the present sculpturing was initiated; that is, when the Cretaceous beds extended in unbroken succession across the tops of the present valleys. If this was so, the faults must have affected the Cretaceous beds as well as the Lias, and were therefore formed during' the post-Cretaceous upheaval.' Though the Ridge fault lies just outside the eastern boundary of Map 3, it is so close to the district that it would be inconvenient not to consider it. The Survey give the down throw as 40 ft. on the east;* as a matter of fact, it is at least 100 ft. t indicated by the displacement of the Red Band that lies a little over 100 ft. above sea level at Westhay Water and cannot be much lower than that at Ridge Water on the western side of the fault. On the downthrow side the Red Band is beneath the beach, since it reappears at the base of the cliff with a westerly dip some 50 yards east of the Ridge fault. There is some evidence that the Ridge fault is in two steps a few yards apart, but until this can be definitely proved it may well be ignored. Of the three step-faults that occur between Ridge Water (Fig. 23, Section B) and the Ridge fault there is little to be * Woodward and Ussher, 19II, p. 30J following Day, 1863, p. 282. t Lang. 1913, pp. 403-4. W. D. LANG ON added to what has already been said (p. 302). It is doubtful how far they affect th e beds above the Belemnite Stone j but wheth er or not they extended f ar above the limits now shown in section, it is more likely that th ey are related to the Ridge f ault as part of it , and not, like th e "first class of faults considered , caused by the late]urassic uplift. The Char vall ey dis tur bance already ha s been described in some detail (pp. 30 1-2). D e la Beche* mak es the fault accom pa nying it run inland up the Wooton valley and northwards to west of Chard, but the Survey now discredit thi s. t The dis turbance can certainly be traced inland as f ar as Newlands Br idge. South of the bridge the Lower Cement Bed may be seen crossing the river as a reef with a strong westerly dip in association with contorted beds, and it again crosses the river Ch ar about 100 yards north of Newlands Bridge. IV.-THE GENERAL SEQVENCE. (Table facing p. 308.) (a) Primary Divisions. The Lias of the Ch armouth Cliffs belongs to the Lower and Middle Divisions of th at form ation. The line between these two divisions, however, is drawn at differ ent horizons by the Geological Survey and by most other authors. The former includes the Bel emnite Marls and Green Ammonite Beds (the Pliensbachi an or Charmouthian of Continental writ ers) in the Lower Li as, while the latter cal] these beds Middle Lias. If the Survey's definition be accepted, a sma ll part only of th e Middle Lias is represent ed on th e Charmouth cliffs, namely, about 150 ft. out of 345 f t. , and that onl y at th e eastern end ; whereas the whole of the Lower Lias is exposed , except some 40 ft. at th e base , that is about 460 ft. out of 51o ft. If th e Continental definitions, however , be taken, of th e 615 ft. ex posed on the Charmouth cli ffs, 280 ft. are Lower Li as and 335 ft. are Middle Lias. (b) Sta ges. Continental authors di vide th e Lias into stages that corre spond with their divisions into Upper, Middle and Lower Lias. T o their Lower Li as, d 'Orbigny, in 1852,:j: gave the name Sine murian j and to their Middle Lias, Oppel, in 1858, § gave the name Pliensbachian , instead of d'Orbigny's name, Liasian II (which is misleading, and not formed in accordance with the international convention th at requires the name of a stage to be founded on that of a locality). Mayer-Eyrnar, ~ later, in 1864, * De la Beeb e, 1839, p. 2 <)0. t W oodw ar d andUssher, '9", p. 66. t d' Orb igny, 1852, p . 433. & Oppel, 1856-8, p . 8'5. II d' Orbigny, 1852, p. 448, , Mayer -E yrnar, 186 ~ . THE GEOLOGY OF THE CHARMOUTH CLIFFS. 305 introduced the term Charmouthian, instead of Pliensbachian; so Liasian, Pliensbachian and Charmouthian have the same connotation, and are merely synonyms. * In 1894, Bonarellit in troduced the term Domerian as a sub-stage of the Charmouthian to indicate what the Survey (but not the Continentals) include in the Middle Lias; but he did not give a name to the part of the Charmouthian below the Domerian. In 1910, Buckman used the term Charmouthian to include this lower unnamed portion, keep ing the term Pliensbachian to cover the two sub-stages as before. t But since, by definition, Charmouthian is synonymous with Pliensbachian, Carixian § was introduced in 1913 to indicate these lower beds. Our Charmouth Lias, then, as high as just below the Armatus Limestone, is d'Orbigny's Sinemurian ; and, above this, Oppel's Pliensbachian (= Liasian= Charmouthian). The Pliensbachian, from its base almost up to the Lowest Tier, is the Carixian; and, above this, the Domerian. Wherever/the Lias occurs, it may be calIed by the name of the stage that includes its horizon; thus stages are world-wide terms, and not, like the series about to be described, mere local divisions. (c) Series. The Survey divide their Lower Lias of Charmouth into four series, recognised by visible lithic characters. The lowest of these they call the Lyme Regis Beds] or Blue Lias. ~ It extends from the base of the Lias to Table Ledge, and contains by far the greater number of the limestones of the formation. It forms the Church Cliffs as defined in this paper (see p. 299) and a great expanse of reefs exposed at low tide between Cockpits and Lyme. The next higher series is the Black Ven Beds**or Black Marl,tt and it extends from Table Ledge to just beneath the Armatus Limestone, and forms the two lower precipices on Black Ven and the bulk of the western end of Stonebarrow Cliff; it consists of blue-black clays and paper-shales, with occasional' tabular and nodular limestones, some persistent and some im persistent. The third series is the Stonebarrow Bedsj] or Belem nite Marl,§§extending from the Armatus Limestone to the Belem nite Stone, inclusive, and forming the highest clay precipice on Black Ven and most of the seaward cliff on Stonebarrow east of the beech and pine wood above the western end of Fairy Dell. The beds are blue-grey marls, appearing pale in contrast to the Black Marls below, and containing indurated bands where, * To these must now be added" Carrumlan," Jukes-Browne, 19131 p. 476. t Bonarelli, 1894, pp, 84'85. t Buckman, 19IO, p. xvi. § Lang. 1913, p. 401. II H. B. Woodward, 1906, p. 325. 'IT H. B. Woodward, 1893, p, 57· ** H. B. Woodward, I906, p. 325, and Woodward and Ussher, 1911, P. 27_ tt H. B. Woodward, ,893, P. 62. tt Woodward and Ussher, '9", p, 30. §§ "Belemnite Beds," Day, 1863. p. 280, and H. B. Woodward, ,893. p. 66.. W. D. LANG ON some segregation of calcium carbonate has taken place, but no limestones. The fourth and highest series is the Wear Cliff Beds* or the Green Ammonite Beds,t of which only the lower half appears on Black Ven, forming a steep slope of broken ground above the Belemnite Stone on the eastern shoulder of that cliff. The whole series appears on Stonebarrow, forming a similar slope of broken ground above the Belemnite Stone throughout its exposure. These beds are darker than the Belem nite Marls, and consist of marly clays and limestones; but at the top, here and there, show indications of the incoming of sandy conditions which are more marked at the base of the Middle Lias of the Survey and become dominant in the upper half of the Middle Lias that lies outside the area of our maps. (d) Zones. In the early descriptions of the English Lias, local sub divisions were made, and the names given to them were not in tended to be applied otherwise than locally. Thus de la Beche, in 1826, divided the Lias of the Dorset coast into Upper Lias Marls and Lias Limestones; and the sub-divisions of these had purely local significance. But Oppel (1856-8) and Quenstedt (1849 and 1858), describing the German Lias, first gave to their sub-divisions designations that could be applied to beds of similar age in other parts of the world. They realised that the necessary correlations for the universal application of their sub-divisions could be made only by means of comparing synchronous faunas. But, while Quenstedt merely divided his Lower and Middle Lias into Lias a and 13, Lias y and 0, Oppel made sub-divisions of these beds, and attempted to correlate his sub-divisions with the local divisions of the Lias in different parts of England and in France, thus giving us the Zone. So much divergence of opinion has existed, and still exists, as to the meaning and use of the term zone, that it is well to make perfectly clear how it is used in this paper. First, Oppel clearly uses the word as a stratigraphical term, indicating so much sediment. This is recognised by Buckman, when he says" the term zone ... is a strictly stratigraphical one." t That is to say the zone is not the time during which a deposit was formed,but, conversely, the deposit that was formed during a given time. The time during which a zone was deposited is a" hemera"§ (though hemera also includes the time during which * Wcodward and Ussher, 19II, p. 3r. t Day, ,863. p. 28,. Strictly speaking, Day referred only to the middle of the series by this name; the top and bottom he referred to as II Grey Marls." H. B. Woodward (,893, p, 68) defined the present use of the name. t Buckman, '902, p. 555. § Buckman, '902, p. 556. THE GEOLOGY OF TIlE CHARMOl;TII CLIFFS. 307 .an organism was at its acme of development). * Nor is a zone an assemblage of fossils, t as defined in the Survey Memoir. Secondly, Oppel clearly intended his zones to have a world wide application; that is to say, a zone is the deposit (if any) that was formed during a given time all the world over. 1£a zone is absent in any locality where the neighbouring zones are present and there is no non-sequence, there was no material deposited there during the time (hemera) of that zone. Thirdly (though the idea of a zone transcends that of its fossil contents), Oppel defined his zones by means of a fauna; that is, he considered that an assemblage of similar forms in two areas was the best criterion for the synchronization of the deposits in which they occurred. The farther we go from the type-locality, the more will the fauna as a whole change; but the change will be gradual, and synchronism will be better established by reference to the presence of a similar fauna than by that of an identical species. ~ evertheless, the presence of a single species characteristic of a given zone is a strong pre sumption in favour of the presence of that zone, and in the absence of other forms may be taken provisionally as indi cating it. Last, Oppel named his zones after a fossil that occurred in the zone in the type-locality. This may be called the zonal fossil. A moment's consideration of the distribution of recent forms will show that in another locality the zonal fossil may be absent altogether, or present in another zone even when it may be absent in its own zone; for at the time when its zone was being deposited in the type-locality it is improbable that the zonal fossil had a world-wide distribution, and though, on the whole, throughout its lateral range, its vertical range was synchronous, yet in detail it is highly improbable that this was so, when the gradual spread of species from local centres is considered. The zone of a fossil, then, must not be confounded with its range. On the contrary, the zone merely bears the name of a fossil as a convenient label, and its doing so implies no more than that the fossil is found in that particular zone in one of the zone's localities. From the above considerations it is clear that when once a zone has been defined, its boundaries theoretically 'are fixed for ever. Thus, because Asteroceras obtusum is found in a small part only of Oppel's obtusus zone, there is no need to limit the obtusus zone, as Buckman apparently has, to the range of Asteroceras obtusum. t Nor is there any need to alter the name of a zone because in a given locality the zonal fossil is absent or uncom mon. Thus, because Deroceras dauai (James Sowerby) is un common at Charrnouth, there is no need to change the name of ,.. Buckman, 1893, pp. 481-2. t II. B. Woodward, 1893, p. 18. t Buckman, 1910, p. xvI. W. D. LANG ON Oppel's daucei zone, as Wright has done, first* to the zone of capricornus, and then t to the zone of henleyi.t Oppel founded 13 zones in his Lower and Middle Lias, namely, from below, upwards, the zone of Ammonites planorbis, of A. angulatus, of A.. bucklandi, of Pentacrinus tuberculatus , of Ammonites obtusus, of A. oxynotus, of A.. raricostatus, of A. armatus, of A. jamesoni, of A. ibex, of A. davai, of A. margari tatus, and of A. spinatus. The top and bottom zones of this series do not come into our maps j they include the Lias from the top of the angulatus to the base of the margaritatus zones. Their correla tions with the local sub-divisions are shown in the accompanying table (inserted opposite this page). IiI certain cases sub-zones also have been used in the detailed description j namely, the sub-zones of Arnioceras and of birchi in the tuberculatus zone j the sub-zones of brooki, planicosta and stellaris in the obtusus zone j the sub-zones of latacosta, Liparo ceras and Oistoceras in the daucei zone. In naming these divi sions sub-zones, the only implication made is that they are sub ordinate in each case to Oppel's zone. Except in this connection, they may be called zones, and themselves be subdivided, if necessary. In other words, it is advocated that, in general, the terms zone and sub-zone should have relative significance only to each other j absolutely they should be synonymous. As an example, Buckman's zone of striatus§ includes the two sub-zones of iataicosta and Liparoceras, but itself it is a sub-zone of Oppel's zone of dauai, It now should be possible to understand the detailed sequence. v -THE DETAILED SEQUENCE. (a) The Angulatus and Bucklandi Zones. II The planorbis, angulatus, and bucklandi zones compose most of the Blue Lias series or Lyme Regis Beds of the Survey Memoir. They consist of limestones separated by thin shales; and the last-named zone with the top of the angulatus zone below it forms the low, vertical cliff between Black Ven and Lyme, * Wright, ,863, p, 79. t Wright, ,879, p. 87· t Except in this particular, the definition and use of the term" zone, I' as here given, agrees on the whole with the account in the Survey Memoir by jukes-Browne. Here, however, the name "zone of Cardiaster {oSSa1'iU5 "is substituted for I' zone of Pecten asper," in a district where the latter fossi is rare [jukes.Browne, 1900, pp. 32-34 and p.63)· * Buckman, 1910, p. xvi. iI Strictly speaking, what the Survey call the" zone of Coroniceras bucklandi" is Oppel's "Bucklandibett" that (on p. 14 of his" Jura ") he SUbdivides into a lower bucklandi zone and an upper geometricus zone. But that he meant the term ., zone of Ammonites buck landi" to refer to the whole of his Bucklandibett is evident on reading further j on P. 822 he actually uses the term" zone of A. bucklandi "in this sense, and so it has been generally understood. Judd, in 1875, introduced the term" zone of Ammonites semicostatus OJ for Oppel's geometricus zone. Judd's semicostatus zone, therefore, lies outside the Survey's, which is the equivalent of our zone of Arnioceras minus the Shales with Beef. To face page 308. PROC. GEOL. Assoc., VOL. XXV. CORRELATIONS OF HORIZONS IN THE LOWER AND MIDDLE LIAS. The comparative thickness of the beds is not indicated. STAGES SUB SUBZONES WRIGHT, 1860 BUCKMAN, DE LA BRCHE, SUBDIVISIONS STAGES WOODWARD AND USSHER, I9II. here adopted. and 1863. 1910• I 1826 and 1839. adopted in this paper. I Zone of Ammonites Zone of Ammonites Zone of Light-brown Sands. spinatus. spinatus. spmatum. i Sands. c Zone ot ~largaritatus Bed Part of the Inferior -e ma,xaritatus. and marly Sands, Oolite. Laminated Beds. OJ E Zone of A maltheus Zone of A mmonites Starfish Bed, Shell o Zone of Ammonites c margaritatus, margaritatus. margaritalus. Zone of Bed and grey Margaritatus Marls. algomanum, micaceous Marls. etc. Three Tiers. ~~---1·------Three Tiers. Zone of Upper Clays. Grey Marl with thin Subzone of Oistoceras. cajJr.,~ornu", ...... ferruginous seams. Upper Limestone. Zone of L ;paroeeras Subzone of Upper Red-band Clays. capricornus and Zone of Ammonites Lioarocerns, Zone of Ammonites capricornus, The Green Ammonite Red-band. L. henleyi. daoan, Zone of Beds, Nodules imbed striatum. Lower Red-band Clays. Subzone of latacosta, ded in grey Marls. Lower Limestone. Grey Marl. '-'.-- ---.------;1------1------11------1------·I-~__,:.:..:...::L,-=;:..:c'----'I Lower Clays. Belemnite Stone. Zone of Ammonites Zone of Ammomtes Belemnite Stone. Zone of valdani. Belemnite Shale. o~ ibex. Io-X. Upper Belemnite OJ Marls. il=P=< Grey Marl. t s Zones of Uptonia Middle Belemnite Zone of Ammonites Zone of jamesoni. Impure Limestone. oJ '- [amesoni and Marls. ~ a Deroceras armatum, [amesoni, Lower Darker Belem c OJ Zone of Ammonites Blue marl. .3v ..'amesoni, nite Marls. (lJP=< Lower Paler Belem Zone of Ammonites Limestone and Marl Zone of armatum, nite Marls. armatus, with Belemnites. Armarus Limestone. -Zone of Echioceras Zone at Zone of Ammonites Limestone and Marl r artcostatum, raricostatum. raricostatus, Rarieostatus Clays. raricostatus, with Zone of Oxynotoceras Zone of oxvnotus, Zone of A. oxynotus. oxvnotum, Oxynoius Clays. Coinstone. lrreg ular bed of Lime Subzone of slellaris. 1,·,.1' Zone of steilare, stone with rounded !Nodulesfrequentlycon Stellaris Nodules; , taining Ammonites. Limestone with Zone of Ammonites I Brachiopods. Zone of Asteroceras obtusus. Subzone of planieosta. Zone of A mmonites Plamcosta Clays. obtusum. obtusus. Zone of Obtusus Shales. obtusum, Upper Cement Bed. Subzone of Il1'ooki. Cement Bed Shales. Lower Cement Bed. -- Brooki Clays. Subzone of b,rch,. Birehl Bed'---- . Shales with Beef. ------."._----_. 'I Indurated Marl con- Zone of Pentacrinus taining small plicated Table Ledge. Subzone of Zone of A rnioceras tubercuiatus, Zone of semicostatum, I Terebratulre. A rnioceras, Zone of Ammonites sernicostatum: turner), , Slaty Marls. .. Saurian Shales. ---PiSh-J1ed-.-_. 1 __E:"rtllL1:i[}leston..:: .\1arls and slaty Marls.: F ish-bed :-> hales. ------.---.-- i iO-I;e-ot·gmt~;~~i~·ns·;,,· -Grey'- Limestone. Zone of Coroniceras ,Zone of A mmonitrs hud· I---'----==-=--Grey Ledge to bucHan"i. !tand'=" Rueklan'11hetr ,. ...'2:"o~le';;1 ';;oli/o;;;';e:'" I Under Copper. Zone of Ammonites .§.~v..c c·~ ~ § ~~~..::,;'--..::...::...<:..!~~- Zone of Schlotheimla I bueklandi. I Zone of marmo,.m. Under Copper Shales ~ ~'E:~ I to Shales below Brick anf[ulata. i Zone of rnepastorna, ur _ iu·:: IfJV~-+-l'"'Cl i Ledge. Zone of Psiloceras .~ 5.2~~ iOllep~~n~;~;.;.~;'iies Zone of planorbIS. Shales and l ~~("J (1) ·_-- I ,_-L:..=::..::.:.-planorbis. __ ''-_...!:.:..=~~_l___------+---~:.:.::..::.:::...--_+_------L-----_+_------l---::::.:..:==---Limestones. I THE GEOLOGY OF THE CHARMOCTH CLIFFS. 309 known as the Church Cliffs. In the absence of fossil evidence to the contrary, I have accepted the Geological Survey's limits of the angulatus and bucklandi zones, and they are coloured accordingly on the map.* The names of the limestones, too, are taken directly from the Survey Memoir, t and the limestones accordingly identified. The Church Cliffs anticline brings up the angulatus beds, so that they take the form of a narrow strip, some 400 yards long, in the corner made by the cliff and the beach, in the middle of the Church Cliffs' extent. They are exposed, however, only at the western end of their outcrop j the rest is covered with talus, reinforced by matter falling from beneath the burning cliff in 1908 j and even this western end is visible only according to the vagaries of the tide, which mayor may not fill the angle between cliff and beach with shingle. Suppose, however, that the beds are fairly exposed, the collector is discouraged by the constant falling of the cliff, generally a stone or two at a time, varying in size, but sufficiently frequent and difficult to foresee to make collecting dangerous. This applies to the whole of Church Cliffs; but all except the lowest beds of the bucklandi zone can be worked (Iesssatisfactorily but with less danger) on the reefs. The beds of the bucklandi zone form the mass of the Church Cliffs j and, coming down to the beach at both ends of the cliff, the limestones from the base of the zone up to Third Quick join up, making concentric rings on the reefs OI) the fore-shore, Above Third Quick, the limestone rings are complete only at the north eastern end of the cliff j at the south-western end they are open, owing to the axis of the anticline emerging from the cliff and running along the reefs, and the consequent warping of the limestones as they turn to plunge under Lyme. Hence the mass of the reefs exposed at low-tide south of Church Cliffs are about on the horizon of Third Quick. It follows that Third Quick is an important limestone for locating others in the sequence. Limestones above Third Quick can be identified on the cliff by counting downwards from Grey Ledge, and those helow it by counting- from Third Quick itself. The characters of the limestones may change so quickly within a few yards that they cannot always be identified at once by their appearance. Some, however, may be known by fairly constant features, and these are useful for identifying the rest. Middle (or Second) Quick, for instance, may be known by the little lime stone Gumption, that, itself only a few inches thick, always occurs a few inches below it; Top Tape is often split into two layers; and Mongrel is a thick, prominent bed. (See Plate 39, Fig. A). * The presence of Coroniceras at about 30 ft. above Tabie Ledge suggests the possi blhty that the bucklandi zone should have a higher extensi~n. The abundance of A rtHoCeras In these 30 ft. does not discount the occurrence of Coronsceras, since A TflJO ceras probably ranges from the angulaius zone up to the Bircki Bed. t H. B. Woodward, ,893, pp. 60-62. PROC. GEOL. ASSOc., VOL. XXV, PART 5, 1914.J 21 310 W. D. LANG ON Other details of these zones are as follows, in ascending order: (I) BRICK LEDGE. (2) SOFT BED SHALES. (3) SOFT BED. (4) LOWER VENTY SHALES. (5) LOWER VENTY. (6) LOWER SKULLS SHALES. (7) LOWER SKULLS. The Survey record Lima gigantea,* L. hermanni* from this bed, and (in June, ~9I4) Spiriferina sp. was found in quantities. (8) UNDER WHITE SHALES. (g) UNDER WHITE BED, Lima gigantea,* Grypha:a araeata," (10) UNDER COPPER SHALES, Schlotheimia angulata," Lima gigantea. * (I I) UNDER COPPER, Lima gigantea," Ryncho nella calcicosta. * (12) IRON LEDGE SHALES. (13) IRON LEDGE, Gryphcea arcuata,* Rhynchonella catcicosta,' (14) UPPER SKULLS SHALES, Schlotheimia angulata (Schotheim), Grypha:a arcuata (Lamarck). (IS) UPPER SKULLS, .Schlotheimia angulata.* (16) UPPER WHITE SHALES. (17) UPPER WHITE BED, Grypha:a arcuata,* Lima gigantea.* (18) SPECKETTY SHALES, GrYPha:a arcuata. (Ig) SPECKETTY BED, Rhynclwnella calcicosta.* This is a prominent limestone. (20) LOWER MONGREL SHAL!, Ledge probably with Grey Ledge, which is absurd j for, standing on Broad Ledge, one may see Grey Ledge directly opposite and capping Church Cliffs. (32) GGMPTION SHALES, Ostrea, (33) GUMPTION, Fish remains.* A limestone two or three inches thick, useful for identifying Second Quick, from which it is divided by an inch or two of shale, though in one or two places it is actually fused with Second Quick. It forms a wide plat form a step below a similar one formed by Second Quick on the reefs beneath Lyme Church, and on it runs the little jetty at the corner where the cliff turns into Lyme. (34) SECO:-JD QUICK SHALES. (35) SECOND QUICK, Isocrinus," Forms a wide, flat expanse for some yards seawards from the base of the cliff beneath Lyme Church, where a wall has lately been built to support the cliff. (36) RATTLE SHALES. (37) RATTLE. Described in the Survey Memoir as "impersistent"; but persistent enough to make the identification of this and the two limestones above easy as a band of limestones occupying the middle of the section in the Church Cliffs anticline. Rattle comes down to the beach just north-east of the supporting wall beneath the church. (38) SECOND BED SHALES. (39) SECOND BED, Nautilus, * Isocrinus," Best and Second Beds reach the beach beneath the supporting wall under Lyme Church. (40) BEST BED SHALES. (41) BEST BED, Large Lima gigantea, * Sdtlotlteimia charmassei. * (42) VENTY SHALES. (;-1-3) VENTY. The reefs made by Venty and Top Quick are poorly developed in the north-east portion of their outcrop. South-westwards these reefs are lost out to sea. (44) Top QL'ICK SHALEs. (45) Top QL'ICK, Coroniceras buck landi.* (46) GLASS BOTTLE SHALES. (47) GLASS BOTTLE, Large Coroniceras buckiand» on the under surface.* A wide, conspicuous limestone with an irregular weathered face. It forms, with Grey Ledge, a single reef at the north-eastern part of its outcrop, and this reef soon runs out to .sca. It is almost certainly repeated with Grey Ledge on the south side of the Cockpits syncline. (48) GREY LEDGE SHALES. (49) GREY LEDGE, Coroniceras bucldandi," Arnioceras semicostatum,* Lima gigantea,* Acicula.* Grey Ledge is easily recognised by being the topmost bed of the limestones of Church Cliffs. Owing to the Cockpits syncline, the reef formed by Grey Ledge (and, probably, by Glass Bottle as well) is found on each side of Cock pits, and the eastern part apparently is repeated by a small fault. (b) T fte Tuberculatus Zone. The tub erculatus zone is the equivalent of the zone of Amioceras semicostatum of the Survey'[ + the Shales with Beef and the Birchi Bed, and = Wright's zone of Ammonites turneri + the Shales with Beef and the Birclti Bed. .. The names marked by an asterisk are recorded by the Geological Survey in the IgIl Memoir (Woodward and Ussher, '9"), pp. 35'38. t Iudd (,875). who founded the zone of this name. used it in quite a different sense. See footnote, p. 42. . 312 W. D. LANG ON This, with the obtusus, oxynotus, and raricostatus zones above, forms the Black Marl Series or Black Ven Beds of the Survey. Table Ledge is given in the Survey Memoir as the upper limit of their semic ostatus zone (which then= Wright's turneri zone), and the 50-70 ft. of Shales with Beef below the Birc hi Bed are included in the obtusus zone above. It is not clear if Oppel included the Birc hi Bed in his tuberculatus zone, but if so, this zone must include the semicostatus zone of the Survey, the Shales with Beef and the Birchi Bed. Buckman (1910, p. xvi) has already recognised a zone of birchi, but beyond naming its order of succession he has not defined its limits, since he refers to it as being doubtfully absent in York shire (the district he is describing). And since Arnioceras is found throughout the Shales with Beef, it is reasonable to regard such of the tubercuiatus zone as lies below the Birchi Bed as the subzone of Arnioceras (which thus includes all the beds above Grey Ledge and below the Birchi Bed) and the Birchi Bed itself as the sub-zone of birchi. * 1. The sub-zone of Arnioceras. (50) FISH BED SHALES. (51) FISH BED OR SPLIT LEDGE, Arnioceras semicosta tum. t A thin limestone. but two or three inches thick, generally visible on th~ cliff about 4 ft. above Grey Ledge. Its V-shaped outcrop can be traced in the Cockpits syncline, and, east of the syncline, it is several times repeated in the faulted fore-shore between Cockpits and Black Veri Rocks. (52) SAURIAN SHALES. Wright records Ichthyosaurus from these beds. (53) TABLE LEDGE, Arnioceras semicostatumct Avicula incequivalvis, t Rhynchonella calcicosta. t Though 3% ft. is given in the Survey Memoir as the thickness of Table Ledge, it will be realised, when the bed is examined, that none but arbitrary limits can be assigned to it, so gradually does it pass into the shales above and below it. Itself but an indurated shale, even at its core it is hardly to be called a limestone, but may be measured arbitrarily by the thickness of the big blocks that cohere when the bed tumbles on to the beach. On the cliff Table Ledge appears as a pale stripe, some 6 in. thick, 12-15 ft. above Grey Ledge, and running in the steep slope above the perpendicular cliff formed by the limestones of the bucklandi zone. (See Plate 39, Fig. B). Brought down by the western limb of the Cockpits syncline, at a point where Grey Ledge nearly reaches the beach, Table Ledge is lost beneath talus, and does not reappear until it emerges on the fore-shore at the extreme head of the bay, and runs out seawards in a reef as the eastern part of Black Ven Rocks. From the condition of the fore-shore reefs opposite where Table Ledge is hidden it * If it is considered that Oppel included the Birchi Bed in his obturus zone, the sub. zone of Birchi becomes a sub. zone of the obtusus zone and the sub-zone of A rnioceras becomes synonymous with the tuberculatus zone, t The names marked by a t are recorded hy the Geological Survey iu the 19" Memoir (Woodward and Ussher, 19I1), pp. 35-38. THE GEOLOGY OF THE CHARMOUTH CLI FFS. 3 I 3 app ears to be let down on the east twice or thrice by small fau lts just before it emerges. T able Ledge is full of fossils, and easy to collect from , either by breaking up the large f all en blocks or by searching the wide expa nse that is exposed (unless there is much sand about) at low tide beneath Black Ven. Amioceras is common, but poorly preserved, and, in the more sha ly parts of the bed, nearl y alw ays broken across, owing to the shale brea k ing into lumps on weath ering. Doubtless this curious weather ing into lumps with curved faces is connected with the segregation that indura ted the marl. Besides the strongly costa te Avicula that occurs in this bed and is common in the shales above, ther e is a smoother Avicula, characte ristic of Table Ledge, and easily noticed by its curious black prese rvation. The R lrynchonella menti oned in the Survey Memoir may be seen on the surface of T abl e Ledge exposed at low tide, occurring in patches of, say, twenty individuals, closely crowded. Shales witlt Beef. The 50-70 ft. of Shales with Beef that lie between Table Ledge and the Birchi Bed, and form the lowest pr ecipice on Black Ven, are given seven subdivisions in the Survey Memoir, and these inclu de several limestones. None of these, however, is persistent j and, after rep eated efforts to identif y the Sur vey's subd ivisions, and, these failing, to trace beds whose lithic characters persist throughout the exposure, so that the exact position of fossils could easily be indicated, I have been drive n to abandon the attempt, and (except at. the Char mouth end of the exposure) to refer any fossil found to its dis tance f rom T abl e Ledge or the Bircbi Bed j and, since the thickness of the. beds as a whole is varia ble, this does not yield very accurate results. As a matter-of practice, however, the case is not so hopeless as it seems. The cliff sections (with exceptions referred to later) yield very few fossils. The Survey Memoir record s none (except Wr ight's " Saurian remains "). But the reefs from Bar Ledge to Raffey's Ledge are in pl aces crowded with fossils, which, though fo r the most part poorly preserved, repay collecting. The easternmost reef is Little Ledge, and probabl y corresponds with a bed of " beef?' about r5 ft. below the Birchi Bed on the cliff above. West of this is Raffey's Ledge (Reef 2 0 on the map ), that perhaps corresponds with two or three impersistent lines of "beef " about 25 ft. below the Birchi Bed on the cliff j and the reef west of this (Reef 19 on the map) is probably the indu rat ed marl, full of Avicula, that is exposed at the base of the cliff just west of the bre ak in the cliff before Charmouth beach is reached. The Birclri Bed is some 33 ft. above this j hence the lower 30 ft. or so of the Shales with Beef are represented in the reefs between that formed by T able Ledge and Raffey's Ledge. Except in one or two spots, the reefs follow one another in orderly stratigraphical succession, dipping east-south-east, so W.D. LANGON that fossil s collected reef by reef repre sent the f aunal succession of at least the lower half of th e Shales with Beef . The reef s are numbered from I to 20 on the map . Since, however, the numbers originally were given in order to locate the first fo ssils collected, and befo re the irr egularities in the succession were realised, it happens that in two instances they do not show successive reefs; thus Reef 7 is the landward extension of Reefs 6 and 8, across a fracture; and Reef I I is the landward half of Reef I2-the two f orm a single reef broken by an oblique channel; nor must it be supposed that the vertical distance between successive reefs as numbered is even approxi mately the same. Reefs I and 2 are practically the top of T abl e Led ge. It was remark ed above that the limits of T able Ledge were arbitrarily drawn, and so on the reefs it is impossible to define the exact limits of this bed . The commonest fossils of the Shales with Beef are Arnioceras, a small, well-preserved Lima, A vicula, Oysters, and several un identified Lamellibranchs. One Oyster is of special int erest ; it is common and characteristic of Reefs 1-4, but has been found as low as Gumpt ion Shales and as high as Reef 7 ; it commonly grows upon, and consequently is moulded to the form of, an Ammonite, so that, until the structure of the shell is noticed , the fossil may be mistaken for an Ammonite. Other detail s of the Sh ales with Beef are as follows: (54) REEF I, Arnio ceras, R ltyncho nella . Reef I is pr actically the top part of T able Ledge. (55) REEF 2, Arnioceras, Avic ula, R llyllchonella. (56) REEF 3, A vicula, B elemn it es. (57) REEF 4, Arnioceras, (58) REEF 5, Arnioceras, Avicula, Myriacantlms. (59) REEF 6, A rnioc eras, L ima, A vicula. (60) REEF 7, Arnio ceras, L ima. (61) R EEF 8, A rnioceras, Lima, Avicula, Ostrea. (62) REEF 9, Avicula. (63) REEF 10. (64) REEF II, A rnioceras, Lima, Ostrea, Rlrync honella. (65) REEF 12. (66) REEF 13, Arnioceras, Lima, Avicula. (67) REEF 14, Arni oceras, Lima. (68) REEF IS. (69) R EEF ] 6, Arnioceras. (70) REEF 17, Arnio ceras, Coroniceras, Ostr ea, At what is, ap parentl y, the horizon of Reef 17 on the cliff above, about 40 ft. below the Birchi Bed, Arnioceras is very abundant in a bed an inch or two th ick, and Coronic eras and Belemnites occur. * (7I ) REEF 18. (72) R EEF 19, A vi cula. An indur ated marl , about .3° ft. below the Bi rchi Bed on the cliff, full of Avicula, and cont aining, too, Arnioceras, is almost certainly the horizon of Reef ]9. (73) REEF 20. Probably represented on the cliff by several lines of "beef " 25-28 ft. below the Birchi Bed. (74) LITTLE LEDGE. Probably represented on the cliff by" beef ," ] 5 ft . below the Birclti Bed . 2 . T Ile sub-zone of /'vl icroderoceras birchi , Throughout '" For the sig nificance of the OCCurrence of Coraniceras, see footno te on p, 30!). THE GEOLOGY OF THE CHARMOUTH CLIFFS. 315 its greater extent the (75) BIRCH! BED consists of nodules, elongated in the direction of bedding, them selves showing bedding, with layers of "beef" above and below that show cone-in-cone structure j the upper layer of " beef" is some three, the lower not more than two, inches thick (see Plate 40, Fig. A). Occasionally a tabular limestone occurs immediately above the line of the Bire/zi nodules. It is probable that this limestone contains Arietites, and consequently belongs to the zone above. The Birchi Bed appears high up on the sloping cliff above the summit of the Church Cliffs anticline, and descends with the eastern limb of that anticline to the height of about 100 ft. above sea-level. The bed appears to be but little affected by the Cockpits syncline, and descends gradually as it approaches Charmouth, reaching the beach level at the end of Lower Sea Lane. It forms the top of the lowest of the three clay precipices on Black Ven. A piece of the bed about 200 yards long is let down some 5-10 ft. between two faults opposite Bar Ledges. As described above, the BircJzi Bed is again let down on the east about 10 ft. at the Char Valley disturbance, appearing at Mouth Rocks, first as a single reef dipping sharply to the east-south-east, and east of this beneath three parallel, steeply-folded anticlines of the limestone lying immediately above it, forming as many reefs (see Plate 40, Fig. B). It is not again seen, though probably it is near the surface on the fore-shor-e east of the river mouth, since on the cliff opposite this point the Lower Cement Bed (40 ft. above the Bire/zi Bed) appears at some height (see Fig. 23, Section A). (c) Tlte Obttcsus Zone. Oppel's zone of Ammonites obtusus comprises all the beds from those immediately above the sub-zone of Microderoceras bircJzi (perhaps including this) below, up to those with Asteroceras stellare above; and the Survey follow him, except that they include in this zone the Birclti Bed and Shales with Beef below it. The ammonite succes sion within 'this zone appears to be, from below upwards, Arietites turneri, Arietites [Asteroceras] brooki, Asteroceras obtusum, Xipheroceras [Amblycoceras] planicosta, Asteroceras stellare. The main point of doubt is the exact horizon of Arietites turneri, Before this is considered, it must be noted that Sowerby* gave two figures of this ammonite, the upper figure on his plate from the drift of Norfolk and the lower figure from Watchet. When Oppel and Wright quote A. turneri from the tuberculatus zone, they mean (presumably) the Watchet form j later palseontologists, however, following that interpre tation of this species given by Wright in his monograph • James Sowerby, 1824,vol, v, P. 75. PI. cccclii, 316 W. D. LA~G 0:-.1 (Wright, 1881, p. 292, PI. XII., Fig. 4), have accepted the Norfolk form as the type.* Body-chambers of specimens resembling this form (that differs from Arietites brooki in having a larger umbilicus and therefore" narrower "-technically lower -whorls),t and preserved in pyrites, are very common on the beach between Cnarmouth and Lyme; and, though I have never been fortunate enough to find one in place, the fishermen (who include them with the more involute and high-whorled forms in the comprehensive name" brookei") say that they occur within a few feet above the Birchi Bed The Birelzi Red forms the top of the lowest precipice on Black Ven ; and, as a consequence, the beds immediately above, forming a terrace sloping gently to the foot of the middle precipice, give no good section, but are broken and talus-covered. Ammonites of the turneri group, then, are not easy to find in place; nor is Arietites brooki, partly because this form is keenly sought for sale in Lyme, partly because, probably, it is commonest in these same rather inaccessible beds within 10 ft. above the Bircki Bed. Both of the only two specimens I have found in place are intermediate in character between the two forms; one came from 5 ft. above the Birchi Bed from the break in the cliff just west of Charmouth beach, and is of the peculiar yellow colour of the type-specimen of A. brooki ; the other is from the contorted beds in the Char valley disturbance (described above), from the river bank, immediately east of the New Cut, and above at the horizon of the Lower Cement Bed. The fishermen sav that" brookei" occurs in the Birchi Bed, by which they probably mean the impersistcnt tabular limestone lying immediately upon the Birchi nodules. How high Arietites brooki ranges is uncertain. The Cement Bed Shales are very barren, and the next beds that yield fossils in any abundance are 8 ft. or so of shales above the Upper Cement Bed (of the Survey Memoir, but not of the fishermen). This is where the large specimens of Asteroceras obtusum occur that are sold in Lyme. I have not found this form in place, bnt have the information from Mr. Thomas Hunter, fisherman, of Char mouth, who has shown me a hole in the section whence one had been taken. The impersistent, lenticular limestone, full of Xipheroceras [Amblycoceras] plam·costa,t which is so abundant on the beach, is said by the Survey§ to occur in the 26 ft. above these Obtusus Shales, and I have obtained Xipheroceras aff. planicosta from the Limestone with Brachiopods (=.c Upper Cement Bed of the fishermen, not of the Survey) a foot or so beneath the nodules that contain Asteroceras stellare. • Selected as early as IB56. See Oppel, IB56, p. B2. 1- It is probable that several stocks at about this horizon pass rom a low (' narrow"}· whorled evolutc to a high-whorled involute shape. and that all the forms havlne the former shape have been called A "ietites tnrneri and those with the latter shape A. brooki; 1 By error, what should be Xipheroceras is printed" A I1lblycocf1·as " on the legend to tbe Maps. § Woodward and Ussher, '9[1, p. 35. PROC. GEOL. Assoc., VOL. XXV. PLATE 40. -;.~::...t-40 ~;:...... ~,t... ~"C.;.~.',.4" ~a-~r;~t~ :· . '. - •: "( • ,>'~.," ....' ~<'< . -.. ,. ' '"It) '" .' ""~'• .,A ""' . . .'. ..~ ~ ~~ ' ...... ~ .. .~ "', ...... ~~,.-. .~ . 'I-"~"'" .• "'.~• •1 . '\. ~.~ ~'.' ~-":" . " ~'J.' . ,... ': t: ' .> ~~ ~t~.,..,..~, -·~ ..:.,. ~~-jooo""'"7":>~.r ~. \'. - ""'"'4_.... .,.k. '.t.t' - ~ t .. ~•.. ,; . -. ~'.:~.~~,,- .; _ ~.• "; .•1 .' I.~.,. t .... .~~., '::;.'_ """ .'" ~.'~"".~ v- -~~~~~ ~~-.;;IlIr---~ ..... ...... ,'" ... .' .' • v . J, - .~ .,. ,..... <; .. -.~ .. .':' .. 1" ~ A . ,.'" [Photo by W. D. Lang, [Photo by W. D. Lang. A.-THE Birchi BED, IN' PLACE, BETWEEN CHARMOUTH B.-ONE OF THE REEFS FORMED BI' AN ANTICLINE OF AND LYME. TH& Birchi BED AT MOUTH ROCKS, CHARMOUTH BE.<\CH. To face page 316. THE GEOLOGY OF THE CHARMOUTHCLIFFS. 3 I 7 T o sum Up: While the ammonite succession in the obtu sus zone is, on the whole, clear , the exact range of each f orm generally is undetermined. Arietites turneri almost certainly occurs immediately above the Birchi Bed j A. brooki ranges above the Birchi Bed and below the Obtusus Shal es) but, further than this, its up ward and downward limits are unknown j Astero ceras obtusum occurs in and is probab ly confined to the Obtusus Shales j Xipheroceras planicosta has been found as high as the Limestone with Brachiopods, but its lower limit is undetermined pr obab ly, however, above the Obtusus Shales j * the range of Asteroceras st ellare lies between the Coinstone above and the Limestone with Brachiopods below. We are now in a position to consider the possibility of sub dividing Oppel's obtusus zone, which, in this district at least, has become too cumbrous fo r convenient handling as a unit. Buckman (1910, p. xvi.) has alrea dy recognised a stellaris zone above his zone of obtusus, but- he has not indicated its limits. We have already seen th at' it need not disconcert us to find that As teroceras obtusum occurs in but a small part of Oppel 's obtusus zone, nor that the exact ranges of the ammonites within the zone are not yet determined. All that is needed is to recognise that the limits of the obtusus zone have been fixed once for all by Oppel and that within the zone the succession is clear. Of course, should Oppel 's deter mination of his. obtusus zone on Black Ven hereaft er prove notto be synchronous with his limit s of the zone in Germany, the boundaries at Black Ven will have to be readjusted. Otherwise they must remain as defined) and we may now divide these beds into sub-zones. There seems to be no need for recognising a sub-zone of Arietites turneri, since its position with regard to A. brooki is as yet only conjectural j besides the zone of turneri has already been defined by Wright (ta king the Watchet specimen as the type), and is the equivalent of our sub-zone of Arnioceras , The proposed sub-zones, then, are as follows: I. The sub-zone of Arietites brooki, including all above the Birchi Bed and below the Obtusus sha les. 2 . T he sub-zone of X iplteroceras planicosta, including all above the Up per Cement Bed (of the Surve y) and below and incl uding the Limestone with Brachiopods (=th'e Upper Cement Bed of the fishermen). 3. The sub-zone of Asteroceras stellare, including all above the Limestone with Br achiopods and below and including the Coinstone. I. T'he sub-zone of Arietites brooki. Besid es the (76) INl P E RSISTENT TA BULAR LIMESTONE LYING ONTHE BIRCHI NODULES, the pa per-shales and clays that lie between 'I • A X iphero ceras , almost ce rta inly In pla ce. was found an inch or two below th e in d urat ed Ma rl so me IO ft. be low th e Lower Ce me nt Bed . W.D. LAlIIG ON the Birclti Bed and the Obtusus shales are traversed by th ree more or less persistent harder beds, of which the most conspicuous and continuous is the (80) LOWER CEMENTBED. * This is situated about 40 ft. above the Birchi Bed, and easily found, though not very conspicuous on Bl ack Ven, since there it lies towards the base of the middl e clay precipice, and consequently is largely hidden from below by the top of the th ird prec ipice, and fr om above by the top of the pr ecipice to which it belongs. East of Charmouth beach it is first seen in a reef running across the river where the New Cut has been mad e, close und er the beginning of Stonebarrow Cliff, and there are indications on the fore-shore opposi te this point of a contin uation of th is reef. The beds here are violently contorted. But if the river bank is f ollo wed east ward the contortions give place to sinuous folds, and th e Low er Cement Bed is seen (very poorly developed) some 2 0 ft . above the beach at a point just east of the river-mouth. It is lost east of this under talus and tr acts of grassed-over cliff, but reappears, strongly developed, at the base of the section wher e th e Belemnite Marls first appear in section on Stonebarrow Cliff. Here is the summit of th e last and largest undulation; the Stone ba rrow anticline, and east of thi s the dip is steadily east-south east, bringing the Lower Cement Bed grad ually dow n to the beach. Just before it reach es the beac h a fa ult, affecting all the beds up to the Coinstone, brings the beds down a few feet on th e east. T he reef called Bl ack Rock corresponds in position to the continuation sea wards of the Lower Cement Bed . About 10 ft. below the Lower Cement Bed, and separated by (79) UPPER BROOKI SHALES, there occur s an (78) INDURATED BAND a few inches thick, with th e (77) LOWER BROOKI SUALES beneath it. I have not been ab le to ascertain wheth er or not it is pe rsistent throughout the cliff -section ; but it may be seen on Black Ven immediately west of th e br eak in the cli ff just west of Ch armouth beach ; and it is important on Stonebarrow fo r showing more clearly than the Lower Cement Bed the undula tions of the beds east of the river mout h, since, being lower than the Cement Bed, it is less obscured on the cliff by slips. The (82) UPPER CEMENT Ban] is the most inconsta nt in character of th e three hard bands in thi s sub-zone. It lies, with the (81) CEMENT BED SHALES int ervening, abou t 15 f t. above the Lower Cement Bed and immediately beneath the Obtusus Shales. It is always distinguisha ble f rom the shales above and below, although in places itself is sha ly ; in fact, it is impossible defi nitely to know from its ap pearance alone, even at a short distance, whether at any point it is hard or sof t. On Black Ven, opposite Black Ven Rocks, the bed is doubl e, consisting of two ban ds of limestone a foot or two apart. On Stonebarrow, though it looks * II . B. Woodward, 1893. p, es. t H.B. Woodward, 1 ~93 . p . 65. THE GEOLOGY OF THE CHARMOCTH CLIFFS. 319 like a limestone, the bed is generally shaly j here and there, how ever, it is indurated. It is probably responsible for the rocks known as Dover Ledge. The fishermen do not recognise it as a definite bed, calling the Limestone with Brachiopods, some 30 ft. above it, the Upper Cement Bed. Besides Arietites brooki (which alone the Survey record from this sub-zone), a small Lima has been found 5 ft. above the Hirclti Bcd, the Xipheroceras, mentioned on p. 317, and a young, as yet unidentified, ammonite from la-IS ft. above the Birchi Bed. 2. Tlte suo-zone of Xipluroceras planicosta. The (83) OBTUSUS SHALES, the lowest member of this sub-zone, form a band of paper shales, about 8 ft. thick, that project from the general surface of the cliff and are a conspicuous feature, even where the cliff is grassed over, since at such places they often project through the grass and can be traced from section to section. A layer of nodules occurs in the shales where they reach the beach under Stonebarrow. Besides Astcroceras obtusum, which is eagerly collected for sale in Lyme, and con sequently hard to find in place, Xi-plteroceras aff. dudressieri" (d'Orbigny) has occurred. Mr. Thomas Hunter, of Charmouth, has obtained Asteraceras obtusum from the rocks between Dover Ledge and the Mumbles rocks, where these shales must run out to sea. The shales and clays lying above the Obtusus Shales «84) LOWER PLANICOSTA CLAY) and below the Limestone with Brachiopods «86) UPPER PLAI\ICOSTA CLAY) are divided, according to the Survey Memoir, by an "impersistent layer of limestone (like Ammonite Marble) with many small Ammonites, A. obtusum, Amblyc oceras planicosta, etc.," and" resembling the famous Ammonite Marble of Marston Magna."] I have not been able to find this (85) PLANICOSTA LIMESTONE in place, but it is very common on Charmouth beach and crowded in places with ammonites, chiefly X ipheroceras [Amblycoccras] planicosta and Cymbites sp. t Above it, the Survey Memoir describes the " Pentacrinite Bed, yielding Extracriuus briareus,' The (87) LIMESTONE WITH BRACIIIOPODS is not specially noticed in the Survey's account. It is a tabular limestone that clearly demarcates the clays with Stellaris nodules above from the Planicosta clavs below. On Stonebarrow Cliff it is verv conspicuous, since it weathers to an ochre-yellow, and thus form"s a coloured line along the cliff. The fishermen call it the Upper Cement Bed, Fallen blocks of it lie strewn on the flat below the precipice ncar the top of which it occurs, and the bed can be reached in place as it comes down to the beach farther east. '" Mr, Buckman kindly identified this specimen. + Woodward and Ussher, 19[1, pp. 35 and 28.. ~ A nodule containing a iarge unidentified body chamber was found at thIs horiaon June, 1914. 3 20 W. D. LANG ON On being broken up it is found to be full of brachiopods pre served in silvery-looking calcite. It also contains Cymbites sp., Xipheroceras aff. planicosta, and a small well-preserved Lima. 3. The sub-zone of Asteroceras stellare, The (88) STEL LAR1S NODULES lie in about 10 ft. of clay bounded by the Limestone with Brachiopods below and the Coin stone above. This 10 ft. band forms the top of the middle clay precipice on Black Ven and the lowest precipice on Stonebarrow cliff. It is difficult of access on Black Ven, but on Stonebarrow it can easily be reached where it descends towards the shore. On the whole, the nodules tend to run in lines, especially on Black Ven, but are often irregular in their occurrence. The (89) COINSTONE is a more or less persistent tabular limestone with an iron-stained, corroded and wavy upper surface. It is a few inches thick, and by no means conspicuous. (d). Tile Oxynotus Zone. The clays placed in this and in the next zone above are gener ally difficult to examine, since, occupying the gentle slope above the middle and below the top clay precipice, they are much disturbed with slides and covered with talus; a clear section in these beds is therefore hard to obtain. They are not very visible on Black Ven, and on Stonebarrow, where they approach the shore, they are generally talus-covered. This year, however (1914), good sections have appeared at the cliff-foot about a mile east of Charmouth beach, and the sequence has been deter mined in some detail. The most remarkable modification of the accounts as yet published has to be made in the raricostatus zone, and will be referred to later. (co) CLAYS ABOVE THE COINSTONE, with? Bifericeras sp., in the lower part extend for about 5 ft., and are capped with some shaly beds that are rather prominent in the section. These (91) OXYNOTUS SHALES give place to the (92) OXYNOTUS BED, the clay in which occur the pyritised forms of Oxynoticeras common in the shops in Lyme. The Oxynotus shales and Oxynotus Bed together are about a foot thick. The zone is thus much thinner than appears in the last Survey Memoir.* The exact thickness of 1his and the next zone is hard to obtain, chiefly because of the difficulty of estimating the angle of slope of the section, and partly because the sections are only some 10 ft. high and have to be pieced together by following a given bed from section to section along the low cliff. Mr. Buckman has kindly examined for me a fragment of a large Ammonite found a few feet above the Coinstone. He has '" Woodward and Ussher, I9II, p. 35. Partly because beds with Ammonites of the densinodum group lying above the Oxynotus bed are here placed in the raricostatus zone, as, apparently, Oppel would have placed them. TilE GEOLOGY OF TilE CHARMOUTH CLIFFS. 321 doubtfully referred it to Deroceras,* There is a small inner row of spines in addition to the larger outer row and the periphery is very flat. (e) The Raricostatus Zone. The remarks concerning the exposure of the ox ynotus zone refer equally to the zone of raricostatus, But the section shown this year on Stonebarrow discloses a thickness of the raricostatus zone at this point quite at variance with that given in preceding accounts. The latest Survey Memoir gives 10-15 ft. from the top of the oxynotus zone to the Watch Ammonite Stone, and as far as can be understood (since the Armatus Limestone is not recognised as such by the Survey), about 2 ft. between the Watch Ammonite Stone and the Armatus Limestone. And since no contradictory evidence was found (and it is quite likely that on Black Ven the Survey's measurements hold), thesemeasurements were accepted and are given in the coloured legend to the map. The Stonebarrow section now exposed gives about 29 ft. from the OX)!llotus Bed to the Watch Ammonite Stone and 16 ft. .from the Watch Ammonite Stone to the Armatus Limestone, a total of 45 ft. Above the Oxynatus Bed are 9 ft. of (93) PYRITIC CLAY, the LOWER PART with ammonites of the densinodum groupt and the (94) UPPER PART with these and a bituberculate Deroceratid, capped by a line of small flint-like nodules of calcium carbonate, the (95) S:\1ALL NODULF. BED. This is followed by about TO ft. of (96) CLAY WITH DEROCERAS of a form resembling in general appearance the type D. armatum (James Sowerby) from Whitby, but far below the armatus zone. It will be of great interest if this form proves to be the true D. armatum, for, in that case, here will be an example of the zonal fossil lying entirely outside the zone that bears its name. Above the Clay with Dcroceras are (97) Clays with thin, impersistent layers of "beef" (fibrous calcite), and then about 10 ft. of (98) LOWER CLAYS WITH RARI COSTATUS in the top part j then the (99) WATCH AM MONITE STONE about I ft. thick, crowded with ammonites of the raricostatus group, and containing, too, Belemnites, Pleuro tomaria sp. and Lima sp. The Watch Ammonite Stone is not quite continuous j occasionally gaps occur, and in these gaps raricostatus ammonites are common. The limestone is generally talus-covered on Black Ven, but may be seen on the eastern slope of that cliff, just below where the outcrop turns inland. Fallen blocks arc not uncommon on Black Ven. Ammonites of the raricostatus group abound in the inch or so of clay above the Watch Ammonite Stone, and here numbers of a Gryp haa re- '" U A blsptnous form apparently between Microderoceras and Deroceras," t Generally placed in the genus, U illicroceras." 322 W. D. LANG ON sembling G. arcuata (Lamarck) have been found. Above the Watch Ammonite Stone are 12 ft. of (roo) UPPER CLAYS WITH RARICOSTATUS, and then a layer of large flint-like nodules of calcium carbonate (about 1 ft.), the (lor) UPPER NODULE BED, then 2 ft. of (r02) CLAYS ABOVE LARGE NODULE BED, capped by a thin, irregular hummocky limestone that probably marks the base of the armatus zone and lies about a foot below the Armatus Limestone. The following summary of this zone and the zone below, as exposed at the base of Stonebarrow cliff, will render the de scription easier to follow: ft. Part of A rmatus Limestone Armatus 14. Armatus Clays. • { }I zone. 13. Hummocky Limestone . 12. Clays above Large Nodule Bed I 3 II. Large Nodule Bed . . f 10. Upper Clays with raricostatus 13 9. Watch Ammonite Stone . I Raricostatus 8. Lower Clays with raricostaius • 8 zone 7. Impersistent layers of fibrous calcite I 45 ft. 6. Clay with Deroceras 10 5. Small Nodule Bed . . . Clays with impersistent beds of } Pyrites, containing "M'icroceras" } 9 4.{ below and bituberculate Dero- ceratid above. ... Oxvnotus 3. Oxynotus Bed zone I 2. Oxvnotus Shales • } 6 6 ft. l I. Clays above Coinstone Part of Obtusus zone Coinstone. 51 (f) The Armatus Zone. Oppel placed a 'doubtfully-recognised armatus zone between his zones of raricostatus below and of [amesoni above. A lime stone containing a large, spiny Deroceras-?D. pugnax, S. S. Buckman-lies at the foot of the Belemnite Marls, which overlie the Black Marl series and consti tute the Stonebarrow or Belemnite Beds of the Survey Memoir. They appear in contrast to the Black Marls below, being pale in colour, in fact, weathering to a very light blue-grey. They form the highest clay precipice on Black Ven, and the whole or greater part of the seaward cliff after the first half-mile or so east of the Char. They are capped by the Belemnite Stone, and between this bed and the Armatus Limestone at their base they contain no really persistent hard bands. Calcium carbonate, how ever, has segregated in the bedding planes along definite tracts, forming more or less indurated bands of a lighter colour. Oppel included in them his armatus, jamesoni, and ibex zones, but gave no indications of the zonal limits; nor has the Survey Memoir TilE GEOLOGY OF THE CHARMOUTH CLIFFS. 323 suggested any. Fossils (other than belemnites), though abundant at certain horizons, arc not easy to obtain in place, and when obtained are poorly preserved, and consequently difficult to determine. Xevertheless, some results have been obtained from the fossils collected. Thc upper limit of the armatus zone has not, however, been determined UPO!1 fossil evidence. Uptonia, occurring at the top of the Middle Belemnite Marls, carries the jamesoni zone to within I7 ft. of the t017 of the series j while Acantho-plenroceras, found a foot below the Belemnite Stone, confirms the inference of the Survey Memoir that the top of the Belemnite Marls represent the zone of ibex. The Belemnite Marls have recently been divided strati graphically into an upper, a Middle, and a Lower series, of which the last (comprising the lower half of the total thickness) is subdivided into Lower Darker Marls above and Lower Paler Marls below." Until more accurate divisions are possible (i.e., divisions according more with Oppel's zones in Germany) it will be convenient to regard the Lower Paler Marls as the zone of Deroceras arniatum, the Lower Darker Marls and the Middle Marls as the zone of Uptonia [amesoni, and the Upper Marls as the zone .of Tragoplt),llouras ibex. Thompsont has recently introduced a sub-zone of Coeloceras pettos into the [amesoni zone, and in that case the other part of Oppel's jamesoni zone requires a new name. But though ammonites of the pettos group have been found at Charmouth, their horizon is uncertain, and until this has been ascertained it is impossible to define the pettos sub-zone. The armatus zone, then, is here considered to include the Lower Paler Marls with the Armatus Limestone at their base, the (103) HUMMOCKY LIMESTOI\E (containing an un named Deroceratid) a foot below this, and the inter vening (104) ARMATUS CLAY. (See p. 322.) On Black Ven the (lOS) ARMATUS LIMESTOI\E is nearly everywhere covered with talus. It is well exposed, however, on Stonebarrow, where it comes down to the beach a mile or so east of the river mouth, and, when not covered with shingle, may be seen as a long shelf running obliquely across the beach. In places it is full of the large, spiny Deroceras already mentioned, and contains, too, a small depressed Dcroccras, besides Dcroceras aff', [Aegoceras] .leckcllbyi (Wright), t and saurian remains. The Lower Paler. Marls (consisting, from below, upwards of (106) LOWER ARMATTJS MARL, (J07) LOWER I"DURATED l\IARL, (108) UPPER ARMATUS :\fARLS, and (J09) 1)PPER b"DljRATED :\IARL) may be seen just above the Armatus Limestone, and form Hawkfish Ledge, a festoon-shaped reef lying off Westhay Water. The dip at this point flattens out, and a little to the east, at Ridge Water, * Lang, IgI3, PP. 4oB-4II. t Thompson, 1899, p. 75. and rgIO. p. 456. :I Mr. L. F. Spath kindly identified these forms. W. D. LANG ON begins to reverse. Hence Hawkfish Ledge, instead of running out to sea as a series of parallel reefs, curves round festoon-wise and encloses a small basin. This is well seen at half-tide, when the wayes may be breaking on the Ledge and again on the beach, while the intervening water is calm enough for the passage of a rowing-boat. (g) T Ite Jamesoni Zone. The rest of the Lower and all the Middle Belemnite Marls are provisionally assumed to be the equivalent of Oppel's [amesoni zone. The (IIo) LOWER DARKER MARLS are very barren, but contain saurian remains, and at the top Inoceramus falgeri, E. von der Linth. They descend to the beach towards Westhay, and their junction with the Middle Marls just reaches the beach at Ridge Water, east of which it rises again to the cliff with the reversal of the dip. The Middle Marls are very fossiliferous, though the fossils on the whole are poorly pre served and not easy to find in place. The Marls consist of six alternating lighter and darker bands, of which the (II6) UPPER DARK BAND is the top-most and the (III) LOWER PALE BAND the lowest. The (II3) MIDDLE PALE BAND itself is divided into five thin beds by three very pale stripes. The subdivisions not mentioned are (II2) LOWER DARK BAND, (II4) MIDDLE DARK BAND, and (lIS) UPPER PALE BAND. They can easily be collected from at Westhay and Ridge Water, and between the latter and the great Ridge fault they are continually made accessible by the succession of small faults that bring them down close to the beach as soon as the dip carries them at all far up the cliff. The commonest fossil, besides belemnites, of the Middle Belemnite Marls, is Inoceramus falgeri, Merian, in Escher von der Linth, and at one horizon-at the top of the Upper Pale Band-Uptonia aff. bronni (Roemer) in some abundance. The inner whorls of the latter form are preserved in pyrites, and doubtless they are what Oppel, finding here, calls young Ammonites jamesoni. Polymor-phites sp., recognised by Mr. L. F. Spath as probably denoting the jamesoni zone, was found in place in the highest part of the Lower Pale Band on Black Ven in May, 1914. The Middle Belemnite Marls also yield Pecten sp., Lima sp., Crinoid remains and crushed Brachiopods (Cincta sp.). (It) The Ibex Zone. While the lower limit of the ibex zone has been but tentatively defined, its upper limit has hitherto been still more uncertain. In the older Survey Memoir the Belemnite Marls were considered THE GEOLOGY OF THE CHARMOUTH CLIFFS. 325 to contain the armatus, jamesoni and ibex zones, and, since their limits were not indicated, all that could be inferred was that the zone was represented by the upper portion of the Marls. In the latest Survey Memoir, * the Belemnite Marls include only the armatus and [amesoni zones, and the ibex zone is omitted, presum ably because, as stated in the former Memoir, Tragophylloceras ibex has not been found at Charmouth. t Though T. ibex, apparently, is absent, yet it is possible to define its zone with some exactness. Oppel recognised its existence at Charmouth by the finding of "Ammonites bipunctatus und Maugenesti in einer Schichte, welche tiefer lag als die des Amm. Davoi und capricornus," t ammonites whose presence was held by him to define the zone; but he did not determine exactly whence they came. It is probable that it was from just below the Belemnite Stone where Acantho pleuroceras ellipticum (James Sowerby) has been found in place. But Oppel also quotes Ammonites loscombi and A. lienleyi as occurring in the ibex zone. Now, at Charmouth, Tragoph.yllo ceras loscombi (James Sowerby) does not occur below the Lower Clays of the Green Ammonite Beds (an allied form has been found in the Belemnite Stone, but nothing like it lower than this). And by "Ammonites henle yi," Oppel almost certainly meant some form of the iatcecosta or striatus groups, which do not range (or, at any rate, are not common) below the Belemnite Stone. It is obvious, therefore, that the upper limit of the ibex zone must be- above the Belemnite Stone (the lowest horizon at Charmouth for ammonites of the loscombi and llenleyi groups) and below the horizon of Deroc eras dauai (James Sowerby), which at Charmouth occurs in the Red Band of the Green. Ammonite Beds and a foot or two below it. Considering that the clays above the Belemnite Stope mark the incoming in force of the Liparoceratidse,' a group that in localities where TragophylZoceras ibex occurs succeeds that form, it will probably be found that if the upper limit of the ibex zone be drawn at Charmouth so as justto include the Belemnite Stone, the zone will synchronise with Oppel's ibex zone inSwabia. The ibex zone, thus defined, consists of the Upper Belem nite Marls. Five stratigraphical horizons are recognised in the Upper Belemnite Marls, namely, from below, upwards, the (117) UPPER PALER MARLS, a thin 2 ft. stripe; the (IIS) UPPER DARKER MARLS, S ft. thick; 3 ft. of (II9) BELEMNITE SHALES, that, weathered, form a rough-looking band below 3 ft. of (120) PYRITIC MARLS containing Acantho-pleuroceras ellipticum (James * Woodward and Ussher, 1911, p. 35. t H. B. Woodward, 189" p, 67. t Oppel. 1858-9 p- 126, Oppel considered A. biounctatus and A. valdani as identical. Two crushed spe~imens, identified by Mr. L. F. Spath as near to or identical with A. valdani d'Orblgny, were found during the Association excursion, June, I9I4, in a fallen block of Belemnite Marls. PROC. GEOL. Assoc., VOL. XXV, PART 5, 1914.J 22 W. D. LANG ON Sowerby), preserved in this mineral, and other fossils, such as numerous belemnites, Nueula sp., Area sp., brachiopods and crinoid remains j and, finally, capping the Belemnite Marl series, a persistent, continuous, very hard, whitish, tabular limestone known as the (121) BELEMNITE STONE. The beds are not very accessible, but can be reached from gullies on the eastern shoulder of Black Ven and rather conveniently in the gully at Westhay Water. The Belemnite Stone can be collected from, either by finding fallen blocks (it is a very easily identified limestone, weathering whitish and crowded with belemnites), or by reaching over the top of the precipice and taking out blocks where they can be reached and are small enough to lift out. Farther east, just beyond Gabriel's Mouth, the Belemnite Stone is in the angle between the cliff and the beach; and the fore-shore at Golden Cap affords a collecting ground for the Upper Belemnite Marls. The Belemnite Stone is very fossiliferous, yielding a Trago phylloeeras very close to T. loseombi (James Sowerby), a Coelo eeras-like ammonite, an involute Liparoceratid, Lytoceras sp., Crenella ventrieosa (Sowerby), Amberleya sp., and crinoid re mains, as well as numerous belemnites. (i) The Davai Zone. Oppel included in his dauai zone all that came between his zones of ibex and margaritatus. At Charmouth, therefore, the zone apparently should include all except the extreme top of the Green Ammonite Beds. The top few feet must be excluded, since they have yielded ammonites of the margaritatus group. The clays from the 3rd to the 7th foot or so below the Lowest Tier have not yet yielded any ammonites, but, below this, ammonites allied to Oistoceras are found, showing the eaprieornus horizon. Wright (1863) calls these beds the zone of Ammonites caprieornus, and in 1878 the zone of Ammonites lzenleyi, but I see no good reason for altering Oppel's zonal name. The Green Ammonite Beds or Wear Cliff Beds of the Survey are parted by three limestones into seven sub-divisions,* namely, from below, upwards, the Lower Clays, the Lower Limestone, the Lower Red-band Clays, the Red Band, the Upper Red-band Clays, the Upper Limestone and the Upper Clays. They are represented on Black Ven as high as the lower part of the Upper Red-band Clays that just appear on its eastern shoulder before being truncated by the Gault. The whole series may be seen on Stonebarrow, but, except for the lowest part, the Green Ammo nite Beds there form broken ground and good sections are difficult to find, especially above the Red Band. They can be seen best in section east of the area of our maps, on the lower slopes of Golden Cap. But, though found on Black Ven and Stonebarrow * Lang, 19J3, pp. 402·7· THE GEOLOGY OF THE CHARMOUTH CLIFFS. 327 only in disjointed sections, on both these cliffs they form good collecting grounds, because when a section does occur it is gener ally accessible; and with a little practice it is easy to determine its horizon. Perhaps the most interesting feature of the Green Ammonite Beds is their variation in thickness. On Black Ven, what remains of them suggests that their thickness there was 35 ft.; at the western end of Stonebarrow they are 50 ft. thick; at Westhay, if what has been denuded is restored according to the measure of what is present, 120 ft. ; on the western face of Golden Cap, 100 ft. ; and on the (probably) eastern side of Golden Cap (vide Survey Memoir), 105 ft. * Their general tendency, then, is to thicken from west to east. (123) THE LOWER LIMESTONE is a discontinuous band of small, hard nodules with a sharp fracture and a tendency to be flattened in the plane of bedding. It lies between the (122) LOWER CLAYS below and (124) LOWER RED-BAND CLAYS IN LATlECOSTA above, and occurs 7 ft. higher than the Belemnite Stone on Black Ven, 10 ft. on the western part of Stonebarrow cliff, 22 ft. at Westhay. Water, and 20 ft. on the western side of Golden Cap. It is thrown down by the Ridge Fault to well below the level of the beach, but reappears again some few hundred yards east of the fault, and rises on the cliff until the dip again becomes easterly just east of Gabriel's Water, where it descends again. The (126) RED BAND, lying between the (125) LOWER RED BAND CLAYS IN STRIATUS and (127) UPPER RED-BAND CLAYS IN STRIATUS, a more or less continuous limestone about a foot thick, readily weathering toa pinkish-red colour, is present on Black Ven at about 7 ft. above the Lower Limestone, since fallen blocks of it have been found on the eastern shoulder above the Belem nite Stone; but it has not been seen in section, and does not occur as far west as the section marked e on Map 2. It can easily be picked up on Stonebarrow as it comes on to the cliff west of Fairy Dell 20 ft. above the Belemnite Stone in the broken ground above the Belemnite Marls, and followed, now on the diff face, now on broken ground, along and under the more inaccessible parts of Fairy Dell, until, before Westhay Water is reached, it is seen (apparently as two bands, owing to the top and bottom surfaces weathering red, leaving the middle fairly hard and grey) in a-semicircular section that lies back a little from the seaward cliff. It can be followed to the gully at West hay Water, where it lies just above the 100 ft. contour line and about 50 ft. above the Belemnite Stone; and east of this it is mostly hidden. Let down by the Ridge Fault, it rises again, as two bands, about 200 yards eastwards', and can be followed obliquely up the cliff towards Golden Cap. • Woodward and Ussher, IgIl, pp. 32 and 35. W. D . LANG ON The (129) UPPER LIMESTONE, lying between th e (128) UPPER RED-BAND CLAYS IN OISTOCERA S below and the (130) UPPER CLAYS IN OISTOCERAS above, does not occur on Black Ven, since the Gault truncates the Li as on this cliff at lower horizons. On Stoneba rrow it may be seen in small sections in the broken ground above the Belemnite Marl s and west of Fairy Dell at 15 f t. below the Lowest Tier, or 35 ft. above th e Belemnite Stone. H ere it is either flaggy and tends to be sand y like the Three T iers, or it is a nodular limestone with a sandy shell above and below. On the western f ace of Golden Cap, where it may be fo und 30 ft . below the Lowest Tier or 70 ft . above the Belemnite Stone, it is a nodul ar discontinuous limestone. Three well-defined ammonite fau nas appear in the Green Ammonite beds; a lower, in which ammonites of the lata costa group predominate, centr es around the Lower Lim estone ; a middle, characterised by ammonites of the striatus group, is found in the Red Band; and an upper fauna, in the Upper Lime stone and the lower part of the U pper Clays, in which Oistoceras is the dominant form . Trago-phylloceras loseom bi is common throughout the zone, wherever other fossils have occurred, and extends upwards into the margaritatus zone. D eroceras daoai (J ames Sowerby) is not very common. One was given me by Mr. Thomas Hunter, of Charmouth, as having come f rom the Red Band; I have fo und one specimen in the Red Band on Stonebarrow, one from a fe w inches below the Red Band, west of Gabriel's Mouth, and one about 2 ft. below the Red Band on Stonebarrow Cliff . Other fossils associated with the lower f auna are Belemnites clauatus, Blainville ; quan tities of small gasteropods of various species; three or four kin ds of S traparollus well-p reserved in iron-pyrites, including both smooth and costate forms ; Area sp, ; Crenella ventrieosa, J ames Sowerby; various brachiopods; crinoid remains ; an urchin, " Hemipedina sp. " ; Dapedius (in a fa llen nodule, that is almost certainly a piece of Lower Lim e stone); and Pala ospinax (fr om the horizon of the Lower Lime stone on Black Ven) . A small crinoid and N ueula sp . are very common in the Red Ban d, also small spira l gasteropods. With Oist oceras in the Upper Clay are associated Belemnites clavat us, Blainville; Area __ N ueula __ small spiral gasteropods ; costate Stra-parollus __ and brachiopods. Buckman* has divided the beds between the ibex zone (his zone of valdani) and the Domerian (Oppel's margarita tus and spinatus zones) into a zone of eaprieornus above and a zone of striatus below. Now, the capri cornus horizon is characterised by Oistoceras, so that if a line is dr awn just below th e Upper Lime stone, all the Green Ammonit e beds (except the top f ew f eet) above thi s would probably represe nt Buckman's capricornus zone, * Buckman, 19 10 , p. a vi, THE GEOLOGY OF THE CHARMOUTH CLIFFS. 329 and, below, his striatus zone. The capricornus zone, however, was originally defined by Wright. and was synonymous with the Green Ammonite Beds, here identified with Oppel's dauai zone j so that if the dauai zone is subdivided, its highest subzone cannot be called capricornus, but it may be called the Oistoceras sub zone. Further, we have seen that the Green Ammonite Beds below the Oistoceras sub-zone (i.e., Buckman's striatus zone) are characterised by an upper-striatus-fauna, and a lower latacosta--fauna, which may be divided 2 or 3 ft. below the Red Band. The sub-zone below that of Oistoceras, then, may be called the Liparoceras sub-zone (we cannot call it the striatus sub-zone, since this has been seen already to have a different connotation), and the lowest division of the Green Ammonite Beds, the lataecosta sub-zone. (j) The Margaritatus Zone. The highest beds of the Lias that come within the area of our maps are the lowest part of Oppel's zone of Ammonites margaritatus. Buckman has called all of this zone that lies below the Starfish Bed the zone of algouianus, Buckman's zone of algouianus, then, is a sub-zone of Oppel's margaritatus zone. It consists of an upper marly division without calcareous sand stone, about "50 ft. thick, the Margaritatus Marls j and a lower division of marls with three bands of fissile and micaceous sand stone, "7-'35 ft. thick, the Three Tiers. The latter division and a few feet only of the Margaritatus Marls are shown in section inthe area occupied by our maps. It is of interest that during the last few weeks (May, "9"4) Amaltheus has been found immediately beneath the Lowest Tier. For a foot below this horizon the beds are sandy (132) LOWER TIER SAND, and below this they pass into clays (131) UPPER CLAYS IN MARGARITATUS. Specimens of Amaltheus have been found in the sandy bed and (one on the Association excursion of "9"4) in the clay within a foot below the sand. Lamellibranchs and a ribbed Straparoltus also occurred in the clay 1-2 ft. below the Lowest Tier. The most westerly appearance of the margaritatus zone is the (133) LOWEST TIER, and the few feet of sand and clay below, seen on Stonebarrow Cliff, west of Fairy Dell, and immediately west of the amphitheatre-shaped sandy hollow formed by a fall just under the pine wood in 1908-9. The Lowest Tier, (134) MIDDLE TIER MARL and (135) MIDDLE TIER, may be seen in the banks on each side of the amphitheatre-like hollow just mentioned. Next, all three Tiers used to be seen in a section just above a large gully at the western end of Fairy Dell. The section, however, foundered in "9"2-"9"3, and when last viewed was very much altered, and did not show much. F'inally, the eastern end of the Fairy Dell 33° W. D. LANG ON at the section (mar ked m on Map 3) that shows the junction between the Gau lt and Li as, two sandy calcareous bands in a marl that probabl y are the Middle Tier Marl s, the Middle T ier, (136) TOPMOST TIER MARL, (137) TOPMOST TIER, and (138) MAR GARITATUS MARLS, are seen towards the base of the section. (See Fig. 25, p. 344. ) The Three Tiers on Stonebarrow are poorly developed com pa red with their appearance on Golden Cap, where they are 35 ft. thick. T hey are about half this thickness at the western end of Stonebarrow. Blocks of the Lowest Tier (tha t is about twice as thick as the two highest) are common on the beach below Stonebarrow and on the more gentle slopes of the seaward cliff. They block the big gully mentioned above as opening into the western end of Fairy Dell beneath the section where the Three Tiers used to be so well exposed. These blocks can easily be split up and yield abundance of Amaltheus and Tragophylloceras loscombi (J ames Sowerby), poorly preserved, as well as small spiral gasteropods. In the two last-mentioned sections the bottom few f eet of the Margaritatus Marls are exposed. Otherwise these beds are represented in the area of 'our maps only in broken ground in F airy Dell on the grassed slopes of the und ercliff beneath West hay Farm and in the meadows landwards of it. The boundary between the margaritatus and the dauei zones to some extent can be roughly tr aced inland by the fact that the upper zone, being sandy , holds water, while the clayey daoa i zone throws it out. T hus on the br oken land on the undercliff beneath Westhay Farm there is much the same appearance as the Gault presents where it overlies the Li as Clays and there is no clean section On Stone barrow and Black Ven, namely, a mar shy, foundered und ercliff traversed by numerous crevasses run ning parallel with the direc tion of the cliff, backed with a small dr y section of hill-creep topped with meadow grass . T he junction of the margaritatus and da ucei zones-s-of the Lower and Middle Lias of the Survey passes f ar below Wes thay F arm , and not, as in the Survey map , through that group of buildings. T he M argaritatus Marls are the highest Lias included in our maps. VI.-HISTORI CAL SUMMARY. There is no better historical summary of early work on the Charmouth Lias than that by H. B. Woodward in his report of the first excursion of the Geologists' Association to Lyme ;* but since the later adv ances in our knowledge of it are mainl y due to his labours, his description is far from complete. • H. B. Wood ward , 18Sg, pp . xxvii-xxix. TIlE GEOLOGY OF THE CHARMOIJTII CLIFFS. 331 Doubtless the earliest geologists of Charmouth were the local residents who collected fossils for sale as curiosities to visitors and travellers. To this pre-scientific period belongs the earliest recorded fossil collector, one Lock, of Charmouth, familiarly known as Captan Cury, or the Cury-man, who flourished about 1790. * As time went on and scientists began to describe the fossils of this district, the local collectors attained a more or less scientific know ledge of the fossils they sold j but by the end of the rSth century it had passed to the pioneer scientists to carryon the geological history of the district. As collectors, the names of Samuel Clark, Robert and Isaac Hunter, of Char mouth, locallv are well known, but far better known to the out side world is-Mary Anning, of Lyme. Born in 1799, she was only twelve when she found an fcIttllyosaurus, the first Lyme saurian scientifically described j and subsequently she supplied Conybeare and Buckland with specimens of Plesiosaurus and Dimorpllodol1, the former new to science and the latter to Eng land. t 'Meanwhile, Hawkins was helping-to make the Lyme saurians famous in his popular works on Icbthvosauri and Sea dragons. ! Of the pioneer scientific geologists, De la Heche, Buckland and_Conybcare stand conspicuous, the first chiefly laying the foundations of the stratigraphy, and the last two of the physical geology and pa lseontology of the district; while James Sowerby and J. de C. Sowerby described several species of Charmouth ammonites .betwcen the years 1812-46. § This pioneer period may roughly be considered to have extended from 1800-1850. With the publication of Oppel's" Juraformation" in 1856-8, with its zones and inter-topical correlations, what may be called a period of specialists began. Oppel blocked out the divisions of the Charmouth Lias that corresponded to his Swabian zones; and Wright, in 1860,§ ga\'e a detailed account of the Charmouth succession from the raricostatus zone downwards. Dav followed in 186, ~ with a similarlv detailed account from the r~ricostatus zone upwards, and so th'e whole succession was particularly .de scribed and correlated with the rest of the English Lias and that of the Continent. Later (1878-86) Wright~ produced his monograph of the Lias ammonites, in which many Charmouth forms were described. Meanwhile Owen was monographing the Lias saurians, II and Egerton'il had written many papers on the fishes which were further described by Traquair *':' and by A. S. Woodward. tt The Crustacea. were receiving attention from * H. B. Woodward, 1889. pp. xxv"ii-xxviil, and 19Ir, p. 20, quoting W. G. Maton, 1797· t II. B. Woodward, 19TI. rr, 63-64. t T. Hawkins, 1834 and 1840 ~ See under these dates in the list of works quoted in the paper. 'I Owen, 1861-188[. ~ Egerton. See references to Egerton's papers in A. S. Woodward, 1889-1901. ** 'Traqualr. See references to Traquair's papers in A. S. Woodward, 1889-1901. II A. S. Woodward, l839-1901. 332 W. D. LANG ON Henry Woodward and Salter,* and the belemnites from Miller and Phillips. t In 1886, H. B. Woodward] published his sections of the coast from Lyme to Bridport, that have been reproduced again and again in geological descriptions of the parts which they include. But the greatest contribution to our knowledge of these Lias beds is his two Survey Memoirs. The first, published in 1893, deals with the Lias of England and Wales; and his second, published in 1906t (second edition, 1911), with the Lias of Charmouth and Lyme only. In these two Memoirs he sums up the former scientific work on the Lias of the district and adds much new matter. With these two works and the reports of the former excursions of the Geologists' Association (1889 and 1906) t in which is incorporated much that is not so technically scientific, and culled largely from Roberts' Histories of Lyme, the reader has as complete an account of the Charmouth Lias as has yet been written. Besides the stratigraphy, physical geology and palseonto logy disclosed by the above-mentioned workers, a small literature is concerned with the fires that from time to time have broken out on these cliffs. Stephens, in q62,t records the spontaneous combustion of the Charmouth cliffs as having occurred as early as q 51, and, curiously enough, his explanation of the cause, namely, the rapid decomposition of iron pyrites owing to par ticularly damp conditions, is as accurate and adequate as that of the latest accounts. But he generalises from this circum stance, and goes on to state that, in his opinion, other subter ranean fires, such as those of Hecla, Vcsuvius and Etna, are due to similar causes! In 1890 Golden Cap took fire, according to an account and sketch in the" Daily Graphic" of Feb. roth of that year. § Needless to say, the Press described the phe nomenon as an eruption. On Jan. roth, 19°8, the cliff between Charrnouth and Lyme caught fire, and a detailed account was contributed by Jukes-Browne to the Dorset X atural History and Antiquarian Field Club, II on information obtained from Cameron, who had already done his best to dissuade the Press from attributing the occurrence to vulcanicity. ~ Subsequently H. B. Woodward ** published a lucid article on burning cliffs in the Geological Magazine, and this was followedtt in the same journal by a short correspondence on the burning cliff at Char mouth. • Henry Woodward, 1863, 1850, 1868, 1877, and Salter and Woodward, 1865. t Miller, 1826, and Phillips, 1865. t See under these names and dates in the list of works quoted at the end of the paper. § Fide H. B. Woodward, '908,p. 562. II [ukes-Hrowne, l00S. ~ ., Bridport News I' for Jan. 24th, 1908, uide H. B. Woodward, 19°8, p. 56r. •• II. B. Woodward, 1908. Pl'. 561-2. 1-t Cameron, 19'J9. p. 336; and "Passer vennensls," Geol, Mag., IJ THE CRETACEOUS. I.-GENERAL CONSIDERATIONS. (a) The Cretaceous Overstep. It was mentioned above that in late Jurassic times the Char mouth district was upheaved so that dry land appeared, and the consequent denudation that immediately began removed all the deposit. that had accumulated during Upper Liassic and Oolitic times, and reduced the land to sea-level. Subsidence then took place, and upon the tilted.edges of the Lias that formed the surface of this plane of marine denudation the Upper Cretaceous beds were deposited. These are the beds now to be considered. Since the Lias beds have, on the whole, an easterly dip, it follows that the approximately horizontal line dividing the Lias from the Cretaceous beds above, as it is followed from east to west, crosses lower and lower beds of Lias. That is to say, the base of the Cretaceous oversteps the Lias from east to west. Since the Cretaceous is now present only on the tops of the hills, its junction with the Lias extends along but short lines. On the western shoulder of Black Ven the Cretaceous rests upon the Middle Belemnite Marls, and in the middle part of the Black Ven section upon the Upper Belemnite Marls. It oversteps the Belemnite Stone beneath Butterfly Dell, and between here and the eastern shoulder it crosses successively the Lower Clays, the Lower Limestone, the Lower Red-band Clays, the Red Band, and (presumably) a little of the Upper Red-band Clays. At the eastern end of its outcrop on Stonebarrow the base of the Cretaceous is resting on the Middle Tier, then upon the Upper Tier, and in Fairy Dell upon the Margaritatus Marls. (b) Tlte General Character of the Beds. Generally speaking, she Cretaceous beds at Charmouth (apart from the Chert Beds)* consist of slightly loamy, glauconitic sands, that become increasingly loamy towards the base. But, as with the Lias, so secondary changes have dealt with the Cretaceous beds, altering the original deposit,and, to some extent, changing its appearance. A segregation of calcium carbonate has affected the beds as a whole j but instead of forming lines of concretionary limestones throughout, as it has done in the case of the Lias, the calcium carbonate, present in the original deposit in the form of organic remains, has been dissolved by percolating water, passed downward through the mass of sands, and, on Black Ven, re-deposited among 'the sand in lines of partly siliceous, * Jukes-Browne, lQOO, p. It has introduced the term" Selbornian .. for the Gault and Upper Greensand, including the Cenomanian Chert Beds of this district. 334 w. D. LANG ON partly calcareous concretions called Cowstones. On Stone barrow and Golden Cap these concretions do not appear to have been formed. But, simultaneously, another process was going on. Per colating water brought down silica in solution from the overlying Chert Beds (now broken up on these cliffs and treated later as part of the Drift), and in some cases the silica replaced such calcium carbonate of the organisms in the upper part of the sand as had been dissolved and carried downwards to be re-deposited as the Cowstones. The result of this two-fold process is that, at the extreme base of the Cretaceous of this district, that is, in the "Gault," calcareous organisms are found. Above the more loamy" Gault" on Black Ven layers of Cowstones containing calcareous organisms occur. Higher' are sands in which the shells of organisms are represented only as spaces in the sand; and, higher still, some of the organisms are represented thus, while some occur as siliceous replacements of originally calcareous shells. The silica appears to have been curiously selective in the shells which it has replaced. It had a distinct preference for the shells of Exogyra and Pecten, which abound; otherwise its choice was capricious. It is re-deposited in the form of" beekite." Even as far as the general sequence is concerned the beds vary from hill-top to hill-top, and the only hope of correlating them in detail in the various sections of the district is by com paring their fossil contents. It becomes increasingly evident that future work lies in the careful collecting of fossils bed by bed, and in their scrupulous identification. It is only thus that divisions other than the broadest can be correlated with those of distant localities or even from hill-top to hill-top in this district, and that evidence of the evolutionary history of the fossils can be obtained. With the information here given the collector has the means of locating his fossils stratigraphically, as a rule to a great extent of detail. There is evidence that under persevering work even the more sandy beds will yield recognisable fossils. * Finally, microscopic examination of washed samples of the various beds for the investigation of their micro-organisms has given results far from discouraging. H.-THE STRATIGRAPHICAL SEQUENCE. (a) The general sequence. Before the exposures are described it is necessary to have a clear idea of the general stratigraphical sequence, and a few hints as to how to find the sections and what to avoid will be acceptable to anyone who wishes to work these beds. * Since this was written the sandy Bed 2 of the Gault has yielded several interruptus zone forms, including the zonal fossil, see p. 34I. TIlE DETAILED SEQUENCE. Derived Chalk fossils. Soil with Chalk flints and pieces of chert. Division I of lr) Zone of Pecten dspe;·. Fossils rare. Broken remains of Chert Beds. Chert Beds of Survey. De la Beche. '" ,,,,," "'" I til ~ Bed 12. o.tlir' ...... ::s c eo ~ '" Bed 11. &':" 0 ~ ~8~~ ~ v 0 tr.l-- ~ Bed 10. F.,o;sils. ~ §.. CO",,,,,~~Bed' 9· . ~J"tli ...:::::::c._ Bed 8. Fossils, " 0 " Ul !i biJ~~~C; ~ .i: eLi til '"'Cl"'0 C Bed 7. il.'<" ~ ~ _"0 ~ ui '"'Cl ::l ~';;;~ Bed 6. Fossils. -8 tli- v v 0 rn. (l;S""'-.:> ::1 Bed 5. 0 ,,6- u ~ ~~~c~~ w o 0 Foxmould Division 2 of ('d.- 0 v 0 '" Bed 4· ~ ~;'i of Survey. De la Beche. ~ p..~~;u CV) ~ Bed 3. . < H .., ...... v..c: ro l-o ~ ;:> .::1 ~ v..c: 8....c:::0 Bed 2. gg ;. o o ~ +-' l::':: Bed 1. .• " ~ ~" --;;":=~';:'i::Roadway on Black Yen. 0'::~_2""a~ ~ Foxmould below roadway on Black Yen, l ~ tli'-< ~ ~ g-o·.;jov ~ U UHCC~ yellow sands. '8 3 " [fl o 00 0 :::::: ::=:<'Cb r~-~.~'- Foxm.ould below roadway on Black Yen, J:-'. """ r.l ...... 00 p..+-, 0 sands with concretions. '::' ." 'f ~ "o grey " c (/) ... 0 .... I boO H N ~~~~ ~ .....v::; ...... ~.5 c T op layer of Cowstones, } 0 g:; 00 ai S::} ~ ~ ~" tI) § ~1: ~c·;:..a Ir,:ervenlOg sand. () '" 0 " ? "," 0 0 s. Cows/ones o ~~~~l-<'''''~~MIddle layer of Cowstones, "0. ~~ tli '" ~ ::r..~g.'" g.. f S tI)~QJ...... -i->~l- The main divisions of the Cretac eous of th e dis trict (see p . 335) were defined as long ago as 1826 by D e la, Beche [De la Beche, 1826, pp. 112 -3]. A top cher ty divi sion, since pl aced by the Survey in the zone of P ecten asper [Jukes-Browne, 1900, p. 64], here occurs only as fragments of chert capping the three cliffs. The middle division of De la Beche is the sand known as F oxmould, and his lowest division comprises all the Cre taceous below this. De la Beche's th ird division reall y con sists on Bl ack Ven of two easily recognised parts, the upper sandy series with nodules ca lled Cowstones, and a lower, more argillaceous, seri es generall y ca lled the Ga ult. Thus D e la Beche's three divisions are now recogni sed as four, defined by the Survey [Jukes-Browne, 1900] as belonging to the following zones: 4. Chert Beds = zone of P ecten asper, 3. Foxmould= zone of AIortoniceras rostratum, upper part. 2. Cowstones e- zone of AIortoniceras rostratum, lower part. :L Gault=zone of Hoplit es interruptus. Such is the general sequence. On Black Ven only of th e t hr ee cliffs und er considerat ion are the Cowst ones found-and since the lowest layer of these has been used to divide the zone of AI. rostratum from that of H . interruptus, this line of division is vag ue on Stonebarrow and Golden Ca p. ( b) T Ite d etailed sequence. The four main divisions having now been established, it remains to be seen how far each has been subd ivide d. The fr agmentary condition of the Chert Beds on the Cha rmouth cliffs is such that they cannot be further stratig raphically divided. Onl y one attempt has been mad e to subdivide the F oxmould above the roadw ay [Lang, 1903] , and that was its division into 12 beds at the Bellows in Char mouth Cutting on Bl ack Ven (see p. 335). These, however, manifestl y are of local value only, and of no use for corre la tion ; the only hope of obtainin g other th an purely local divisions at this spot is by careful fossil collecting, beca use the lithic characters, though similar in the main, change in detail. But the fossils are not common, and) unl ess silicified, generall y consist of infillings of more or less incoherent sand, almost impossible to remove whole from the section and difficult to identify. Future work , however, must be in this direction, and, so far, little use has been made of such fossil evid ence as can be got. Where the Co wstones are present the layers of these con cretions subdivide their horizon ; but on Stonebarrow and Golden Cap, where hitherto they have not been apparent , the Cowstone horizon is lithicall y indistingui shable fr om the F oxmoul d, and THE GEOLOGY OF TilE CHARMOUT II CLIFF S. 337 the prod uction of fossil evidence is the only hope left for further subdivisions and corre lations with the layers on Black Ven. The subd ivisions of the Gault remain for considerat ion. On p. 335wi ll be found noted ten beds (exclusive of the Pebble Bed), described in 1904 as pr esent on Bla ck Ven [Lang, 1904]. Of these the best known is Bed 3, because it contains man y Gault fossils. It is also most important because, besides being present on all thr ee cliffs, Black Ven, Stoneba rrow, and Golden Cap, it can he recognised in all the other published detai led sections of the Gault of these cliffs, and thu s help s to correlate the sub divisions. The detail ed published sections referred to are (I) Gault on B1E.ck Ven [Jukes-Browne, 1900, p. 187] , (2) Gault on Golde n Cap [Jukes--Browne, 1900, p. I85J, and (3) Gault on Black Ven [Wood ward and Ussher, 1906, p. 44, and 1911, p. 46]' The Gold en Cap section will be referred to later ; it is quite intelligible. But the two Black Ven sections, though agreeing in general, in detail tally neither with each other nor with that published by the author in 1904 [Lang, I90·~, p. 130]. H ence the importance of the bed with many Gau lt fossils (Bed 3), which is common to all j and it will be convenient now to consider first the beds above Bed 3 and next those below it. The only section on Black Ven which shows comp letely the passage fr om Gault to Cowstones is Section d (Map I, d, and p. 339), described in 1904, and presumably that of Jukes-Browne [1 900] and of Woodwar d and Ussher [1906 and I9II]. The leading fea ture in the 1904 sub-divisions between Bed 3 and the Cowstones was the presence of three Hard Bands, Beds 4, 6 and 8. Beds 5 and 7 were loams separating the Hard Bands, and Beds 9 and 10 were the less and more sandy loams intervening between the Highest Band (Bed 8) and the Cowstones. There is no room then for the misunderstanding, and the only criticism that subsequent experience of the section has evoked is that the thickn ess of the beds is rath er overestimated in the 19°4 de scr iption. Traces only of the H ard Bands have been found on Stonebarrow (Section j, p. .141, and Map 2 , j) and none on Golden Cap. It is probab le, then. that Reds 4 - I O, with the top of Bed 3-the S er-p ula concava Beds-r-are local , and thi n out eastwards [Lang, 19° 7, p . 156J. An interesting point in connection with Bed .3 is the prevalence of Serpula coucaua in its top portion on all three cliffs. In contrast to Beds 4 to 10, Beds I, z and 3, though var ying in thickness, are constantly present on all three cliffs. The demarcation between Bed s 2 and 3 is fairly shar p, but that between I and z is gradual ; nevertheless, it is generally easy to determine in which bed any exposure lies . Bed I has an argillaceous base, but is sandier above and throughout is very black. Bed 2 is sandy, dark-green and yellow. Bed 3 is very argillaceous at the base and black or blu e. The agreement of W. D. LANG ON th ese divisions on all the thr ee cli ffs corroborat es the correctness of th e 1904 description. The interest of Beds rand 2 has hithert o chi efly lain in the possibility of one or both repr esenting the mammillatus zone. Though placed hy the Survey with Bed .) in the interruptus zone, the absence of fo ssils has till now left thi s mere conjecture. The next exposure of the Gault east of thi s district that has been describ ed , that at Okeford Fitzpaine [Newton, r897], pr esented the mammillatus zone. Now, how ever, the interruptus zone fossils (Hoplites interruptus, Natica gentii and Gram matodon carinalum ; see pp. 344-5) have been found ncar the top of Bed 1 on Sect ion III in F airy Dell , Stone barrow, and H oplit es interruptus and other forms in Bcd 2 on Section h-i in the same undercliff. This reduces the poss ibility of the occur rence of the mammillatus zone to the middle of bottom of Bcd r , The Pebble Bed is thin and impersistent on Black Ven, be coming 'thicker, sandier, and containing more than one layer of pebbles as it is traced eastwards. III.-, THE SECTIONS. (a ) General R emarks , Such is the general and detail ed sequence. A few remarks ar e her e added on th e practical working of th e sectio ns before these are themselves described. No special hin ts are needed for working th e F oxrnould and Cowstones. Being sands, the y are ap pr oachable in any weath er, and thou gh much overgrown and often marred by rabbit burro ws, there are pl ent y of exposed sections. These are, however, often hidden by a layer of fallen sand, which has to be dug through before the true surfac e is reached. With the interruptus zone it is different. Rest ing upon Li as clays which hold up the water, the beds of this zone are always found in boggy land, and, having clay in their own composition, arc less easy to work when very wet. Landslips ofte n happen And give pl ent y of level places for abundance of vegetati on to flourish. Generally speaking, the higher bed s of th is zone are in comparatively dry ground, concealed, wher e expo sures would otherwise occur, by bracken and sloe thickets ; whil e the lower beds arc in boggy land covered with Salix bushes, reeds and various coarse herbs such as S cro-p hularia and Epilobium. It is best to work in fairly dr y weath er in winter and spring before the br acken has grown and the dense tangles of other vegetation which the mild climate encourages. The filmy Gault fo ssils are hard to extract if th e loam is either too dr y or too wet. Another advantage of working in winter and early spring is the absence THE GEOLOGY OF THE CHARMOUTH CLIFFS. 339 then of adders, which are not to be despised. They are curiously local. Though they are said to be found there, I have seen one only (dead) on Black Ven j but on Stonebarrow they abound. Experience shows that they are dangerous in two ways j first, they move out of the way but leisurely when they see anyone approaching, and therefore are liable to be stepped on before seen, especially when the bracken is long j and secondly, being often hard to see, they may easily be accidentally grasped by anyone scrambling up an overgrown bank. Leather gaiters to some extent obviate the first danger. (b) Details of the Gault Sections. The Gault exposures on Black Ven and Stonebarrow are shown on Maps I, 2 and 3, and wiII be mentioned in order from west to east. 1. Section a (Map I, a). At the top of the third Lias precipice on Black Ven (that formed by the Belemnite Marls), beneath a ridge running south wards from the roadway, at a point about 540 yards east of the mile-stone on the Charmouth-Lyme road, one mile from Lyme, the Pebble Bed and the base of Bed I form just the top foot or so of the precipice. Last observed, August, 1908. 2. Section b (Map I, b). On the eastern face of the north and south ridge mentioned under Section a, about thirty yards north of Section a and about seventy yards west of the municipal boundary between Char mouth and Lyme, Bed 3 (IJY; ft.), with many Gault fossils and Serpula concava common at its top, is seen in a small exposure. Bed 2 may be exposed by digging for about a foot beneath the section. Above Bed 3, two hard bands, Beds 4 and 6, are shown. Last observed, August, 1908. 3. Section c (Map I, c). The westernmost exposure described in 1904, [Lang, 1904, p. 131], about 15-20 yards west of Section d. Bed 3 is 4. Section d (Map I, d). The midmost section described and figured in 1904 [Lang, 1904, p. 129, and text-fig. 4 on p. 130], and almost certainly that described in the Survey Memoirs [Jukes-Browne, 1900, p. 187, and Woodward and Ussher, 19°6, p. 44, and 1911, 34° W. D. LANG ON p. 46]. It lies beneath a promontory running south-east from the roadway just east (about 50 yards) of the municipal boundary between Charmouth and Lyme and about 150 yards east of the north and south ridge beneath which lies Section a. Part of Bed 2 is exposed and all the beds of the interruptus zone above Bed 2, upwards into the Cowstones. Between June 1909, and June, 1910, a big fall happened at this spot, which has spoiled the section for working purposes, and it is now precipitous, with a more or less impassable and dangerous bog beneath. Last observed, June, 1913. 5. Section e (Map 2, e). The easternmost section described and figured in 1904 [Lang, 1904, p. 126, and text-fig. Ion p. 125]. It lies on a slope above the precipice formed by the Belemnite Marls and directly south of the Bellows, Charmouth Cutting, on the Charmouth Lyme road; about 245 yards east of Section d. The Pebble Bed, Bed I and part of Bed 2 were exposed. Between June, 1912, and June, 1913, this section foundered, and when last visited (1913) showed but little. It was visited by the Geologists' Asso ciation at Easter, 1906 [H. B. Woodward, 19°6, pp. 323, 324]. 6. Section g (Map 3, g). Immediately beneath and seawards of the pine-trees on Stone barrow Cliff west of Fairy Dell. Between June, 19°8, and June, 1909, there was a large fall at this point, which carried with it at least one of the pine-trees. This fall exposed the whole succession from the Pebble Bed to the Foxmould; but the section is marred by the quantity of loose Foxmould which has fallen and concealed much of it, a circumstance to be regretted because no so complete a section has been found west of Golden Cap. At the eastern side, however, the following section was measured in June, 1910. ft. in. 6. Sand of Foxmould and Cowstone horizon .. about 30 0 5. Beds 3-10 of "Gault." Sandy loam above, with more clay below. Junction with 6 gradual ..• 6 0 4. Bed 2 of ••Gault." Sandy loam. More sandy, greener, and more coarse-grained than Bed 3. Junction with Bed 3 rather sharp...... 9 0 3. Bed I of "Gault." Black sandy loam. Finer-grained than Bed 2 and with more clay locally, especially towards base. Junction with Bed 2 rather gradual. 4 6 2. Pebble Bed at base of "Gault". .. o IO~ The top 8! inches are sand-with-pebbles or clay, the luwer 2 inches are clay. 1. Lias. Mm'garitatus Mads. THE GEOLOGY OF THE CHARMOUTH CLIFFS. 341 The points of most significance in this section are (I) the locally sandy character of the Pebble Bed and its in creased thickness compared with its appearance on Black Ven, (2) the absence (though thorough search was not made) of fossils in Bed 3 and of the Hard Bands (Beds 4, 6, and 8), and (3) the absence of Cow stones. Otherwise the characters of the beds are such as have already been described for Black Ven. It is probable that a more careful search will produce the fossils, and possibly the vanishing remains (see Section j) of the Hard Bands beneath the covering of fallen Foxmould. 7. Section h (Map 2, h). Sections h to 0 are in Fairy Dell; It, i, and j are at the western end, above the point where the footpath leading into the Dell becomes lost in an overgrown swamp. Section h,_ previously described and figured [Lang, 1907, pp. 152-3, text-fig. 2], shows Bed 3 with fossils and the junction with Bed 2. It is just above the footpath east of the point where this is broken by a slip necessitating a climb. Last examined, June, 1914. 8. Section i (Map 3, i). This section occupies a little bluff a few yards east of and below Section It. Doubt was expressed in the previous descrip tion [Lang, 1907, p. 152] as to its horizon, A fall, however, between June, 1913, and June, 1914, has connected Sections h and i, showing Section i to be in Bed I, and the intermediate part in Bed 2. Fallen masses from the latter were found by the Association on the 1914 excursion to be full of fossils, of which the most conspicuous were H oplites interruptus, Pholadomya madibula, P. plicata, Leptosolen moreana and Tellina inaqualis. Last examined, June, 1914. 9· Section j (Map 3, j). This shows the top of Bed 2, Bed 3 with many fossils in the lower part and Serpula eoncatra at the top, traces of the Hard Bands and the passage upwards into Foxmould. It was described and figured in 1907 [Lang, 1907, pp. 153-154, text fig. 2]. It is a few yards north-east of Section i, on the land ward cliff, where it trends inland. Last examined, August, 19°7· 10. Section k (Map 3, k, and Fig. 24)· Section k is in a gully, and consequently very wet. Though it is the most extensive exposure in the Dell of Beds 1-3, there PROC GEOL. Assoc., VOL. XXV, PART 5, 1914·J 23 <,It'i ~ ~?'\ ;I~ tN ~),) r" ?~ ('f" "\1 l, ~ r '\~ () ' , 0 'iii \\, -.. «. ? .... r;, j '" ""r- '. ' 1{1\\" { r''\ ( ( "'-')' /'~ ' M"""l '1 C 3 'f\C ~ 111\\\" ...... - s. ~ tl •• .6-_ r-~ -. - t"' 1 ' - _....- :- -.-.-. -. > ...:-; -:- - Z ,Iv , _ 'V/ : :. I;'l ,.,.m c...("t'1 {( ,. o ~ z ~~;.~~tl~i~~·6~:·;~1;1!§~?.~~~;~~:~;~ ~ ""->1.'- :$- -=- -= )-1 ·~,, ~/I.\. . -. --. ' ¥ --. -_. '--.- .- -. -_ .- .k::- ;<~';"".-- vr :J --. _. -- -- . -_. -- (~, .- - - -- ' », -]t - _. -.--.-. - .1. - .,\v ~"'\4 lV - - --- . .r'1 //I1\/i 1 . .: -: f:. 1)11 FIG. 24.- :\1AP (ON LEFT) AND P~OFII.E(ON R IGHT) AT SECTION /; ( MAP 3, 1<), IN THE G AULT, FAIRY DELL, STONEBARROW CLIFF, CHARMOl:TlI. Measu red Jul y, 19° 9.- W. D. Lang. 6. Soi l, fall en sa nd , etc . 5. Bed 3. Loam. Sn ·pula COJ1cal'a commo n at LOp ; other fossils sca rce ex cept towards the base ; ab out 91 ft. 4. Be d 2 . G reen and yell ow loamy sand ; ahout 20 ft. 3. Bed 1. Green and black sandy loam with more clay than Bed 2 ; about IO ft. 2 . Pebble Bcd : pebble. in a rusty . sa ndy matr ix, a few inches. Junction with Li a s at abou t 3 10 ft. I. Lias of the Ma rgar ita/lis mar l horizon. THE GEOL OGY OF THE CHARl\lOlJTH CLIFFS . 343 is no continuous vertical section, but the beds can be made out by digging into the bank which for ms the eastern side of the guIly. The top of this bank forms a rid ge, run ning, roughly speaking, north and south , and ending in a steep slope of Lias. This Lias section, running east and west, form s a small cliff, very much overgrown in places, and is an important featur e of the undercliff. H ere and there, where it is higher than usual, a section showing the Pebble Bed at the base of the Gault appears. In Section k the Pebble Bed is seen where the ridge above mentioned joins the Lias bank. Probably the beds have slipped a little down the hill and seawards at this point, since the Pebble Bed which can be seen running across the marsh in the gully bottom (see text-fig. 24) appears there to be a few feet higher. Moreover it is likely that on the edge of a ridge, such as that in the present instance, the beds would tend to bend or fault a little downhill (cf . Section 0). Bed I can be traced up the gully side passing gradually into Bed 2, and this, with rath er a sudden passage, into Bed 3, which has fossils near its base. The highest exposure in the gully contains few Gault molluscs and many Serpula concava, indicatin g the top of Bed 3. To reach this section, enter the Dell by the footpath between the pine-trees and climb down it to the foot of Section k. If the Dell is very wet, follow the base of the lan dward cliff past Section [, and pas t the beech wood j then turn seawards and keep along the top of an overgrown bank which here rises above the Lias bank in the middle of the Dell, and descend to the section along the rid ge which forms the section's eastern boundary. If not too wet, cross f rom below Section i to the western pond (marked on Map 3), passing along its seaward side; thence cross a bog to a gap in the sloe thick et which lies to the east of the eastern pond j emerge upon an expanse of bracken with a willow wood inland between the bracken and the Lia s bank j proceed parallel with the willow wood for some fifty yards, and then cross the wood where it is thinner and where the stream traversing it is less boggy, and follow the Lias bank eastwards to the gully. The lower way is easier, but wetter. These somewhat elaborate dir ections, if followed, should save much time in reaching a section which is difficult to locate and by far the most difficult in the Dell to reach. Last observed in June, 1909. I I. Sections I, m and 0 (Map 3, I, m, 0;' Fig. 25). Sections east of k and n can be reached from Section k by f ollowing the Lias bank along; but far more easily by entering the Dell from the top of the land ward cliff, where this ceases to be precipitous at about 50 or 100 yards east of its summit. The positions of the sections should be noted from above, and when the Dell is reached the way to them picked throu gh the bracken. 344 W. D. LANG ON Though marked, and originally described, individually, the last visit (June, 1914) showed the Sections I, m and 0 to be more or less continuous, and the figured section (m) may' be taken as .-. .- ..- ~~ ~~ ~~ :, :-~-:- .. ~, ~.;~ 7~ : .::-..-=.:.- ,'. .~ .~ .. -:. ..--. .. . - .- .. -: "--: . ---_-.~ -' .- -- ' ...:..::..-.; :_... . _'-: . - . -- ', -' -- ' ' - :-. _"..'-. '-.' . - - . - ~ •,__-.- '_ 0, '__.' "- . 0 _ • -. _. _ -=-- ~ . :..~':~:?:::;~;~~.~~~~_~:~~O~t~~:'·~::·r~~~:~·;~-~:;:::~.~;:r~~~~~~i\"~: .... : ': \., ./'10\"''; 1':' ;. ,. ' ',Q ;:•• "l:.••~••~ •• ~~ ;.t ·r: "':, · ·:",,'p : ..;"'I ~~~ f. --'_. -- '--'-'-'-- --'-- '--. -- ' . -_. __ . -.-' - '--_. --'. -- ' -_ . -_ . -- . -' -- . --. FIG. 25.-PROFILE AT SECTION m (Map 3, m) IN THE GAULT, FAIRY DELL, STONEBARROW CLIFF, CHARMOUTH. Measured June rfith, 1909.-Tv. D. Lang. 7. Soil. 6. Fallen Sand, etc. 5. Bed 3. Sandy loam with fossils. 4. Bed 2. Green and yellow loamy sand, 6 ft. The X in this and the bed below mark the horizon whence fossils have been obtained. 3. Bed I. Green and black sandy loam, 10 ft. 10 ins. 2. Pebble Bed: at base, pebbles in iron-stained sand, 2 ins. ; in middle, loamy sand 2 ins. ; at top, loamy clay, 2 ins. The whole thickness is exag gerated in the diagram. I. Lias with the Middle and Highest Tier in the Three Tiers. typical of them all. In Section I, Beds 1 and 2 were found to be remarkably thin, together only about 8 ft., while in Section m together they are about 16Yz ft. Section m (Fig. 25) is,remark- THE GEOLOGY OF THE CHARMOUTH CLIF FS. 345 able for having yielded fossils at about 14 in. from the top of Bed I and one about 6 in. from the base of Bed 2 (see Fig. 25), until thi s year the only find of fossils below Bed 3. This year, however, the Geologists' Association- found man y inter rup tu s zone fossils in Bed 2, Section h-i (see p . 341). Like Sections a and 11, Section 0 shows the P ebble Bed and a little of Bed 1 above thi s. Considered \vith thi s section is a stretch of bank some yards to the east, where the P ebble Bed continues to ap pear. It is remarkable that in Section 0 the junction of the Gault with the Lias has descended to below the 300 ft. contour, and for the snort distance to which it can be traced eastwards of this it descends still lower. A glance at the map will show that Section 0 is well to the eastward of the summit of Stonebarrow Hill, of which Stonebarrow Cliff is an irregul ar bi section. It was pointed out that the Gault apparentl y bent or slipped downhill on the ridge that juts seawards at Section k. So here there is prob ably- a small downward movement of the bed s as a whole on approaching the surface of the hillside. This would account for the unexpected drop in height of the ba se of the Gault at the eastern end of F airy Dell. These three sections were last visited, June, 1914. 1 2 . S ection n (Map 3, n). This is merely an exposure ofthe P ebble Bed and a foot or SO of Bed I at the top of the Lias bank. It can be reached from Section k by following the Lias bank along, hut is troubl esome to reach from above, from below, or from the east. Last examined, June, 1909. 13. A S ection in th e Gault 011 Golden Cap (Fig. 26) . Though outside the area of our maps, it is not inconvenient to consider here the Gaul t on Golden Cap for compar ison with those sections described on Black Ven and Stonebarrow. Jukes-Browne has described a section in the Gault on the eastern face of Golden Cap [Jukes-Browne, 1900, p . 185] . The section here described is on its south-western face, and differ s from the other chi efly in being considerably thicker and in ha ving a lower base. Both of the Golden Cap sections are remarkable for showing the whol e of the Gault in practically unbroken succession from the junction with the Lias below to the Fox mould above. With the exception of the much-covered Section g, exposed only since 19° 8-19°9, nowher e on Black Ven or Stone barrow is the succession compl ete, but was pieced together by combining the sections. On Golden Cap the section here de scribed is continuous excep t for about a foot above and below W. D. LAKG ON '960 1156 QO: O:·c::>~o . Q" p 4 7 6 .' . - 4271- . . :::-_~ _0 _0. 5 4/6 ...... ;;._~ ~ . - 4 • - . 394 t---...... ;=----==------\ -.-.- 3 2 382 0 _ - ' _ "__ . -_ . _0_0 __ .- '- '- 0 _ __.__._ . __.__,_ .--0 _ 0 _._ FIG. 26.-PROFILE OF SECTION ON THE S.W. FACE OF GOLDEI' CAP. IV. D. Lcmg. 8. Soil. 7. Fragmentary remains of Chert Beds, etc. 6. Loamy sand of Cowstone and Foxmould horizon (M. rostratum zone) ; 29 ft. 5. Bed 3. Black and blue loam with more sand above and more clay below, Strpula concaua common above, other fossils rare; fossils other than Serpula concaua common below; II ft. 4. Bed 2. Dark-green and yellow loamy sand ; 22 ft. 3. Bed I. Green and black loam; 9 ft. 2. Pebble Bed, 3 ft: at base, pebbles in consolidated sandy matrix, 4-6 ins. ; then sand, I ft. 3 ins. ; then pebbles, I in. ; then sand, I ft.; and at top pebbles, 3 ins. 1. Lias. Yellowish loam; high in margaritatus zone. Junction with Gault at about 380 ft. THE GEOLOGY OF THE CHARMOUTlI CLIFFS. 347 Bed 3, where there is something of a ledge, useful for approach ing the middle of the section, which otherwise would be difficult of access. In jukes-Browne's section six sub-divisions of the Gault are given. Of these, the bottom four constitute the much thickened Pebble Bed; the fifth, Beds I and 2 j and the top sub division, Bed 3. The south-western Golden Cap section can be reached from the main road about half a mile east of Morecombe Lake. Here Muddyford Lane runs southwards, and should be followed to a stile on the left leading across one field to Filcombe Farm j a cart track leads across two or three fields from the farm to the neck of land between Golden Cap and Langdon Hill, and from this neck the western side of Golden Cap should be skirted below the 400 ft. contour, some yards below the higher hedge, until the edge of the cliff is reached. * From the cliff edge, at about the height of 450 ft., the Gault section can be seen immediately below, but is inaccessible from this point. It may be reached by getting on to the cliff a little way down the hilI, either close to the upper hedge, or, more easily, some yards below this and at about the 400 ft. contour, and then by clambering down the section. There is something of a path through the vegetation if the cliff is entered at the lower of these two spots. The way described is given as the easiest from Charmouth, the alter native being to ascend from St. Gabriel's, getting there, either by road from Morecombe Lake or by a rough walk over Stone harrow, or by a rougher walk over the beach, or, best of all, by boat; the landing, however, at Gabriel's mouth is only advisable in the calmest weather. IV.-A COMPARISON OF THE GAULT BEDS ON BLACK VEN, STONEBARROW AND GOLDEN CAP. (a) The Pebble Bed. t On Black Ven this bed is only a few inches thick, and im persistent. Among the pebbles are a few, derived, (?) Lias fossils, e.g., belemnites, and the matrix is a very argillaceous loam. On Stonebarrow the Pebble Bed is more persistent, of greater average thickness, and the pebbles generally are in a matrix of rusty sand; moreover, in Section g, two layers of pebbles were noted, the higher in loamy clay and the lower in rusty sand, with a few inches of loamy sand between. Where it first appears on the western face of Golden Cap, in occasional exposures west of the described section, the Pebble Bed is a foot or so thick, the base being pebbles in a hardened matrix of sand, and above * It was not ascertained whether any right of way exists between Filcombe Farm and Golden Cap. Certainly there is none along Langdon Hill, which makes a shorter track and does not lnvelve so much unnecessary descent. I ..~ ned 1 of the Gault in the section at Black Yen (Woodward and Ussher 1905 P·44)· W. D. LANG ON this more pebbles in clay. On the Golden Cap section here described the thickness of the Pebble Bed has increased to 3 ft., and there are three distinct lines of pebbles, the bottom-most and the thickest being in a consolidated sandy matrix; between this and the topmost layer of pebbles the matrix is loose sand; the topmost layer of pebbles is in cla y. On the east face of Golden Cap the Pebble Bed is described [Jukes-Browne, 19°0, p. 185] as 6 ft. thick and otherwise resembles that on the south western face. To sum up: the P ebble Bed thickens from west to east, becoming complicated by the addition to its base of sand and more lines of pebbles. It contains derived Lias fossils on Black Ven, and, probably, a thorough search would produce them on Stone barrow and Golden Cap. (b) B eds I and 2.* These are glauconitic loams, the lower containing more clay. The junction of these two beds is gradual, and consequently the line of demarcation between them somewhat arbitrary, causing a difficulty in comparing their respective thicknesses in the various sections. In those sections, however, in which these beds can be expected to occur, they are constantly present and easily recognised , showing that the sequence of the lowest part of the Gault of Black Ven, Stonebarrow and Golden Cap is essentially the same. The difficulty of defining their junction does not entirely account for the apparent variation in thickness of these beds ; for .if the two be taken together, as was done in the paper describing Section h, i and i [Lang, 19°7], the sum of their thicknesses varies considerably in passing even fr om one section to the next, e.g., from Section I to Section m, In the paper just mentioned it was held that these two beds as a whole were thickening from west to east. Their irregularities in Stone barrow show that though this is generally true (as may be seen by taking their average thicknesses on the three cliffs, 14 ft., IS ft., and ar Tt.), there cannot be said to be any change in their thickness when followed from one end of Stonebarrow to the other. On Golden Cap, though generall y thicker than on Stonebarrow, they are not so thick on the eastern fac e (Jukes Browne's section) as in the south-western section. Hitherto no fossils had been obtained from these beds, but now interruptus zone fossils have been found in Beds I and 2 of Section m and from Bed 2 in Section hoi, as previously speci fied (p. 34I). Several pounds weight of Beds I and 2 from Black Ven yielded no micro-organisms when washed, but a sample of Bed 1 fr om Stonebarrow, from Section m, from the spot where the fossils were found, yielded a few foraminifera. • 1 esBed 2 of th e Gault in th e Bla ck Ven section of W oo dward and Usshe r, 1906, p . 44, while Bed 2 1=Bed 1 of Jukes-Browne, ' 900, p. 187. in hi s Black Ven Gault section. THE GEOLOGY OF THE CHARMOUTH CLIFFS. 349 (c) Beds 3 to 10.* The characters of Bed 3 are very constant throughout, though it varies irregularly in thickness within fairly small limits. It is an argillaceous loam, containing more clay below than above, and generally is crowded towards its base with interruptus zone fossils, which occur, however, less frequently throughout the higher part. It is above Bed 3 as defined on Black Ven that changes are noticeable as the beds are followed eastward. On that cliff the top of Bed ;) was defined by the lowest of three Hard Bands, in which Serpula concaua is abundant. This worm is also common throughout the higher parts of Bed 3. A sug gestion only of a Hard Band above the Serpula concava loams of Bed 3 appears in the west end of Stonebarrow (Section j). At the east part of Stonebarrow, Section k alone reaches as high as the Serpula loams, and there is not enough exposed to show if any Hard Band appears above these. On Golden Cap the passage from Serpula concava loams to Foxmould is fairly abrupt, but the section is not absolutely continuous on the south western face at this point, and no Hard Band is shown. If it were there, however, doubtless the section would project at this point, and not, as is the case, give way for a foot or so to a gentle overgrown slope. There is no mention in Jukes-Browne's Golden Cap section of any Hard Band. In the former paper on Stonebarrow [Lang, 19°7] it was maintained that the interruptus zone above Bed 3 showed signs of thinning from west to east. There is, however, the difficulty of defining the upper limit of the zone owing to the absence or rarity of fossils near the top, and on Stonebarrow and Golden Cap to the absence or Cowstones, a lithic character imposed, in the absence of fossils, as the upper limit of the interruptus zone on Black Ven. But the behaviour of Bed 3 can be com pared on the three cliffs by taking the Serpula concaua loams as marking its upper limit. It is then seen to be 10 ft. thick on Black Ven, 6 to 10 ft. on Stonebarrow, and II ft. on Golden Cap. Thus the decrease in the upper part of the zone must be due to the thinning or absence of the loamy beds above the Serpula concaua loams and below the loamy sands on the Cow stone horizon (indistinguishable, in the absence of Cowstones, from the Foxmould), unless these loams have altered their lithic character. Of the interruptus zone as a whole, it may now be said that from west to east the part above Bed 3 either entirely changes its lithic characters or thins out nearly or quite to ex tinction j Bed 3 shows no comprehensive change j while below Bed 3 the zone as a whole thickens. * Bed 3 of the Black Ven Gault section, Woodward and Ussher, Ig06, pp. 44=Bed 3 of this paper, while their Bed 4 probably= Beds 4-8 of this paper; their Beds, Bed 9 of this paper; and their Bed 6, Bed 10 of this paper. Jukes-Browne's Beds 2 and 3 (lg00, p. 187)=Bed 3 of this paper, and his Bed 4=Beds 4-10 of this paper. W. D. LANG ON V.-STRATIGRAPHICAL SUMMARY. a. Nowhere on Black Ven, Stonebarrow and Golden Cap are the Chert Beds exposed in an undisturbed condition. They occur as broken remains, b. Owing to the absence of Cowstones on Stonebarrow and Golden Cap, this division is there indistinguishable from the Foxmould, and fossil evidence alone will enable these beds to be subdivided and correlated on the three cliffs. c. Beds 4-8 of the Gault, developed on Black Ven, are seen in a very attenuated form at the west end of Stonebarrow, and disappear east of this (unless their lithic character changes), and they become indistinguishable from the sands of the Cowstone horizon above. d. Bed 3 of the Gault, though varying somewhat in thickness in the different sections, remains on the average about 10 ft. thick on all three cliffs. e. Beds I and 2 of the Gault thicken when traced from west to east. t. The Pebble Bed thickens considerably, becomes sandier, and contains more pebble layers when traced from west to east. g. Interruptus zone fossils have been found on Stonebarrow as low as the upper part of Bed I, thus reducing the possibility of the occurrence of the mammillatus zone to the middle and lower parts of Bed I. THE POST-CRETACEOUS DEPOSITS. I.-THE CHERT BED REMAINS. The post-Cretaceous deposits of Charmouth are to be found mainly on the hill tops, in the valley bottom, and on the beach; though the drift of the first-mentioned spots is largely distributed over the slopes, owing to "hill creep." The hill-top accumulations are the least understood of all the Charmouth deposits. At their base they consist of angular Chert fragments in a sandy matrix, and above of more or less angular flints and cherts in a matrix of loam. The lower deposit, though fragmentary, certainly is more or less in place, that is to say,' ill so far as it has moved, it has merely subsided, or slipped with the hill-slope, and has not been transported from another place.* It might with propriety have been treated at length with the rest of the Cretaceous, since the Foxmould passes upwards into the Chert Beds (zone of Pecten asper) that may be seen in place west of Lyme and in an unbroken state as near as the top of Haddon (Hardown) Hill; though even in the latter locality • Buckland and de la Beehe, ,835. p. 7, and de la Beehe, ,839. p. 256. THE GEOLOGY OF THE CHARMOUTH CLIFFS. 351 they are said to have "settled down in mass"* owing to the removal by percolating water of the sand with which the cherty slabs are interbedded. In the ditch bordering the north-east side of the road, at the top of Greenway Hill on the Axminster Road, a section is seen showing the Chert Beds as slabs. On the Charmouth cliffs, however, they are broken into comparatively small fragments, probably through the continued action of the sand beneath them being washed out and the Cherts settling upon the cavernous bottom thus formed. De la Beche ] refers to the Chert beds as occurring unbroken on Black Ven, where now the most that can be said is that occasionally very large lumps occur behind the cliffs on Timber' Hill. t The surface of pieces of chert on the cliff slopes is often found to be covered with a chalcedonic rind, due to weathering, of peculiar shades of pink and blue and mauve. When fresh, the chert is horny or glassy, but on weathering is seen to be made up of sponge-spicules § with glassy interstitial silica. This interstitial part weathers away first, leaving the mass of spicules isolated. Hence it is not uncommon, on breaking a chert fragment, to find it brown, clear and undifferentiated in the middle, becoming paler and opaque, with visible imbedded spicules nearer the surface, while the outside, for a depth of ?i-Yz in., is cancellate, whitish, and with the spicules isolated. The chalcedonic rind above men tioned seems confined to the intermediate state, that is, to frag ments in which the outside has not yet reached the last-mentioned stage of decomposition. n.-THE PLATEAU DEPOSITS. The more or less angular flints and cherts with loam that lie above the weathered remains of the Chert beds is Cretaceous and perhaps Eocene debris. It seems certain that clays, sands and gravels of Eocene age are present in place as near as Combe pyne ;11 and, this being so, it renders it improbable that the spots now occupied by the Charmouth cliff tops escaped a certain amount of Eocene deposits. And upon whether we consider that this was so or not must depend our view of events subsequent to the deposition of the highest part of the Chalk in this area j for, if there is any Eocene deposit here, all the Cretaceous above the Chert Beds must have been denuded before Eocene times. From sections west of Lyme it is clear that upon the Chert Beds the Cenomanian Limestone was deposited, and upon this the Chalk as high as 'the Micraster cortcstudinarium zone.' How * jukes-Browne, 1900, p. 191. t De la Beebe, ,822, p. 4I, and ,835, P. 7. : Jukes-Browne. 1900, p, 191". § Lang', in Woodward. 1906, p, 329. II H. B. Woodward, 'g02, p. 5'5. ,. Rowe, 1903, p. 2. W. D. LANG ON much more than this was deposited we do not know ;* but since, wherever in England the base of the Eocene has been found it rests upon a denuded surface of Chalk, there must have been an uplift in pre-Eocene times all over England, that conse quently included our area, and began to remove by denudation the highest Cretaceous beds of the district. If Eocene deposits are considered as occurring here, the upward movement at this time was probably slow, and denudation approximately kept pace with it; so that on the arrival of Eocene times there was a plane of marine denudation uplifted to just above or depressed to just below sea level, that marked the removal of all the Cretaceous deposits in our particular area down to the level of the Chert beds. If above sea level, an Eocene river, depositing in its lower reaches loams and shingle, left patches of this deposit upon the surface of the plane of denudation; or, if above sea level, similar substances were laid down as shore deposits near the mouth of the Eocene river. Elevation that had been in terrupted, and possibly disturbed with small oscillations at about sea level in Eocene times, then proceeded and culminated in the great Miocene uplift, which overtook the whole British area and raised the post-Cretaceous plane to somewhere about its present level. The present system cf drainage was then initiated; but temporarily or permanently modified during Glacial times, when there was much torrential action owing to the periodic melting of snow, and the Eocene deposits and debris due to Cretaceous denudation were then possibly re sorted and spread over areas which before they had not covered. t Such, in the briefest outline, is the probable story which, with some modification, is arrived at by the piecing together of various accounts. t Nothing but a systematic drift survey of the south of England, which should refer to its source of origin all the drift material, can settle with any certainty the post Cretaceous history of this region. IlL-THE CHAR VALLEY DEPOSITS. There is little to be said of the deposits formed by the present river Char. The modern alluvium and older gravels occupying the flood-plain between Newlands bridge and the sea have not been represented on Map 2. They can be well seen in the river banks near the mouth, and the latter consists chiefly of Chert * It is not generally realised how great, probably, was the post-Cretaceous denudation over Engtand, The highest English Chalk is that of the mucronata zone.: In Denmark (Faber ann Spencer, 191:4. PP 171-176) there are 1,980 ft. of mucrcwaia Chalk. ~lowinga rapid thinning of the Chalk westwards, one must still suppose that over England a great thickness of mucronata Chalk has been removed, even where remnants ot that zone still appear. t Ussher, 1878, P. 455, and Woodward and Ussher, I9II, pp. 69-70. t De la Beebe, 1839, pp. 255-256; Jukes-Browne, 1897; Clayden, 1906, pp. '47-158 H. B. Woodward, '906, p. 330; Woodward and Ussher, 19u, PP. 67-70. THE GEOLOGY OF THE CHARMOUTH CLIFFS. 353 fragments j old river terraces also border the present flood plain j remains of a still older and higher Char or Lyme valley gravel existed on Church Cliffs as late as 1834 j* and Buck land] records Rhinoceros and Elephant remains from the gravels of these two valleys, also the remains of a submerged forest at the mouth of the Char. Water-logged timber, probably parts of this, were observed at Mouth rocks by the author in 1913. Close to the mouth the river gravel is largely mixed with beach material that has been flung up by storms and imbedded in the river bank, that here coincides with the cliff base. IV.-THE BEACH. Charmouth beach consists of mixed sand and shingle, now the one and now the other predominating in different parts of the beach. Blocks of Lias Limestone of some size form rocks beneath Black Ven, and mixed with these are a good number of Cowstones. Where there is shingle, the larger pebbles are formed of Lias Limestone, and the smaller material of Chert that appears to break up much more readily under the action of the waves than do the limestones. There are also a good many medium-sized Chalk flints. The sand is capricious in its appearance and distribution. Sometimes, for instance, it covers Table Ledge beneath Black Ven, and at other times the slabs of this indurated marl are bare. There is always some sand at low tide beneath Charmouth beach proper, and generally a fair amount immediately east of the river mouth, where the shingle is small. This, however, gradually diminishes as the coast is followed eastward and the shingle gets larger, until it passes into a steep peeble-beach beneath Westhay Water, that becomes still steeper with larger pebbles at St. Gabriel's Mouth, making Janding from a boat difficult except in the calmest weather. Pebbles of other composition than Lias Limestone, Chert and Flint are rare, and their presence is no guarantee of their natural occurrence j in fact, the chances are that they are ballast from ships at Lyme. t Moreover, the fishermen move rock from one part of the coast to another in ballasting their open boats. Thus a large block of White Lias was carried from Pinney Bay to Charmouth in this way on one occasion within the author's experience j whereas pebbles of White Lias have not been observed on Charmouth beach. Two kinds of pebbles, however, may be mentioned as of such comparatively frequent occurrence as to make it probable that they are naturally there j pebbles of dove-grey limestone with a silky fractured surface and with bright-red veins, almost certainly Devonian limestone j and flattened liver-coloured pebbles of quartzite that are almost * Hawkins, 1834. p. 12. +Buckland, 1822, p. 102. ~ A rolled Eocene shell (Clavalithes longcevus), probably from the Barton Beds of Hampshire, was found on Charmouth beach, May. 1914. 354 W. D. LANG ON certainly from the Budleigh Salterton Bunter Pebble Bed, though they are of a darker colour than is usual with those Bud leigh pebbles that contain fossils. The general drift of the beach is from west to east, as is seen by the way in which the river mouth has been pushed up against Stonebarrow Cliff. The same is seen in the case of the Axe. That the river mouth is liable to shift, presumably after a storm has removed or broken the shingle bar, is proved by old drawings of Charmouth beach. In sketches made probably about fifty years ago that were in the possession of the late Miss H. Templer, of Charmouth, the mouth of the Char is shown close to the end of Lower Sea Lane. Pieces of wet-clay, falling from Black Ven, often roll down the slopes, and thus assume a more or less spherical form. On reaching the beach, where it is composed of small shingle, they become plastered all over with this material, and, when they come to rest, present curious-looking bodies that resemble spherical masses of compact shingle, whose true nature is not seen until the mass is broken. BIBLIOGRAPHY. A list of the titles, &c., of works referred to in this paper and others pertaining to the Geology of the Charmouth District. This list contains as complete a bibliography of the Cretaceous of the three cliffs, Black Ven, Stonebarrow and Golden Cap., as has been possible to compile, in addition to the titles of other works mentioned in the paper. 1762. STEPHENS, J .-" An Account of an uncommon Phenomenon in Dorsetshire." In a letter from John Stephens, M.A., to Emanuel Mendes da Costa, F.R.S. Phi!. Trans. Roya! Soc., vol. Iii, part I, pp. II9-123· J797. MATON, W. G.-" Observations relative chiefly to the Natural History, etc., of the Western Counties of England," 2 vols., 8vo, Salisbury (vol. i, pp, 75-76). [I have not seen this reference, but quote from H. B. Woodward, 1889. p. xxvii.] 1812-1845. SOWERBY,JAMES (1812-1822), and J. DE C. SOWERBY (1822 1845).-" The Mineral Conchology of Great Britain," vols. i-vi, and Supplement. 8vo. London. 1822. BECHE, H. T. DE LA.-" Remarks on the Geology of the South Coast of England, from Bridport Harbour, Dorset, to Babbacombe Bay, Devon." Trans. Geol, Soc., series II, vol. i, pp. 40-47, pls, iii-viii. 1822. BUCKLAND, W.-" On the Excavation of Valleys by diluvian action, as illustrated by a succession of Valleys which intersect the South Coast of Dorset and Devon." Trans. Geol, Soc., series II, vol. i. pp. 95-102, pIs. xiii and xiv. PI. xiii is a geological map of this district. 1823. ROBERTS, G.-" The History of Lyme Regis, Dorset, from the Earliest Periods to the Present Day." 8vo. Sherborne. 1826. BECHE, H. T. DE LA.-" On the Lias of the Coast in the Vicinity of Lyme Regis, Dorset." Trans. Geol. Soc., series II, vol. ii, pp. 21-30. 1826. .-" On the Chalk and Sands beneath it, usually termed Greensand, in the Vicinity of Lyme Regis, Dorset, and Beer, Devon." Trans. Geoi. Soc., series II, vol, ii, pp, 109-II8. THE GEOLOGY OF THE CHARMOCTH CLIFFS. 355 1826. MILLER, J. S.-" Observations on Belemnites." T1"<7ns. Ctol. Soc., series II, vol. ii, pp. 45-62. 1826. SOWERIlY, G. B.-" Description of a new Species of Astacus found in a Fossil State at Lyme Regis in Dorsetshire." Zooi. :l0ltrn., vol. ii, No. viii, pp. 493-4, pl. xvii, figs. 1-2. 1826. SOWERBY, J. DE C.-See under James Sowerbyand J. de C. Sowerby, 1812- 1845. 1829. BUCKLA:"ID, W.-" On the Discovery of a New Species of Ptero dactyle in the Lias at Lyme Regis." Trans. Geo], Soc., series II, vol, iii, pp. 217-222. 1829. .-" On the Discovery of Coprolites, or Fossil Freces, in the Lias at Lyme Regis and in other Formations." Proc. c.«. Soc., vol. i, p. 97, and Trans. Ceol. Soc., series I I, vol. iii, pp. 2Z3-236. IS30. WOODWARD, S.-" A Synoptical Table of British Organic Remains." 8vo. London and Norwich. 1831. BECHE, H. ·T. DE LA (and edition, 1832 ; 3rd edition, 1833).-" A Geological Manual." 8vo. London. A German translation of the second edition was published in 1832 by Dechen. I833-I835.-LI:'WLEY,]., and HUTTO~.-"The Fossil Flora of Great Britain." Vol. ii. p. 155. 8vo. London. 1834. BECHE, H. T. DE LA.-Map, Sheet 22, the Geological Survey of England and Wales. (Revised in 1839.) 1834' HAWKINS, T.-" Memoirs of Ichthyosauri and Plesiosauri." Fo!. London. 1834. ROBERTS, G.-" The History and Antiquities of the Borough of Lyme Regis and Charmouth" (2nd edition). Contains a geological map of the district by De la Beche. 1835. BUCKLA:"ID, W., and BECHE, H. T. DE LA-" On the Geology of the Neighbourhood of Weymouth and the adjacent. parts of the Coast of Dorset." Trans. Geol. Soc. Series II, vol. iv, pp. 1-46, pIs. i-iii. 1835. EUDES- DESLO:"lGCHAMPS, E. -" Memoire pour servir a l'histoire naiurelle des Crusraces fossiles." Mtm. Soc. L11m. de Normandie, vol. v, pp. 37-46. Names Orythia labtSchii, a crab from the Cowstones. r836. FITTON, W. lL-" Observations on some of the Strata between the Chalk and the Oxford Oolite in the South-east of England." Trans. Clol. Soc., series II, vol. iv, pp. 1°3-389, pIs. vii-xxiii, 1837. BRODERIP, W. J.-" Descriptions of some Fossil Crustacea and Radiata found at Lyme Regis, in Dorsetshire." Trans. Geoi, Soc., series II, vol. v, Pl'. 171-174, pl. xii. 1839. BECIIE, H. T. DE LA.-" Report on the Geology of Cornwall, Devon, and West Somerset.' Altm. Geol. Suro, of England and Wales. 1840. HAWKINS, T.-" The Book of the Great Sea-dragons." Fcl, Lon-lon, 184I. BOWEJ 1852. BECHE, H. T. DE l.A.-Horizontal section 21, Geol. Survty England and Walts. (Revised in 1873). 1852. D'ORBIGNY, .'1.-" Cours e.ementaire de Paleontologie et de Geologie Stratigraphiques.' Dec Paris. 1856·8. OPPEL, .'1..-" Die j ur aforrnation Englands, Frankreichs und des Siidwestlichen Deutschlands." 8vo. Stuttgart. 1857-1878.-WRIGHT, '1'._" Monograph on the British Fossil Echinodermata of Oolitic Formations." Vol. i, The Echinoidea. Pal. Soc. 1858. QUENSTEDT, F . .'1..-" Der Jura." 8vo. TUbingen. 1860. JONES, J.-" Rambles round Chard with a hammer." 186::>. WRIGHT, T.-" On the zone of Atncula contorta and the Lower Lias of the South of England." Quart. Journ. Geoi. Soc., vol. xvi, Pp·374-411. 1861-1881. OWEN, R.-" A Monograph of the Fossil Reptilia of the Liassic formations," Pal. Soc. 1863. BELL, '1'.-" A Monograph of the Fossil Malacostracous Crustacea of Great Britain." Part ii, "Crustacea of the Gault and Green sand." Pal. Soc. 1863. DAY, E. C. H.-" On the Middle and Upper Lias of the Dorsetshire Coast." Quart. younl. Geol, Soc., vol. xix, pp. 278-297. 1863. WOODWARD, HENRY.-" On a new Macrurous Crustacean (Scaphlus ancylochelis j from the Lias of Lyme Regis." Quart. yourn. Geol, Soc., vol. xix, pp. 3IR-32 I, pl. xi. 1863-1880. WRIGHT. '1'.-" A Monograph on the Fossil Echinodermata from the Oolitic Formations," vol. ii. Pal. Soc. 1864. MAYER.EYMAR, C. D. W.-"Tableau synchronistique des Terrains J urassiques.' Zurich. 1865. DAY, E. C. 1I.-"On the Lower Lias of Lyme Regis." Ceol. Mag., dec. i, vol. ii, pp. 518-519. 1865. HUXLEY, '1'., and ETHERIDGE, R.-" A Catalogue of the Collection of Fossils in the Museum of Practical Geology." Mtm. GlO/. Suro: 1865-1909. PHILLIPS, J .-" A Monograph on British Belemnitidee : Jurassic." Pal. Soc. 1865. SALTER, J. W., and WOODWARD, HENRY.-" A Descriptive Catalogue of all the Genera and Species contained in the accompanying Chart of Fossil Crustacea." Svo. London. 1866. :.\IEYER, C. J. A. ,. Notes on the Correlation of the Cretaceous Rocks of the South-east and West of England." Geol. Mag., dec. i, vol. iii, pp. 13-18. Tbe first attempt at a detailed correlation of the Black Yen section w.th the sequence at Folkestone and the interv-ning sections. 1866. WOODWARD, HE:-.IRY.-" Notes on the Species of the Genus Eryon, Desm., from the Lias and Oolite of England and Bavaria." Quart. younl. Geo]. Soc., vol. xxii, pp. 494-502. 1866. " On a New Crustacean (Alga AIm'dlri, H.W.) from the Lias of Lyme Regis, Dorsetshire.' Geo], Mag., dec. i, vol. iii, pp. 10-13. 1868. ------" Contributions to Fossil Crustacea." Geol, Mag., dec. i, vol. v, pp. 258-261 and pp. 353-356. 1869. COQUAND, H.-" Monographie du genie Ustrea, Terrain Cretace." Svo and fol. Marseilles, Paris, etc. 1872. CARTER, 1.-" On Orithopsis Bonntyi. a new Fossil Crustacean." Geoi. Mag., dec. i, vol. ix, pp. 529-532, pI. xiii, fig. I. 1874- MANSH-Pu:ym:LL, J. C.-(2nd edition, 1895).-" The Flora of Dorsetsnire.' 8vo. Dorchester. Some account of the geology is given in both editions, ami a geological map in the second edition. 1874. MEYER, C. J. A._" On the Cretaceous Rocks of Beer Head and the adjacent Cliff Sections, " Quart. youl'n. Geoi. Soc., vol. xxx, pp. 369-393. THE GEOLOGY OF THE CHARMOUTH CLIFFS. 357 1874. RANCE, C. E. DE.-" On the Physical Changes preceding the Deposition of the Cretaceous Strata in the South-west of England." Geoi. Mag., dec. ii, vol. i, pp. 246-253. Until that in 19°7, here is the only definite record (repeated in 1889) of the Gault on Stone barrow. 1875. GARDNER, J. S.-" On the Gault Aporrhaidee.' Geol. Mag., dec. ii, vol. ii, pp. 49, 124, 198, 291,and 392. 1875. JUDD, J. W.-"The Geology of Rutland," Mem. Geol, Surv., England and Wales. 1875-1878. WRIGHT, T.-" A Monograph on the British Fossil Echinoder mata from the Cretaceous Formations." Vol. i, parts vii and viii. Pal. Soc. 1876. BARROIS, C.-" Recherches sur Ie Terrain Cretace Superieur de l'Angleterre et de l'Irlande." Mhn. Soc. Geoi. Nord., vol. i, mem.I. 1876. ------" L'age des couches de Blackdown (Devonshire)." Ann. Soc. Geol. Nord., vol. iii, pp. 1-8. 1876. WOODWARD, H. B.-" The Geology of England and Wales." First Edition. Svo, London. 1877. WOODWARD, HENRY.-" A Catalogue of the British Fossil Crustacea with their synonyms and the range in time of each genus and order." British Museum. 1878. ETHERIDGE, R., and NEWTON,E. T.-" A Catalogue of the Cretaceous Fossils in the Museum of Practical Geology." Mem. Geol. Surv. 1878. USSHER, W. A. E.-" The Chronological Value of the Pleistocene Deposits of Devon." Quart. yourn. Geol. Soc., vol. xxxiv, PP·449-458. 1878-1886. WRIGHT, T.-" Monograph on the Lias Ammonites of the British Islands." Pal. Soc. 1880. eASLEY, G. (and Edition 18-, 3rd Edition 1899).-" Geology of Lyme Regts." r arno. Lyme Regis. 1885. DOWNES, W.-" The Cretaceous Beds at Black Ven, near Lyme Regis, with some supplementary Remarks on the Blackdown Beds." Quart. yourn. Geo!. Soc., vol. xli, pp. 23-27. 1886. -----.-" On the Tunnel Section near Honiton, Devon:' Geol. Mag., dec. iii, vol. iii, pp. 308-3Il. 1886. GRANTHAM, R. B.-" Lyme Regis and Charmouth," in Topley. " Report of the Committee ... for ..• inquiring into the Rate of Erosion of the Sea-coasts of England and Wales." Rep. Brit. Assoc. for 1885, p. 422. Aberdeen. 1886. WOODWARD, H. B.-" Axmouth to Eype," in Topley, oj. cit. under last reference, pp. 423-425. 1887. .-" Geology of England and Wales." and Edition. 8vo. London. 1889-1901. WOODWARD, A. S.-" Catalogue of Fossil Fishes in the British Museum." Parts i-iv, 1889. WOODWARD, H. B.-" Preliminary Excursion to Lyme Regis. Report by the Director." Proc. Geol. Assoc., vol. xi, pp. xxvi-xlix. A good historical survey of the geology of the district. 1892. GEIKIE, A.-Sheet 14 of the" Index Map of England and Wales." Geol. Surv. England and Wales. 1893. BUCKMAN, S. S.-" The Bajocian of the Sherborne District." Quart. yourn. Geol. Soc., vol. xlix, pp. 479-522. 1893. WOODWARD, H. B.-" The Jurassic Rocks of Britain," vol. iii. "The Lias of England and Wales (Yorkshire excepted)." Mem. Ceol. Surv. 1894. BONARELLI, G.-" Contribuzione alia conoscenza del Guira-lias. lombardo.' Atti della R. Acad, delli Sciene» di Torino, vol. xxx, pp. 81-96. PROC. GEOL. Assoe., VOL, XXV, PART 5, 1914.J 24 W. D. LANG ON 1894. GORDON, MRS.-" The Life and Correspondence of William Buckland." 8vo. London. 1895. MANSEL-PLEYDELL.-"'The Flora of Dorsetshire," and Edition. 8vo. Dorchester.-Contains a geological map and short account of the geology of the district. 1896. NEWTON, R. B._" On the Identification of the Acanthoceras mammil latum and Hoplites interruptus Zones at Okeford Fitzpaine, Dorsetshire." Geol, Mag., dec. iv, vol. iii, pp. 198-200. 1897-8. JUKES-BROWNE, A. J._.ll TheOrigin of the Vale of Marshwood and of the Greensand Hills of West Dorset." Proc; Dorset Nat. Hist, Club (1897), vol. xviii, pp. 174-184. Reprinted, with a few altera tions, in Geol. Mag. (1898), dec. iv, vol. v, pp. 161-168. 1897. NEWTON, R. B._" An Account ofthe Albian Fossils lately discovered at Okeford Fitzpaine, Dorset." Proc, Dorset Nat. Hist, Club, vol. xviii, pp. 66'99. 1898. CARTER.-" A Contribution to the Palreontology of the Decapod Crustacea of England." Quart. yourn. Geol. Soc., vol, liv, pp. 15-44· 1899. THOMPSON, B._" Geology of the Great Central Railway: Rugby to Catesby." Quart. Journ. Geol. Soc., vol. lv, pp. 65-88. 1899-1913. WOODS, H.-I< A Monograph of the Cretaceous Lamellibranchia of England." Pal. Soc. 1900. JUKES-BROWNE, A. J., contributions by WILLIAM HILL.-" The Cretaceous Rocks of Britain." vol. i. II The Gault and Upper Greensand of England." Mem. Geol. Surv. A condensed account of former records with much new information, notably a described section on Golden Cap, a section with fossils on Black Veil, and the description of the j unction with the Lias on these two cliffs. 1902. BUCKMAN, S. S.-I< The term 'Hemera.''' Geoi. Mag., dec. iv, vol. ix, pp. 554'557. [902. JUKES-BROWNE, A. J.-I< On a Deep Boring at Lyme Regis." Quart. yourn. Geo] Soc., vol. lviii, pp. 279-289. 1902. LUBBOCK, J.-I< The Scenery of England and the Causes to which it is due." 8vo. London. 1902. WOODWARD, H. B.-I< Note on the Occurrence of Bagshot Beds at Combe Pyne, near Lyme Regis." Geol, Mag., dec. iv, vol. ix, pp. SIS, 516. 1903. LANG, W. D._" On a Fossiliferous Bed in the Selbornian of Char mouth." Geol, Mag., dec. iv, vol. x, pp. 388-392. 1903. ROWE, A. W._" The White Chalk of the Devon Coast." Proc, Geoi, Assoc.; vol. xviii, part I, pp. 1-5 r. 1904. LANG, W. D._" The zone of Hoptites interruptus (Bruguiere) at Black Ven, Charmouth.' Geot. Mag., dec. v, vol. i, pp. 124-131. 1904. WOODWARD, H. B. (second edition 1907, third edition 1914) II Stanford's Geological Atlas of Great Britain." 1906. CLAYDEN, A. W._" The History of Devonshire Scenery." 8vo. Exeter and London. 1906. WOODWARD, H. B., and USSHER, W. A. E., with contributions by A. 1. JUKES-BROWNE (second edition, 19II).-I< The Geology of the Country near Sidmouth and Lyme Regis." Mem. Geoi, Suro, England and Wales, and Map, new series, sheet 326. 1906. WOODWARD, H. B. (with notes by LANG, W. D.).-I< Report of Excursion to Lyme Regis." Proc, Geol, Assoc., vol. xix, pp .. 320 340. Hoplites interruptus first recorded from this district. 1907. LANG, W. D._" The Selbornian of Stonebarrow Cliff, Charmouth." Geol, Mag., dec. v, vol, iv, pp. 15°-156. 1908. JUKES-BROWNE, A. J,_I< The Burning Cliff and the Landslip at Lyme Regis." Proc, Dorset Nat. Hist, Field Club, vol. xxix, pp. 153-160. THE GEOLOGY OF THE CHARMOUTU CLIFFS. 359 Ig08. W[oqnwARD1. II. B.-" Burning Cliffs." Geol. Mag., dec. v, vol. v, pp. 56r, 562. 1909-1912. BUCKMAN, S. S.-" Yorkshire Type Ammonites." Vol. r. 8vo. London. 19o9. CAMERO:-l, A. C. G.-" On a Well-section at Ware House, near Lyme Regis, and the Fossils obtained therefrom." Geol, Mag., dec. v, vol. vi, pp. 169-171. Mnrtonictrar rostratum first recorded from this district (as" Amm. [Schll>'nbachiaj rostra/us "). Igog. ------.-" The Burning Cliff at Lyme Regis." Geol, Mag., dec. v, vol. vi, P: 336. Igog. GREGllI{Y, J. W.-" Catalogue of Fossil Bryozoa in the Department of Geology, British :.\Iuseum: The Cretaceous Bryozoa," vol. ii. IgCg. "PASSER VEN!' EXPLANATION OF PLATES 39 AND 40. Plate 39A.-Blue Lias Limestones (in the bucklandi and angulalus zones) at a point 500 yards N.R. of Lyme Church. The limestone (with a thin limestone immediately beneath it) exactly half way up the section (measured on the right-hand side of the photograph from the beach to the skyline) is Middle Quick, and the little limestone beneath it, Gumption. Above these is a group of three, from below, upwards, Rattle, Second Bed, and Best Bed. Above, again, after an interval of shale, two prominent limestones, Venty below and Top Quick above; and, at the top of the section, another pair, of which the lower and thicker is Glass Bottle, and the upper and thinner. Grey Ledge. The prominent and overhanging limestone below Gumption is Third Quick. At a shorter interval below Third Quick is Top Tape, followed .immediately by Second Tape, Top Copper, and Mongrel (a very thick band), A little way below Mongrel, Second Mongrel (thin) and Specketty, thick and prominent. Below Specketty is a very dark shadow separated from another line of very dark shadow by Third Tape j then a thin irregular bed, Upper Skulls, lying on Iron Ledge (thick) and Under Copper (rather thinner). Under Copper is the lowest bed of the bucklalldi zone. A dark shadow separates Under Copper from Upper White, at the top of the angulatus zone, and the remaining visible irregular limestones are Lower Skulls. Plate 398.-The base of the Black Marls and top of the Blue Lias Series, about! mile N.E. of Lyme Church. The Nodular limestone at the top of the section is the Birchi Bed. The cliff which this caps lies back from the main cliff in the figure, whose top is seen a little way above the bright thin band on the right-hand side of the photograph. This bright thin band is Table Ledge, and lies some 16 ft. above the main mass of the Stone Beds. Fish Bed, a very thin limestone, 4 ft. above Grey Ledge, is hardly indicated. Grey Ledge is the top limestone of the Blue Lias series, and lies above Glass Bottle, the palest and thickest limestone in the photograph, lying just above the head of the lady. The lady's arm lies over Top Quick, while Venty is at the level of her knees. Best Bed is seen at the base of the cliff on the left hand side of the photograph; Second Bed forms a prominent ledge on the beach, while Rattle is just indicated in the foreground. A fault, throwing down 011 the r:get Glass Bottle, Top Quick, ar.d Verity only of the limestones shown, traverses the section just to the left of the middle of the picture. Plate 40A.-A single nodule of the Birchi Bed, in. place, about 1,100 yards west of the end of Lower Sea Lane, Charmouth Beach. The nodule, showing bedding-planes, is surrounded by a shell of fibrous Calcium Carbonate (" beef ") that is thicker on the upper than on the under side. Th'e" heef , exhibits cone-in-cone structure, just indicated at the extreme right of the upper layer. Plate 40B.-A reef formed hy an anticline in the steeply-folded strata at the horizon of the Birchi Bed, at Mouth rocks, Charmouth Beach. The tabular limestone, prominent in the two limbs of the anticline, is that occasionally lying immediately upon the nod ules of the Birchi Bed, and probably-con taining Ammonites of the turn.ri-5rooki group. One of the true Bi"chi Nodules is seen at the nearer end of the farther limb underlying a slab of the tabular limestone. The photograph is taken from the seaward. The middle distance is formed hy the pebble-ridge through which the River Char filters into the sea. The far distance is the western corner of Stonebarrow Cliff, with Stonebarrow Farm on the skyline. The trees on the skyline over the ridge are at N ewlands,