177

EXCURSION TO TENBY, EASTER, I9c9.

APRIL 8TH TO 15TH.

Director: ARTHUR L. LEACH.

Excursio» Secrctary: RAY~[OND H. CK\NDLER.

(Rt/ort by THE DIRECTOIL)

THE official party left Paddington at I I.30 a.m., on Thursday, April Sth, and arrived at Tenby at 6.30 p.m.; but many members had assembled at the headquarters, the Coburg Hotel, during the ~ay, and upwards of sixty sat down to dinner on Thursday evemng. Fridav, April 9th.

UPPER A:\D Lowrr, CARI30NIFEROUS ROCKS. Favoured by delightful weather the party walked to the south side of the harbour, where the Director drew attention to the chief features of the coast. A heat-haze overhung Carmarthen Bay, veiling 'Worm's Head, in Gower, which, like Tenby, is on the south crop of the Carboniferous Limestone, but Ragwen,

~lJ."fort· .-'-...~I.", Casl kH~ 1.

f .." + - - - - ..2.- --

FIG. 12.-DIAGRA~IMATIC SECTION OF THE CARI30NIFEROUS LIMESTONE (Avonian), TENllY.-rf. L. leach.

5 "U pper subb·zone fl Seminu!,I-zO:lC. a. Lamiflosa-dolomite. S t : L ower su -zcne b. Caninia-oolite. Cs' Upper sub-zone l S.l'ringoth.vns- c. Shales and impure limestones. C r- Lower sub-zone j zone. d. Massive Limestones (with Michelinia Zz' Upper sub-zone-Zaphrmtis-zone. megastoma). x. Prominent band of Productus e. Thin-bedded reddish limestones. " giganteus." ./. Massive Limestones.

Length of Section, 2,000 feet.

on the north crop, could be discerned. Between Ragwen and Tenby extends a remarkable coast section through the greatly­ disturbed heds of the western extension of the South Wales coal-field. The north side of Tenby stands on the edges of the PROC. GEOL. Assoc., VOL. XXI, PART 4, 19°9] 14 E XCURSION TO T E N RY, EAST ER, 19° 9. upturned and locally overfolded beds composing the southern border of the coal-field. In the immediate foreground a set of brownish grits dipped steeply south into the cliff, and 100 yatds to the north-west a group of black Upper Carboniferous shales was seen also dipp ing south, apparently under the Carboniferous Lim estone. These shales, extending nearly ISO yards along the foreshore, are separated from still higher Carbon iferous rocks by a great fault,'*' recently mapped and described by NIl. E. L. Dixon, who names it the " Ritec " fault, since it runs westward several miles along the valley of that stream. On closer examination the shales were seen to include large " bullions " (ellipsoidal conc retions), thin limestones, and carbonaceous layers. De la Beche (l lfolt. Ceol. Survey, vol. i, p. 134), after describing a thick er series (1,600 ft.) of black cherty shales overlying the" Rottenstones " (Carboniferous Limestone) at Bishopston in Gower, remarked: "At T enby we recognise the continuation of these beds, though but a few feet thick, in the carbonaceous shales, with nodules and irregul ar seams of dark argillaceous limestones (containing Goniatites) and the hard sandstones which there really succeed the Carboniferous Limestone in ascending order, th ough the contortions have been such, that beneath the town where this part of the series is well-exposed, these beds have the deceptive appearance of dipping und er the limestone." In De la Beche's opinion these shales were part of a lenti cular mass (thinning off east and west) interposed between the Carboniferous Limestone and the true Coal Measures, not definitely corresponding to the Millstone Grit of the North of England and of the north crop of he South Wales coal-field, but appearing to be a continuation of the black limeston es above the Pilton and Petherwin groups in Devonshire. In Gower, and at T enb y, " it is," he remark s, "difficult to draw fine lines of distinction between the Car­ boniferous Limestone and the Coal Measures." T his difficulty probably explains the discrepancy between Horizontal Section No. I, Sheet :2 (1844), in which only Coal Measures are indicated, and the r-inch geological map ( [845), which shows a broad out­ crop of Millstone Grit between Tenby and Waterwynch. After the Director's state ment of these views the shales were examin ed. From the "bullions " Dr. Wheelton H ind obtained C lyphioceras diadema, Pterinopecten papy rai:ea, Posidonie!la lcevis, P osidonomya cr. memoranacea, Orthoceras sp. (?), .Jfachrocheilina e!egans, several gasteropods, and ostracods in abundance. The peculiar form of Glyphioceras diadema found in the bullions possessed coarse ribs, an acutely angular periphery and a very wide umbilicus, exposing all th e whorls, corresponding thus to the variety which is characteristic of the Chokier beds of Belgium, and of beds of the same horizon at Lisdoonvarna, Co. Clare. • S um . Prog; CeDI. S urve)' for 1904 and subsequent years . EXCURSION TO TENBY, EASTER, 19°9. 179

The whole fauna appeared to Dr. Hind to link the "bullion beds" with his Pendleside Series, a group occurring between the Carboniferous Limestone and the Millstone Grit in the English Midlands, and containing a characteristic assemblage of fossils. This series is well shown at Chokier, and is represented in the West of Ireland; Dr. Hind claims also" a limited but definite Pendle­ side fauna, Posidonieiia iaois and Glypht'oceras btl£ngue,"* for the black shales of Bishopston in Gower, but the Bishopston shales are assigned by Dr. Strahan to the Millstone Grit, t the true grits of the north crop being held equivalent to the shales of the south 'Crop. In response to a request for an expression of opinion, Dr. Wheelton Hind writes: "The' bullion' beds exposed along the North Shore belong to the Pendleside series of the Midlands, the Namurian of Belgium, rather than to the true Millstone Grit series, to which they bear little resemblance in fauna or lithology." Leaving the bullion beds and noting "barrel-post rock," a breccia on the line of the Ritec fault, the folded and faulted shales and grits of the north cliff were examined. The structures shown in the cliffs afforded good illustrations of the powerful disturbances which have affected the coal-field. Near Middle Rock a sharp anticline showed in its almost vertical north limb and the more gently inclined south limb features which characterise most of the anticlines in this district, and indicate pressure from a centre of disturbance in the south. . The exact horizon of these beds is doubtful. Mr. E. L. Dixon] says: "The section exposes shales, with various lamellibranchs but no Goniatites, which cannot be correlated at present with any part of the series [Millstone Grit, Coal Measures] outcropping to the north." Some fossils obtained during the excursion are therefore of interest. On the south side of First Point in a curious rubbly bed, with plant fragments and annelid tracks, Gastrioceras iiszer! was found, and a shale imme­ diately south of this bed yielded a species of Carbonico/a in abundance. Dr. Wheelton Hind considered these fossils to indicate Lower Coal Measures rather than Millstone Grit, since Gastrioceras l£stfr£ characterises the upper part of the Millstone Grit and the Lower Coal Measures of the Midlands. Thus the most important and interesting feature of the section ex­ posed along the North Shore from the" bullions" to First Point is its resemblance to the Belgian sequence where the Namurian (only about 150 feet thick) with Glypht'oceras diadema succeeds the Visean conformably. The Namurian in Belgium is classed with the Lower Coal Measures.

* Geol, Mag. (Ig06), p. SOl. t "The Country around Swansea." Mem; Geol, Survey (Ig07). t Sum. Prog: GeJl. Suru., Ig05, P. 65· 180 EXCURSION TO TENBY, EASTER, 1909.

The party now returned to the harbour and went thence to the Castle Hill. Near the Life-boat house thinly-bedded lime­ stones with abundant chert nodules were seen overlying a thick grey oolite. Above the chert beds come highly crinoidal lime­ stones with Zaphrentids and a brachiopod, probably Spirifer aff. clathratus. Some time was spent on the summit of the hill in studying the general view of the coast-line before descending to the South Sands. The limestone on the south side of the Castle Hill was seen to be much brecciated and unfossiliferous. From St. Catherine's Rock the section shown in Fig. 12 was first examined as a whole, and afterwards the party worked along the base of the cliffs to study the details of the sequence.

FIG. I3·-SECTION SHOWING BRECCIA, PROBABI.Y OF TRIASSIC AGE, LYDSTEP CAVERNS, TENBY. (See page 185.)

The lowest beds in the axis of the anticline are much jointed and weathered dolomitic limestones-the Laminosa-dolomites of C1-containing few fossils except occasional specimens of Zaphrentis omalusi, Syringopora d. reticulata, and small crinoid ossicles. Only a thin band of white oolite-Caninia-oolite­ intervenes between these dolomites and the thinly-bedded shaly C~ and gritty beds at the base of C2• These lowest beds of indicate probably a temporary upheaval of the floor of the Carboniferous sea, producing thus shallow-water conditions of deposition at this point. At Pendine, about 7 miles to the EXCURSION TO TENBY, EASTER, 1909. 181 north-east, where greater movement must have occurred, a con­ glomerate intervenes in this position between the Zaphrentis and Seminula zones.

The sequence is continued by dark massive limestones still in C2, abounding in Michelinia cf. megastoma and Bellerophon, and con­ taining also Orthoaeras sp. Caninia cylindrica, Zaphrentis cornu­ copiee, Syringopora cf. reticulata and large crinoid stems; these are followed by redder limestones, apparently unfossiliferous, until Lithostrotion cf. martini appears a few yards above a little fold in the northern limb of the anticline. A mass of this coral was seen just at the beginning of the wall which ends the section north of Lexden. In the southern limb of the anticline the sequence is con­ tinued nearly to the top of 82, Under Belmont Caninia cylt"n­ drica and Cyathophyllum 1> characterise horizon 0, the overlap of C2 upon 81> and a few feet higher Lithostrotion cf. martini becomes very abundant, thus marking the establishment of 81, Above this point massive limestones, upwards of 500 ft. thick, extend nearly to the top of 82- No sharp line can be drawn between 81 and 82, but just east of Bacon's Hole an 82 fauna is found (x in Fig. 12). The Productus "giganteus"-band of 82 is better shown in the Wreck Field quarry, where this fossil occurs in thousands, asso­ -ciated with Seminuia jicoidea, Cyrtina carbonaria, L. cf. martini, Alveolites septosa, Carcinophyllum, Productus hemisphericus, Syringopora cf. distans. The cliff section ends in 82, at a point which cannot be far below the base of the Dibunophyllum-zone. The details of this important section were easily examined from the shore, and most of the characteristic fossils were shown in situ. The section does not form a good collecting ground, since the lower rocks are much water-worn, and the higher parts of the cliff are inaccessible. Under Gunfort Dr. Vaughan spoke on the differences in the faunas of the Syringothyris-zone at different localities and emphasised the dependence of the charac­ ter of the fauna upon the conditions-shallow or deep water­ of deposition. At Giltar, a mile to the south, after a welcome interval for lunch, the fine cliff section C1 to DI> between the rifle range and Giltar Point, was examined and certain lithological differences were noted for comparison with the Tenby section. Caninia­ oolite of C1 occurs ina small quarry (not visited) south of the rifle range, and oolites form a large part of the cliff section, but the thin shalyand gritty beds (C2), seen in the morning under Gun­ fort, are not here represented by any similar beds. From the oolite at the lowest point of the cliff section the Director had obtained a .)pirifer (undescribed), recognised by Dr. Vaughan as one commonly found in C2• Above this point thicker and paler oolites were seen with Michelinia cf. megastoma, Bellerophon sp. and Syringopora cf. retiasiata, corresponding evidently to the beds EXCURSION TO TENBY, EASTER, 1909. seen under Lexden earlier in the day. Horizon 0 was marked by Caninia, Cyathophyllum ~, Chonetes d. comoides, and at the entrance to the large quarry Lithostrotion cr. martini was seen with Michelinia cr. megastoma and Cythophyllum ~ in abundance above it. This association is very interesting, since Mz"chelinia and Cyathoph}'llum 1> are essentially C2forms, while L. cr. martini is typical of S1' The Seminula-zone is fully developed a few yards higher, as shown by the abundance of Lithostrotion cr. martini. A Productus-band associated with S2 fossils was noted a few yards west of a small cave in a little projecting piece of cliff. This little projection shows several interesting features. It is composed mainly of fault-rock traversed by two vertical slickensided fault­ planes which unite in the foreshore rocks, and on a narrow ledge about 15ft. feet above the shore a patch of "raised beach" remains. The bedding is here lost for some distance in the fault-rock, but, beyond, the S2 beds become very fossiliferous: thick oolites were noted and a line of chert nodules occurred a few feet below the base of the Dibunophyllum-zone. The characteristic fossils of D1 were found in abundance in a massive oolite at the base of the zone and in the rocks at the north­ east corner of the Point, where they are thrown southward b'{ a dip-fault and form an excellent collecting ground. From the top of Giltar Point the long coast-section to the west showed striking contrasts in the outlines of the Carboniferous and Old Red Sandstone headlands: the latter, exemplified in Old Castle Head, sloped seaward at about 45°, but the limestone headlands Giltar, Lydstep and Stackpole, eight miles to the west, all ended in vertical cliffs. Beneath the blown sand on Giltar Point lie the remains of an extensive" kitchen-midden," and some discussion took place near a "hearth," probably prehistoric, showing charcoal and abundant marine shells, which was seen near the edge of the large quarry, as to possible changes in the physiography of the district since the period of these hearths; a bare, wind-swept headland, such as Giltar is now, seems a very unsuitable site for a primitive settlement. The hearth, it was noted, now lies below about 3 ft. of the blown sand. The rest of the afternoon was devoted to the examination of the fine range of cliffs stretching westward towards Lydstep. The special points to be noted were the fossiliferous Semimtla-beds. and the effects of denudation. Amongst the fossils collected were Lithostrotion cr. martini; Syringopora cr. distans, Carano­ phyllum and Chonetes cf. papilionacea abound in excellent pre­ servation, with A Iveolites, Seminula, Cyrtina mrbonaria, Athyris expansa, Bellerophon, Euomphalus sp., Productus giganteus, P. cor­ rugato-hemisphericus, P. hemisphericus and other 82forms. Near Proud Giltar chert, often containing silicified corals and E XCURSION TO T ENEY, EASTER, 1909. 183 brachiopods, was found abundantly in nodules and thin bands in the upper Seminula-beds. T he effects of denudation, marine and sub-aerial, were seen to be very remarkable, particularly as regard s cave-formation. It is hardl y an exaggeration to describe this range of cliffs as " honey-combed" by caves. The Director pointed out man y vertical " blow-holes " communicating below with large caverns, " pipes" filled with clays and sandstones, and ancient, probably in great part pre-Triassic, waterways, and remarked that the part here played by the sea in cave-formation appeared to be mainly the enlargement of the pre-existing waterways of a vanished system of drain age. Under the brilliant sunshine which flooded the cliffs with midsummer heat and light, many of the party now began to display a readin ess to rest and admire the view. The day's excursion, which had already comprised a great variety of geological interests, reached its limit a few hundred yards west of Proud Giltar at a fine "cauldron" with vertical walls rising 100 ft. above its boulder-strewn floor. Tea unfortunately could not be obtained near this part of the coast, so turning inland the party walked through Penally into Tenby. On the way home a small party visited the Wreck Field quarry to see a remarkable bed of U pper-Seminula limestone con­ taining upwards of 10,000 specimens of Produclus " giganteus." (See Plate VI., Fig. 2.)

Saturday, April l oth.

OLD RED SANDST ONE AN D C AR BO NI FE ROU S LIMESTONE.

Accompanied by a few local people and favoured by delightful weath er, the memb ers left Te nby by train at 9.15 a.m. for Manorbier. The whole party num bered about seventy. On the way int o the village Mr. E. L. Dixon, of H .M. Geo!. Survey, who has recently mapp ed this district, drew attention to a fault by which the Upper Carb oniferous Rocks are thrown northward at Norton , and demonstrated very clearly the physical features by which the extent and direc­ tion of the movement were determined. After passing through Manorbier to Skrinkle Farm the party, by permission of Mr. G. Protheroe, went over the fields to Old Castle H ead, so named from a small neolithic camp on the extreme point of the headland. Within the camp the Director gave an account of the lithology of the Lower Old Red Sandstone which compo ses the headland; the grits, cornstones, red marls, and sandstones were splendidly displayed in the great rifts, both parallel and perp endicular to the beddin g-planes, by which the cliffs are intersected. Since the dip is vertical the transverse rifts initiated by fault planes expose a great thickness of beds. A greenish EXCURSION TO TENBY, EASTER, 1909.

quartzite weathered out from the softer marls, and running like a wall through one of the longitudinal rifts, was particularly noted, and near it the Director showed a red marl full of green circular markings, some nearly an inch in diameter, which he considered had arisen around worm-burrows by chemical action between the organic matter of the animals and the ferruginous constituents of the marls. The green circles are the ends of green cylinders, roughly U-shaped, which link the circles in pairs; a dark spot seen at the centre of each circle continues as a dark axis through the cylinder. With the exception of a few fragments of Pteraspis these worm-burrows afford the only indications of animal life yet obtained on Old Castle Head. Mr. Dixon drew attention to certain red marls traversed by curved slickensided planes which he thought were developed by movements confined to the beds and not by earth-movements. These slickensided planes are strongly developed in particular beds throughout the Lower Old Red Sandstone; generally at right angles, approximately, to the curving planes there are vast numbers of elongated rod-like " race" nodules which do not appear to be intersected by the planes. The weathering of the abundant race nodules gives a characteristically deeply pitted surface to these marls. An hour quickly passed on these rocks, but no more time could be spared here. On the way back towards Skrinkle Mr. Dixon drew atten­ tion to the seaward end of the steep syncline in which an outlier of Upper Carboniferous rocks is preserved at Lydstep. The dip shown by Giltar cliffs along the north of the syncline could be seen to be fairly high (4S0 to 60°), but the beds in the south limb are all thrown up to verticality. A very steep and winding cliff path led down into Skrinkle Haven. At the foot of the descent the Director indicated the main features of the fine section shown in the bay, where 1,000 feet of beds, dipping vertically, range from the top of the Lower Old Red Sandstone to the base of the Syringothyris-zone of the Carboniferous Limestone. Reference was briefly made to the descriptions by De la Beche (184S), Ramsey (184S), and Salter (1863), of the passage between the Old Red Sandstone and the Carboniferous rocks. Since the introduction of Dr. Vaughan's system of palreontological zones for the Lower Carboniferous rocks (Tournaisian and Visean), the great cliff section extending from Skrinkle to Lydstep Haven has been found to display the

whole sequence up to the lower Dibunophyllum-zone (D 1). After Mr. Dixon had stated his reasons for regarding the thick conglomerate (Ridgeway conglomerate) on the south side of the bay as the upper limit of the Lower Old Red Sand­ stone (see Sum. Prog. Geol. Survey, 1905, p. 4S), the group of sandstones, quartzites and conglomerates composing the Upper Old Red Sandstone was examined, but the passage beds to the Carboniferous rocks, where fossils begin to appear, EXCURSION TO TENBY, EASTER, Iy09. received most attention. The shales and limestones of the lower Cleistopora-zone proved abundantly fossiliferous. After lunch the tide had fallen sufficiently to allow the adjoining inlet to be reached through the " Church Door." Here the upper Cieistopora beds are well developed. The lower Zaphrentis­ zone showed a thick group of limestones with abundant chert nodules, but a part of this sub-zone is cut out by a fault; the highest Zaphrentis beds were found crowded with fossils. In the inlet under the" Horsesback" where Horizon y-the junction of the upper Z(lphrentis- and the lower Syringothyris­ zone is well exposed, Prof. Delepine, of Lille, gave an interesting discourse on the differences between the British and Belgian developments of the Tournaisian. It was now necessary to leave Skrinkle: most of the members did this with regret, since the bay is so beautiful and interesting, but much yet remained to be seen. Very fossiliferous Z, beds were seen in a quarry in a field above the bay, and from Skomar, within a small cliff camp, the section in Triassic breccias (" gash­ breccias") shown in Fig. 13 was noted. At Lydstep Caverns, where a descent was again made to the beach, the cliffs on each side of the rocky path to the shore were seen to be almost wholly composed of these breccias, the constituent blocks often being of many tons weight. Here and there between the blocks were patches of the red stalagmitic marls, probably Triassic, which gave Mr. Dixon a clue to the age of the breccias. * (See report of Thursday's Excursion, p. 192.) Amidst the boulders on the shore near high-water-mark, the Director showed an erratic boulder of norite (enstatite-gabbro), probably glacially transported from the intrusive rocks of St. David's Head. After glancing at the great "Smugglers' Cave," the steep slope was re-ascended to the headland. A thick deposit of "head" or rubble-drift on the Black Miskin was seen as the party passed on to view a well-marked Raised Beach platform carved in the cliff west of Whitesheet Rock. The platform forms a broad ledge 100 yards long by about 10 yards wide. No beach shingle now remains upon it, but its level agrees with that of the patches of beach seen at Giltar, and the Director mentioned that an excellent exposure of the pre-glacial Raised Beach would be seen at Caldey. The Lydstep "Raised Beach" platform is cut mainly in Triassic breccias ("gash-breccias") just below the base of the Semimtla-zone; very massive limestones form the bulk of the zone, but the cliffs are too dangerous for detailed examination by a party. A quarry at the Point displays the upper Seminula (52) beds excellently, and fossils are abundant, but time did not permit any pause here for collecting, nor could the Dibunophyllum (D 1) beds along the south side of Lydstep Haven * Sum. Prog, Geol, Survey, 1904, p. 46. 186 EXCURSION TO TENBY, EASTER, 1909. be examined, but their position was indicated from the cliff above. By the courtesy of Lord and Lady St. David's the party was entertained to tea at Lydstep Haven, and some time was after­ wards spent in the gardens and shrubberies. Miss Hewatt, who welcomed the party, was heartily thanked by the President for the hospitality extended to the Association and asked to convey the thanks of the members to Lord and Lady St. David's, who were abroad at the time. Brakes had been provided to convey the members into Tenby, and the majority were well content with this ending to the excursion, but a dozen or more preferred to walk the four miles into the town. The Director wishes to record his thanks to Dr. A. Vaughan and to Mr. E. L. Dixon, of H.M. Geol. Survey, for assistance. kindly rendered before and during the excursions on Friday and Saturday.

Monday, April 12th. COAL MEASURES. Rain fell as a large party started for the Local Museum, which, by courtesy of the Committee, had been thrown open to the members of the Association during their visit to Tenby. Mr. Bartlett Span, the Hon. Secretary, Mr. G. E. Mainland, and Alderman J. Leach welcomed the party on behalf of the Com­ mittee. The collections illustrative of local geology, rocks, minerals, fossils, cave remains, implements, etc., were examined, and some of the members found time to glance at the birds, shells and archseological exhibits. In asking Mr. Span to convey to the Committee the thanks of the Association, the President spoke appreciatively of the excellent manner in which this self­ supporting museum is maintained. Despite the rain upwards of 40 members left for Kilgetty by the 10.55 a.m. train; before noon the rain ceased and the rest of the day was dry and pleasant. Below Stepaside the valley road was taken to the shore at Wiseman's Bridge, where the Director gave a brief account of the local Coal Measures, and of the great disturbances which have affected them. Dr. Strahan (Sum. Frog. Geol. Survey, 1905) has described at length the coal­ field and the magnificent coast section between Amroth and Tenby. Wiseman's Bridge is just within the border of the most highly disturbed region, and in the cliff a few hundred yards to the east the beds were seen to be folded and broken in an extraordinary degree. Below a considerable land-slip, very carbonaceous shales crowded with plant fragments were seen resting on an underclay full of pyrite and clay-ironstone nodules, which were formerly worked for iron. In a massive yellowish grit, just east EXCURSION TO TENBY, EASTER, 1909. of the land-slip, large circular pat ches, 4 ft. to 5 ft. in diameter, of brownish-red grit attracted much attention j they did not appear to be du e to iron-staining by infiltration along joints, but no satisfactory explanati on of their origin was suggested. Below Hean Castle a very fine anticlinal structure was seen to be dissected just as it pitches seaward : the cliffs give a vertical, and the shore rocks a horizontal section, and from the centre, where the dip appears to be qua-qua-versa), the beds can be seen curving vertically upwards in the cliff and outwards on the shore, between the limbs of the fold. The Low Level coal-vein was traced in the cliff from the spring of the arch to its descent to the beach, 300 yards farther south. On the foreshore several fine specimens of Sigillaria were discovered in sidi in an und erclay. After an interval for lunch the party passed through Saunders­ foot to the Coal Measures south of the harbour. Anthracite is brough t down to Saun dersfoot by rail from the Bonville's Court Colliery and shipped thence to the south coast of England for use as a malting coal, and to the Continent for dome stic use. The great disturbances shown in the cliffs might lead one to consider coal-mining an almost impossible operation in so disturbed a region, but few of the disturbances extend far below the surface. Dr. Strahan remark s (Sum. Frog. Ceol. Suruey, 1905; p. 59), " Of the innumerable folds and thrusts observable on the surface, not one in fifty exists at tha t depth rI 50 yards] ; only the main folds or faults which define the principal belts of the coalfi eld can be recognised." Beyond the harbour the folds were seen to becom e more striking, and the dislocations perhaps more complex than tho se previously noted. A very promin ent anticline, rising 50 feet above the beach at the bathing place, was particularly admi red, but even finer were the great folds at Monk stone Point. The headland itself is an anticline with an infold along its axis, a "buckled" anticline in fact. To the south the beds ran down in a great syncline, and then, suddenly turning, rose in a magnificent arch nearly 300 feet above the beach at Trevane. The stru ctures were most impressive, and -the view has an histori cal interest, since some of the folds were sketched by De la Bech e to illustrate the extraordinary cont or­ tions of this coal-field. Some time was spen t in collecting plant remains from shales in the north limb of the Trevane anticline. Close by several large cylindrical and spheroidal concretions were noted. After a scramb le over a terribly rocky foreshore, some fossiliferous shales near the waterfall at the mouth of the Lodge Valley were reached and yielded many interesting things before the incoming tide forced the party to beat a hasty retreat. A few of the members found their way into Tenby along the cliffs; the remainder ascended the steep path to Trevane, where carriages were waiting, and drove thence into T enby. 188 EXCURSION TO TENBY, EASTER, 1909.

Tuesday, April 13th.

CALDEY: OLD RED SANDSTONE AND CARBONIFEROUS LIMESTONE. By the courtesy of the Abbot of Caldey the little steamship Firfjly was placed at the disposal of the members of the Associa­ tion. The first party left Tenby at 9.3°, and on reaching the island were welcomed by Brother Illtud on behalf of the Abbot. At Sandy Bay the Director drew attention to an excellent section in Raised Beach, about 12 to 15ft. above the shore, consisting of closely packed pebbles with a few shells, overlain by reddish sand, the whole being about 3 ft. thick and resting on a well­ marked platform of limestone; he indicated also the position of other patches at corresponding levels on the Giltar cliffs, north of Caldey Sound, and briefly recounted the evidence for the age of the Gower Raised Beaches, with which the Pembroke­ shire beaches are probably contemporaneous, although no glacial drift has yet been found clearly overlying them. (See Plate VI, Fig. 1,) The deposits associated with the Raised Beach in Gower, which occur in a definite order and are grouped as the Raised Beach Series,* comprise (I) Beach-shingle, with shells of recent species, cemented into a firm mass; (2) on the shingle an impersistent reddish sand, probably blown-sand; (3) a talus (head) or rubble of strictly local rock fragments. Upon this series rest giacial deposits. It is therefore clear that the Raised Beach is older than the local glacial drifts. In South Pembrokeshire the same order of superposition is found, but usually one member or more of the series is missing. The Zaphrentis (Z2) beds north-west of Sandtop proved fairly fossiliferous and yielded Chonetes d. hardensis, Productus cf. martini, Spirifer aff. dathratus and various crinoids. While the party now went down into Sandtop Bay to examine the junction of the Old Red Sandstone and the Carboniferous Limestone Series, the Director returned to Priory Bay to meet those who were coming by the Firfjly's second trip; about 40 finally assembled at Sandtop Bay. In the Upper Old Red Sandstone, a marine band with Serpuia advena was seen. This fossil, first noted by J. W. Salter, t has not been found at Skrinkle, 3 miles to the west, but at West Angle, 18 miles west of Sandtop, Salter noticed a similar band well below the base of the Carboniferous rocks. After lunch the party crossed the fields to the ancient Bene­ dictine Priory, which still remains in almost complete preservation. Here the members divided, some going on to Drinkim Bay, while the majority, under the guidance of Brother Illtud, inspected the r jth Century Priory and the well-known Ogham stone with its inscriptions of the sixth and ninth centuries. A strong spring in * A/em. CeDI. Suro., The Country around Swrnsea,"p. IIg. t Quart. Jour. Geoi. Soc. Vol. xlx, P.496. 1,163. l'ROC. G I::O L. A ssoc., '"I)[ .. X XI. P LATE Y T.

lI 'ht'/o b)' .1. L. Lt".,.-h. FIG. I.-RAISED BEACH OVERLA IN Ill' R U Il IlLE DRIFT, S AN DY BA Y, C.-\.LD E\'.

[t'/N t

Wednesday, Apri] qth.

OSSIFEROUS CAVES. SILURIAN AND OLD RED SANDSTONE.

In delightful weather nearly 30 members set out for The Hoyle and Longbury Bank, several who had already visited the caves proposing to join the party later in the day. From the Marsh Road the massive and deeply "piped" limestones in Black Rock quarries could be seen, and a large "pipe" choked with day and sand was noted in the quarry at Holloway Cottage. At The Hoyle the Director briefly related the story of the explor­ ation of the cave by Col. Jervis (r840), the Rev. G. N. Smith EXCURSION TO TENBY, EASTER, 1909.

(about 1860), and subsequently by the Rev. H. H. Winwood, Prof. Boyd Dawkins, 1\1r. E. Laws and other cave-hunters. A great part of the human and animal remains which were obtained are now in the Tenby Museum. The cave is known to extend 16o feet into the hill as a series of small chambers and con­ necting passages. It is probably part of an old "swallet "-cave, or underground waterway, formed by a stream which flowed from the Old Red Sandstone ridge on the south and cut an underground channel soon after reaching the limestone out­ crop. Many small streams are still absorbed in this way along the foot of the Ridgeway. The Director reminded the members of the numerous caves-" swallet "-caves in origin-seen by them along the Giltar and Lydstep cliffs, and referred to the Mendip and Derbyshire limestone districts, where at the present day enormous caves are being formed by underground streams. Since The Hoyle conveyed a stream a new system of stream­ drainage has undoubtedly been developed j the old caves have run dry and new channels are being formed at lower levels in the limestone. Candles had been provided for the examination of the cave, and most of the party penetrated to the last large chamber, but few attempted to squeeze into the Treasury-the final chamber­ beyond which the passage is choked by stones and cave earth. The old stalagmite floor has everywhere been broken up, but traces of it were seen as ledges on the walls of the chambers. On the rocky ground above the cave indications of a "chip­ ping-floor" were afforded by the many small flakes of flint' lying in the soil, and here Miss Pearse found a small, beautifully pre­ served tooth, which M1. E. T. Newton identified as that of a young hippopotamus. At Longbury Bank it was necessary to clear a path to the cave, which even then could not be entered, since a barrier of stones and prickly bushes had been built in the entrance. The cave was seen to run quite through a narrow ridge of limestone. It was thoroughly explored in 1877-8 by Prof. Rolleston and Mr. E. Laws, and yielded abundant evidence of human occupa­ tion in neolithic and later times. Like The Hoyle, it is in origin a "swallet"-cave, and less than fifty yards away a small stream was seen disappearing into a "swallow-hole" in the little valley east of the cave. On the way to Penally a boulder weighing 9 cwt, was noted on the roadside near Holloway Farm. The stone has lain there many years, but until it was examined by Mr. R. H. Chandler last summer it was not known to be an erratic. It is an enstatite­ gabbro (norite), identical with the intrusive rocks of 51. David's Head, whence it has probably been glacially transported. From Penally the 12.53 p.m. train was taken to Lamphey. The party, numbering now about 36, reached Freshwater East EXCURSION TO TENBY, EASTER, 1909. about 2 p.m., and had lunch on the shore before commencing work on the rocks. On the north side Silurian grits were seen underlying a coarse conglomerate with large quartz pebbles, the basement bed of the Old Red Sandstone; red marls, cornstones, sandstones and conglomerates, upwards of 3,5°° ft. thick, succeed the basement conglomerate, but only a small part of this group (Lower Old Red Sandstone) could be examined. .A few Lingula: were obtained in greenish shales upwards of 80 ft. above the base; these, with a few fragments of Pteraspidean fish and indeterminable plant remains, appear to be the only fossils of these rocks. On the south side of the bay, where again the base­ ment conglomerate is well shown, the interest lies chiefly in the fossiliferous Silurian rocks. These are sandy limestones much ·decalcified and iron-stained, crowded with fragile sand casts, of decalcified fossils. The rest of the afternoon was spent in collecting from these rocks; many interesting things were obtained, but the specimens were found to need careful handling. The whole outcrop of Silurian rocks running westward from Freshwater East is classed as Lower Ludlow on the Geological Map (Sheet 38), but during the recent re-survey Mr. Dixon has found Ordovician (Arenig) shales at Kingsfold." The anticline thus exhibits a double unconformity-Silurian unconformable upon Ordovician, and Old Red Sandstone unconformable upon the Silurian Ludlow Beds. The Arenig Shales are not seen in the cliff section. As the members retraced their steps across the beach the beautiful colours and characteristic profiles of the long range of Old Red Sandstone cliffs stretching eastward to Old Castle Head aroused the admiration of all. After a pleasant walk through the fields to Lamphey, some of the members paid a hurried visit to the ruins of the episcopal palace before returning to Tenby by the 6.10 p.m. train.

Thursday, Apri! 15th

ST. GOVAN'S AND THE STACK ROCKS.

The last excursion took the form of a long drive to the southernmost cliffs of Pembrokeshire. A party of 24, in two brakes, left the hotel at 9. I 5, and drove along the Ridgeway to Pembroke, where time was spared for an inspection of the outer walls of Pembroke Castle, and thence through Bosherston to St. Govan's. The weather throughout the day was perfect, and the magnificent coast features could hardly have been seen under better conditions. At St. Govan's the Director led the way to the tiny chapel where "once upon a time" a hermit dwelt alone on these wild cliffs. With so long a coast section eo examine only a short time could be spent here, but the * Sum. Prog: Geol, Surv., 1907, p. 40. EXCURSION TO TENBY, EASTER, 1909.

"countless steps," the wishing-niche and the well could not be left unvisited. Near the top of the steps leading to the chapel a recent excavation showed a considerable thickness of soft banded red and white marls, probably of Triassic age, bedded in a "pipe " in the limestone. The coast between St. Govan's and The Stacks showed very remarkably the effects of marine erosion upon rocks previously highly folded and faulted, and penetrated by numberless ancient " pipes" and "swallet" caves. In a brief report only a few of the many features seen along this range of cliffs can be recorded. At Mewsford Point there was seen a fine boulder of enstatite-diabase weighing about 32 cwt.: it is one of the largest erratics in South Pernbrokeshire, and must have come from St. David's Head, 30 miles to the north-west.* Beyond Bullslaughter Bay the Triassic breccias (" gash-breccias") were seen near the great Cauldron, which lies within a fine neolithic earthwork. Similar breccias were seen on Monday in the Giltar cliffs, and on Tuesday at Lydstep. Here they form quite remark­ able features of the cliffs in the vicinity of Stackpole and St. Govan's Head. Mr. Dixon suggests the following explanation of their origin :t "The red stalagmite and marl point to a Triassic or pre-Triassic age for the aggregation of the fragments, and the sizes of the masses of breccia, and the fact that the walls of undisturbed limestone occasionally overhang, suggest that this remarkable rock originated as debris in great caves in the lime­ stone at a time when it was elevated above the saturation-level. This was probably the condition of the land after the operation of the pre-Triassic movements, which have so powerfully affected this district. Subsequently, in Triassic times, the masses of cave­ debris were bared by denudation, and at the same time solution was replaced by deposition, the interspaces in them being filled up, generally completely, with calcite, or with stalagmite coloured red by material brought in from the surface, or even with red marl itself. " Few birds, comparatively, had arrived at The Stacks at this early date except kittiwakes and other gulls: some small flocks of e1igugs (guillemots) were by-and-by discerned floating near the rocks, but during May and June The Stacks become the breeding-place of thousands of these birds. The Stacks are geologically of much interest, since they probably represent the last stages of structures due initially to underground stream­ action. The transformations of a " swallet " cave into an ocean cavern, thence into an arch in a cliff buttress, and its final collapse, are all illustrated in the adjacent cliff. As the weather continued delightful, and the coast interests

* Recently (Aug., 1909) the Director has found a large igneous erratic on St. Govan's Head, the extreme southern point of Pembrokeshire. t Sum. Prog: Geot, Suroey, '904, p. 47. EXC URSION TO T EN BY, E.\ STER , 1 9°9. 1 93

were so manifold, it was decided to prolong the excursion as far as possible, and th e Excursion Secretary wired from Flimston to headquart ers to have dinn er delayed. 'Vest of The Stacks the cliffs near The Wash yielded fine specimens of Caninia, LithostrotlOJl cf martini, 's)'ringopora, Chonetes cf. comoides, with other forms characteristic of the lower Semiuula-zoue, and on the enormous ledge forming the feature known as The Wash, great circular masses of Limostrotion stood up promin ently on the bedding surfaces j one group exceeded 8 ft. in diameter. Arrangements had been mad e for tea at Flimston Coastguard Station, where this welco me refreshment was enjoyed in the gard en. Soon after 6 p.m. the homeward journey began, and ab out 9 2 0 the brak es drew up at headquarters. After dinner on Tuesday even ing the President proposed and Mr. Wh itaker seconded a vote of thanks to the Director for the trou ble he had taken in planning such an interesting excursion. The Excursion Secretary (Mr. R. H. Chandler) was also thanked, on Mr. E. T. Newton's proposition, for the excellent way in which he had discharg ed his duties, an d the President was also thanked on the motion of Mr. D. A. Louis and Dr. A. Vaughan. REFERENCES. Ol d Serie s r- inch Ge ologi cal Map, No. 38, Sout h Pembrokeshire. H orizontal Sections (C~o'. SurV~I), illustrating ma p N o. 38 (supra). Sheet I, Section 2.-St. Govan's Head to F ishguard i an d Sheet II, Section I .-Tenby to Llandewi Velfrey. Vertical Sections ( C~ol' S urvey). Sheet No. 12.-Secti ons illustrati ve of the passage of th e Old Red Sandstone into Carbonifero us Lim eston e ... at West.A ngle, Skrinkle, Cal dey, etc. OWEN, GEORGE (155 2-1613). -" The Co urse of the Strata of Coal and Lime in Pembrok eshire." See Fenton 's Historical Tour in P~mbrokl­ shirt, 1810. App endix 17. George Owen's De scription of Pem­ brokeshire in MS. is in the Bri tish Mu seum (HarMan MS. 6250). I t was prin ted in 1892 und er title" O wen's Pem brokes hire," Cy mrnrodorion Record Soc ., Series No. I. T he geological part is of interest, 1826. DE LA BECHE. Si r H. T.-" O n the Geology of Southern Pembroke. shir e." Tra ns. Geo], Soc., second ser ies, vol. ii , 1836. MURCHISON, Sir R. 1.-" On the Geological Structure of Pembroke ­ shire, more partic ular ly on the Extension of th e Sil uria n System of R ocks into the Coast Cliff; of the Co unty ," Proc, Geol. Soc., vol. ii , p. 226. 1839. MURCHISON, S ir R. 1. - The SiluriaJl Sys /m z, p. 520. 1842. BUCKLAND , R ev. Prof -" O n the Agen cy of L and S nail s in Corroding and Making Deep Excavations in Compact Limestone Rocks." Proc, Cwl. Soc., vol iii, p. 430. 1846. DE LA BECHE, Sir H. T.-" On the formation of the R ocks of South Wales and South Western E ng land." iY.ftm. Geot. Survey, vol. i, pp . 1-2 96. 1846. R AMSEY, Sir A. C.-I< O n the Denu dation of South Wales and the adjacent Co un ties o[ England ." .l1em. Geo], S uroey, vol. i, pp . 297-335 · 1860. SMITH, Re v. G. N.-I< On th e T enby Bone Caves." R ead before the British Associat ion at Ox ford. PROC. GEOL. Assoc., VOL. XXI, PART 4. 1909.J 15 [94 VISIT TO CAPE COPPER COMPANY'S WORKS, BRITON FERRY.

1863. SALTER, J. W.-" On the Upper Old Red Sandstone and Upper Devonian Rocks." Quart. :tourn. Geoi. Soc., vol. xix. 1865. WINWOOD, Rev. H. H.-" Exploration of the Hoyle's Mouth Cave. near Tenby." Geol. Mag., p. 471. 1874. BOYD-DAWKINS, W.-eave-Huntmg. 1877. LAWS, EDWARD.-" On a Kitchen-Midden found in a cave near Tenby." Journ. Anthrop. Inst, 1878. "Report of a Committee .•. examining Two Caves," etc. Rep. Brit. Assoc. 1882. JONES, E. L.-" On the Exploration of Two Caves in the Neighbour­ hood of Tenby." Quart, Journ. Geol. Sic, vol. xxxviii, 1884 (circa). ROBERTS, THOMA'.-" A Sketch of the Geology of Tenby," in Mason's Guid» to Ttnby. 1888. LAWS, EDWARD.-" History of Little England beyond Wales." (The Hoyle, Longbury and Black Rock Caves). 1892. PRESTWICH, Sir J.-" On the Raised Beaches and Head or Rubble Drift," etc., Quart..'lourn Geo/, Soc., vol. xlviii. 1905 et uq. "Summary of Progress of the Geological Survey," etc. Mem. Geol. Survey, IS. each. The Summaries for 1904-5-6-7 deal with the re-survey of South Pembrokeshire. 1905. VAUGHAN, Dr. A.-" On the Palseontological Sequence in the Bristol Area." Quart. Jcurn. Geol. Soc, vol. lxi, 1908. LEACH, ARTHUR L.-Article ,. Geology" in Guide to Tenby. 1909, CHA;>IDLER, R. H.-" On some Unrecorded Erratic Boulders n S. Pembrokeshire." Leol. Mag. Dec. V., vol. vi., p. 220.

VISIT TO CAPE COPPER COMPANY'S WORKS, BRITON FERRY.

FRIDAY, APRIL 16TH, 1909.

Director .. J. M. V. MONEy-KENT, A.M.I.C.E., M.I.MECH.E., M.LE.E.

Excursion Secretary: A. C. YOUNG. (Report by PROF. H. BAUERMAN, A.M.LC E., F.G.S.) ON the return journey from Tenby a section of the party, numbering 10 in aJl, alighted at Neath, where they were met by Mr. Money-Kent, and proceeded by special train to the Cape Copper Company's Smelting Works at Briton Ferry. On arrival at the Company's private station the party was met by Mr. Simmonds, the General Manager, and other members of the staff, and proceeded under their guidance to an inspection of the works. The material smelted is largely derived from the Com­ pany's own mines in Namaqualand, and Tilt Cove, Newfound­ land, the former arriving partly as rich ore, mixed purple and yeJlow sulphides of copper, and partly concentrated to a 50 per cent. copper regulus from the poorer ores, which are smelted at Nababeep in Narnaqualand. The Tilt Cove ore is essentiaJly iron pyrites, containing a small proportion of copper