see 
 
 6 
 
 IRLF 
 
 B 3 fiMD flM7 
 
 UEMOIRS OF THE GEOLOGICAL SURVEY. 
 
 ENGLAND AND WALES. 
 
 THE GEOLOGY OF THE 
 
 SOUTH WALES COAL-FIELD. 
 
 PAET VI. 
 
 THE COUNTRY AROUND 
 
 BRIDGEND. 
 
 BEING AN ACCOUNT OF THE REGION COMPRISED IN 
 SHEETS 261, 262 OF THE MAP. 
 
 BY 
 
 AUBREY STRAHAN, M.A., F.R.S., F.G.S., 
 
 AND 
 
 T. C. CANTRILL, B.Sc. 
 
 (With parts by H. B. WOODWARD, F.R.S., F.G.S., and R. H. TIDDEMAN, 
 
 M.A., F.G.S.) 
 
 PUBLISHED BY ORDER OF THE LORDS COMMISSIONERS OF HIS MAJESTY'S TREASURY. 
 
 LONDON: 
 
 PRINTED FOR HIS MAJESTY'S STATIONERY OFFICE, 
 BY WYMAN & SONS, LIMITED, FETTER LANE, E.C, 
 
 And to be purchased from 
 
 E. STANFORD, 12, 13, and 14, LONG ACRE, LONDON ; 
 
 JOHN MENZIES&Co., ROSE STREET, EDINBURGH; 
 
 HODGES, FIGGIS & Co. , GRAFTON STREET, DUBLIN ; 
 
 From any Agent for the sale of Ordnance Survey Maps ; or through any 
 
 Bookseller from the Ordnance Survey Office, Southampton. 
 
 1904. 
 Price, Is. Gd. 
 
BERKELEY 
 
 LIBRARY 
 
 UNIVERSITY OF 
 CALIFORNIA 
 
 HP 
 
 EARTH 
 
 SCIENCES 
 
 LIBRARY 
 
 
 
 EXCHANGE 
 
2O1, 262. 
 
 MEMOIRS OF THE GEOLOGICAL SURVEY. 
 
 ENGLAND AND WALES. 
 
 THE GEOLOGY OF THE 
 
 SOUTH WALES COAL-FIELD. 
 
 PAKT VI. 
 
 THE COUNTRY AROUND 
 
 BRIDGEND. 
 
 BEING AN ACCOUNT OF THE REGION COMPRISED IN 
 SHEETS 261, 262 OF THE MAP. 
 
 BY 
 
 AUBREY STRAHAN, M.A., F.R.S., F.G.S., 
 
 AND 
 
 T. C. CANTRILL, B.Sa, 
 
 (With parts by H. B. WOODWARD, F.R.S., F.G.S., and R, H. TIDDEMAN, 
 
 M.A., F.G.S.) 
 
 PUBLTSHBD BY ORDER OF THE LORDS COMMISSIONERS OF HIS MAJESTY'S TREASURY. 
 
 LONDON: 
 
 FEINTED FOR HIS MAJESTY'S STATIONERY OFFICE, 
 BY WYMAN & SONS, LIMITED, FETTER LANE, E.C, 
 
 And to be purchased from 
 
 E. STANFORD, 12, 13, and 14, LONG ACRR, LONDON ; 
 
 JOHN MENZIES&Co., ROSE STREET, EDINBURGH; 
 
 HODGES, FIGGIS & Co., GRAFTON STREET, DUBLIN; 
 
 From any Agent for the sale of Ordnance Survey Maps ; or through any 
 
 Bookseller from the Ordnance Survey Office, Southampton. 
 
 1904. 
 Price, Is. 6<L 
 
W3 
 
 / 
 
 313043 
 
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 c 
 o 
 a, 
 
 CUD PS 
 O x 
 
 "-Zj 
 
P K E F A C E. 
 
 The country around Bridgend, which is described in this the 
 Sixth Part of "the Memoir on the Geology of the South Wales 
 Coal Field, is illustrated in Sheet 261-2 of the New Series One- 
 inch Map. The area is occupied for the most part by Lower 
 Lias, and by the Rhaetic and Keuper subdivisions of the Trias, 
 but it includes a small part of the South Crop of the Coal Field 
 and numerous inliers of Carboniferous Limestone which project 
 through the Secondary strata. 
 
 The original survey was made by Sir H. T. De la Beche, Sir 
 W. E. Logan, D. H. Williams, W. T. Aveline, and T. E. James 
 on the Old Series One-inch Maps 20. 36, and 37, which were 
 published about the year 1845. The separation of the Rhaetic 
 strata and a revision of the area south of the Coalfield were 
 begun by H. W. Bristow in 1864, and completed by Mr. H. B. 
 Woodward in 1871. The revised edition was published in 1873. 
 
 The re-survey was made on the six-inch scale under the super- 
 intendence of Mr. Strahan and was published in 1901. The 
 western half of the map was surveyed by Mr. Tiddeman, the 
 eastern half by Mr. Oantrill, with the exception of the north- 
 eastern margin which was surveyed by Mr. Strahan. The 
 present volume includes the description of the eastern half by 
 Mr. Cantrill and of the western half by Mr. Strahan, based on 
 the notes left by Mr. Tiddeman on his retirement from the 
 staff. Mr. Woodward supplies an account of the Liassic and 
 Rhaetic tracts which were examined by him for the purposes of 
 the General Memoir on the Lias of England and Wales. The 
 principal changes made in the map as the result of the re-survey 
 consist in the extension of the Lias of Cowbridge over a 
 district formerly thought to be occupied by Old Red Sandstone, 
 the discovery of further inliers of Carboniferous Limestone in 
 the Lias near Wick, and the distinction of the literal from the 
 normal type of Lias throughout the whole area. 
 
 The Old Red Sandstone includes, in its upper part, some 
 quartzitic and pebbly grits ; the whole, so far as exposed, appears 
 to correspond in character to the Brownstone subdivision, but in 
 the absence of fossils it cannot be definitely referred to either 
 Upper or Lower Old Red Sandstone. 
 
 The Carboniferous Limestone maintains the same general 
 character as in the Cardiff district. Thick but impersistent 
 limestones appear locally in the Lower Limestone Shales. 
 
 The Millstone Grit is covered for the most part by Secondary 
 Rocks. It consists of shales with subordinate sandstones, and 
 belongs therefore to the type which characterises the South 
 Crop rather than to that of the north side of the Coal Field. 
 
 The small tract of Coal Measures which falls within the 
 margin of the map contains representatives of the lower seams, 
 
 7665. 750. Wt. 18408. 12/04. Wy. & S. 2044r. A 
 
(iv) 
 
 which, however, have been only partly proved and worked 
 to a very limited extent. 
 
 The Old Red Sandstone and Carboniferous Hocks were 
 thrown into great east and west folds and subjected to denuda- 
 tion on an enormous scale before the Secondary Bocks were 
 laid down upon them, so that those later strata rest unconform- 
 ably upon all the earlier formations. The detailed mapping 
 moreover has rendered it possible to recognise many of the 
 features of the pre-Triassic landscape, and to trace step by step 
 the submergence cf the old land-surface beneath the Keuper 
 and Rhaetic waters, and its final disappearance in the Liassic 
 sea. The Carboniferous Limestone, then as now, stood out in 
 bold escarpments and formed an island, the margin of which 
 has been traced with much precision. 
 
 Some later (post-Liassic) movements have been worked out 
 in detail. They follow generally the lines of the older distur- 
 bances, though they rarely agree with them precisely in position. 
 
 The map includes a part of what appears to have been the 
 southern margin of the South Wales glacial system. In its 
 north-eastern part large tracts are overspread by a gravelly 
 drift derived from the north and north-east and partly from 
 the immediate neighbourhood. At Pencoed this local drift over- 
 lies a stiff boulder-clay containing boulders from a distant source. 
 These erratics, which were first noticed by the late John Storrie, 
 have been microscopically examined by Messrs. Howard and 
 Small, with the result of showing that they can be matched 
 in West Pembrokeshire. 
 
 In Chapter XI will be found an account of the economic 
 products of the district. The most important of them was the 
 haematite yielded by the Carboniferous Limestone where that 
 rock was or had been overlain by Keuper. The mines are 
 now all abandoned. In the same chapter the principal sources 
 of water-supply are enumerated. 
 
 The map is issued in two editions. On the edition for Solid 
 Geology the glacial deposits are omitted, while on the edition 
 for Superficial Geology, those deposits are shown by colour, as 
 well as the Solid Geology, where not concealed by them. 
 
 J. J. H. TEALL, 
 
 Director. 
 Geolo'jtcal tinrrei/ Office, 
 
 .j^y, JcniLi/ii titiwt, London, 
 4th November, 1904. 
 
(v) 
 
 TABLE OF CONTENTS. 
 
 Page. 
 PREFACE BY THE DIRECTOR iii 
 
 CHAPTER I. INTRODUCTION AND TABLE or STRATA 1 
 
 CHAPTER II. OLD RED SANDSTONE 4 
 
 CHAPTER III. CARBONIFEROUS LIMESTONE SERIES. (1) Eastern part; 
 
 (2) Western part 6 
 
 CHAPTER IV. UPPER CARBONIFEROUS ROCKS : MILLSTONE GRIT. 
 
 COAL MEASURES 16 
 
 CHAPTER V. TRIAS : Introduction. Keuper : Eastern park Western 
 
 part 20 
 
 CHAPTER VI. TRIAS (cont.) Rhcetic Beds .'Introduction. Eastern part. 
 
 Western part ------ 35 
 
 CHAPTER VII. LIAS: Introduction. Eastern part. Western part. 
 
 Coast Section, Sutton to Aberthaw - - - - - 58 
 
 CHAPTER VIII. FAULTS AND DISTURBANCES 89 
 
 CHAPTER IX. GLACIAL DEPOSITS -.Introduction. Eastern part. 
 
 Western part 95 
 
 CHAPTER X. POST-GLACIAL DEPOSITS 103 
 
 CHAPTER XI. ECONOMIC PRODUCTS : Building Stone and Road Metal. 
 
 Lime, Cement and Silica. Galena. Hcematite. WATER SUPPLY - 106 
 
(vi) 
 
 LIST OF ILLUSTRATIONS. 
 
 Plate. Gliff at Southerndown showing Lower Lias resting unconformably 
 upon Carboniferous Limestone. From a photograph by R. H. 
 TIDDEMAN Frontispiece. 
 
 Fig. 1. Map of pre-Triassic Folds. By T. C,- GANTRILL 8 
 
 i; 2. Map showing Triassic Geography. By A. STEAHAN - - -24 
 
 3. Section of cutting south of St. Mary Church Road Station. By 
 
 T. 0. OANTRILL 43 
 
 4. Section at south end of Cowbridge cutting. By T. C. GANTRILL 46 
 
 ,, 5. Section of the cliffs at Sutton, Southerndown and Dunraven. 
 
 By H. B. WOODWARD 63 
 
 6. Fault in Lower Lias, east of Dunraven Castle, Glamorganshire. 
 
 By H. B. WOODWARD 87 
 
 7. Section across Llanbleiddian Hill. By T. G, GANTRILL - - 91 
 
 8. Section from the Coast near Sutton to near Laleston. By A. 
 
 STRAHAN 92 
 
 9. Transverse section, Mwyndy Mine. By S. VIVIAN - - - 108 
 10. Transverse section, Mwyndy Mine. By S. VIVIAN - - - 108 
 11. Transverse section, Trecastle Mine. By S. VIVIAN - - - 109 
 
GEOLOGY 
 
 OF THE COUNTRY AROUND 
 
 CHAPTER I. 
 
 INTRODUCTION AND TABLE OF STRATA. 
 BY A. STRAHAN. 
 
 This map includes the western half of the tract of Secondary rocks 
 which constitutes the Vale of Glamorgan, and extends northwards 
 to the south crop of the coalfield. The Triassic and Liassic strata 
 rest unconformably upon highly tilted Carboniferous and Old Red 
 rocks. Without doubt they once overspread the whole vale, but 
 denudation has bared the more prominent features of the surface 
 on which they were laid down. Among the pre-Triassic features 
 thus revealed may be mentioned the escarpment of Carboniferous 
 Limestone which runs from Bonvilston to Cowbridge on the south 
 side of the Cowbridge-Cardiff anticline ; the corresponding escarp- 
 ment which forms the northern limb of the same anticline ; some 
 tracts of Old Red Sandstone between these two ; the limestone 
 which appears at the surface in several domes on the line of this 
 anticline westwards ; and lastly, the rocks forming the southern 
 margin of the coalfield, which there is reason to think formed approxi- 
 mately the limit of the area originally overspread by the Secondary 
 rocks referred to. 
 
 The waste undergone by these old physical features is evidenced by 
 the vast amount of debris which they have contributed to all the 
 Secondary strata, and, no doubt, accounts for the fact that none 
 of them rise to any great height. The limestone reaches its greatest 
 elevation above the sea at Lillypot, 447 feet, at St. Jlilary Down, 
 440 feet, and at Tair Onen, 424 feet. Elsewhere in the south escarp- 
 ment it falls short of 400 feet. The northern escarpment reaches 
 400 feet south of Llanharry, but in most other parts falls short of 
 300 feet. The domes further west slightly exceed 300 feet in places, 
 but never reach 400 feet. The Trias and Lias generally form a 
 gently undulating tract occasionally reaching 300 feet above 
 the sea. 
 
 7665. B 
 
2 Introduction. 
 
 The region is drained by the Ely, the Dawen, the Ewenny, and 
 the Ogmore (Ogwr) rivers, and a few small streams which have 
 independent courses into the sea (Fig. 2, p. 24). The Ely rises in the 
 coalfield, on the north side of the Pontypridd anticline. Flowing 
 across this and across the south crop it traverses the escarpment 
 of the Carboniferous Limestone at Miskin, and thus gains the Cow- 
 bridge-Cardiff anticline. Thence it runs eastwards to Cardiff, along 
 a valley which tends to follow the anticlinal axis. The Dawen rises 
 on the north side of the Cowbridge-Cardifi anticline, but keeps its 
 course across it to the coast at Aberthaw. The Ewenny and Ogmore 
 rise in the coal-field and cross the south crop on to the Liassic 
 plain, keeping a south-westerly direction to their union at Merthyr- 
 mawr, and thence to the sea. 
 
 Except for a colliery near Pont Clun, there are no mines in opera- 
 tion within the area under description, nor are there any large 
 manufacturing towns, the population generally being occupied in 
 agriculture. There are lime-works, however, at Stormy, Bridgend, 
 Llanharry, and Aberthaw. 
 
 As would be anticipated from the geological conditions, there is 
 much variety in the land in the northern part of the map. Cal- 
 careous soils, however, whether in the form of Triassic conglomerate 
 or Liassic and Carboniferous limestones, predominate, and much of 
 the land is, or has been, under the plough. The Lias which occupies 
 most of the southern part of the map yields generally a stiffer clay- 
 soil, much of which is under pasture. Merthyr-mawr Warren, 
 Newton Burrows, and Kenfig Burrows are large tracts of blown sand. 
 
 From a purely geological point of view, the relation of the Trias 
 and Lias to the older rocks over which they were distributed con- 
 stitutes one of the most interesting features in the region. In 
 previous Parts of this memoir, it has been explained that these older 
 rocks have been bent into sharp folds, ranging in an east and west 
 direction, and that the flexures are obviously of pre-Triassic age, 
 inasmuch as the Trias lies horizontally upon them. This fact is 
 admirably illustrated in the Cowbridge-Cardiff anticline ; for that 
 great upheaval was not only accomplished before the Triassic era 
 commenced, but there was time for the removal of so much material 
 along the axis of upheaval as to convert it into a valley, which 
 subsequently was filled up by horizontal sheets of Secondary rocks. 
 Especially interesting also are the proofs of the gradual submergence 
 of many limestone-crags, which for a time formed islands in the 
 Liassic waters. 
 
 It resulted from the unusual conditions under which they were laid 
 down that the Secondary rocks assumed an abnormal character. 
 The Keuper Marl passes into a limestone-breccia near its margin, 
 the upper beds showing the change as fully as the lower. The 
 Rhyetic group loses its character as a shale with thin limestones, and 
 becomes a thick white and yellow sandstone distinguishable with 
 difficulty from Millstone Grit ; while the Lias not only becomes con- 
 glomeratic near its margin, but assumes a variety of abnormal 
 forms, some of which closely simulate Carboniferous Limestone, 
 
Table of Strata. 8 
 
 The following subdivisions of the rocks and of the superficial 
 deposits are distinguished by colour upon the map : 
 
 Table of Strata. 
 
 Blown Sand ^ 
 
 Alluvium 
 
 Peat VRecent and post-Glacial 
 
 Estuarine Mud 
 
 River Gravels (terraces) J 
 
 Boulder Clay and contemporaneous \ r , . , 
 Sand and Gravel / W 
 
 Lower Lias W . 
 
 Lower Lias of a literal type J ] 
 
 Rhaetic * "j 
 
 j e (Green and red marls passing into > Trias 
 ^Breccia and conglomerate J 
 
 Lower Coal series Coal Measures 
 
 }*. 
 
 Limestone and \Carboniferous Limestone 
 
 Shale J 
 
 Red sandstone with | old Red Sandstone 
 
 Quartz-conglomerate J 
 
 7665. B 2 
 
CHAPTER IT. 
 
 OLD RED SANDSTONE. 
 BY T. C. CANTRILL. 
 
 The Old Red Sandstone comes to the surface in someinliers at the 
 western end of the Cowbridge-Cardiff anticline. The largest and 
 most conspicuous is that which extends from Groes-faen on the 
 north-east past Miskin Manor, and widens out in the high grounds of 
 Hensol Park on the south-west. Much, however, of this outcrop is 
 concealed by drift. 
 
 The beds consist of red sandstones and marls with impersistent 
 bands, at about 150 feet from the top, of red quartzitic sandstone or 
 grit containing numerous small quartz-pebbles. Blocks of these 
 conglomerates abound on the fields immediately south of Llwyn-y- 
 penau, but a road-cutting south of Crofftau shows only dull-red 
 shales, marls, and sandstones, some of the last being micaceous. 
 The next exposures occur at the northern extremity of Hensol Park, 
 where the pebbly grits form the higher parts of a picturesque escarp- 
 ment extending for a mile in a south-westerly direction. The grits 
 dip about north-north-west at 25 to 30, but at the south-west end 
 of the ridge they roll over and dip south at 30 in a quarry opposite 
 the western horn of the lake. Below the conglomeratic horizon 
 there lie some thin-bedded red sandstones with thin grit-bands, 
 which are exposed in some small quarries at the northern extremity 
 of the Park. The beds above the conglomerates, though nowhere 
 well seen, appear to be soft sandstones and marls. 
 
 The Old Red Sandstone mass of Hensol Park, although apparently 
 consisting of an anticline the axis of which trends about east-north- 
 east and west-south-west, has weathered out as a north-east and 
 south-west ridge, the features seemingly ignoring the geological 
 structure. This denudation dates probably from pre-Triassic times, 
 when the ground no doubt stood up as a hill while the Triassic 
 deposits were accumulating in the surrounding waters. 
 
 The conglomeratic beds and the overlying strata may be referred 
 to either the Grey Grits of the Upper Old Red Sandstone, or to the 
 plateau-beds* of the Brownstones of the north crop of the coalfield. 
 The beds be-low the conglomerates resemble the Brownstones. 
 
 Still farther west a minute ir.lier of Old Red Sandstone occurs at 
 Llwyn-iiwydog, on the west side of Morfa Ystradowain. The rock 
 crops out on a wooded bank 100 yards south of the farm, and forms 
 a scarp overlooking the marsh ; it consists of micaceous yellow and 
 red gritty sandstone containing flakes of green marl. It dips about 
 
 The Country ;t round. AU-rthyr Tydfil (Man. 6W. Surv(-y), pp. C, 7. 
 
Old Red Sandstone. 5 
 
 north 40 west, towards the lowest Carboniferous Limestone strata 
 exposed in the farmyard. Along its south-east side the inlier appears 
 to be cut off by a fault which throws down the lowest Carboniferous 
 beds under the marsh. 
 
 Turning now to the southern side of the main anticline we have 
 evidence of another exposure of Old Red Sandstone along the foot of 
 the Carboniferous Limestone escarpment of Cottrell, though it is 
 almost wholly concealed by drift. A faint feature parallel to the 
 strike of the Lower Limestone may be attributed to the outcrop of the 
 pebbly red quartz-grits which lie about 150 or 200 feet below the top 
 of the Old Red Sandstone. Though they are nowhere exposed, some 
 little debris which occurs on the slopes south of Ty'n-y-pwll suggests 
 their presence. 
 
 The next section is afforded by the dingle south of Cae'r-wigau-isaf , 
 soft red marly sandstones and gritty sandstones are visible about 
 100 yards south of the farm, and are followed at a higher horizon 
 by yellow flags, exposed in a small quarry a few yards below 
 Cae'r-wigau-ganol. The beds dip south 30 west at about 15. These 
 yellow flags appear to lie at about the same horizon as the pebbly 
 red grits, and both are doubtless of Upper Old Red Sandstone age. 
 
 To the west of this dingle the country is so thickly overspread with 
 gravelly drift as to make the course of the Old Red Sandstone out- 
 crop a matter of inference. On the old series geological map (Sheet 
 36) it was represented as extending north-westwards over a large 
 area north of Welsh St. Donats. There is, however, direct evidence 
 that much of this ground is occupied by Lias (see p. 69), though the 
 drift precludes our gaining a detailed knowledge of the structure. 
 
 The last exposure of Old Red Sandstone occupies the northern 
 part of Stalling Down, near Cowbridge. The rock comes to the sur- 
 face in a broad anticline trending a little north of east and south of 
 west. Good sections are rare, but there is abundant debris of 
 pebbly red grit scattered over the fields west of the Down, and on 
 the Down itself there is a small quarry, some 300 yards north- 
 west of Llan-Chwian-fach, in thin irregularly-bedded red sandstones 
 and grits, containing a few small quartz-pebbles. All the sandstones 
 appear to be more or less quartzitic and frequently pebbly. They 
 no doubt belong to the upper division of the Old Red Sandstone. 
 
CHAPTER III. 
 CARBONIFEROUS LIMESTONE SERIES. 
 
 (1). Eastern Part. 
 BY T. C. CANTRILL. 
 
 The Carboniferous Limestone Series of the map under description 
 shows a considerably greater development than that of the neigh- 
 bourhood of Cardiff (Sheet 263). It presents the following de- 
 scending sequence : 
 
 Carboniferous Limestone Series. 
 
 Light-grey oolite, thick-bedded, forming about 
 
 half the mass. 
 Dark-blue crinoidal limestone, thick-bedded, 
 
 Main Limestone. 
 
 forming the lower half. The lowest beds 
 
 are brown and grey earthy limestone, thin- 
 bedded, with shale -partings ; fossils (crinoids 
 and spirifers) silicified. 
 
 /-Dark shales weathering yellow (200 to 300 feet)* 
 
 T T . Q , , including bands of limestone from a few 
 
 Lower Limestone Shales, J incheg * p tQ ^ ^ ^ ( = the Lower Qr 
 
 I " Bastard " Limestone). 
 
 From observations of dip at Crofftau, a mile east of Miskin, the 
 thickness of the Main Limestone appears to be about 1,600 feet, 
 and that of the Lower Limestone Shales about 275 feet, including 
 75 feet as the thickness of the Lower Limestone. North of Cardiff, 
 on the contrary, the thickness of the Main Limestone amounted 
 to only about 700 feet, and that of the Lower Limestone Shales to 
 150 or 200 feet.* 
 
 -There are numerous local modifications of these types of lime- 
 stone ; sometimes the grey oolite takes on a darker hue owing to a 
 greater amount of bituminous matter, and all the rocks are liable 
 in places to a purple stain from the Trias. The Lower Limestone is 
 usually a massive brown or purple oolite, frequently rich in crin- 
 oidal remains. Its upper and lower limits are thin-bedded and 
 shaly. 
 
 All varieties of the limestone have been at one time or other ex- 
 tensively quarried and burnt for lime throughout the district, and 
 several kilns were still in operation in the neighbourhood of Groes- 
 faen. Mwyndy, and Miskin. The Llanharry Limestone Co. crush 
 the rock, chiefly grey oolite, for roadstone, and also burn it for lime, 
 at Llanharry Station on the Cowbridge railway. The limestone is 
 worked for roadstone for local use at several small quarries. 
 
 * The Country around Cardiff (Mem. Oeol. Survey), p. 22. 
 
Carboniferous Limestone. 7 
 
 The Carboniferous Limestone forms the two limbs of the great 
 Cowbridge-Cardiff anticline. On the eastern edge of the map this 
 structure is obvious. For some two miles westwards of Cottrellthe basal 
 scarp is easily traceable, and the dips gradually change from about 
 south-south-east to south, and then to south-south-west, but beyond 
 that distance, complications due to subsidiary folding set in ; and 
 here too the limestone-base disappears under the Lias and drift south- 
 east of Welsh St/Donats. The south-south-westerly dip persists as 
 far as Pen-y-ffordd-fawr, where the limestone formerly quarried is 
 probably not far above the base. Here again the outcrop is lost to 
 view under a patch of Lias ; but it is clear that the limestone rolls 
 over in a gentle anticline somewhere near Pen-y-flordd-fawr, for at 
 Welsh St. Donats it dips north-west. The base therefore should 
 trend towards the north-east ; but it must swing round again into 
 a south-west direction and form a syncline somewhere between 
 Welsh St. Donats and Ystradowain in order to gain its known posi- 
 tion at Pen-llin Castle, where a southerly dip prevails. The faulted 
 anticline of Pen-llin may be regarded as lying on the axis of the main 
 anticline, and on this axis lies the approximately horizontal lime- 
 stone of Pen-y-lan south-east of Llansannwr. North of this axis 
 the general dip is towards the north-north-west, which carries the 
 base past Llansannwr and Ystradowain where, however, a sharp 
 syncline interrupts the regularity of outcrop. Beyond this point 
 the minor folds die out and the base runs continuously across the 
 district past Tal-y-garn, Miskin, and Groes-faen, where the northern 
 limb forms a well-marked escarpment. 
 
 It thus appears that the great Co wbridge- Cardiff anticline not 
 only loses intensity westwards, but also changes form. At its east 
 end it spans a tract of Old Red Sandstone nearly four miles across in 
 one grand arch, but westwards it buckles down into a series of 
 minor parallel anticlines and synclines (Fig. 1) which overspread 
 the same width of country with a corrugated sheet of limestone 
 bordered by a strikingly sinuous margin. 
 
 It is still more difficult to trace the base of the Lower Limestone 
 Shales which border the main mass of the limestone. Along the south- 
 ern limb of the anticline near Cottrell the shales contain at their 
 base a well- marked rock which gives rise to a minor escarpment. 
 This Lower Limestone can be traced with some certainty westwards 
 as far as the Lias area of Welsh St. Donats, but there its position 
 becomes quite conjectural. The base presumably turns northwards 
 in a sinuous line more or less parallel to the base of the Main Limestone 
 and rounds the Old Red Sandstone of Hensol Park. Beyond this 
 it continues in a north-easterly direction, but the Lower Limestone 
 seems to have thinned out while a similar band makes its 
 appearance at a higher horizon. The shales are shown on the map 
 as occupying the low-lying core of the main anticline extending 
 westwards from Morfa Ystradowain as far as Pen-llin, but this 
 tract is almost wholly masked by drift and it is quite possible 
 that some of it may be occupied by Old Red Sandstone. 
 
The map forming Fig. 1 represents the probable outcrops of the 
 Lower Limestone Shales and the base of the Main Limestone in the 
 eastern part of the area, the overlying Secondary and glacial deposits 
 being supposed to be removed. The boundaries where purely con- 
 jectural are dotted, and where more or less uncertain are broken. 
 
 Fig. 1. Map of pre-Triassic Folds, 
 BY T. C. CANTRILL. 
 
 :. ^SANDSTONE 
 
 Donats :;:.'. "-:."'"'. 
 ''*&:'.-'. ' 
 
 of M/'/es 
 t An tic//na/ Axes 
 
 -X- Syn cf/na / .Axes, 
 indicates nip or Strata + indicates Horizontal Sb 
 
 At the north-east corner of the map the limestone-series emerges 
 from beneath the Trias, and forms a gentle escarpment to Miskiii. 
 Throughout this tract the beds dip usually about N. 15 W. at 
 about -30 C to -10. 
 
 The Lower Limestone is well exposed in some deep old quarries 
 at Maes-mawr, where it consists of blue, brown, and purple oolite 
 irregularly dolomitized. Thin strings of galena in barytes occur. 
 Between Groes-faen and Llwyn-y-penau two dip-faults break the 
 continuity of the outcrop, both being westerly downthrows ; the 
 eastern one produces a lateral displacement of about 100 yards, the 
 western only 15 or 20 yards. The outcrop has been deeply quarried 
 at Llwyn-y-penau, the highest beds being flaggy and alternating 
 with shale. An old quarry immediately west of the house shows 
 thick-bedded impure limestone resting on buff shale exposed for 
 6 feet. This is underlain by crinoidal limestone. In an old road- 
 side quarry south-east of CrofTtau the limestone dips N. 10 W. at 
 30 ; but rolls over southwards in an anticline and is broken by a 
 
Carboniferous Limestone. 9 
 
 small fault, probably a thrust, parallel to the strike and inclined 
 towards the north at an angle of some 50 from the vertical. South of 
 this fault the beds rise again to the south. The limestone in this 
 quarry is clearly closer to the base of the Main Limestone than that 
 seen at Llwyn-y-penau, and is possibly not the same band. Below 
 it there come in shales, as we may infer from evidence afforded by 
 sections south of Miskin. The shales overlying the Lower Limestone 
 form a belt of flat ground at the foot of the Main Limestone escarp- 
 ment, but are seldom visible. 
 
 South of Crofftau the outcrops of the Lower Limestone and the 
 Shales are masked by gravel, through which the former has been 
 quarried at several points, especially in Miskin Park. Near the 
 village of Miskin a small section in buff shales overlying impure 
 crinoidal limestone containing small gasteropods (? Natica) was 
 exposed on the south side of the River Ely opposite the corn-mill, 
 where limestone was formerly dug from under the drift gravel. 
 
 The Main Limestone throughout this tract east of the Ely is ex 
 posed in numerous quarries and small outcrops. Light-grey oolite 
 prevails in the upper part and a crinoidal rock in the lower. The 
 lowest beds form a well-marked escarpment, and the underlying 
 shales throw out several powerful springs ; one occurs west of Cwrt- 
 y-carnau and several others at College. The top is concealed by 
 drift and Trias, the latter everywhere slightly overstepping the 
 base of the Millstone Grit ; the highest limestones exposed at 
 Mwyndy appear to be grey oolite. 
 
 The existence of a large westerly downthrow at Miskin is assumed 
 in order to explain the southward shift of the base of the limestone- 
 series between that place and Caer-gwanaf-isaf . The shift amounts 
 to no less than 500 yards, which indicates a vertical displacement 
 of at least 200 yards. 
 
 West of the Miskin Fault the Lower Limestone Shales are exposed 
 at Caer-gwanaf-isaf. The Lower Limestone where quarried west of the 
 farm is a grey oolite overlain by a few feet of shale. A red stain 
 and traces of haematite may be attributed to the rock having been 
 once overspread by Trias. Below, the limestone becomes flaggy 
 and impure, as shown in some outcrops among the farm-buildings. 
 A fault between the farm and the main road seems to be a down- 
 throw west of several yards. On the fields at about 100 yards 
 south of the old quarry a thin band of limestone appears to have been 
 dug out, from which we must infer the existence of some thickness 
 of shales with thin limestones below the Lower Limestone. 
 This conclusion is confirmed by the fact that such beds were 
 proved in a well near Bolgoed, and that at least 20 feet of 
 shales under gravelly drift are shown in an adjacent gully, all 
 at some distance south of the outcrop of the Lower Lime- 
 stone. This latter cannot be traced beyond some swallow-holes 
 about 400 yards west of Bolgoed, either having thinned out or being 
 effectually concealed beneath the drift. Towards Ystradowain and 
 Welsh St. Donats the position of the Carboniferous base becomes 
 a matter of inference, owing to the prevalence of glacial gravel. 
 
10 Carboniferous Rocks. 
 
 The Main Limestone between the Ely Valley and that of the 
 Dawen is greatly obscured by drift, but between Miskin and Nant 
 Dyfrgi is exposed in numerous old quarries, the impure nature of 
 the basal beds and the silicified condition of the fossils being well 
 shown at Pant-y-cwestau. At Tal-y-garn the limestone emerges 
 from the drift as a bold escarpment in which are several quarries, 
 notably one a few yards south-west of Adam's Well, where the rock 
 is earthy and stained red. Between this exposure and Bryn 
 Saddler, massive blue and grey oolite is quarried through the drift, 
 and again north-east of Llwynau ; and a deep old quarry at 
 Tal-y-garn Church exhibits similar rock under 6 feet of drift. 
 
 South-east of Rhyd-halog the lower beds are well exposed on the 
 slopes overlooking Morfa Ystradowain, where dark bituminous 
 crinoidal limestone underlain by grey and brown impure rock with 
 silicified fossils was worked. At their base these beds become still 
 more flaggy and earthy, and so tend to pass into the Lower Lime- 
 stone Shales, of which traces are exposed. 
 
 The low ground followed by the railway at Rhyd-halog coincides 
 with what appears to be a line of fault. The base of the limestone 
 on the east side is too far south to fit on to the same line on the west 
 side of the valley at Fforest-fach, which would be accounted for 
 by an easterly downthrow. The fault, if it follows a south-south- 
 westerly course, will serve also to account for the occurrence of 
 pieces of yellow sandy shale with obscure fossils, presumably Car- 
 boniferous, in a ditch at the foot of the Old Red escarpment at 
 Llwyn-nwydog. The Old Red Sandstone here (p. 4) dips in a 
 north-westerly direction. Above this sandstone is a gap occupied 
 by the beds, probably shales, on which stands the farm-house. In 
 the north-western corner of the farm-yard a band of oolite crops 
 out, dipping N. 40 W. This is apparently separated from the Main 
 Limestone of Crofftau and Fforest-fach by some shales which can 
 be seen in a swallow-hole at the first-named farm. It may lie at 
 about the same horizon as the Lower Limestone where we last saw 
 it at Caer-gwanaf-isaf. 
 
 The Main Limestone of the tract between Crofftau and Llanharry is 
 opened up in numerous old quarries, and a good section is afforded 
 by the Llanharry Limestone Co.'s workings in oolite near Llanharry 
 Station. The actual top is overstepped by the Trias, but the highest 
 beds exposed consist of grey oolite varied by a dark fine-grained 
 rock ; at lower horizons a blue crinoidal rock prevails. The less 
 pure limestones near the base are exposed in a large old quarry 150 
 yards south of Fforest-fach, and the lowest have been worked along 
 a low feature extending north-eastwards from Crofftau, and in 
 quarries just east of the farm-yard. From the farm a feature which 
 presumably marks the base of the Main Limestone abruptly turns 
 south-eastwards, and the next exposures are afforded by several 
 old quarries by the side of the Cowbridge road ; the rock is chiefly 
 crinoidal, but some dark oolite occurs. The beds dip south at 15 
 to 44, as compared with N. 25 W. at Crofftau, there being an 
 anticline a few yards south of that house. 
 
Carboniferous Limestone. 11 
 
 The structure of the ground about Ystradowain is exceedingly 
 obscure owing to the general prevalence of gravelly drift. Presum- 
 ably the Main Limestone rises rapidly to the south, thus assuming a 
 synclinal form, for it gives rise to a bold escarpment running south- 
 westwards from Ash Hall towards Llansannwr. Several large 
 blocks of grey faintly-oolitic limestone lying at the south-east 
 corner of the Gaer near Ystradowain Church suggest the presence 
 of the Lower Limestone Shales, but may be no more than boulders 
 in the drift. 
 
 Half-a-mile farther to the south-west, however, between Llan- 
 sannwr and Tre-rhingyll, the Lower Limestone Shales form the slopes 
 of a small plateau capped by an outlier of the Main Limestone. A 
 thick band of oolite emerges from the drift at Pen-cyrn, where it is 
 quarried ; though rolling somewhat it is practically horizontal, and 
 can be traced through old quarries along the wooded scarp running 
 southwards. After a gap of several hundred yards a similar, and 
 probably the same, band appears in a large quarry at Newton Farm, 
 again in a horizontal position. It consists of thick-bedded crinoidal 
 dark oolite exposed for at least 25 feet, under about 6 or 8 feet of 
 flaggy beds. Beyond Newton Farm it is lost to sight under the 
 drift. On the north-west side of the plateau, in Coed y Brain, oolitic 
 limestones have been quarried in several places ; presumably they 
 are interbedded in the shales, but none can be certainly identified 
 with the band worked at Newton Farm. Above the limestone at 
 Newton there is a considerable thickness of shales containing thin 
 crinoidal limestones, as may be seen in the lane leading down from 
 Pen-y-lan to Tre-betin, and in an old pit in the field above Newton 
 Farm. These shales emerge from beneath the Main Limestone in 
 the lane north of Coed y Brain. 
 
 The highest Carboniferous rock of the plateau is a crinoidal dark- 
 grey earthy limestone containing Fenestella which is exposed in 
 several small openings above Coed Pen-cyrn, and again in an old 
 quarry on the upper edge of Coed y Brain. It is probably an outlier 
 of the lowest bed of the Main Limestone. The shales between it 
 and the next lower limestone would seem to be only 10 or 15 feet 
 thick at Pen-cyrn, whereas above Newton Farm there must be at 
 least 60 or 70 feet. 
 
 There are no exposures of whatever beds underlie the Newton 
 limestone, and the low ground of Tre-rhingyll has been represented 
 on the map as occupied by Lower Limestone Shales, but the upper- 
 most beds of the Old Red Sandstone may possibly crop out beneath 
 the gravel. 
 
 Most of the outcrop of the Main Limestone north of Ystradowain 
 and Llansannwr is overspread with gravel. The highest rock ex- 
 posed in Brigam Wood west of Llanharry is a light oolite, and most 
 of the limestone in the neighbourhood of City is of the same cha- 
 racter ; south of this, a dark crinoidal rock prevails. The lowest 
 beds are well exhibited on the eastern side of the Dawen Valley at 
 Llansannwr, and consist of the usual crinoidal earthy rock, with a 
 band of purple oolite at about 180 feet above the base. 
 
12 Carboniferous Rocks. 
 
 West of Llansannwr the Lower Limestone Shales emerge from 
 beneath the Main Limestone, but are soon cut off on the south-west 
 by a fault ranging towards Ham Farm ; and thence the base of the 
 Main Limestone probably coincides with the edge of the gravelly 
 and alluvial deposits of Pen-llin Moor as far as the Pen-llm Fault, 
 which accompanies the dominant anticline of the district, and brings 
 up the shales again. 
 
 South of this anticline the beds dip a little west of south, and the 
 base of the Main Limestone gradually descends the fine wooded 
 scarp below Pen-llm Castle. Its subsequent course is a matter of 
 inference alone ; it presumably turns north-eastwards under the 
 Lias of Maendy. The only evidence bearing on the question con- 
 sists in a tradition of limestone having been worked through the 
 gravel in the bottom of a dingle half-a-mile due west of Llwyn-du. 
 There are signs of old quarrying operations on the west side of the 
 dingle under the gravel, and two or three small pieces of crinoidal 
 blue limestone (Carboniferous) which were lying here may indicate 
 the presence of either the Main Limestone or a band in the Lower 
 Limestone Shales. The latter interpretation has been adopted on 
 the map. If it be correct the base of the Main Limestone must come 
 on higher up the hill somewhere under the Lias of Bodlonga. It 
 ultimately emerges from the Lias south-east of Welsh St. Donats 
 (p. 7). 
 
 The limestone tract lying between Welsh St. Donats, Llanbleid- 
 dian, and Llantrithyd is traversed by the well-marked anticline of 
 Stalling Down, where the Lower Limestone Shales, with a definite 
 band of limestone at their base, wrap round a core of Old Red Sand- 
 stone. A small quarry on the west side of the Aberthin brook at 
 Llan-chwian-fach north of Llwyn-celyn, shows some few feet of 
 shale with thin limestones, over purple oolite exposed for 3 feet, all 
 dipping about S. 30 E. at 28. As Old Bed Sandstone debris occurs 
 close by, the bed in the bottom of the quarry must be nearly if not 
 quite at the base of the Lower Limestone Shales. Though it cannot 
 be traced up the hill towards the south-west, it is occasionally ex- 
 posed along the north-east side of the valley almost to the Court 
 Farm at Aberthin. Above it there follow shales with thin seams of 
 similar limestone ; some of the shales are very sandy and a thin bed of 
 sandstone crops out on the side of the valley thirty yards south-east 
 of the quarry at Llan-chwian-fach. The shales are well exposed in 
 a gully 500 yards north of the same farm. The band of limestone 
 shown on the map as running north-east to south-west, and crossing 
 the same Aberthin brook 100 yards south-east of the farm, is a red and 
 purple crinoidal oolite, and appears to be the same basement-bed 
 brought up by a fault. It is exposed in the brook and in one or two 
 quarries, in one of which it is at least thirteen feet thick. It is over- 
 lain by shales. 
 
 The lower beds of the Main Limestone at Llwyn-celyn are much 
 disturbed, and a crinoidal limestone, formerly quarried there, is 
 traversed by spar- veins, one ranging N. 52 W. and another a little 
 north of east. These disturbances are probably due to the fault 
 
Carboniferous Limestone. 18 
 
 which throws the Main Limestone against the Old Red Sandstone 
 westwards of Llwyn-celyn. The fault does not appear to affect the 
 Trias and Lias near Cowbridge, and therefore is probably of the same 
 pre-Triassic age as the anticline withVhich it is associated; it cannot 
 be traced east of Llwyn-celyn. Eastwards of this point the base of 
 the Main Limestone can be readily followed past the ruins of Llan 
 Chwian Castle, and along the wooded scarp crowned by the earth- 
 works of Twr Gron ; and also on the north side of the valley till it 
 joins the Cowbridge fault west of Pwll-y-daren. 
 
 The Main Limestone throughout this district exhibits the usual 
 prevalence of dark crinoidal rock in the lower parts extending from 
 Welsh St. Donats as far as the Cowbridge-Cardiff road ; south of that 
 line light-grey oolite predominates. From an old quarry 500 yards 
 south of Pwll-y-daren a tooth of Psephodus magnus, Ag. was ob- 
 tained. The small inlier of light oolite, pierced by a cave, at Tre- 
 Aubrey near Llantrithyd is the most southerly exposure of 
 Carboniferous Limestone in the map, and must be high up in the 
 series ; but whether the Millstone Grit comes on a little to the south 
 beneath the Lias, or whether the limestone rises again in that 
 direction there is no direct evidence to show. 
 
 The Lower Limestone Shales emerge from beneath the Lias south- 
 east of Welsh St. Donats, and though their outcrop and that of the 
 lowest horizons of the Main Limestone are everywhere concealed 
 under an unbroken cloak of gravel, yet it is possible to recognise here 
 and there their characteristic features. This is the case at Lilly pot 
 north of Bonvilston, and the observation is confirmed by two small 
 exposures of the Lower Limestone south of Ty'n-y-pwll, both of 
 which are marked on the map. In one of them, at a small pond, 
 impure crinoidal limestone is seen under three feet of pinkish-yellow 
 sandy beds, all dipping south at 30 ; in the other, at a quarry by the 
 side of the road half a mile north-west of Cottrell, some fifteen feet of 
 crinoidal dark limestone with oolitic bands are exposed under gravel, 
 the dip here being 20. It is possible that some few feet of shales 
 may underlie this limestone.* Some old quarries in Cottrell Wood 
 well display the earthy lowest horizons of the Main Limestone ; the 
 most westerly shows silicified fossils and at the bottom reaches 
 shale. South of these sections the outcrop is overspread with gravel. 
 
 (2.) Western Part. 
 By R. H. TIDDEMAN. 
 
 The central axis of "the Cowbridge-Cardiff anticline ranges from 
 Pen-llin by Crack Hill, passing thence two- thirds of a mile south of 
 Ewenny Priory and just north of Ogmore Castle. It next traverses 
 the Merthyr Mawr Burrows and passes due west out to sea at Porth- 
 cawl. So much, however, is the limestone masked by patches of 
 later rocks, that this line is by no means apparent without a careful 
 study of the dips. Thus on the north side of the anticline, the actual 
 
 * The Country around Cardiff (M em. Geol. Survey), pp. 23, 24. 
 
14 Carboniferous Rocks. 
 
 top of the formation can be fixed in one place only, viz., in the rail- 
 way and tramway opposite Angeltown Asylum, while on the south 
 side its underground extent beneath the newer rocks is unknown, 
 except for some three or four inliers. 
 
 Of these inliers, none of which had been previously detected, one 
 consists of a narrow strip of limestone, one mile long, brought up 
 between two faults. It is well seen in the Vale of Glamorgan Rail- 
 way at Clemenston, and is here and there covered with patches of 
 conglomerate which are apparently of Liassic age, but are not easily 
 distinguished from the Carboniferous Limestone. Another example 
 occurs as a large inlier of erosion in the south-east end of Clemenston 
 Park, where, as the limestone dips north, there may be reason to 
 suspect the existence of another anticline south of the large anti- 
 cline mentioned. A third inlier is exposed in a small quarry, also 
 with a northerly dip, half a mile west-north-west of Wick. A fourth 
 which, however, is only doubtfully referred to a Carboniferous age, 
 lies half a mile north of the last, and consists of tufaceous limestone 
 with traces of conglomerate. 
 
 In lithological character the limestone varies greatly, but usually 
 presents itself as a well-bedded rock, grey or black in tint, but vary- 
 ing to light-grey and drab -brown. White shelly limestone, such as 
 is common in the north of England, is seldom seen, but fossils abound, 
 especially in the lower beds, as at Pen-llin. Corals and large speci- 
 mens of Productus occur in fine preservation, dotted over the bedding- 
 planes, near Southerndown and Porthcawl. In many places a 
 water-worn surface displays false bedding on a small scale, and in 
 such cases the rock appears to consist almost wholly of small 
 drifted shell-fragments. 
 
 Oolitic structure is common and occurs both high up and low 
 down in the Carboniferous Limestone. Thus little else is seen in the 
 road between Southerndown and St. Brides Major, and in Heol-y- 
 Slough to the west of St. Brides, where the rock lies almost in the 
 axis of a syncline and must be high up in the formation. Oolite 
 exposed between Merthyr Mawr and Candleston, on the other hand, 
 is in nearly the middle of the anticline and belongs to a much lower 
 horizon. Another oolitic band of considerable thickness crosses 
 Newton Down, between Laleston and Newton Nottage, and though 
 high up in the limestone is by no means near the top. A singular 
 cavernous bed, to a great extent filled up with chalcedonic silica, 
 but containing also small crinoid ossicles, occurs near the base of the 
 limestone at Pen-llin. Cherts are not uncommon, but are perhaps 
 most abundant at the Witches' Point, Southerndown. 
 
 Some of the limestones of Mumbles Head and other parts of 
 Gower (Sheet 247) exhibit pitted bedding-surfaces. The structure 
 extends for some miles in Gower, but was first noticed in a quarry at 
 Newton Nottage in the sheet under description, fourteen miles east of 
 Gower. It characterises a high horizon in the limestone, and con- 
 sists of a number of small pits irregularly distributed over one or 
 more of the bedding-planes. Many of them contain a mass, or 
 irregularly shaped nodule, apparently of dolomite, and their edges 
 
Carboniferous Limestone. 15 
 
 in the immediate neighbourhood of the pit are frequently raised a 
 little above the general level. A similar exposure will be found in 
 the cliff north of Hutch wns Point west of Porthcawl. Two-thirds 
 of a mile north of the point a conglomeratic bed has been noticed 
 in the Carboniferous Limestone. 
 
 The topmost beds of the limestone, as seen in the small inlier near 
 the County Lunatic Asylum, are associated with a marly limestone 
 with trilobites, chert, and shale, which probably represent the 
 radiolarian cherts and rottenstone-beds of Gower (Sheet 247), but 
 owing to disturbances or slipping of the side of the cutting the 
 succession is not well seen. 
 
 Few opportunities of measuring the thickness of the limestone 
 occur in the Vale of Glamorgan, either the top or the bottom, or both, 
 being generally hidden by Secondary rocks. Near Miskin where 
 both are clear the breadth of outcrop of the Main Limestone indicates 
 a thickness of some 1,600 feet. To this must be added 275 feet for 
 the Lower Limestone Shales, making a total thickness of 1,875 feet 
 for the Carboniferous Limestone Series. 
 
 Near Stormy it would appear that there must be a thick- 
 ness of 4,500 feet of limestone, with little or no shale, in con- 
 sideration of the fact that the limestone dips continuously north- 
 wards without any apparent break. There may, however, be some 
 repetition by unknown faults. 
 
 The Lower Limestone Shales come to the surface in the centre of 
 the anticline near Pen-llin, but nowhere further west. A bold 
 scarp of the Main Limestone runs up below the castle from the 
 alluvial flat, and crosses the little valley in which the village lies. 
 The shales with interbedded limestones are well shown in the lanes 
 which lead up from the river- plain, and like the limestone dip steadily 
 southwards. 
 
 Sharp as the anticline is there is not room for these shales to turn 
 over northwards and pass under the Main Limestone in that direction 
 without faulting, and there is other evidence also of a fault running 
 in an east and west direction. Springs rising from the alternating 
 shales and limestones near Penllin Court quickly disappear on reach- 
 ing the position assigned to it. The scarp referred to soon dis- 
 appears westwards under Lias, but yellowish and greenish shales and 
 clays with decalcified crinoidal limestones or rotten-stones are 
 exposed for some distance west of the village. These strata have 
 hitherto been mistaken for Rhsetic shales, and their correct identi- 
 fication throws a new light on the structure of the anticline. The 
 fault referred to is probably the continuation of the lode which has 
 been tried for lead at Llangan and other places. 
 
CHAPTER IV. 
 
 UPPER CARBONIFEROUS ROCKS. 
 MILLSTONE GRIT. 
 By A. STRAHAX. 
 
 The Millstone Grit, so far as it occurs within the limits of the area 
 described in this volume, calls for little remark. An account of the 
 part of its outcrop which lies north of the margin of the map will be 
 found in the Geology of Pontypridd and Maesteg (GeoL Survey 
 Memoir), p. 6, and in those parts where it lies within that margin 
 there are few opportunities for examining it. Its thickness is 
 believed to lie between 1,800 and 1,500 feet, and it consists mainly of 
 shales with bands of grit or quartz -conglomerate. The lower part 
 of it, as shown near the County Asylum, Bridgend, presents a 
 sequence quite unlike that of the north crop, where a massive quartz- 
 conglomerate immediately succeeds the limestone. Here on the 
 contrary shale was first laid down, and was followed only at intervals 
 by sands, in this respect the section comparing more nearly with 
 that of Gower (Sheet 2-i7). The remainder of the outcrop is 
 concealed by Secondary rocks or drift. 
 
 Millstone Grit continued. 
 By T. C. CANTRTLL. 
 
 In the north-east corner of the map the Millstone Grit is not 
 exposed, and its boundaries are laid down by inference from the coal- 
 workings in ground lying to the north. The outcrop is soon over- 
 stepped by the Trias of Mwyndy, which passes over it on to the upper 
 beds of the Carboniferous Limestone. Some of the haematite- 
 workings near Mwyndy after traversing the Trias encountered black 
 shales, frequently stained red, which probably belong to the Millstone 
 Grit. Detritus of similar shale with some pieces of quartzose sand- 
 stone was brought up from a trial-shaft in search of haematite, 1200 
 yards south-west of Llantrisant station. A little farther west, at 
 old haematite-workings at Ty-du, dark-grey shale was brought up 
 from the shafts together with some limestone which presumably 
 immediately underlies it. West of this point the Millstone Grit is 
 concealed under the Trias of Llanharry, and though it probably 
 emerges again in the valley east of Llanilid it is everywhere covered 
 with gravel. 
 
17 
 
 COAL MEASURES. 
 
 By A. STRAHAN. 
 
 The Lower Coal Series enters the map under description at 
 Pont Clun, and leaves it five miles to the west. For a general 
 account of the South Crop reference should be made to the part 
 of this Memoir referred to above, descriptive of the country around 
 Pontypridd and Maesteg. So far as this small tract is concerned, 
 a short extract from that volume will suffice. Several thick bitu- 
 minous seams are known to occur, which as a group may be corre- 
 lated with the principal steam-coals in the Rhondda Valleys, though 
 individually they are not recognisable. The series commences with 
 an impersistent and generally thin coal known as the Cribbwr-fach 
 which lies a short distance above the Millstone Grit. The principal 
 seams above the Cribbwr-fach are enumerated below in descending 
 order : 
 
 Bodwr-fach.: Slatog. 
 
 Bodwr-fawr.- Six-feet. 
 
 North and South Fawr; Nine-feet: 
 
 Trydedd.; Cribbwr-fawr. 
 
 In Coed-yr-Hendy attempts have been made to work the Cribbwr 
 by level, and shafts, probably to the same vein, have been sunk 
 through the Trias. On the south side of Coed-yr-Hendy a shaft 
 sunk in search of haematite traversed a small thickness of Triassic 
 conglomerate and then entered sandstone and shale stained red, but 
 probably belonging to the upper part of the Millstone Grit. The 
 base of the Coal Measures is accordingly shown as running through 
 the southern part of Coed-yr-Hendy. At Pont Clun it is believed 
 to be shifted by the Miskin Fault, the evidence for which is found 
 in the limestone (p. 9). 
 
 The Cardiff Navigation Colliery is situated on an alluvial flat 
 half a mile north-west of Pont Clun and was sunk through 
 21 yards of superficial deposits before reaching the rock (p. 103). 
 The measures dip at 35 to the north, and the shaft intersected 
 the Trydedd Vein at 150 yards from the surface, the Cribbwr, so 
 called, at 210 yards, and ended in mine-ground at a depth of 280 
 yards. Three headings have been driven from the shaft north- 
 wards with the view of proving the North and South Fawr and 
 Bodwr Veins, but all the coals were squeezed out and worthless 
 with the exception of the Trydedd, which apparently owed its pre- 
 servation to the fact of its being overlain by a strong rock. The 
 sections proved in the headings agreed neither with one another 
 nor with that proved in the shaft. The Trydedd has been worked 
 continuously from its outcrop in Tre-castell Wood to beyond the 
 shaft, but in spite of the general disturbance no large faults were 
 found, and only two small overthrusts. 
 
 7665. C 
 
18 Carboniferous Rocks. 
 
 
 
 The Cribbwr Vein was estimated to crop out about 120 yards 
 south of the Trydedd. Among many old slants and pits in Coed 
 Tre-castell there seem to be only two crops of any importance, the 
 one at 340 yards and the oher at 450 yards south of the shaft. 
 The more northern crop can be traced by old workings for about 
 1,000 yards westwards in the direction of Cwm-gran ; the other, 
 as proved by shafts sunk through the Trias, appears to follow a 
 parallel course. Both range for Gwaun Llanharry, where there 
 are many old pits, about which nothing could be ascertained. 
 
 At Torgelli what was supposed to be the Cribbwr Vein \vaa 
 reached at ninety yards depth in a shaft 180 yards north of the farm- 
 house, and again at 203 yards depth in the Llanharry Colliery, 500 
 yards north of the farmhouse, the dip apparently being one in 
 three. The following section of the Torgelli Pit was furnished by 
 Mr. David Evans, of the Meiros Colliery, while that of the Llanharry 
 Pit was given from memory by a fireman to Mr. F. W. Dunn ; the 
 Batter does not agree with other sections of the South Crop. 
 
 Torgelli Pit. 
 
 Depth from 
 Surface. 
 YDS. 
 
 Third f Trydedd] Vein, 4 to 4| feet - 
 Old Nine-feet [ ? Slatog] Vein, 4 to 4| feet 
 Six-feet Vein, 5 to 6 feet - 
 
 Nine-feet Vein with a clod of 4 to 15 inches, 9 feet - - - ti() 
 Cribbwr Vein with a clod of 4 to 15 inches, 7 feet - - - 96 
 
 Llanharry Pit. 
 
 (Dip said to have been about 15 inches to the yard). 
 
 YDS. 
 
 North Fawr Vein, trace of supposed ----- 6 
 Coal, 3 feet - - 35 
 
 Third [ Trydedd J Vein - - 70 
 
 Slatog Vein 110 
 
 Six-feet Vein, coal 5 to 6 feet, holing 7 inches, and coal 1 to 1 
 
 feet - 140 
 
 Nine-feet Vein, coal 4 to 5 feet, holing 6 inches, and coal 2 feet - 167 
 Cribbwr Vein, soft carbonaceous shale-roof 9 inches, coal in beds 
 
 4 feet, clod 1 to 1 feet, coal 3 feet 203 
 
 Coal, 7 inches 231 
 
 Sandstone, with water, proved to 18 yards in a borehole - - 252 
 
 A trial-pit, 930 yards a little north of west from the colliery, is 
 said to have proved the Esgyrn Vein at a depth of five or six yards. 
 This name is given to a coal which lies above the North Fawr near 
 Tondu. The Cribbwr was found at two or three yards depth in Pen- 
 y-waun farmyard, and the Six-feet Vein at six or seven yards depth 
 in a pit 400 yards north-west of Pen-y-waun. 
 
 Farther north, near Bryn-y-cae, the South Llanharan Colliery 
 was started, but abandoned without any coal being worked. Twu 
 
Coal Measures. 19 
 
 shafts were sunk, and a section proved of which the following is 
 an abstract : 
 
 Abstract of Sinker's Journal of the South Llanharan Colliery. 
 
 (Communicated by Mr. F. W. Dunn.) 
 
 Depth from 
 Thickness. Surface. 
 
 YDS. FT. IN. YDS. FT. IN. 
 
 Shale and thin rock 
 
 6 
 
 - 29 
 
 u 
 
 2 
 
 
 
 6 
 
 
 
 Coal 
 
 - 
 
 
 
 4 
 
 33 
 
 ] 
 
 Shale 
 
 - 6 
 
 1 
 
 11 
 
 
 
 Coal - .... 
 
 - 
 
 1 
 
 9 
 
 40 
 
 1 
 
 Shale and thick sandstone 
 
 - 28 
 
 
 
 2 
 
 
 
 Lantern (Cannel 
 
 - - 
 
 
 
 4 
 
 
 
 
 
 
 
 | 
 
 O r* 
 
 
 
 
 
 / 1 
 
 & (> 
 
 Shale 
 
 2 
 
 2 
 
 8 
 
 
 
 Coal 
 
 - 
 
 1 
 
 8 
 
 
 
 Shale 
 
 - 
 
 
 
 6 
 
 
 
 Coal 
 
 - 
 
 1 
 
 6 
 
 75 
 
 2 10 
 
 Shale and ironstone .... 
 
 - 16 
 
 2 
 
 10 
 
 
 
 Coal 
 
 - 
 
 1 
 
 7 
 
 93 
 
 1 3 
 
 Sandstone 
 
 - 7 
 
 2 
 
 9 
 
 
 
 Coal, inferior ... 
 
 - 
 
 
 
 8 
 
 
 
 Shale ... 
 
 - 
 
 
 
 G 
 
 
 
 Coal 
 
 - 
 
 2 
 
 
 
 
 
 Shale 
 
 - 
 
 
 
 4 
 
 
 
 Coal 
 
 - 
 
 2 
 
 
 
 103 
 
 6 
 
 Shale and ironstone .... 
 
 - 28 
 
 2 
 
 10 
 
 
 
 Bodwr-fach Vein 
 
 - 2 
 
 1 
 
 
 
 134 
 
 1 4 
 
 Shale .... . 
 
 - 8 
 
 1 
 
 6 
 
 
 
 Coal .... . 
 
 - 
 
 1 
 
 
 
 
 
 Shale .... . 
 
 - 
 
 2 
 
 
 
 
 
 Coal .... . 
 
 - 
 
 
 
 5 
 
 144 
 
 3 
 
 Shale .... . 
 
 - 
 
 
 
 3 
 
 144 
 
 6 
 
 The dip was fifteen inches to the yard near the top of the shaft, and 
 ten inches to the yard near the bottom ; a slight correction, there- 
 fore, in the figures given above will be necessary. The identifica- 
 tion of the Lantern and Bodwr-fach Veins is given as in the 
 original. A vein, supposed to be the Lantern, was reached at twenty- 
 three yards depth in a shaft 150 yards south of the sinking, and was 
 used for the engine. Several old pits in the fields eastwards appear to 
 be on the crop of this vein, but there is nothing to indicate the crop of 
 the Bodwr-facn. One of the higher veins crops out in a wood 500 
 yards south-west of Whitehall. 
 
 At Ty'n-y-caeau-fawr a trial was made for the Six-feet Vein. 
 This same vein was got at twenty yards depth on the south side of the 
 -Great Western Railway, and at sixty yards depth on the north side 
 of the line in a shaft 300 yards west of the Mountain Hare (Sheet 
 248), but the Cribbwr and Nine-feet have not been proved. Follow- 
 ing the railway eastwards we come to the workings on the Bodwr 
 Veins at Brynau-gwynion.* 
 
 * Geology of Pontypridd and Maesteg (Mem. Geol. Survey], pp. 43, 44. 
 7665. C 2 
 
20 
 
 CHAPTER V. 
 TRIAS. 
 
 INTRODUCTION. 
 By A. STRAHAN. 
 
 The Triassic rocks of South Wales include representatives of the 
 RluiBtic and Keuper formations, and rest upon a deeply denuded 
 surface composed of strata ranging in age from Silurian to Coal 
 Measures. For reasons given in a previous part of this memoir, the 
 upper limit of the Keuper is drawn at the top of some green and buff 
 shales with thin inorganic limestones, which constitute the " tea- 
 green marls " of old authors.* Upon these rest the strata in which 
 Avicula contorta makes its first appearance, and which accordingly 
 are placed in the Rhsetic group under the name of the Avicula 
 cantorta-zone. 
 
 Though no unconformity has been detected between the Keuper 
 and Rhietic groups as thus defined, we have evidence of a somewhat 
 abrupt change of physical conditions. The Avicula was closely 
 followed, if not accompanied, by a true marine fauna, and, whereas 
 the Keuper limestones are of inorganic origin and are associated 
 with sediments in which fossils are extremely rare, the Rhsetic lime- 
 stones consist largely of organic debris. The horizon at which the 
 change took place can be readily determined to be constant over a 
 large area in the south-west of England and in Wales. 
 
 To these facts may be added a further argument for the classi- 
 fication now adopted. In the region under description the Rhaetic 
 strata exhibit a remarkable lithological change as they are traced 
 westwards, the shales and limestones which constitute the group at 
 Penarth being replaced by thick sandstones not unlike Millstone 
 Grit at St. Mary Hill and thence westwards to Pyle. The " tea- 
 green marls," on the contrary, show comparatively little change, 
 when traced over the same ground, their aspect at their western- 
 most occurrence being much the same as elsewhere. It appears 
 then that the conditions under which Keuper Marl was deposited 
 prevailed uniformly over the whole region up to a certain date, 
 but that after that date, when once the sea had gained access, the 
 physical geography was changed and no such uniformity existed. 
 Though the change was locally abrupt, and even accompanied by 
 some slight erosion here and there, it would be easy to over-estimate 
 its importance from a classificatory point of view. The green marls 
 themselves mark the commencement of the change, for lithologi- 
 cally they strongly resemble parts of the Rhaetic, but, more than 
 this, we find evidence high up in the Rhsetic of a brief recurrence 
 
 * Country around Cardiff (Mem. Geol. Survey), p. 38. 
 
Introduction. 21 
 
 of the conditions under which Keuper Marl was laid down, both 
 in this and in other parts of the British Isles (p. 36). Never- 
 theless, the subsidence which led to the burying of the old rocks 
 under Triassic and Jurassic sediments may have been continuous, 
 for some cause other than re-elevation may have sufficed to 
 restore temporarily the conditions which prevailed through Keuper 
 times. 
 
 These conditions may be inferred to have been continental, for the 
 reason that they indicate the existence of large tracts of water having 
 no communication with the sea. The absence of such communication 
 is proved by the nature of the material formed. A red clay, much 
 of it devoid of bedding, but in parts evenly laminated, makes up the 
 bulk ; bands of rock-salt, though not known in South Wales, occur 
 elsewhere, together with bands or concretions of carbonate of lime 
 and magnesia, sulphate of lime as gypsum and sulphate of strontia 
 as celestine, the formation of all of which indicates a water in which 
 surplus was removed by evaporation and not by overflow. 
 The water moreover was so highly charged with iron-salts as to 
 redden most of the rocks it touched. At its margin the clay inoscu- 
 lates with bands of talus roughly arranged in layers, but often 
 scarcely at all waterworn. The preservation of footprints in this 
 area, and of suncracks and rain-pittings elsewhere, proves that the 
 water receded at times and was therefore shallow, which indeed 
 might be inferred also from the nature of the marl. All these cir- 
 cumstances can be matched in the shifting sheets of shallow water 
 which characterise many desert regions at the present day,* and it is 
 interesting to find that in Leicestershire some of the granite-bosses 
 upon which the marl there rests show a smoothed and terraced surface 
 with signs of wind-polishing.f Probably lack of opportunity alone 
 has prevented observation of a similar phenomenon in South 
 Wales. 
 
 The paucity of organic remains in the Keuper Marl also suggests a 
 desert environment. The character of the water may account for 
 the absence of a lacustrine fauna such as teemed in the Purbeck and 
 parts of the Wealden, but it would not explain the absence of plants, 
 insects, and other organic remains which would have been washed or 
 blown into it, had they existed in any abundance. It is to be noted 
 also that the Keuper Marl of South Wales, though it fills depressions 
 in the old land-surface, never assumes a fluviatile character. No- 
 where can we point to a river-channel or a gravel such as could be 
 attributed to a running stream ; everywhere, except of course in its 
 literal type, it presents the same uniformity of red clay. 
 
 In its literal type the Keuper Marl consists of breccias or con- 
 glomerates, inorganic limestones and sandstones, the whole constitu- 
 ting the " Dolomitic Conglomerate " of old authors, a name which is 
 
 * As suggested by Prof. Lapworth, Proc. Ged. Assoc., vol. xv., p. 388 
 (1898).; 
 
 f Report by Prof. Watts on an Excursion to Gharnwood For* st, Proc. Ged. 
 Assoc.i vol. xvii., p. 379, and plate xviii; (1902); and Oeograph. Journal for 
 1903, p. 623 
 
unsuitable lor reasons given elsewhere.* In this part ol Glamor- 
 ganshire, these litoral modifications are exhibited not only in the 
 Keuper Marl, as was the case further east, but in the Rhsctic and 
 Lias also. The distribution of the litoral type, with other evidence, 
 makes possible a fairly precise restoration of the geography of the 
 region in Triassic and Liassic times. The features of that old land- 
 scape were due primarily to the effects of denudation upon the 
 sharply folded Palaeozoic rocks. Then, as now. the Carboniferous 
 Limestone formed scarps and the Old Red Sandstone stood up as 
 rounded hills. Around and between these features the marl was 
 spread out, mixed at its margin with the debris which fell from their 
 sides. As the subsidence continued the marl and breccias extended 
 further up the slopes, but though they had covered the small crags, 
 they had failed to surmount the higher tracts when they were suc- 
 ceeded by the green marls. Gradually diminishing in size these 
 same tracts can be easily recognised through the period of the green 
 marls, of the Rlwtic, and of part of the Lias, but they all finally 
 disappeared during the deposition of the Lower Lias. Subsequent 
 denudation has so far disinterred the buried landscape as to admit 
 of its partial reconstruction. The distribution of land and water at 
 the moment when the Rharfic fauna overspread the region is given 
 in the map forming Fig. 2. 
 
 The contents of the conglomerates are generally easy of determina- 
 tion. Carboniferous Limestone forms an overwhelming majority of 
 the fragments in all of them, whatever rock they rest on, but some 
 grit-pebbles occur abundantly in a few places and suggest by their 
 perfect rounding that they have been derived from a pre-existing 
 conglomerate, such, for example, as that which occurs in the lower 
 division of the Old Red Sandstone of Llanishen.f Though in some 
 bands the limestone-fragments also are well-rounded, they are more 
 generally angular, and in this respect differ from those which fell into 
 the Liassic sea. The one suggests scree that has fallen into water 
 and been roughlv sorted, but not rounded, the other a beach that 
 has been exposed to surf. 
 
 The matrix of the conglomerate is generally a calcareous mud, with 
 included fragments ranging from scarcely visible specks to large 
 blocks. Presumably it was derived from the attrition of the lime- 
 stone of the adjacent coasts, but the source of the red clay of which 
 so much of the Keuper consists is not so obvious. Though its strati- 
 fication proves that it was laid down by water, its distribution was 
 not improbably, like that of the loess, due to wind. In South Wales 
 much of the material might be attributed to the waste of the vast 
 thickness of Coal Measures which overspread the region, which would 
 also yield a water such as would account for the mineral contents 
 of the marl. It is true that the Keuper Marl preserves its cha- 
 racter in other parts of the kingdom where it spreads over other rocks, 
 but it must be remembered that it was formed at a time when Coal 
 
 The Country around C.irdifT (Maruiir (Jcal. AV/vw/), p. 40. 
 t The Country around Curd ill' (iMtrnoir (Jrol. Xnrrcy), |>. 17. 
 
Introduction. 23 
 
 Measures occupied a larger area than now, and when they were under- 
 going denudation on a vast scale. 
 
 There is abundant evidence, however, that an enormous mass of 
 material had been denuded before the Triassic period commenced. * 
 In South Wales the thickness of strata removed before the Keuper 
 Marl was laid down amounted in places to upwards of 7,000 feet. 
 Near Cardiff, for example, where the Silurian rocks are laid open to 
 a depth of 500 feet, the whole of the Old Red Sandstone as well as all 
 the Carboniferous rocks had been swept away. In the area now 
 under description, the denudation had reached the upper part only 
 of the Old Red Sandstone, but all the Carboniferous rocks were 
 probably thicker and the aggregate thickness removed may have 
 been not much less than in the region referred to. 
 
 The map forming Fig. 2 shows the distribution of land and water 
 at the close of the Keuper period, with the addition of the present 
 coast-line and the courses of the principal rivers. The Keuper 
 coast-line has been drawn by reference to the overlap of the Rhsetic 
 and Lias. For example, it was considered that the fact of the 
 Rhgetic or Lias lying directly upon the Carboniferous rocks at any 
 spot proved that Keuper had never overspread that spot, inasmuch 
 as we have no evidence of any pre-Rhaetic denudation to account for 
 its absence. That spot would, therefore, form part of the Keuper 
 land. On the other hand, the absence of Keuper at the present day 
 on spots not overlain either by Rhsetic or Lias proved nothing, inas- 
 much as it might have been due to post-Liassic denudation. The coast- 
 line of the principal Keuper island could be fixed nearly all round by 
 evidence of this description. Part of its southern margin, however, is 
 doubtful ; we can say little more of it than that it must keep south 
 of Wick and of Dunraven Castle, near both of which Lias rests on 
 Carboniferous Limestone, and of Whitmore Stairs, where the Lias 
 belongs to the litoral type, and may be inferred to rest on the older 
 rock. 
 
 The coast of what we may call the mainland is doubtful almost 
 everywhere. Near Llantrisant, the Keuper breccias end off against 
 a steep Pennant scarp, and can scarcely have extended many yards 
 beyond the line shown. Elsewhere we have proof that the Keuper 
 extended close up to the scarp, and it has been assumed that its 
 limits were determined by that great feature all through, the tract 
 shown on the map. The limestone on either side of the Taff, near 
 Taff's Well, is believed to have been overspread by the Trias on the 
 evidence of the large deposits of haematite in it. 
 
 Certain rocks, such as those near Wenvoe, Cadoxton, and others, 
 though submerged before the end of the Keuper period, formed 
 islands till near the close, and have accordingly been indicated by 
 stippling. 
 
 The rivers have been added to the map for the purpose of showing 
 that their courses have no connection with the Triassic geography. 
 For example the Ogmore and Ewenny on issuing from the Coal 
 
 *See also Ramsay, On the Denudation of South Wales (Mem. Geol. Survey} 
 Vol. 1, p. 297 (1846). 
 
24 
 
 Field, the margin of which approximately coincides with the coast 
 of the Triassic mainland, cross the site of a Triassic strait in which 
 Keuper Marl of normal typo was deposited, and then traverse a 
 region in which Lias rests on Carboniferous Limestone, and which 
 therefore was Triassic land. At their junction they enter an inlet 
 of Trias which is indicated by two outlying patches, one on either 
 
 side of the river, but, with the exception of this short length, they 
 show complete indifference to the Triassic features. The Dawe.n 
 again rises in the Triassic strait referred to, but, so far from following 
 it, cuts across the Triassic land southwards. The Ely also ignores 
 the Triassic strait, but, on the other hand, it crosses the ridge of 
 
Introduction. 25 
 
 Carboniferous Limestone by a gap which may be of Triassic age. 
 The evidence, which is suggestive but not conclusive, is given on 
 p. 29. The Cadoxton River rises in the site of a Triassic strait which 
 separated the islands of Michaelston and St. Lythans in pre-Rhaetic 
 times ; it flows not along the strait, but right across the Michaelston 
 crag. These examples will suffice to show that the existing river- 
 system is independent of the Triassic features. It probably origin- 
 ated when the region was buried under Jurassic and Cretaceous 
 rocks.* 
 
 One more point in connection with the map (Fig. 2) remains to 
 be mentioned. The area of land shown as forming a Triassic 
 island of course stood higher than the tracts on either side of it. 
 It does not do so everywhere now, and a consideration of the changes 
 of level which it has undergone enables us to estimate the effect of 
 later earth-movements. The simplest method is to take the base 
 of the Rhaetic as having been a Triassic contour-line, which it seems 
 safe to do in view of the fact that it marks the incoming of the sea 
 over a large tract of country. The base goes to or below sea-level at 
 Penarth, Lavernock, and Barry. Thence northwards it rises to 200 
 feet at Leckwith and Dyffryn near St. Lythans, Llantrithyd and 
 south of St. Hilary, the steady ascent northwards being easily 
 detected in the valleys south of the two last-named villages. Near 
 St. Nicholas it reaches 300 feet, and the eame height at Bonvilston ; 
 at Tair Onen 400 feet, and at St. Hilary 300 feet. Here it reaches 
 its greatest height, for farther north near Maes-y-llech it is 250 
 feet, and about 100 feet at St. Brides-super-Ely and Peterston, 
 rising to 200 feet again a mile or two to the north. At Pendoylan 
 it is 200 feet and three miles to the north 160 feet above the sea. 
 The level in a faulty district from St. Mary Hill westwards ranges 
 from 300 feet to about 180 feet near Pyle. Lastly, we may remark 
 that the Rhaetic base sinks an unknown depth below sea-level 
 south of Dunraven. 
 
 One fact comes out prominently from a consideration of these 
 levels, namely, that there has been an uplift of the Rhaetic 
 along the Carboniferous Limestone escarpment on the south of the 
 anticline east of Cowbridge, as compared with the Rhaetic lying 
 along the axis of the anticline. In other words, the post-Liassic 
 anticline is parallel to but nearly three miles south of the pre- 
 Triassic anticline. The uplift may be partly due to a fault, of 
 which there is reason to suspect the existence, for farther west 
 from Cowbridge to Southerndown the course of a fault producing 
 such an effect has been traced on good evidence. Though the 
 post-Liassic uplift diminishes westwards it can still be located in 
 the Ogmore Valley, between Merthyr-mawr and Sutton, here again 
 some distance to the south of the pre-Triassic anticline. For 
 further details on the post-Liassic movements reference should be 
 made to Chap, viii., Figs. 7 and 8. 
 
 Quart. Journ. Geol, 8oc. t vob Iviii., p. 218 (1902). 
 
:?(> 
 
 KEUPER (Eastern Part). 
 By T. C. CANTRILL. 
 
 The Keuper of the eastern part of the map occurs in three areas 
 determined by the position of the Cowbridge-Cardiff anticline, 
 namely a tract around Pendoylan situated within the anticline, the 
 strip extending along the outcrop of the Millstone Grit and base of 
 the Coal Measures on the north of the anticline, and lastly the ex- 
 posures which intervene between the anticline and the Lias plain 
 on the south. 
 
 Within the Anticline. 
 
 The Pendoylan area is so largely concealed by drift that the 
 nature of the underlying rocks is often doubtful, and it is even 
 possible that part of the ground may be occupied by Old Red Sand- 
 stone. 
 
 The greatest thickness of Trias is exhibited in ground lying 
 north-west of Pendoylan, and the following appears to be the 
 general succession of the deposits : 
 
 The lowest beds, consisting of red and purple gravelly somewhat 
 incoherent conglomerates, make their appearance around Bryn- 
 helygen, though there are no good sections. The rock is made up 
 of small often well-rounded pebbles of red and purple quartzite and 
 sandstone embedded in a dark red sandy and ferruginous matrix. 
 The pebbles at times are parallelepipeds with the solid angles 
 rounded off. Associated with these conglomerates are beds of hard 
 rocky marls containing calcareous concretions or ' race.' The con- 
 glomerates come to the surface at the side of Bryn-helygen farm- 
 house. About the year 1860 two trial- shafts in search of haematite 
 were sunk here; one, which lies about 160 yards north-east of the 
 house, is said to be 60 feet deep ; the other, in Coed Llwyn-Hywel,* 
 to be 100 feet deep. In both, red rocky marl with ' race ' seems to 
 have been the chief deposit proved ; haematite in workable quantity 
 was not obtained. Conglomerates similar to those here described 
 occur at Dyffryn-lloff, probably at about the same horizon. 
 
 A red marl succeeds these conglomerates and marls. It crops 
 out at Clawdd-coch, where there are several old marl-pits, and may 
 be traced across several fields southwards of the cross-roads nearly 
 as far as an old barn a few yards north of Ty'n-y-cae. 
 
 Next follows a grey limestone of inorganic origin containing 
 numerous more or less angular fragments chiefly of Carboniferous 
 Limestone. This is seen at the old barn near Ty'n-y-cae, and it 
 also crops out in the lane west of Tre-Dodridge. 
 
 Lastly, there come red and yellow sandy marls overlain by green 
 marls, all containing thin bands of pebbly yellow rock and breccia, 
 or even in places being wholly replaced by breccia. They re- 
 present the ' Tea Green Marls ' of old authors and form the top of the 
 
 * In this wood there appears to be a small earthwork or camp. 
 
Keit/per. 27 
 
 Keuper marls, being immediately succeeded by the Avicula con- 
 torta shales of the Rhaetic group. Red and yellow sandy marls 
 with included fragments are exposed in an old pit at Ty'n-y-cae, 
 and can be traced up the lane west of Tre-Dodridge. 
 
 At about 150 yards along the footpath running south-east from 
 Ty'n-y-cae Rhsetic limestone can be recognised in the soil, but a 
 little farther on the Keuper beds are brought up again by a fault 
 which appears to range in a south-westerly direction and repeats 
 most of the Keuper series. Thus, the red marls of Clawdd-coch 
 recur immediately south-east of the fault, and are well-exposed in 
 a quarry on the road to Pendoylan, while a pebbly limestone above 
 them is worked for roadstone in the south part of the same quarry 
 and can be traced thence to the south-west. It is probably this 
 rock that is quarried also near the smithy a quarter of a mile south- 
 west of Plwcau-Dafydd, where the following succession is disclosed. 
 
 FT. 
 
 Breccia, thick-bedded, grey, of subangular fragments of 
 Carboniferous Limestone in a calcareous matrix, ex- 
 posed for - - 3 
 
 Rocky marls, hard, yellowish-green, with thin partings of 
 softer, more shaly, and greener marl ; the upper two 
 feet soft. Some of these beds contain small Carboni- 
 ferous Limestone fragments - 9 
 
 Breccia, like the upper bed, but coarser and harder, exposed 
 
 for - - 10 
 
 Both the matrix and the contained limestone- fragments of the 
 breccias are more or less dolomitic. 
 
 Some yellow rocky marls , once dug in some pits in a coppice 
 west of the Lodge at Plwcau-Dafydd may be referred to the same 
 or a slightly higher horizon ; while in the hedge on the western 
 side of the roadside coppice immediately north of the Lodge there 
 occur traces of the Avicula contorta shales. 
 
 A hard yellowish-grey breccia which may correspond to the grey 
 limestone mentioned on p. 26 is shown in an old pit 200 yards north- 
 east of Pendoylan Church ; with it are associated yellowish-green 
 and grey rocky marls and pebbly grey limestone. They dip south- 
 wards and presumably underlie some buff, green, and red marls 
 exposed at Ffynnon Cattwg 150 yards farther south, which cannot 
 be' more than 50 feet below the Rhsetic base. 
 
 These details, together with the fact that pebbly green rocky 
 marls were met with under the Avicula contorta shales in the trial- 
 pit at Ty-du, referred to on p. 69, make it clear that the topmost 
 beds of the Keuper are liable to assume the literal type, though 
 the Rhsetic group shows no such change for some distance farther 
 west. 
 
 The remaining exposures of this area of Trias present less detail ; 
 on the south some old pits east of Cae'r-wigau exhibit two types of 
 rock : one, a coarse red conglomerate made up of pieces of red-stained 
 Carboniferous Limestone and red sandstone probably of Old Red 
 age, in a dark red calcareous matrix ; this is to be seen in an old 
 
28 
 
 quarry on the hill-side '.\00 yards south of Maes-yr-haul. The other 
 type is a yellow breccia exposed at Cae'r-wigau-isaf and at the 
 adjacent mill. A little farther south. Old Red Sandstone props out 
 in rlie brook (p. 5). 
 
 A few yards north-west of Llwyn-Gibbwn, some red gravelly con- 
 glomerate, exposed by the edge of the alluvium, apparently dips 
 north at .>2 . an appearance which may be due to false-bedding ; it 
 contains subangular pebbles of fine purple sandstone and quartzite, 
 but no Carboniferous Limestone. Similar conglomerates, alterna- 
 ting with red marls, are exposed in the lane leading up to Llanwen- 
 san : while, from some small exposures and from the character of the 
 soil, it appears that conglomerates extend past Gelli-wen and form 
 a small outlier north of Llanerch. There are some doubtful indica- 
 tions of a small patch of breccia also at Tre-Gwilym, one-third of a 
 mile south-west of Miskin. 
 
 The present limit of the Keuper can be traced near Groes-faen. 
 South-oast of Llwyn-y-penaii an old quarry shows coarse well- 
 cemented limestone conglomerate, and on its northern edge Old 
 lied quartz-conglomerates which appear to be in place. Coarse 
 breccia was quarried and apparently burnt for lime a little nearer 
 (Iroes-faen, and red sandy marls and grey and pebbly limestone were 
 brought up from an adjacent trial-shaft. Yellow breccia was got 
 in pits south of the Church and crops out in the Cardiff road, between 
 the Church and Ty-nant, and again at a pond 100 yards south of 
 Cwrt-y-carnau, where it rests on the Carboniferous Limestone. At 
 Ty-nant the breccia is overlain by cream-coloured earthy limestone ; 
 the beds dip about east at 12 and in the bye-lane turning north- 
 eastwards are followed by buff shales, and green marls with thin 
 rocky bands exposed near the mill. These rocks evidently corre- 
 spond to the tea-green marls and dip towards the RluTtic shales 
 which crop out on the east side of the brook. 
 
 The Keuper marl resumes its normal type near the Peterston Lias 
 outlier, and exposures at Maendy .show tea-green marls overlying 
 red marls. 
 
 With regard to the source of the debris which forms these con- 
 glomerates and breccias, it is clear that the Carboniferous Limestone 
 detritus could have been derived from the neighbouring escarpments, 
 but the source of the pebbles of purple and dark-red sandstones, grits, 
 and quartzite is not so clear. They do not resemble the, quartz- 
 itic grits near the top of the Old Red Sandstone as seen at Hensol 
 and west of Groes-faen ; but on the contrary their rounding suggests 
 that they have come from a pre-existing conglomerate. Such con- 
 glomerates though they have not been certainly detected in the area 
 under description have been found in some abundance in the Old 
 Hed Sandstone of the arealying farther east.* It is even possible that 
 some of the conglomerates attributed to the Trias in the foregoing 
 descriptions may really belong to the Old Red Sandstone, such, for 
 
 * The Countryaround Card ill' (.)///>// (l^ol. /S'nnv//) pp. 17, 20. Jh. Newport, 
 pp. Hi, 17. 
 
Keuper. 29 
 
 example, as those at Llwyn-Gibbwn and Llan-cos-lech. The possi- 
 bility, of course, exists only in the case of those conglomerates which 
 are devoid of pebbles of Carboniferous Limestone. 
 
 The original limits of the Trias may be inferred on the following 
 evidence. The Carboniferous Limestone at Welsh St. Donats 
 remained above the waters until the close of the Keuper, inasmuch 
 as the Lias was the earliest sediment to be deposited upon it. Near 
 Bonvilston for the same reason we infer that the limestone was not 
 covered till Rhsetic times. The Trias margin must, therefore, have 
 run between Pendoylan and Bonvilston, and thence east of Welsh St. 
 Donats. It must then have kept eastwards of Ystradowain, but how 
 far the Old Red hill of Hensol Park was covered, there is no means 
 of deciding. The presumed outlier of Trias at Llanerch, though in 
 the line of strike of the durable Old Red grits of Hensol Park, 
 nevertheless lies in a hollow, which suggests a pre-Triassic valley 
 running in the direction of Miskin and Pont Clun. The occurrence 
 of red shale apparently brought up from a trial-shaft at Hendy-isaf, 
 if it be not stained Millstone Grit, confirms this supposition, so that 
 it is not unlikely that the Trias within the centre of the Cowbridge- 
 Cardiff anticline was continuous along this depression with that to 
 the north. 
 
 North of the Anticline. 
 
 This northern tract of Trias follows the outcrop of the Millstone 
 Grit and the lowest beds of the Coal Measures. It has been cut 
 through, however, by the Ely Valley, for it was not met with in the 
 shafts of the Cardiff Navigation Colliery. 
 
 The deposit is largely concealed by drift, but may be examined 
 in the old haematite-workings near Mwyndy and Llanharry. It 
 consists chiefly of a well-cemented coarse conglomerate of large 
 more or less rounded Carboniferous Limestone pebbles, ranging up 
 to two feet in diameter at Llanharry. The pebbles are iron-stained, 
 and embedded in a sandy, marly, calcareous, and ferruginous matrix. 
 Occasional pebbles of purple grit such as make up the gravelly con- 
 glomerates of the Pendoylan area (p. 26) have been found, as for 
 example at Rhyd-y-castell, north-east of Llanharry. If, as seems 
 certain, they were derived from the Old Red Sandstone, they must 
 have travelled westwards or northwards. It is noticeable that even 
 where the Triassic conglomerates rest on Coal Measures they consist 
 almost wholly of Carboniferous Limestone detritus. By this fact 
 also a northward trend of the material is suggested. Nearer Cardiff, 
 on the contrary, there is reason to suspect an eastward trend.* 
 
 With the coarse limestone-conglomerate there are often associated 
 red marly sandstone containing calcite-crystals, single or in groups ; 
 sandy marls with occasional detrital fragments ; and beds of unmodi- 
 fied red marl. The red marly sandstone is prevalent in the Bute 
 
 * The Country around Cardiff (Mem. GeoL Survey), 1902, p. 40. 
 
30 Trias. 
 
 haematite-workings at Mwyndy and at the Llanharry Iron Ore 
 Works ; it contains haematite in streaks and also diffused through the 
 rock. 
 
 All these deposits rest nearly horizontally on highly-inclined Mill- 
 stone Grit and Carboniferous Limestone, and some of the old haema- 
 tite excavations have revealed the steeply-sloping shore of lime- 
 stone against which the Trias was laid down. At Llanharry village 
 the sinuosities in the margin of the Trias are due to its having 
 run up shallow inlets in the old coast-line. 
 
 Besides old quarries the old haematite-workings which extend 
 westwards from Bro-fiscin-fach to Hendy, and again from Ty-du as 
 far as Pen-y-waun on the north and Fron-wen on the south, yield 
 many opportunities of examining these rocks. Farther west the 
 conglomerate emerges from the drift as a ridge at Pen-y-coed-uchaf , 
 but around Llanilid all the rocks are hidden by drift. 
 
 South of the Anticline. 
 
 To the south of the Co wbridge- Cardiff anticline the Keuper is 
 frequently overlapped by the Rhaetic and Lias. A small quarry 
 100 yards south of Redland shows the Avicula contorta-sh&les over- 
 lying a hard yellow dolomitic rock of tea-green marl age, while Car- 
 boniferous Limestone, apparently in place, crops out on the opposite 
 side of the road. Here then we can fix a point on the Keuper coast- 
 line, for the limestone-ground to the north was still above water at 
 the close of the Keuper Marl period. 
 
 Coarse yellow breccia reappears in Bonvilston, and extends west- 
 wards as a tongue which evidently occupies an original Triassic 
 channel. A cutting on the Cowbridge road shows the rock filling 
 the channel to be a yellow conglomerate of subangular limestone- 
 detritus. Its southern margin round the curious Carboniferous 
 Limestone ridge of Leige Castle and Tilau can be clearly traced, and 
 the junction is exposed near a footpath at 200 yards north-east of 
 the latter farm. The hedge is rooted in a thin band of irregularly- 
 bedded buff fine-grained impure limestone containing fragments and 
 pebbles of Carboniferous Limestone ; the lower part contains 
 irregular patches of chert, attached to one of which was a pebble of 
 Carboniferous oolite which had been converted into chert. This was 
 cut for the microscope and the slide (E. 2867) is thus described by 
 Dr. Flett : 
 
 A fine example of oolitic chert in which the concentric structure of the 
 oolitic grains is well preserved. The grains are composed of very fine 
 grained chalcedonic silica, the matrix forms a coarser mosaic. Patches of 
 carbonates occur in the heart of the grains and in the matrix ; they are 
 probably dolomitic as they effervesce only slowly with acid and do not 
 stain. The rhombohedral form, usually very perfect in dolomitic crystals, 
 is not well seen. The oolitic grains are brownish, the cementing matrix 
 clear and nearly colourless. 
 
 This Triassic breccia rests on an irregular and broken surface of 
 dark-blue Carboniferous Limestone ; though exposed for several feet 
 the dip in the latter is difficult to determine, but appears to be 
 south-west at about 45. The rock appears to be dolomitizecl. 
 
Keuper. 31 
 
 There is an old kiln and quarry in the breccia north of Ty'n-y- 
 coed, and a quarry 100 yards south-east of the farm shows the 
 junction with the Carboniferous Limestone again, the Triassic base- 
 ment-bed being a grey calcareous rock with much angular detritus. 
 This is overlain southwards by thick-bedded sandy calcareous 
 rocky marls and impure limestone, all more or less yellow. A 
 buff rock containing few if any detrital fragments prevails here, 
 and a specimen (E. 2866) taken from the roadside opposite White- 
 well Farm is thus described by Dr. Flett : 
 
 Dirty yellow, somewhat ferruginous limestone, which contains a few 
 grains of quartz and areas of crystalline calcite with dolomite rhornbohedra. 
 It appears to be made up mostly of small well-rounded limestone pebbles in 
 a limestone matrix. The rock contains no fossils, and both the pebbles and 
 the matrix are composed of a mosaic of small grains of crystalline calcite. 
 
 Probably all these rocks, and certainly the highest, belong to the 
 tea-green marls. 
 
 West of Ty'n-y-coed the Keuper is overlapped by the Avicula con- 
 forta-shales, but its original margin ran westwards to Llantrithyd, 
 where it reappears, filling up old channels in, and wrapping round 
 knolls of, the Carboniferous Limestone. It consists of the usual 
 yellow breccia, but in its upper part, which evidently represents the 
 upper part of the tea-green marls, it contains bands of yellow and buff 
 shales and rocky marls generally free from detritus. These rocks 
 are well shown in the road north of the church and between the 
 village and Tre-Aubrey, but north of the latter place are overlapped 
 by the Rhsetic, never having extended over some of this ground. 
 A small outlier however of yellow breccia north of Tair Onen 
 shows that the Bonvilston Trias extended up a gulf as far as this 
 point. 
 
 West of Tre-Aubrey the Keuper, brecciated up to its top, is over- 
 lapped by the Rhsetic and Lias, but it reappears at St. Hilary in the 
 form of two narrow strips along the north side of a fault. It consists 
 of greenish-grey breccia and pebbly marls, and is proved to be of tea- 
 green marl age by the fact that it is immediately overlain by Rha3tic 
 sandstones. The original margin comes out clearly, as shown on the 
 map, between The Cross and the village of St. Hilary ; it emerge? 
 from below the Rhaetic again at the Vicarage and must then have 
 turned north-westwards. 
 
 The Dawen Valley near Llandough cuts down deep into the Trias, 
 which is here at least 150 feet thick ; in the lower part, exposed in 
 Coed-y-Grabla, it is a coarse limestone-conglomerate with 
 a red tinge. The deposit is pebbly to its summit, but farther off- 
 shore, in the valley half a mile south-west of Llandough, and again 
 at How Mill, green and buff more or less rocky marls of the normal 
 type may be detected just below the Rhsetic base. Occasionally 
 grey fine-grained limestone occurs, as in an old quarry on the west- 
 tern side of the Dawen Valley north-west of How Mill. 
 
 At Llanbleiddian the original limit of the Trias ran westwards 
 towards Nash, but the Lias spreads northwards over it. 
 
 The Cowbriclge Keuper appears to have been deposited at the 
 extremity of an inlet which ran north-westwards and northwards from 
 
32 Triaif. 
 
 St. Hilary as far as Aberthin, but the margin there turned sharply 
 south-westwards under Cowbridge, past Llanbleiddian Castle, and 
 thence south-westwards, there being no reason to think that the 
 Keuper extended over Xewton Moor. A coarse red breccia which 
 forms the lower part makes the bold scarp of Coed-y-llwyn, where it 
 must be at least 100 feet thick. As shown in the Cardiff Koad 
 south of Slade it contains pockets of red marl only a few feet below 
 its top. It is remarkable to how small an extent detritus from the 
 Old Red Sandstone enters into the composition of the breccia even 
 at only a few feet distance, as may be observed in the small outlier 
 south of Aberthin. The breccia has been quarried and apparently 
 burnt for lime on the north side of a dry valley north of Slade. 
 
 The highest part as shown in the railway immediately south of 
 the bridge on the Aberthin road is a massive grey rock made up of 
 angular and rounded fragments of oolitic and crinoidal Carboniferous 
 Limestone. The fragments, which range in size from mere grains to 
 pieces two inches across, are embedded in a fine-grained grey or 
 dark cream-coloured calcareous matrix, probably more or less dolo- 
 mitic. Chert also occurs in strings and concretionary nodules. The 
 actual top of the breccia is exposed on the east side of the cutting at 
 about nineteen yards south of the bridge ; the uppermost six inches 
 consist of hard dark cream-coloured or pale-brown rock, compara- 
 tively free from detrital fragments, and fine-grained and flinty in 
 fracture. This is overlain by a trace of sandstone, followed by pale- 
 green marls, one foot eight inches thick (p. 45). 
 
 At the south end of the same cutting, which crosses the Lias 
 outlier of Cowbridge, the Keuper is represented by an impersistent 
 band, one foot thick, of grey hard breccia containing fragments of 
 Carboniferous Limestone, chert, and quartz. This conformably 
 underlies the Rhsotic beds and rests unconformably on the Carboni- 
 ferous Limestone. The pebbles, some of which are subangular, 
 range up to one inch in diameter. In places strings and patches of 
 chert are present, and chert seems here and there to take the place 
 of breccia. The surface of the Carboniferous Limestone is fissured 
 and contains strings of chert, and the Triassic basement-bed is so 
 firmly cemented to it that the exact junction is difficult to locate. 
 The older rock is dark-grey and crinoidal, and dips 8. 30 
 \Y. at 45, whereas the breccia and the overlying Rhaetic and Lias 
 beds clip about X. 10 W. at 20, thus showing considerable 
 post-Liassic movement along the line snewn in Fig, 1>. The rapid 
 southerly thinning of the Keuper is here evident, and may be 
 ascribed to an approach to land or to a paucity of detritus. 
 
 KKI TKR continued. (Western part.) 
 By A. STRAHAN, from notes by R. H. TIDDEMAN. 
 
 A largo tract of Trias runs along the north side of the Cowbridge- 
 Cardiff anticline by Coychurch and Coity. It consists almost wholly 
 of conglomerate, often coarse, packed with fragments of Carbonifer- 
 ous Limestone and a few other rocks. Haematite has been found 
 
Keuper. 33 
 
 below these conglomerates at Rhythin, but attempts to work it 
 appear to have met with no success. On St. Mary Hill Down the 
 conglomerate is immediately overlain by, as well as faulted against, 
 Rha3tic beds. 
 
 At Coychurch also the same sequence may be observed, but the 
 yellow tint of the uppermost part of the conglomerate indicates that 
 it represents the tea-green marls. One and a half miles further 
 north the green marls resume their normal aspect as shown in a clay- 
 pit at Hendre : 
 
 Hendre Clay-pit. 
 
 FT. 
 
 Sandy beds - - - - 3 
 
 Green and yellow marl - - 15 
 
 Hard marl with race and gypsum - - 2 
 
 Clayey red marl .... -2 
 
 Clay and marl, proved in a well - 30 
 
 A thin impersistent band of quartz-sand occurs in places near the 
 bottom of the pit, but except for this the section differs little from 
 those observable in East Glamorgan. The fact is interesting, for it 
 shows that the Keuper deposits had space to develop in normal form 
 in the strait which separated the Triassic island from the mainland of 
 the Coal Field (Fig. 2, p. 24). At Coity conglomerate is faulted 
 against Rhaatic and Lias except for a small space occupied by red 
 marl at and east of the church. 
 
 The Keuper near Cwrt Colman consists in part of red marl ; it is 
 faulted down on the north against Millstone G rit, but passes south- 
 wards under yellow and green shales and marls, which, however, seem 
 to be thin. 
 
 At Pyle a complete sequence can be obtained in the Keuper as well 
 as in the Rhaetic group. A pit close to the " Pyle Inn " shows a 
 Rhsetic sandstone (p 55), while a steep slope down to the house 
 exposes characteristic green Keuper marls which lie immediately 
 below the sandstone. Below these again come red marls, which 
 in a railway east of Pyle Inn Quarry contain a band of limestone 
 between two beds of conglomerate. The limestone (3821) is 
 described by Dr. Flett as granular, coarsely crystalline and without 
 organic structures, but with a few grains of quartz. The 
 green marls are well developed again on the south side of the Porth- 
 cawl Railway on the road to North Cornelau ; buff and grey 
 marls, with black and green shales and thin nodular limestones, being 
 visible in several places close along the Rhaetic base. From beneath 
 these come red marls normal in aspect and sequence, but at North 
 Cornelau conglomerate sets in, and the whole of the Keuper which 
 circles round Newton Down by Ivenfig to Newton Nottage consists 
 of that literal type. The fact that red marl formed the marginal 
 Keuper deposit a mile to the east of Cornslau well illustrates the 
 extremely sudden variations to which the formation is subject in this 
 region. It may be noticed, however, that the conglomerates have 
 7665, D 
 
:u T 
 
 clustered chiefly along the west and south sides of Xowton Down 
 while near Cardiff they are more abundant on the eastern sides of 
 some of the limestone-inliers.* 
 
 The rocks which project here and there through the sand of 
 Kenfig Burrows nearly all consist of Triassic conglomerate. In some 
 bands the pebbles are well rounded, and include grit as well as 
 limestone ; in others rounded material alternates with angular 
 breccia. Specks of galena are not uncommon. 
 
 A quarry west of Newton Nottage which is indicated on the map 
 by a dip of 4 shows a coarse gravelly conglomerate resting on fine- 
 grained calcareous flags with small angular fragments of limestone. 
 The flags show foot-prints and ripple-marks and closely resemble 
 a slab which formerly lay in the village, but was subsequently trans- 
 ported to the Cardiff Museum. That slab bore the impressions of 
 five footprints, which were figured and described by Prot. Sollas 
 as being those of a Dinosaur, Brontozoum ThomasiJ The occurrence 
 of footprints proves that the flags were laid down on a foreshore 
 that was occasionally dry. The conglomerate is terminated at 
 Porth-cawl by a fault, but an interesting proof of its former ex- 
 istence to the west of the fault is found in a Triassic cave near Lock's 
 Common. The cave w r as rilled in with Triassic gravels, marls and 
 travertin. 
 
 Small patches of Triassic conglomerate lie on either side of the 
 river at Ogmore. A larger mass is intersected by the coast-line near 
 Sutton. Some of the included blocks of Carboniferous Limestone 
 must fall but little short of ten tons in weight, which suggests that 
 the deposit is quite local. Further proof may be obtained of the 
 same fact within a few yards, for at the top of the hill where the 
 Lias comes on there is no Trias under it. It. follows that the hill 
 formed an island in Triassic times and that the deposits of that age 
 thinned of! against its flanks. 
 
 * The Country aroun I Cardiff (Memoir (Ic.ol. Siircct/) 1902, p. 40. 
 t (}n irt. Joiirn, (J<">1. Sue., vol. xxxv., p. 511 (IS^U). 
 
35 
 
 CHAPTER VI. 
 
 TRIAS continued. RRMTW BEDS. 
 
 INTRODUCTION. 
 
 By A. STRAHAN. 
 
 It will be understood from the remarks made on p. 20 on the classi- 
 fication of the Keuper that the Rhsetic group is taken as com- 
 mencing with the strata in which Avicula contorta makes its first 
 appearance, and that it does not include the uppermost green marls, 
 or " tea-green series " of old authors. Allusion was made also to 
 the fact that, apart from a litoral modification in the immediate 
 neighbourhood of Triassic land, the Keuper marls retain their 
 normal aspect to their westernmost limit, wherever there was room 
 for their proper development, as for example in the neighbourhood 
 of Pyle. 
 
 Such was not the case with the Rhsetic, though the extent of 
 open water was greater than in Keuper times. The shales and thin 
 limestones which constitute the normal type at Penarth, and in the 
 south of England and Wales generally, begin to give place near Cow- 
 bridge to massive sandstones, often simulating Millstone Grit, nor 
 so far westwards as they have survived do they tend to revert to 
 the normal type. As a first stage in the change the Rhsetic shales 
 assume the character of calcareous marls and limestones, or more 
 generally of oolitic limestone containing so much sand as to weather 
 into a sandstone. The development of massive oolite has been 
 noticed in the Lias also, as an indication of near- shore conditions 
 (p. 59),* and it is interesting to find the Rhaetic strata assuming 
 the same condition, and thus differentiating themselves from the 
 Keuper in which oolitic limestone is not known. Chert, however, 
 which abounds in the litoral type of Lias does not occur in the 
 Rhsetic. 
 
 Another type of rock which is developed in the Rhsetic Beds re- 
 sembles the Sutton- stone which is conspicuous in the Lias towards 
 the western part of the area. It may be described as a massive 
 limestone composed of fragments of shells and corals firmly cemented 
 by calcite. When deposited it was probably a shell-marl, made 
 up of the debris of shells living in the neighbourhood, but drifted 
 into a mass. It usually contains fragments of Carboniferous Lime- 
 stone and in this as in its general character constitutes such a rock 
 as would be formed perhaps not on the beach, but close along a 
 shore that was not exposed to heavy surf. Glauconite occurs 
 sparingly in the Sutton-stone. This mineral appears at the present 
 
 * See also The Country around Cardiff (Memoir Gwl. Survey), p. 69. 
 7665. D 2 
 
36 Rhcetic. 
 
 day in greatest abundance in comparatively shallow water along 
 nigh and bold coasts where no rivers enter the sea and where 
 accumulation is not rapid. The distribution of these litoral types 
 in the Lias and Rhaetic differs from that of the litoral Keuper in 
 the respect that they covered a wider area. The Keuper breccias 
 are clustered along the Keuper coast-lines, but the Rhaetic and 
 Liassic oolites and the Sutton-stone were laid down in wider belts. 
 
 The change undergone by the Rhaetic from shales into sandstone 
 is capable of more than one explanation. In the first place the 
 area of exposed Carboniferous Limestone was contracting. The 
 island shown in Fig. 2 had only slightly diminished in size, but all 
 the others had disappeared. The coast-lines therefore consisted 
 mainly of Millstone Grit and Coal Measures. But we may also 
 suppose that the opening of a communication with the sea effected 
 a change in the circulation of the water. Currents such as could 
 not exist in the land-locked Keuper water would come into action 
 and the distribution of sediment would be changed. The sand- 
 stones have been described as an estuarine form of Rhaetic, but it 
 is perhaps wiser to avoid the use of the expression. They are not 
 confined to the strait shown in Fig. 2, but appear both to the 
 south and east of its eastern entrance. Their fossils, though not 
 abundant, are all species which occur in the normal type of Rhaetic 
 strata. 
 
 Mention was made on p. 20 of a temporary recurrence of Keuper 
 Marl conditions in the Rhsetic period. The evidence for this con- 
 sists in the interbedding of some thin bands of red and green marls, 
 indistinguishable from the Keuper Marl, in the upper part of the 
 Avicula contorta zone. This interbedding has been noted in several 
 places west of Bridgend, and especially in the church-quarry near 
 Pyle (p. 55). A similar recurrence was found in the upper part of 
 the Rhaetic group of Belfast by Mr. R. Tate, who remarks that but 
 for the well- marked succession and the presence of Cardium rhceti- 
 cum the strata might have been referred to the Keuper.* It is 
 noteworthy also that a fresh-water fauna has been described by 
 Mr. E. Wilson in parts of Somerset at apparently the same horizon. j- 
 The reasons for supposing the Keuper Marl to have been deposited 
 in landlocked waters have been given on p. 21. It must be supposed 
 that the sea was temporarily shut out again from a part of the 
 Rhsetic area, either by the formation of sand-banks or some other 
 barrier, or by a slight re-elevation of the land. 
 
 The identification of the sandstones of Pyle as Rhaetic was due to 
 Bristow and Etheridge, and the Rhsetic boundaries were added in 
 1864 to the Old Series Map 36, by Bristow and Mr. H. B. 
 Woodward. The strata were described in detail by E. B. Tawney 
 in 1865, in a paper which was one of the earliest of a long 
 series on the Rhaetic question. The following list includes the 
 more important of those which have a bearing upon the Lower 
 Lias and Rhaetic rocks of South Wales. 
 
 * Quart. Journ. Geol Soc., vol. xx., p. 107, 1864. 
 f Quart. Journ. Geol, Soc.; vol xlvii., p. 548, 1891,- 
 
Introduction. 37 
 
 1860. 
 
 Wright, T. On the zone of Avicula contorta, and the Lower Lias of the south 
 of England. Quart. Journ. Geol. Soc., vol. xvi., p. 374. 
 
 1864. 
 
 Bristow, H. W. On the Rhaetic or Penarth Beds of the neighbourhood of 
 Bristol and the south-west of England. Geol. Mag., vol. i., p. 236. Also 
 Rep. Brit Assoc. for 1864 (pub. 1865), Sections, p. 50. 
 
 Jones, J., and Tomes, R. F. [Letters on the Sutton Beds of Glamorgan- 
 shire.] Proc; Cotteswold Club, vol. iii;, p. 191. 
 
 1866. 
 
 Tawney, E. B. On the Western Limit of the Rhaetic Beds in South Wales, 
 and on the position of the " Sutton Stone," with a note on the Corals by 
 P. M. Duncan. Quart. Journ. Geol. Soc., vol. xxii., p. 69. 
 
 1867.- 
 
 Bristow, H. W. On the Lower Lias or Lias -Conglomerate of a part of Glamor- 
 ganshire. Quart. Journ. Geol. Soc., vol. xxiii., p. 199. 
 
 Duncan, P. M. On the Madreporaria of the Infra-Lias of South Wales, 
 Quart. Journ. Geol. Soc., vol. xxiii., p. 12. 
 
 A Monograph of the British Fossil Corals. Second Series, Part 4, 
 
 No. 1. Corals from the Zones of Ammonites Planorbis and A. 
 Angulatus in theLiassic Formation [S. Wales, pp. 6-23, 27-35]. Pal. 
 Soc. 
 
 Moore, C. On Abnormal Conditions of Secondary Deposits when connected 
 with the Somersetshire and South Wales Coal-basins ; and on the age 
 of the Sutton and Southerndown Series. Quart. Journ. Geol. Soc., vol, 
 xxiii., p. 449. 
 
 Tatc, R. On the Fossiliferous Development of the Zone of Ammonites 
 angulatus, Schloth., in Great Britain. Ib. p. 305. 
 
 1868. 
 
 Duncan, P. M. A Monograph of the British Fossil Corals. Second Series, 
 part 4., No. 2. [Liassic] Appendix : '* Note on the Age of the Sutton 
 Stone and Brocastle, etc., Deposits," p. 69. Pal. Soc* 
 
 1868.; 
 
 Duncan, P. M. First Report on the British Fossil Corals. Rep. Brit. Assoc. 
 for 1868, p. 75. [Sutton and Brocastle, pp. 99-110.] 
 
 1872, 
 
 Etheridge, R. On the Physical Structure and Organic Remains of the Penarth 
 (Rheetic) Beds of Penarth and Lavernock, etc. Trans. Cardiff Nat. Soc., 
 vol. iii., part 2, p. 39. 
 
 1873. 
 
 Lee, J. E. Notice of Veins or Fissures in the Keuper, filled with Rhaetic Bone- 
 bed, at Goldcliffe, in Monmouthshire. Rep. Brit. Assoc. for 1872, Sections 
 p. 116. [See also his Notebook of an Amateur Geologist, 1881, p. 72, 
 and plates 171, 172.] 
 
 1877. 
 
 Moore, C. The Liassic and other Secondary Deposits of the Southerndown 
 
 Series. Trans. Cardiff Nat. Soc., vol. viii., p. 53. 
 Toines, R. F. On the Stratigraphical Position of the Corals of the Lias of the 
 
 Midland and Western Counties of England and of South Wales, Quart, 
 
 Journ. Geol % Soc.. 1878. vol. xxxiv., p. 179.- 
 
38 Trias. 
 
 1883. 
 
 Storrie, John. The Fossils at Penarth (Rhsetic and Lias). Trans. Cardiff 
 Nat. Soc. vol. xiv. p. 100. 
 
 1884. 
 
 Tomes, R. F. A Comparative and Critical Revision of the Madreporaria of 
 the White Lias of the Middle and Western Counties of England, and of 
 those of the Conglomerate at the Base of the South Wales Lias. Quart. 
 Journ. Gaol. Soc., vol. xl., p. 353. 
 
 1885. 
 
 Lucy, W. C. Southerndown, Dunraven, and Bridgend Beds. Proc. Cottes- 
 wold Nat. Field Club for 1884-5, p. 254. 
 
 1886. 
 
 Duncan, P. M. On the Astrocoenise of the Sutton Stone and other Deposits of 
 the Infra-Lias of South Wales. Quart. Journ. Geol. Soc.., vol. xlii., p. 101. 
 
 1888. 
 
 Woodward, H. B. Notes on the Rhsetic Beds and Lias of Glamorganshire- 
 Proc. Geol. Assoc., vol. x., p. 529. See also Rep. Brit. Assoc. for 1888, 
 p. 900. 
 
 1893. 
 Tomes, R. F. Description of a new Genus of Madreporaria from the Sutton 
 
 Stone of South Wales. Quart. Journ. Geol. Soc., xlix., p. 574. 
 Woodward, H. B. The Jurassic Rocks of Britain, vol. iii. The Lias of 
 
 England and Wales, Yorkshire excepted. If em. Geol. Survey. 
 
 1897. 
 
 Howard, F. T. Notes on the Base of the Rhaetic Series at Lavernock Point. 
 Trans. Cardiff Nat. Soc., vol. xxix., p. 64. 
 
 1898. 
 
 Howard, F. T. The Geology of the Cowbridge District. Trans. Cardiff 
 Nat. Soc., vol. xxx. 
 
 1899. 
 
 Strahan, A. Geology of the South Wales Coal Field.- Part 1. The Country 
 around Newport. Mem. Geol. Survey. 
 
 1902. 
 
 Strahan, A. and T. C. Cantrill. Geology of the South Wales Coal Field. Part 
 3. The Country around Cardiff. Mem. Geol. Survey. 
 
 Eastern Part. 
 By T. C. GANTRILL. 
 
 An outcrop of Rhaetic strata fringes the Liassic tract from Bonvil- 
 ston to Cowbridge and also the eastern side of the Liassic plateau 
 near Welsh St. Donats. The same rocks form an outlier at Pen- 
 doylan, and border the Lias outliers of Peterston and Castell-y- 
 mynach, which lie partly within the eastern edge of the map. 
 
Rkretic. 39 
 
 Castell-y-mynach Outlier. The Rhsetic beds are visible only along 
 the eastern bank of a stream at Ty-nant, near Groes-faen. At a 
 spring on the southern edge of a wood between the mill and the 
 Cardiff road, there may be seen dark shelly limestone with 
 Protocardium rhceticum, black shale, and very dark coarse sand- 
 stone with remains of Gyrolepis Alberti, the whole being 
 some 20 feet thick, and resting on buff rocky marls belonging to the 
 tea-green marls of the Keuper. They evidently belong to the 
 Avicula contorta zone, but whether they are succeeded by any 
 representative of the White Lias could not be determined. They 
 are not noticeably modified by literal conditions, a fact which 
 suggests that the original Rhsetic margin lay some distance farther 
 north. 
 
 Peterston Outlier. The Rhaetic shales are poorly exposed in a 
 brook between Maendy and Allt-isaf. South of the first-named 
 farm on the top of the tea -green marls there follow with a sharp 
 line of demarcation beds referable to the A. contorta zone, the 
 lowest being an impure limestone, about two inches thick, which 
 weathers into friable ferruginous earth and contains fragments of 
 what appears to be buff Keuper marl. Upon this there rest grey, 
 dark, and black shales, with a line of calcareous nodules, and bands 
 of limestone containing Pecten valoniensis. A few yards farther up 
 stream thin-bedded cream-coloured limestones and shales and shelly 
 marls crop out which probably represent the White Lias ; the Lias 
 comes on a little farther east. 
 
 Bonvilston to Cowbridge. The Rhsetic outcrop enters the map 
 east of Bonvilston. Black paper-shales overlie the Keuper at Red- 
 land (p. 30), and may be detected in the sides of the road for some 
 distance towards Blackland. Pieces of dark limestone containing 
 Pecten and Protocardium, and traces of black paper-shales, may be 
 found in the low ground north-west of Coed-yr-Aber. North of Red- 
 land Wood no Keuper rocks are exposed, and the Rhaetic soil can be 
 recognised so close to the brow of a large quarry in Carboniferous 
 Limestone as to suggest that the Keuper is here wholly overlapped, 
 as shown on the map. 
 
 Black shales with Pecfeft-limestone containing fish-remains (Gyro- 
 lepis Alberti, Ag.) crop out at two wells on the north-west side of the 
 Lias outlier south of Bonvilston, and similar beds can be traced 
 southwards along Llancarfan Brook nearly as far as Abernant. 
 On the west side of this valley the outcrop spreads out east of Leige 
 Castle and overlaps the Keuper, so as to rest directly on the Carbon- 
 iferous Limestone. The actual junction may be seen in a small 
 roadside section 200 yards north-west of Ty'n-y-coed. The section 
 shows one foot of brownish and greenish-yellow clay with fragments 
 of black paper-shales, and near the bottom a weathered band, one 
 inch thick, of dark limestone containing Pecten valoniensis and fish- 
 teeth. The clay rests on decomposed Carboniferous Limestone, 
 with crinoid ossicles. The Rhsetic beds dip south at about 5 
 while the Carboniferous Limestone dips in the same direction at 15 
 to 20. Although both here and at Redland Wood the Rhsetic strata 
 
40 Trias. 
 
 come into contact with the old land, yet they show no lithological 
 change such as appears farther west. They seem to have been 
 laid down on a gently sloping shore devoid of coarse debris. 
 
 Small exposures of the black shales with Pecfen-limestones which 
 have yielded a scale of Gyrolepis Alberti may be detected around 
 Castell-ar-Foel, and just within Llantrithyd Park a piece of lime- 
 stone yielded Pecten valonicnsis ? and a reptilian bone. 
 
 Thence south-westward the Rhaetic beds locally disappear, but as 
 the Lias shows no signs of literal modification, and as there is conse- 
 quently no reason to suppose the Rhsetic to be overlapped, the dis- 
 appearance is attributed to a fault. They emerge south-east of 
 Wren Castle, and here for the first time exhibit signs of the oncoming 
 of a more arenaceous type in the intercalation of bands of greenish- 
 grey sandstone. These may be traced southwards along the valley, 
 but are especially well shown in a road- cutting at Tre-gyfT, though 
 the beds undulate gently down the road westwards at such an angle 
 that only a few feet are exposed They consist of sandstone with 
 Protocardium philippianum and Avicula contorta, blue sandy marls, 
 a thin conglomeratic band containing pebbles of Carboniferous 
 Limestone and chert, and black limestone with Pecten valoniensis. 
 Several sandstone-blocks lying by the side of the cartroad to Tre- 
 gyff are covered with casts of worm-burrows, with a few impres- 
 sions of Avicula contorta. 
 
 This accession of sandy sediment becomes much more pronounced 
 as we trace the outcrop westwards and northwards, and is due to the 
 influence of some sand-bearing currents invading the area of deposit 
 from the west rather than to the immediate proximity of a coast-line 
 of Carboniferous Limestone cliffs. 
 
 Simultaneously with this appearance of sandstones in the Avicula 
 contorta zone, thin bands of white flaky limestone like Sutton-stone, 
 containing fragments of Carboniferous Limestone and broken shells, 
 develop in the White Lias zone, this modification making its first 
 appearance between Tre-Aubrey and Ty-draw. Sandstone, some- 
 times pebbly, predominates at Ty-fry, and is exposed at Ffynnon-y- 
 cae, but between Ty-ganol and Pentre it contains some Pecten-lime- 
 s tones. The Rhsetic outlier at Pentre is thrown down by a fault 
 which passes through an old quarry, now a pond, 200 yards east of 
 the road ; on the north side of the quarry is exposed Carboniferous 
 Limestone, sparry, and containing traces of galena, but on the 
 south, four feet of dark-brown Rhsetic shales are shown under 
 limestone, while fragments of limestone containing fragments of 
 shells and bone lie on the adjacent hedgebanks. 
 
 A bare surface of Carboniferous Limestone upon which the road 
 at Ty-uchaf runs is remarkably smooth and is probably the water- 
 worn floor on which the Rhsetic deposits were laid down. Three 
 hundred yards north of Pentre two small old marlpits or quarries 
 show sandy limestone and shales, yellow sandstone, and dark lime- 
 stone containing fragments of what looks like carbonised wood. 
 Farther north, on the extremity of the Lias, and 300 yards south- 
 east of Tair Onen, there is a large excavation encumbered with 
 
Ahcetic. 41 
 
 growing timber ; the floor at the east end is formed of a nearly 
 horizontal bedding- surf ace of conglomerate, the well-rounded pebbles 
 therein being mostly of Carboniferous Limestone, with a few of 
 chert, and more rarely some small rounded fragments of black 
 carbonaceous matter, possibly wood. At a higher horizon, yellow 
 clay is to be seen on the western bank of the pit, and above it are 
 large blocks of white flaky limestone resembling Button- stone, above 
 which the O^rea-beds of the Lias crop out. The conglomerate here 
 probably belongs to the Avicula contorta zone ; the rock like 
 Sutton-stone is probably at the top of the Rhaetic, but may be at 
 the base of the Lias. 
 
 At Tair Onen a brown rotten sandstone, white or pale-green 
 and calcareous where unweathered, has been quarried ; it contains 
 Carboniferous Limestone fragments and casts of Pecten valoniensis. 
 On the south-west this sandstone is apparently overlapped by Lias 
 of litoral type, which abuts directly against the Carboniferous 
 Limestone ; but it emerges again north of Garn, and is to be seen in an 
 old quarry one furlong west of the second milestone from Cowbridge. 
 It is succeeded by pebbly limestones and light-coloured marls 
 poorly exposed in old pits north of Garn. 
 
 In and near St. Hilary the Rhaetic sandstones are frequently 
 exposed, e.g., in the sides and floor of the lane north of Coed Hills, 
 where they yield Pullastra arenicola, and at The Cross, where they 
 contain thin streaks of black shale of the ordinary type. The 
 highest beds, as may be seen along the southern edge of the 
 tongue of Lias west of Garn, consist of fine-grained limestones 
 and a conglomerate or bone-bed, the latter poorly exposed in 
 an old pit 350 yards south-east of Eastdown. From this rock 
 Schizodus ? has been obtained. A bone-bed is recorded by Buck- 
 land and Conybeare* as occurring " at the village of St. Hilary, 
 near Cowbridge." 
 
 The Rhaetic outcrop extends southwards as far as Gigman Bridge 
 near St. Mary Church Road Station, grey sandy and oolitic Rhaetic 
 limestones cropping out in the lane east of the bridge. North of the 
 station a deep and long cutting traverses 'a gentle anticline in thin- 
 bedded Lias limestones and shales (Ostrea-beds) ; at the bottom 
 some soft dark shales and marls are brought up for a length of about 
 500 feet, though nowhere exposed for a greater depth than three feet. 
 They differ wholly in appearance from the overlying O^raz-flags, 
 and are evidently Rhaetic. The following details were noted at about 
 the middle of the anticline : 
 
 Railway -cutting north of St. Mary Church Road Station. 
 
 FT. IN. 
 
 Limestones, thin-bedded, blue, somewhat nodular, or 
 breaking into blocks ; 2 to 6 inches thick, with shale 
 partings 3 to 4 inches thick - - 10 to 15 
 
 Limestone-flags, 2 to 6 inches thick, with thin partings 
 of shale ; strongly jointed ; full of Ostrea liassica. 
 (The O^rea-beds) - 94 
 
 * Trans. Geol< tioc. Series 2, voU i. (1824), p, 301, 
 
42 T*'i<t. 
 
 FT. IN. 
 
 1. Shales. dark-brown, lissilo. soft - f> 
 
 '2. Marl, hard, dark-grey, shaly Q 
 
 3. Shales. grey ,-, 
 
 Rn.^Tir 4. Marl, dark-grey, hard. becoming in places a lime.itone 3 
 
 .">. Shales, grey 4 
 
 (i. Marl, grey, lianl 4 
 
 7. Mails, shaly. dark-grey, exposed for 1 
 
 A few oysters occur in beds '2 and 4. Dr. F. L. Kitchin has identi- 
 fied the following additional fossils : In bed 2, Modiola minima, 
 Ccrithium sp. ; in bed 4, Ccrithium sp., Protocardium, Modiola 
 minima, Pleuromya sp., Phasianetta ? Plcurophorus elon- 
 gatus, Protocardium philippianum ? 
 
 Bed 1 appears to represent the laminated limestone or ' slate ' 
 which lies immediately below the CMrea-beds at Penarth, and 
 the grey shales and marls below it correspond to the blue marls with 
 Modiola. etc., which are found at the top of the RlhTtic group of 
 that section. 
 
 South of the station a shallow cutting traverses the Ostrca-bcds, 
 and, farther on, a gentle anticline which brings up to view about 
 six and a half feet of the underlying R ha? tic shales and marls, as 
 shewn in Fig. 3. 
 
 Railway-cutting south oj St. Mary Church Road Station. 
 
 FT. IN. 
 
 LIAS Limestones, thin-bedded, flaggy, blue ; (the Ostrea-hcds) 10 
 / Shales, brown, thin, and platy 8 
 
 Marl, light-brown, fossils 4 
 
 Shales, brown, with impersistent limestone ; Outre a 
 
 liassica, Modi old 9 
 
 Marls, light-brown 3 
 
 p j Shales, brown and blue ; Osirea liax^ica and other fossils 
 
 not determinable, including gasteropoda 3 
 
 Limestone, hard, line-grained, light-blue, highly fossil- 
 iferous Modiola minima ? Protocardium philip- 
 pia n u in . Pie uropJi or us ? 6 
 
 Oolite, f sandy, blue-hearted, but weathering to a brown 
 
 sandstone ; exposed for - 1 
 
 The fossils have been identified by Dr. F. L. Kitchin. 
 
 A small fault crosses the cutting obliquely a little south of the 
 centre of the anticline, having a direction of about W. 30" X., and 
 a downthrow X. 30 E. of five feet. Beyond this fault Ili<- dip, about 
 4 or 5. soon brings down the Osf/ra-beds to the level of the rails ; 
 and not far beyond this these flaggy limestones take on a stronger 
 dip, and more nodular limestones weathering to a lighter buff colour 
 are thrown against them by a concealed fault probably of ten feet or 
 so. Beyond this fault for about 115 feet distance the section is 
 obscured, but then flags resembling the Ostrca-buds reappear and 
 dip obliquely to the cutting at about 30. They soon flatten 
 however, and a little farther on are cut by a fault which, although it 
 makes little show, has a considerable downthrow north and brings 
 up again the Rha'tic beds, the sandy oolite being exposed for a 
 depth of about ten feet. A few yards farther on two small faults 
 
Rhcetic. 
 
 
 
 m a >> 
 
 ,2 ,2 -a 
 cs '% a 
 
 cross the cutting ; the more northerly, which has a downthrow south 
 of four feet, is clearly visible on the west, but not on the east side of 
 the cutting ; the other has 
 a downthrow in the same 
 direction of two feet nine 
 inches. A point of in- 
 terest about this latter 
 is that the fault-plane 
 shifts laterally south- 
 wards for four feet eight 
 inches on passing down- 
 wards from the soft marls 
 into the harder sandy 
 oolite, there having evi- 
 dently been some hori- 
 zontal movement of the 
 soft over the hard beds 
 along the bedding-planes. 
 Beyond this point the 
 Ostrea-beds and the over- 
 lying more nodular lime- 
 stones gradually descend 
 to the bottom of the 
 cutting. 
 
 The most noteworthy 
 fact exhibited by this 
 cutting is the replace- 
 ment of a large part of 
 the soft Rhaetic marls 
 and shales, as seen at 
 Penarth, by massive 
 sandy oolite. The re- 
 placement may be re- 
 garded as an intermediate 
 stage in the conversion of 
 the normal type of Rhaetic 
 into soft yellow sand- 
 stones as developed at 
 St. Hilary and west of 
 Cowbridge. The oolite 
 probably represents the 
 nodular beds, number 5, 
 and some of the beds 
 beneath, of the south 
 end of the Cowbridge 
 cutting (p. 47). It has 
 been sliced (E. 3252) 
 and examined under the 
 microscope, and is thus described by Dr. Flett : 
 
 Oolitic limestone with a few shell fragments. The oolitic grains have in 
 
44 Trias. 
 
 most cases a centre of calcite of or quartz which seem to be rounded grains 
 around which a deposit of oolitic character has formed. There is little room 
 for doubt that the rounded quartz is of detrital origin, and the calcareous 
 fragments are sometimes crinoidal, sometimes pieces of limestone. The 
 cementing matrix is granular calcite. There are also one or two pieces of 
 felspar in the heart of oolitic grains. 
 
 The existence of oolitic structure in the Rhaetic strata then 
 included in the Lias was noticed by Buckland and Conybeare. 
 Speaking of the Lias of the south-western districts of England they 
 remark that " between the white lias and the black shale, are 
 strata of dark-grey marl .... sometimes perfectly stony, and 
 then acquiring a granular and coarsely- oolitic structure. In this 
 state it is known by the name of corn-grit."* The authors do not 
 state where this oolitic rock occurs ; but Murchison,f a year or so 
 later, quotes this paper by Buckland and Conybeare as the source 
 of his knowledge of the existence of oolitic Lias at Cowbridge. 
 
 Farther along the Rhgetic outcrop towards Cowbridge there are 
 road-sections between How Mill and The Herberts and elsewhere 
 which show sandy limestones with traces of black shale under- 
 lying the Ostrea-beds of the Lias and overlying green rocky marls, 
 the topmost beds of the Keuper. On the edge of the valley east 
 of Llandough Rectory the Rhaetic sandstone has been quarried for 
 additions to the church and schools. Thence the outcrop can be 
 followed as far as the north-west corner of Coed-y-castell, 200 yards 
 east of Newhouse ; but the occurrence on the fields below the house 
 of pieces of sandstone, one containing fish-remains, indicates that 
 the Rhaetic extends thus far before it is overlapped by the Lias. 
 
 Rhaetic strata at Cowbridge were first recognised by Mr. F. T. 
 Howard J in 1897 ; they were laid open on the construction of the 
 Aberthaw railway, which intersects the Lias outlier and shows it to 
 consist of a syncline ranging in an east and west direction. The 
 beds are exposed at the southern end of the Cowbridge railway- 
 cutting, and there are good reasons for believing that certain 
 rocks which crop out at the northern end of the same cutting are 
 also of Rhaetic age. 
 
 North end of the Cowbridge railway-cutting. 
 
 FT. IN. 
 10. Limestones, hard (south of Gardiff-road bridge) ; 
 
 Ostrea and other lamellibranchs, about - 45 
 
 I J 9. Sutton-stone (north of Oardiff-road bridge) - - 70 
 
 v 8. Limestones, thin-bedded, blue ; Ostrea liassica ? - 90 
 7. Limestones, thicker-bedded, impure and marly ; 
 
 Ostrea liassica ; about 40 
 
 6. Marls and shales, hard, friable, calcareous, greenish- 
 buff, with occasional pebbles ; Cardium ? 00 
 
 RILETIC ? 
 
 5. Limestones, sandy (? oolitic) ; Cardium? - - 50 
 4. Rock like Sutton-stone, white, pebbly, with shell-frag- 
 ments and a coral 26 
 
 * Trans. GeoL Soc., series 2, vol. i. (1824), p. 300. 
 t Trans. Geol. Soc., series 2, vol. ii. (1826), p. 362. 
 
 % The Geology of the Cowbridge District. Tranti Cardiff Nat t Soc., vol. 
 xxx, (1897-8)* 
 
Rhcetic. 45 
 
 FT. IN. 
 
 (3. Marls, pale-green - 1 8 
 
 2. Sandstone, impersistent 
 1. Breccia, exposed for 6 
 
 The top of the breccia (1) is exposed on the east side of the cutting 
 nineteen yard south of the Aberthin Road bridge ; it consists of dark 
 cream-coloured rock (see p. 32). Adhering to its somewhat uneven 
 surface there are one or two inches of (2) pale-green very fine- 
 grained calcareous sandstone visible at about fifteen yards south of 
 the bridge. Four yards farther on, however, there rests directly on 
 the breccia pale-green, soft, friable calcareous marl (3), which contains 
 at its base small well-rounded pebbles of Carboniferous Limestone, 
 chert and quartz. No fossils having been seen in either the green 
 sandstone or the green marl, it is difficult to determine their age ; 
 the former may be Rhsetic and the latter a reversion to Keuper 
 Marl conditions, such as we have at Pyle (p. 36); but on the whole 
 it is perhaps safer to regard them as Keuper. 
 
 Above these doubtful beds succeeds (4), a massive white or light- 
 grey limestone containing rounded and angular fragments of Car- 
 boniferous oolite up to eight inches in length, but averaging about 
 one or two inches. In the apparently amorphous matrix of the 
 lighter coloured parts there are numerous small cavities such as 
 might be due to the dissolving out of shell-fragments, but some of 
 the hollows are evidently due to the decomposition of small frag- 
 ments of impure limestone, and in such cases contain a loose brown or 
 yellow material. In this condition the rock corresponds in character 
 to Sutton-stone as described on p. 59. 
 
 Above this comes (5) an obscurely oolitic sandy limestone, brown 
 but blue-hearted, and irregularly bedded ; it contains a few small 
 detrital fragments of limestone, together with an occasional cast 
 of a lamellibranch (possibly a Cardium), and fragments of what 
 appears to be wood. Treated with acid, this rock leaves a con- 
 siderable residue of fine sand which consists chiefly of rounded 
 grains of quartz, some few angular chips of brown chert, and oc- 
 casional fragments of felspathic material. The quartz-grains were 
 presumably derived from a distant source, but the angularity of 
 the chert-chips suggests a local origin. 
 
 The strata seen next consist of alternating buff marls and shales 
 (6), with a thin conglomerate of small limestone-pebbles ; they 
 contain a few dwarfed oysters, some fragments of wood, and casts 
 of small lamellibranchs. 
 
 Above these, finely oolitic limestones (7) and (8) set .in again, 
 averaging nine inches to a foot in thickness ; they contain a few 
 specimens of Ostrea, probably 0. liassica, and continue as far as 
 the north side of the Cardiff Road bridge. 
 
 With regard to the systematic position of these poorly fossi- 
 liferous beds, it is safe to regard everything above the top of bed (3) 
 as post-Keuper ; but whether beds (4),( 5), and (0) are Rhsetic or not 
 is uncertain. That they are of this age is suggested by the strong 
 probability that bed (8) with, possibly, (7), represents the Ostrea^ 
 beds of the Lias. 
 
46 Trias. 
 
 Above the beds last described, there lies a rock having the same 
 general characters as bed (4), but devoid of large fragments of lime- 
 stone ; it crops out immediately north of the Cardiff Road bridge. 
 Above it, and south of this bridge, the cutting enters very hard 
 thicker-bedded limestones without many pebbles, and without marl 
 or shale partings. At about thirty or forty yards south of the bridge, 
 and forty feet above the base of the Lias as seen at the south end of 
 the cutting, and presently to be described, the limestonesare unusually 
 massive, and contain angular chips of chert ; but at the axis of the 
 syncline, near the milepost 23, they are more evenly stratified, and 
 average only about one foot in thickness ; here also one or two thin 
 bands of fine conglomerate occur. A rock half-way up the west side 
 of the cutting yields ossicles of Pentacrinus, with Ostrea (cf. irregularis, 
 Miinst.), 0. liassica, and another species of Ostrea large and coarse- 
 ribbed, and somewhat resembling 0. multicostata. This horizon is 
 about sixty feet above the base of the Lias, and is markedly fossi- 
 liferous, though the specimens are broken and difficult to extract. 
 
 Fig. 4. Section at south end of Cowbridge Cutting. 
 By T. C. CANTRILL. 
 
 N. 
 
 Old Lane. 
 
 Level of Rails. 
 
 L.L. Lower Lias limestones. 
 
 RH ETIC. d, shales and marls, c, limestones, b, marls, a, black shales. 
 KEUPER. K, T.reccia. C.L., Carboniferous Limestone. F., Fault. 
 Length of section about 160 feet. 
 
 Between Bridges 27 and 28 lower beds come into view, con- 
 sisting of oolitic blue limestones varying from two to six inches in 
 thickness, and separated by thin shale-partings ; Ostrea liassica 
 occurs in profusion, but in poor preservation. Chert-nodules abound, 
 but there are no foreign fragments. 
 
 That the lowest of these limestones are the Ostrea-beds is put 
 beyond doubt by an examination of some shales, marls, and lime- 
 stones which rise from beneath them. These make their first appear- 
 ance half-way between bridges 27 and 28 ; they are shown to a depth 
 of seven feet on the eastern side of the cutting and extend for 
 twenty- four feet, when they are thrown out of sight on the south by 
 an east and west fault which brings down the Lias. The beds 
 exposed are number? 1 to 5 of the following section (p. 47).^ 
 
47 
 
 At forty-seven feet south of the fault they reappear, which enables 
 us to ascertain the throw of the fault to be ten yards. In this second 
 exposure, which extends for. a horizontal distance of about seventy 
 feet, the cutting traverses the whole group and shows that it is about 
 twenty feet thick. It proves also that it rests on a thin and im- 
 persistent grey* breccia, apparently Keuper, and that this in turn 
 reposes unconformably on the Carboniferous Limestone. The accom- 
 panying sketch illustrates the unconformity. 
 
 Mr. F. T. Howard* gives an illustration of this cutting, and records 
 details of the Rhaetic beds in his paper on Cowbridge. 
 
 The complete succession of the beds here in descending order is 
 as follows : 
 
 South end of the Cowbridge Cutting. 
 
 LOWER LIAS, Ostrea beds. Ostrea liassica. 
 
 FT. Ix. 
 
 inch 
 
 RH^TIC. 
 19 ft. 8 in. 
 
 shale - 
 
 1. Shale ; fissile, dark-brown, weathering cream 
 
 colour, fossils 
 
 2. Marl ; hard, brownish-green, fossils and wood 
 
 3. Marl ; friable, light-brown, more shaly at base 
 
 Limestone ; pebbly and highly fos- 
 
 oiliferous - - 1 
 
 Shale -parting - - - 1 
 
 4. I Limestone ; few fossils - - 3 
 
 Shale-parting - - - - 
 
 Limestone, few fossils - - 4 
 
 Marls, hard - - 4 
 
 5. Limestone ; impure, nodular, few fossils 
 
 6. Limestones ; marly, thin-bedded, with 
 
 partings ... ... 
 
 7. Marl or marly limestone ; hard, brown - 
 
 8. Marls and shales, alternating ; brown 
 
 9. Limestone, impersistent ; with pebbles of limestone 
 
 and chert. Fish- teeth - 3| inches to 
 
 10. Marl ; a few limestone-pebbles and fish-teeth 
 
 11. Marl; fine-grained, with flinty fracture ; pebbles 
 
 up to three-quarters of an inch in length - 
 
 12. Limestone ; shelly and pebbly, like Sutton-stone 
 
 13. Marl ; hard, buff ... 3 inches to 
 
 14. Marl ; similar 
 
 15. Marl ; harder, pebbly, fossils .... 
 
 .16. Shales; black, locally sandy, pebbly at base. 10 in. to 1 
 
 8 
 
 5 
 
 3 
 
 1 2J 
 
 1 4 
 
 4 
 
 1 
 
 9 
 
 2 8 
 
 4 
 
 7 
 4 
 
 TRIAS. 
 
 Breccia ; grey, hard, with cherty patches ; frag- 
 ments of limestone, chert, and quartz 
 
 CARBONIFEROUS LIMESTONE; 
 
 1 
 
 The shale and marl (1 and 2) weather away from the overlying 
 Osfrea-flags in such a way as to render the junction highly conspicu- 
 ous. The shale is crowded with obscure remains of a small lamelli- 
 branch, and contains also Avicula and Modiola. It probably 
 represents some dark-grey and brown paper-shales which occur in 
 
 Trans. Cardiff Not. Soc., vol. xxx (1897-8). 
 
4* Tria*. 
 
 a similar position at Penarth, and which Mr. H. B. Woodward * 
 groups with the Lias. The marl (2) resembles Bed 6 of the section 
 at the north end of the cutting. 
 
 Bed 9, which is a markedly conglomeratic band, thins 
 out on the east side of the cutting among sandy marls, while a 
 similar pebbly rock comes in immediately below and underlies the 
 first for a distance of ten inches, passing northwards into marls. 
 Bed 12 differs in no obvious respect from the Sutton-stone of the 
 Lias ; the included limestone -pebbles range up to one and a half 
 inches in diameter. 
 
 The following fossils have been determined by Dr. F. L. 
 Kitchin : 
 
 Rhcetic Fossils, South end of Cowbridge Cutting. 
 
 Bed 1. Modiola, Avicula. 
 
 2. Modiola minima, Sow., Pleuromya ?, Cerithium sp., Area ?, and 
 indeterminable lamellibranchs, gasteropods, and wood 
 fragments. 
 
 3. Protocardium pTiilippianum ? Dunk. 
 
 4. Modiola minima, Sow., Ostrea, Pleuromya ?, Schizodus. 
 
 9. Saurickthys acuminates, Ag., Gyrolepis Alberti, Ag. Pecten valoni- 
 
 ensis, Defr. 
 
 10. Gyrolepis Alberti, Ag. 
 
 15. Cardium cloacinum, Quenst., Pecten valoniensis, Defr. Myophoria 
 . nov. sp. ? (cf. eleyans, Alberti). Protocardium. 
 
 This section differs from that of Penarth in that the thickness of 
 Rhaetic beds is ten feet less, in the greater development of marls 
 of the White Lias type at the expense of the black paper-shales, and in 
 the occurrence of conglomerates. 
 
 The Ostrea-beds are less readily recognised at the north end of the 
 cutting owing to their modified character and the scarcity of Ostrea, 
 but are probably represented by some limestones, containing a few 
 specimens of that fossil, which have been quarried in the yard of 
 Slade Farm. Again, according to a measurement made at the south 
 end of the cutting, the base of the Lias ought to lie about twenty 
 feet below the top of the seven-foot band of Sutton-stone at the Cardiff 
 Road bridge. There is, therefore, space enough for not only the 
 Osrea-beds, but also some part of the Rhaetic group. The distance 
 is only 500 yards, yet there is only the faintest likeness between the 
 two sections. All that can be attempted in the way of correlation is 
 to point out that Bed 6 at the north end resembles Bed 2 at the south. 
 
 Presumably these Rhaetic strata are soon overlapped, for no certain 
 evi dence of their existence elsewhere round the Lias outlier has been 
 obtained. 
 
 The Lias beds in the cutting, judged by their aggregate thickness, 
 represent not only the Os^raz-beds and overlying limestones of the 
 A. planorbis zone, but also part of the overlying marls and shales 
 (Lavernock Shales) of the zones of A. angulatus and A. BucJclandi 
 of Penarth ; all, however, have assumed the condition of hard 
 limestones. 
 
 f The Jurassic Rocks of Britain, vol< iii,-, p. 119, Mem, Geol, Surv,. 
 
Rhcetic, 49 
 
 An analysis of one of the Rhaetic limestones overlying the black 
 shales at the southern end of the Cowbridge cutting was made 
 at St. Mungo's College, Glasgow, under the superintendence of 
 Prof. T. Rhymer Marshall, for Mr. F. T. Howard, with the following 
 results : 
 
 J^ree mca 
 pi a ,. 
 
 
 lO'OJ- 
 
 06 
 
 CaCO., 
 
 TTI -C<f~\ 
 
 
 - 78-97 
 
 .OO 
 
 FeCO 3 
 
 MgCO ;5 
 Moisture, etc. 
 
 
 42 
 6-39 
 62 
 
 The rock is therefore a somewhat sandy magnesian limestone. 
 
 Pendoylan Outlier. In the Pendoylan outlier sections are poor. 
 A well recently sunk in a field on the west side of the main road, eighty 
 yards north-west of the school, is said to be fourteen feet deep ; it 
 passed through the Rhaetic black paper-shales with Pecten-limQ- 
 stones containing spines and tubercles of Acrosalenia? and 
 fish-remains, and entered cream-coloured rocky marls, presum- 
 ably the top of the Keuper. Pieces of Pectew-limestone occur at a 
 pond 100 yards south-east of the vicarage, and debris of black paper- 
 shales and limestone along the western edge of a coppice at Plwcau- 
 Dafydd, apparently bounded on the east by a small fault which throws 
 down the Lias. A minute Rhaetic outlier south-east of Ty'n-y-cae on 
 the north-west side of the Cowbridge Fault has been already referred 
 to on p. 27. 
 
 The outcrop of Rhaetic beds which runs from this fault north- 
 westwards is largely conjectural, the whole country being buried 
 under drift. It was to be expected, however, that the tea-green 
 marls and breccias exposed in the lane leading westwards from 
 Tre-Dodridge would be succeeded by Rhaetic at the foot of the rising 
 ground occupied by Coed Leyshon, and this expectation was fulfilled 
 on the sinking of .a small pit in search of coal, about the year 1888, in 
 the north-east corner of the field containing the foundations of Ty-du, 
 closa to an ancient entrenched mound on the Cwm Farm. The 
 shaft passed through some gravel into black paper-shales containing 
 Rhaetic fossils (shell-fragments and a tooth of Sauriehthys acumin- 
 atus, Ag.), and then into pebbly green rocky marls, the top of 
 the Keuper, How far to the north-west this outcrop extends is 
 problematical, but it is certainly overlapped before it reaches 
 Ystradowain. 
 
 Western part. 
 By A. STRAHAN, in part from notes by R. H. TIDDEMAN. 
 
 The Rhaetic outcrops which have been described in the foregoing 
 pages lie south of the Triassic island shown on the map forming 
 Fig. 2. The survival of this island into Liassic times is proved by 
 the fact that neither Rhaetic nor Keuper were deposited upon it, and 
 we therefore have to cross to its northern margin to regain 
 
 7665. E 
 
50 Trias. 
 
 a Rhaetic outcrop. Though the map shows the distribution of 
 the land at the close of the Keuper, it serves in great part also 
 to illustrate the close of the Rhaetic period. A good deal of 
 land had disappeared near St. Hilary and Bonvilston, as can be seen 
 by the fact that the Rhaetic overlaps the Keuper at those places, 
 and no doubt the island had shrunk in other places also, but the 
 general distribution of land and water remained much the same. 
 The tract now to be examined occupies the site of the Triassic 
 strait shown on the north side of the Rhaetic island. It will 
 of course be understood that the present outcrop of the 
 Rhaetic strata has been determined by unequal upheaval and denuda- 
 tion, and does not coincide with the original margin. 
 
 The change in the Rhaetic sediments, the progress of which has 
 been traced near Cowbridge, here reaches a further stage. Sand- 
 stones have^ taken the place of the sandy oolitic limestones, and 
 shales have become quite subordinate. The exposures range from 
 St. Mary Hill to Pyle, and will be described in geographical order 
 from east to west. 
 
 West of Pencoed a strip of Rhaetic beds has been let down between 
 two faults ranging west-north-west. The strata consist mainly of 
 sandstones which have been worked for building- stone at Saunder's 
 Quarry on the south side of the brook and at Hendre Quarry on the 
 north side, where they have also been used for silica in firebrick 
 making. The rock may be described as a rather fine-grained free- 
 stone, white but with light-greenish bands. Ripple-marks are not 
 infrequent on the bedding-planes. The rock from a trial-drift a 
 little to the north of Saunder's Quarry contained Puttastra arenicola, 
 while scales and fragmentary bones of Gyrolepis Alberti, Ag. were 
 collected in the road to Dyfiryn. In the Hendre Quarry about 30 
 feet of sandstone are exposed, the lower part being massive and 
 the upper part more thinly bedded. The rock rests upon 
 the Keuper Marls (tea-green beds) described on p. 33. 
 
 A small outlier of this rock is faulted in on the top of Coed Mwstwr. 
 A yellow limestone-conglomerate,which can be seen west of the fault, 
 and presumably crops out also round the east side of the outlier, 
 may represent the tea-green marls in their literal type, though the 
 Hendre section showing these strata in their normal type is only 
 about 600 yards distant. By comparing the levels of this outlier 
 with the Hendre rock, we ascertain that the throw of the fault 
 between them cannot be less than 100 feet. It probably increases 
 eastwards, but it is lost to view under the drift of the Ewenny valley. 
 The fault which throws the Hendre rock on its north side against 
 Millstone Grit is probably much greater. 
 
 In approaching the St. Mary Hill Rhaetic outcrop from Coychurch 
 we pass a quarry in the Ostrea-beds, 300 yards east of the mill at 
 Persondy. They dip to the south-west and from beneath them 
 there rise in succession White Lias, green Rhaetic marls with a red 
 band, and then the sandstone which forms the lower part of that 
 group. This is followed by a space in which the uppermost green 
 Keuper Marls probably crop out, and then by light-coloured 
 
Rhcetic. 51 
 
 conglomerate. The sandstone has yielded obscure fossils (Mollusca) 
 with bone-fragments and scales of Gyrolepis Alberti. On St. Mary 
 Hill Down huge blocks of the Rhaetic sandstone are scattered about, 
 giving much the appearance of a Millstone Grit moorland. The 
 sandstone lies in the form of a compound anticline, striking east- 
 south-east and much broken by strike-faults. It probably rests 
 on conglomerates. The joints of several of the blocks are covered 
 by a quartzose fault-rock. 
 
 In these sections the occurrence of red and green marls high up in 
 the Rhsetic group should be noted especially. In appearance they 
 precisely resemble red Keuper Marls and, though thin, they may be 
 recognised at intervals all the way to Pyle. The conclusions to be 
 drawn from this recurrence of the Keuper Marl type of sediment have 
 been previously mentioned. 
 
 The road from Coychurch to Coity runs for the most part on the 
 Rhsetic outcrop. The sandstone is exposed occasionally and forms 
 a scarp below the road. To the south of the road gentle slopes lead 
 up to the outcrops of the upper Rhastic strata and the Ostrea-beds 
 which are visible in a few little quarries. 
 
 In Coity a road-section west of the Castle exhibits sandstones 
 and shales with greenish colouring and a little red mottling. The 
 strata at first sight much resemble Keuper, but they yield Modiola 
 minima in abundance, a fossil which is plentiful in the upper part of 
 the Rhsetic group. A fault close by brings up red marl and con- 
 glomerate which are certainly Keuper. The massive sandstone 
 which forms the lower part of the Rhsetic group crops up in several 
 places in the village. 
 
 At Quarella this sandstone is extensively worked for building and 
 other purposes. The rock is white or pale-green and is sawn into 
 large slabs and blocks. Of the two quarries which are being worked 
 the deeper lies to the south of the lane and yields the following 
 section : 
 
 Mr. M'GauVs Quarry, Quarella. 
 
 FT. IN. 
 
 Lower / Blue limestone, Ostrea liassica and Pleuromya - 2 
 Lias I Glay, about - .... 1 
 
 Clayey limestone representing the Cotham Stone, 
 variable grey and green clay with variable cal- 
 Rhsetic-] careous bands which have been burnt for cement - 
 
 making. Lima sp. and other lamellibranchs - 2 6 
 Hard and soft white and pale-green sandstone, used 
 
 for building, grindstones, etc., seen to 35 
 
 The stone from this quarry has been examined under tbe micro- 
 scope by Dr. Flett, who furnishes the following description : 
 
 3816. An impure, rather fine-grained, pale-green sandstone, consisting of 
 small grains of quartz and felspar, with a little chert, iron-ores, chlorite, 
 zircon, etc. The green colour arises from the presence of a chloritic (?) 
 mineral in the fine-grained material between the sand-grains, and partly 
 also in the weathered felspars. The rock contains a few pieces of tourmaline 
 and practically no carbonates. 
 
 7665. 
 
52 Trias. 
 
 In a pamphlet on the Quarella Quarries* it is stated that the 
 three best beds are the White Bed, 10 feet, the Grey Bed, 4 feet, 
 and the Green Bed, 9 feet thick. The average densities are, White 
 Bed 2-33, Green Bed 2'39, Grey Bed 2'40, and top rock 2'46. 
 
 The White rock absorbed 6 per cent, of its weight of water, the 
 Green 4*5 per cent., the Grey 4'33 per cent., and the top rock 3*25 
 per cent., after having been immersed in water for 12 hours. The 
 cement by which the grains are bound together in the rock is 
 siliceous. Two six-inch cubes of the, white and green stones 
 crushed respectively at 546' 4 and 438*4 tons per square foot, 
 according to Mr. D. Kirkaldy. An analysis by Mr. J. S. Merry 
 gave the following result : 
 
 Silica - 91-20 . 
 
 Alumina - - - 3-35 
 
 Protoxide of Iron 0-58 
 
 Lime - 1-23 
 
 Magnesia - - - 0-25 
 
 Combined Water 2-57 
 
 Loss, and possibly a little Soda - - 0-82 
 
 Another quarry to the north shows, under some gravel and loam, 
 a massive sandstone, fifteen feet thick, underlain by twenty feet of 
 more rubbly sandstone. Exposures of the sandstone may be seen 
 in the river south-west of the Quarella railway-bridge, and again at 
 the bend south-east of the asylum. 
 
 A large quarry opposite the Angeltown Asylum was opened for 
 building-stone for that structure. The section is now obscured, 
 but Rhsetic fossils may be seen in the quarry-rubbish. 
 
 The railway-section at Cwrt Colman, which was described in detail 
 by E. B. Tawney in 1865,'f is now partly overgrown, but some of the 
 beds examined by him on the south side of the railway can now be 
 seen on the north side. The following descending section is con- 
 structed from the descriptions given in his paper (loc. cit., p. 71.) 
 
 Cwrt Colman, south side of the Great Western Railway. 
 
 Section by E. B. Tawney. 
 
 FT. IN. 
 
 White, pale-green and yellow sandstones and sands - - 17 
 
 Shales, marls and sandstones - 9 
 
 Three beds of siliceous limestone with fish-scales, Anomia. 
 Shales - 3 
 
 Soft chocolate-coloured sandstone with Avicula contorta and 
 
 Pecten valoniensis 1 
 
 Dark shales 3 
 
 Siliceo-micaceous limestone with irregular marly surfaces. 
 
 An occasional quartz-pebble and reptilian bone with 
 
 an abundance of teeth and scales of the fishes named 
 
 (op. tit.) The Aust Bone-bed. Two inches to 3 
 
 Shales, including a grey and green marly limestone, the 
 
 grey part being full of shells - 3 
 
 White or yellowish massive sandstone with a few small 
 
 quartz -pebbles ; coprolites at the top - - - - 8 to 10 
 
 * Quarella Quarries, Bridgcnd, 1893. 
 
 t Quart. Journ. Geol. 8oc., vol. xxii., p. 70 (1866). 
 
Rhcetic. 53 
 
 All these strata were referred by Tawney to the Rhsetic group, and 
 the scarcity of calcareous and aluminous matter as compared with 
 Penarth was commented on. For the reason stated the details 
 could not be verified, but a somewhat different succession can now 
 be determined in a road south of Melin Cwcw. We there obtain in 
 descending order : 
 
 f Blue limestone with Ostrea liassica, Pleuromya crowcombeia ? Tate 
 ( non Moore, and a coral (Ostrea-beds). 
 
 Buff marlstone weathering white, probably representing the Gotham 
 
 Stone. 
 Green marls with a band of red marl, closely resembling Keuper 
 
 Marl. 
 
 Calcareous sandstone, several feet thick. 
 Tough shelly limestone, in part resembling Sutton-stone. 
 
 Rhaetic 
 Beds. 
 
 The strata exposed in the north side of the railway-cutting evi- 
 dently rise from beneath these, and themselves rest on the thick 
 Rhsetic sandstone which forms the crest of the hill of Cwrt Colman. 
 They include the bone-bed referred to by Tawney and some soft 
 strata. In this locality again the observation that red and green 
 marl are associated with the upper part of the Rhsetic group is con- 
 firmed. Higher up the valley some old pits show black shales resting 
 on graen limestone and white marly limestone. The green limestone 
 is full of shells, which, however, cannot be broken o^t, but there is 
 little doubt that the strata belong to the upper part of the Rhaetic 
 series. 
 
 The following results of microscopic examination of specimens 
 from this neighbourhood have been furnished by Dr. Flett : 
 
 3818. Melin Cwcw ; in upper part of the Rhsetic, among green marls. 
 Very fine-grained grey limestone, with a few rounded spots and elliptical 
 areas of crystalline calcite. This looks as if it had been originally a fine 
 limestone- mud. When treated with acid it leaves a considerable amount of 
 fine yellow argillaceous residue. I can find no organic structures in it. 
 
 3820. Melin Cwcw [the "tough shelly limestone" of the section given 
 above]. Shelly limestone, in which the numerous shell -fragments have been 
 replaced by a mosaic of crystalline calcite similar to that of the matrix. 
 The rock has throughout a highly crystalline character, but the outlines of 
 the shells have been preserved. A few rhombohedra of ferriferous dolo- 
 mite (?) are present. 
 
 3822. Melin Cwcw, close to 3820. [A very shelly limestone which looks 
 like a sandstone.] Shelly limestone, with worn shell-fragments which 
 internally consist of a coarse calcite -mosaic, though the external form is 
 retained. Dissolves in acid, leaving only a small residue. Matrix also of 
 crystalline calcite ; a few grains of dolomite. 
 
 3815. South of the railway and south-west of Cwrt Colman. Greenish, 
 cherty, concretionary or brecciated limestone. The green colour is due to 
 glauconite or chlorite. In the green matrix lie irregular fragments of com- 
 pact creamy limestone. The rock shows no fossils, and the appearance 
 of the slide would lead to the opinion that it is concretionary, as 
 coarsely crystalline and finely crystalline patches alternate, and there are 
 traces of cavities filled with caleite, chlorite, and chert. 
 
54 Trias. 
 
 The Rhaetic outcrop broadens out southwards to Laleston. The 
 ground north-west of the village is underlain by sandstone, but above 
 that rock there are indications of black shale, and there was formerly 
 an exposure of limestone, the age of which led to dispute. The only 
 section appears to have been the Laleston Churchyard Quarry re- 
 ferred to by Tawney (op. cit., p. 77). According to him it showed 
 Sutton limestones beneath " the Monofo's-beds," and in sonn shales 
 there he found spines and portions of the test of an echinoderm 
 (Hemipedina ?). His complete list from the locality " Laleston " 
 (op. cit., p. 79), included the following species : Avicula contorta, 
 Portl., Axinus elongatus, Moore, A. cloacinus, Moore, Myophoria 
 poster a, Qu., Modiola minima, Anatini precursor, Qu., Monotis 
 decussata, Ostrea liassica, Strickl., Hemipedina sp. On this evidence 
 Tawney identified the rock as Rhaetic and quoted it in support of his 
 contention that the Sutton-stone was of that age. 
 
 Moore, however, redescribed the quarry in the following year.* 
 He found in it a block containing an abundance of Lima gigantea, 
 Plicatida intusstriata and Ostrea liassica, and stated that the bed is 
 crowded with a coral, not, however, the species of the Sutton-stone 
 of Brocastle. Upon it there rested 1 foot of marl with perfectly pre- 
 served impressions of plants, together with Entomostraca and 
 Monotis decussata in abundance. He further points out that 
 Monotis decussata had been proved by him to range above the Rhaetic, 
 and states his belief that the rock belongs to the horizon of Ostrea 
 liassica. To this we may add that the'occurrence of Lima gigantea 
 and of corals supports Moore's view. The quarry is now covered up 
 so far as the lower rocks in it are concerned, and no other exposure 
 has been made. 
 
 At Cae Tor the OsZraz-beds have been quarried. Beneath them 
 there is some red and black marl, and then a coarse calcareous grit 
 with a few pebbles, in close association with a shelly and detrital 
 limestone containing fragments of corals, molluscs and echaioclerms, 
 together with small fragments of an older granular limestone and 
 grains of quartz. Dr. Flett finds under the microscope that there 
 ia also secondary quartz, sometimes with good crystal outlines, 
 replacing the calcareous material of the rock. The rock lies upon 
 or close above Triassic conglomerate, and is presumably of Rhaetic 
 age ; but it is evidently a beach-deposit, for it thins out within a few 
 yards to the south on the shores of the island shown in Fig. 2, p. 24. 
 Presumably it is below the limestone of the Laleston quarry, but 
 there is no direct evidence of their relations. The Stormy Down 
 sections, though they come next in geographical order, will be better 
 considered after a discussion of the fine exposures at Pyle. 
 
 A quarry to the south-east of the house formerly known as Pyle 
 Inn was opened about the year 1896, to get stone for railway- 
 viaducts, etc., It yields a section of the lower part of the Rhaetic 
 group, extending nearly if not quite to its base. 
 
 * Quart. Journ, Geol. Soc,, vol. xxiii., p, 519 (1867 V 
 
Rhcetic. 55 
 
 " Pyle Inn." 
 
 FT, IN. 
 Soft drab and green sandstone with shell-beds. Natica pylensis, 
 
 Cylindrites oviformis, Myophoria - 12 
 
 Ochreous bed 4 
 
 Fine sand 13 
 
 Green and grey clay - 36 
 
 Calcareous nodular bed. Acrodus minimus 3 
 
 Shales 13 
 
 Calcareous nodular bed with fish-remains ... 3 
 Shales - 1 8 
 Fine whitish sandstone with plants, and at top a seam of quartz- 
 pebbles with remains of Hybodus and Acrodus ; seen to - 12 
 
 The uppermost green marls of the Keuper are exposed in a slope 
 leading down to the house, just below the lowest rock reached in the 
 quarry. 
 
 The Rhaetic sandstone has also been much quarried west of Pyle 
 Church, the outcrop having been followed for a considerable distance. 
 Much stone was got here for the building of the modern residence at 
 Margam Abbey. Near the entrance a white sandstone is seen to a 
 thickness of 6 or 7 feet, with casts of Pullastra arenicola near its base. 
 Upon it then rests a greenish marl with about 6 inches of red marl, 
 corresponding, no doubt, to the green and red marls previously noted 
 at Cwrt Colman and St. Mary Hill. Further on in the quarry the 
 sandstone, where it has been more recently worked, shows bright- 
 green marly partings with ripple-marks, and yields Anatina precursor, 
 Myophoria, and Axinus doacinus, while Natica has been obtained 
 from the quarry-rubbish. The occurrence of the green and red 
 marls next above this sandstone, suggests that that rock lies high in 
 the Rhaetic group, and probably corresponds to the upper of the two 
 sandstones in the " Pyle Inn " quarry, which also yielded Natica 
 and other fossils. * 
 
 Of the many scattered openings on Stormy Down the greater 
 number have been made in search of sand for silica-bricks. One 
 
 * Some of the beds in the lower part of this quarry were stated by Tawney 
 in his paper already quoted (Quart. Journ. Geol. Soc., vol. xxii., p. 70.) 
 to be " very similar to the white Keuper sandstone near Bridgend," and on 
 page 72 (op. cit.) he shows that he is referring to the Quarella stone, and that h3 
 regards that rock as b^ing low down in the Keuper. That the Pyle and Quarella 
 stone are similar is true, but that they are not of Keuper but of Rhaetic age is 
 proved by the evidence given in these pages. Tawney remarks that he is 
 obliged to dissent from an opinion expressed by De la Beche in the Geological 
 Survey Memoir, vol. 1, p. 252, that the sandstones near Pyle Church are in- 
 ferior to the red marl. The words used by De la Beche were, " we here find, 
 near the church, greenish grey, grey and red sandstones, and we also observe 
 these to be covered by red or variegated marls in the same vicinity, support- 
 ing lias." It seems certain that De la Beche referred to the green and red 
 marls visible in the church- quarry above the sandstone, and not to the 
 Keuper marl. Tawney also noticed these variegated strata in the church- 
 quarry, and remarked of them, " These belong to the Avicula contorta series, 
 and not to the Keuper." It would seem, then, that there was really no 
 disagreement between these eminent observers as to the stratigraphical posi- 
 tion of the variegated marls. 
 
50 Triti*. 
 
 of these, lying south-west of the chemical works, shows about 20 
 feet of massive sandstone, much like a Carboniferous sandstone, but 
 resting on and containing thin seams of greenish clay. A little 
 further west there is a scarp of somewhat similar sandstone, and close 
 beneath it a swallow-hole into limestone, which at first sight looks 
 like Carboniferous Limestone, but which on closer examination 
 proves to be a purely chemical deposit devoid of organic remains. 
 The sandstone seems to represent the lowest sandstone of the " Pyle 
 Inn " Quarry, while the limestone is probably of Keuper age. 
 
 Further east, sandstones with green and yellow clays are exposed 
 in a long line of excavations. Some of the sandstones are bright- 
 green and ripple-marked, with a resemblance to the upper beds of 
 the { " Pyle Inn " Quarry. They contain casts of Avicula contorta, 
 Pleuromya ? and other lamellibranchs, in an extremely fragile 
 condition. A disturbance runs through the excavation in an east- 
 south-east direction. 
 
 The ' ; Little Cement Quarry " on the edge of the Down, south- 
 south-east of the Stormy Works, shows a bed of extremely shelly 
 white limestone, resembling those which occur on both sides of the 
 valley three-quarters of a mile west of Cwrt Colman. There, how- 
 ever, the shelly limestone lies above a white marly limestone, where- 
 as here it lies below such a rock. The material thrown out in deepen- 
 ing a well close by yielded Natica pylensis, Myophoria sp. (cf. 
 poster a, Moore) and Cylindrites oviformis. The white marly lime- 
 stone is similar to the rock formerly used for making cement. A 
 specimen has been examined under the microscope by Dr. Flett, 
 who reports as follows : 
 
 3819. Green-spotted fine-grained argillaceous limestone, with more or 
 less of a nodular concretionary structure. It contains no organic structures, 
 but the fine matrix is traversed by irregular patches and veins of clear 
 crystalline ealcite. It leaves an abundint fine argillaceous residue after 
 treatment with acid. 
 
 Some Rhsetic marls were formerly used for cement at Stormy 
 Works and were exposed at the time of Mr. Woodward's visit to the 
 locality, though they are no longer visible. He gives the following 
 section : 
 
 Stormy Cement Works. 
 
 Lias; S"^ P- 7-1. 
 
 FT. IN. 
 
 f Limestone-shales - --08 
 
 Hard compact limestone (like Sun-bed) 10 
 
 Shaly parting- 
 Rhac'tic J Hard compact and rather shaly limestone - 8 
 
 Beds. \ Black shales with thin bands of limestone, Pcctcn valoni- 
 [ part of J I cnsi$ 1 
 
 (Jrey and greenish marls with hard nodules (formerly 
 I used for cement) seen to depth of - -36 
 
 The thick Ilhnritic sandstones form an escarpment of coarse white 
 and yellow conglomerate near the top of Stormy Down. On some 
 of the big blocks casts of lamellibranchs may be seen, but in other 
 
Rkcetic. 57 
 
 respects the stone might be taken for Millstone Grit. Such blocks 
 are scattered all across the Down, and it was in one of these that the 
 impression of a large reptilian jaw was discovered by Mr. John 
 David. The specimen was presented to the Museum of Practical 
 Geology, and has been described by Mr. E. T. Newton as a left 
 dentary bone of a megalosauroid reptile, Zanclodon cambrensis* 
 There is scarcely room for doubt that the specimen occurred in true 
 Rhsetic strata of the zone of Avicvla contorta. 
 
 Anatina precursor, Quenstedt, and MyopJioria postera, Quenstedt, 
 from the Rhsetic sandstone of Stormy Down ; Pleurophorus elongatus, 
 Moore, Gervillia precursor, Quenstedt, and Anatina sp. from the 
 sandstone at Ty-fry, are preserved in the Cardiff Museum. 
 
 Quart. Journ. Geol. Soc., vol. liv., p. 646, 1899. 
 
58 
 
 CHAPTER VII. 
 
 LIAS. 
 
 INTRODUCTION. 
 By A. STRAHAN. 
 
 The map under description includes the western part of a broad 
 tract of Lias which occupies much of the Vale of Glamor an, and of 
 which the eastern pari was described in a previous part of this 
 Memoir.* 
 
 The following table gives in descending order the Liassic zones 
 existing in South Wales. They belong to the lower part of the 
 Lower Lias. 
 
 Zone of Ammonites^ [Arietites] semicostatus. 
 Bucldandi. 
 
 ,, [Schlotheimid] angidatus. 
 
 ., [Psiloceras] planorbis (including the Ostrea-beds). 
 
 The Lias alone of the Secondary rocks existing in South 
 Wales covered the whole area embraced in this map. The 
 island however which forms so prominent a feature in the Triassic 
 map (forming Fig. 2, p. 24), and which survived through Rhsetic 
 times with its main features little changed, remained above water 
 during part of the period of the Lower Lias. The proof of its sur- 
 vival lies chiefly in ths changing character of the Liassic strata 
 as they approach its shores. No doubt the lower strata thinned 
 out against the land, as did the Rha?tic and Keuper before them, 
 and were overlapped by higher beds as the subsidence proceeded, 
 but from the fact that the Liassic strata, whether shales or lime- 
 stones, tend to pass into massive limestones of which the horizons 
 are extremely difficult to determine, it has proved impossible to 
 work out the overlapping in detail. Though the existence of the 
 island therefore is abundantly evidenced by the fact that Lias rests 
 directly on the Carboniferous Limestone, and contains abundant 
 wave-worn detritus derived from it, the moment of its disappear- 
 ance cannot be determined, further than that it probably ceased to 
 exist during the period of the zone of Ammonites angulatus. 
 
 It will be understood that what was the highest ground in Liassic 
 times is not necessarily the highest ground now, owing to post- 
 Liassic earth-movements. For example, a post-Liassic antic-line 
 
 *The Country around Cardiff (Mem. Geol. Survey), chap. vii. 
 
 f In this table the original names of the zones are retained as a matter of 
 convenience. The names now used for the zone-fossils are added in square 
 brackets. 
 
Introduction. 59 
 
 has raised the Liassic base near Bonvilston to about 300 
 feet above sea-level, and the denudation which ensued has removed 
 the Lias from a tract about six miles long. Further north, though 
 there are patches to prove its former extension, the Lias has suffered 
 still more from subaerial waste, so that its present margin gives no 
 clue to the position of the original shore-line. The absence of 
 marginal types of limestone suggests that the shore lay a good deal 
 farther north, though at the same time it is hardly probable that 
 the Lias overlapped the Pennant scarp. Of the two types of Lias 
 therefore, the normal occurs throughout all the part of the map 
 which lies south of a line drawn through St. Mary Church to the 
 coast between Dunraven and Marcross. The same type is found 
 also near Bridgend and north of Pendoylan. The intervening area, 
 covering the site of the Triassic island referred to, has been and is 
 still in part occupied by Lias of litoral type. 
 
 To the normal type a description given of the Cardiff Lias is 
 equally applicable here. It consists in its lower part of hard slabby 
 limestones, crowded with Ostrea, passing up into evenly bedded 
 alternations of limestone and shale crowded withal m. [Psiloceras] plan- 
 orbis. Above these lie some thick sha 1 s or marls, almost devoid of 
 limestones, which belong to the zone of Am. angidatus, but which 
 we may conveniently call the Lavernock Shales, and these are 
 followed again by strata in which limestones predominate, and 
 which belong to the zone of Am. Bucklandi. To the varying re- 
 sistance offered by these rocks to denudation much of the Liassic 
 scenery is due. The Os^rea-beds stand cut as a platform and low 
 escarpment founded upon a slope of the softer Rhsetic shales, 
 while the limestones of the Am. Bucklandi-zone form a second and 
 inner scarp and overlook wooded slopes occupied by the shales of 
 the zone of Am. angulatus. 
 
 The litoral type includes a variety of limestones, and conglom- 
 erates or breccias. Generally it is characterised by an absence of 
 shale and consequently by a more massive bedding than the normal 
 type, by the prevalence of oolitic : tructure, and by an abundance of 
 chert in nodules or as a replacement of the carbonate of lime in fossils. 
 Many of the limestones assume the character of the Sutton-stone, as 
 was the case with some of the Rhsetic strata. This rock, which 
 has been much used in the neighbourhood for building, may be de- 
 scribed as a shell-sand or shell-marl, mixed with a variable amount of 
 small detritus from the Carboniferous Limestone. It has been ce- 
 mented by partially crystalline calcareous matter, which, however, has 
 not always filled all the inter-granular spaces, so that the rock has a 
 cavernous and tufaceous appearance. The shells consist, so far as 
 the fragments can be recognised, of the fossilsproper to the horizon, and 
 are chiefly lamellibranchs but sometimes include much coral-debris. 
 The type of rock occurs not only in mass, as a local basement-bed 
 to any of the lower Liassic zones, but appears in thin bands among 
 both Rhsetic and Liassic limestones of normal type. It often 
 contains large angular or rounded fragments of Carboniferous 
 Limestone sparsely scattered through it, and in this and other re- 
 
60 Lias. 
 
 spects constitutes a near-shore deposit such as might have been 
 anticipated under Liassic conditions. Some evidence of coral- 
 growth also has been obtained by Mr. Tiddeman round an inlier 
 near Wick. Galena occurs frequently both in Sutton-stone and in 
 the other conglomeratic limestones both Liassic and Triassic. It 
 usually appears as strings or isolated crystals formed in place in 
 the matrix, nofc as derived fragments. At Candleston, according 
 to De la Beche, it fills the cavities left in Sutton-stone by the dis- 
 appear mce of shells, and at Dunraven it enters into the joints of 
 the jet-like plants contained in the Lias limestone.* 
 
 Specimens of Sutton-stone from Sutton (E. 1253 and E. 3827), 
 and Tair Onen near Cowbridge (E. 3829), have been submitted 
 to examination under the microscope by Dr. Flett, who reports 
 as follows : 
 
 One of these specimens is a compact white or slightly creamy limestone 
 full of broken fragments of shells of mollusca and brachiopods. There is 
 little crystalline calcite, but when the broken surface is examined with a 
 hand-lens many small rounded grains are visible ; they resemble the oolitic 
 grains of oolitic limestones. The rock, however, is not an oolite; these 
 grains are rounded shell-fragments which are coaled with a thin layer of 
 fine crystalline calcite. Most of the limestone is composed of small pieces of 
 shells of molluscs and brachiopods with d6bris of corals. A few broken 
 echinodermal plates may also be seen. The cementing material is crystalline 
 calcite in fine granular mosaic. E. 3827 shows angular cavities in the hand- 
 specimen which appear to have originated from the removal of shell-matter 
 in solution. It contains also pebbles of a dark -coloured limestone, one of 
 which is well rounded and nearly an inch in diameter. This differs a good 
 deal from the Sutton-stone in structure and composition; it is more 
 crystalline and is full of crinoidal fragments, and tests of foraminifera. 
 
 The included fragments in the literal Liassic rocks consist ex- 
 clusively of Carboniferous Limestone. Though generally water- 
 worn and often in this respect contrasting with ,the cliff- talus which 
 forms the marginal type of Keuper, angular material occurs also in 
 thin bands. The scarcity of rocks other than limestone is remark- 
 able when we consider that only the crests of a few of the limestone- 
 ridges remained above water, whereas there must have been a long 
 shore close by formed of Pennant. The Liassic marginal deposits 
 of that shore have all been removed by denudation ; apparently 
 they were strictly confined to its neighbourhood, from which we may 
 infer that locally at least the Liassic sea was not troubled by power- 
 ful tides or by heavy surf. The inference' is supported by the 
 character also of the normal Liassic sediments. 
 
 It follows from the fact that the Liassic sea was encroaching upon 
 subsiding land that each zone overlaps its predecessor. Conse- 
 quently the base of the Lias, at any point where it rests upon the 
 older rock, may not be the true base of the formation, and as a 
 fact the Ostrea-beds are rarely present save where the Rhaetic group 
 exists beneath. In such cases the abnormal character of the local 
 basement-bed makes its zonal identification extremely difficult. 
 
 * Memoirs of the Geological Survey, vol, I, pp, 9-72, 273, 
 
Introduction. 61 
 
 The following history of a discussion on the relations of the 
 Sutton-stone of Button and Southerndown is by Mr. H. B. Wood- 
 ward.* 
 
 Introduction continued. 
 By H. B. WOODWARD. 
 
 The peculiar characters of the basement-beds of the Lower 
 Lias, where they rest on the Carboniferous Limestone, at Southern- 
 down and Dunraven near Bridgend, and at other localities in Gla- 
 morganshire, were pointed out many years ago by De la Beche ; he 
 noticed that the limestones became more or less conglomeratic, 
 and were associated with a whitish limestone known as Sutton 
 Stone.f 
 
 Since the recognition of the Rhsetic beds in this country (1860-61), 
 there has, however, been much discussion on the age of the " Lias 
 conglomerate " of South Wales, and on the question whether the 
 Rhsetic beds are or are not represented in it. 
 
 In 1863 Mr. R. F. Tomes " claimed for the basement-beds a date corre- 
 sponding to the Rheetic age," on account of the presence of Plicatula intus- 
 striata% ; but this view proved to be based on an insecure foundation, as 
 the species occurs sometimes abundantly in the Lower Lias. 
 
 In 1866 E. B. Tawney expressed his opinion that the whole of the Con- 
 glomerate series was Rhsetic in age ; he divided the beds as follows : 
 
 2. Southerndown Series (about 50 feet thick at Southerndown and about 
 
 12 feet at Dunraven). 
 1. Sutton Series (about 40 feet thick). 
 
 The ordinary beds of Lower Lias, overlying the Southerndown Series, were 
 grouped by him in the zone of Ammonites Bucklandi. 
 
 lawney's conclusions were shortly afterwards contested by Charles Moore,|| 
 H. W. BristoWjIT and Prof. Ralph Tate,** who maintained that the beds were 
 Lower Lias ; while Prof. P. M. Duncanft adopted a sort of compromise by 
 applying to the strata the term Infra-Lias, which includes both White Lias 
 (Rhaetic Beds) and the zones of A. planorbis and A. angulatus. 
 
 Bristow, who maintained that the beds belonged to the Lower Lias, disputed 
 the sequence pointed out by Tawney, urging that there was but one series, by 
 whatever name it may be called ; the Southerndown Series being merely the 
 easterly prolongation and the representative of the Sutton Stone, and the 
 total thickness being from 35 to 37 feet. He admitted, however, that as the 
 Sutton Stone reposes on the upturned edges of the Carboniferous Limestone, 
 and fills up irregularities and undulations in that rock, the thickness is some- 
 what variable in different places. 
 
 Subsequently Tawney abandoned his view on the Rhsetic age of the de- 
 posits, JJ and for a time the question appeared to be settled. In 1884, however, 
 
 * Jurassic Rocks of Britain (Geol. Survey Memoir], vol. iii., pp. 99, 100. 
 
 t Mem. Geol. Survey, vol. i. pp. 269, &c. ; Geol. Observer, Ed. 2, pp. 482, &c. 
 
 j Proc. Cottesw. Club, vol iii. pp. 191, 202. 
 
 Quart. Journ. Geol. Soc., vol. xxii. p. 69.- 
 
 || Ibid., vol. xxiii. p. 511 ; and Proc. Bath Nat. Hist. Club, 1865. 
 
 f Ibid., vol. xxiii. p. 199 ; see also pp. 202, 203. 
 
 ** Ibid., p. 307. 
 
 ft Quart. Journ. Geol. Soc., vol. xxii. p. 89 (1866) ; vol. xxiii. p. 15 (1867) ; 
 vol. xlii. pp. 101, 113, 139 (1886) ; andSupp. to Fossil Corals, Palceontogr. Soc. 
 
 JJ This statement is made on the authority of Mr. Etheridge. Quart. Journ. 
 Geol. Soc. t vol. xl. p. 375 (1884). 
 
62 Liti*. 
 
 Mr. Tomes expressed his conviction that the conglomerate-bed at Stormy 
 Down near Bridgend " is the true representative of the Sutton Stone of 
 Sutton and West, of the ; Guinea ' led of Bint on and Graf ton in Warwick- 
 shire, and of the White Lias of that county and the West of England ; v f 
 a view taken also by .Mi 1 . W. ('. Lucy.;;; who had accompanied Mr. Tomes on 
 a visit to the South Wales district. At the same time Mr. Llliei'idge, who 
 had previously considered that the Sutton Stone and white conglomerate 
 might be of Rh;ctic age, observed that their precise position was still an 
 open question. 
 
 Xo doubt sonic difficulty is experienced in making out the precise 
 relations of the white Sutton Stone and conglomerate to the ordinary 
 Lower Lias of the area. This arises in part from the cliffs being 
 to a great extent inaccessible, while portions of the coast can only 
 be visited for a short time when the tides are at their lowest ; and 
 we have to scramble over ragged rocks. Moreover the strata 
 themselves are subject to variations, and are shifted in three or four 
 places by faults, in situations where it is difficult to estimate the 
 precise amount of the displacement. By measuring the strata in 
 detail at several points, I was enabled in time to make out the 
 sequence, and to satisfy myself that while the white Sutton Stone 
 and conglomerate (with occasional bluish modifications) form the 
 base of the series, both at Sutton and Dunraven, these beds pass up 
 insensibly into the blue and grey conglomeratic (Southerndown) 
 beds, which are overlaid by the ordinary beds of the Lower Lias. 
 The sequence, therefore, that was pointed out by Tawney is correct, 
 although the Sutton beds merge upwards into the Southerndown 
 Series without any definite plane of demarcation (see Fig. 5). 
 The total thickness of the conglomeratic series, where it could be 
 definitely measured, varies from lift}' to eighty feet, but it increases 
 still more in its western development between Sutton and Southern- 
 down. 
 
 The whole of these beds may be regarded as the basement-beds 
 of the Lower Lias, representing the Osrea-beds and other portions 
 of the zone of Ammonites planorlis, and including perhaps portions 
 of the zone of A. angulatus. They are overlain conformably by 
 limestones and shales exhibiting the ordinary characters of Lower 
 Lias, and belonging partly to the zone of A. angulatus, but mainly 
 to that of A . Bucklandi. 
 
 Eastern Part. 
 By T. C. CANTRILL. 
 
 The Lias of the eastern part of the area covered by the map forms 
 a broad belt fringing the coast, and lies generally south of the Cardiff- 
 Cowbridge anticline ; it also extends from Cowbridge in a north- 
 
 t Quart. Joiirn. <}<:<>l. Hoc., vol. xl. pp. .'{.">.'}, .'}.~>0 (18S4) ; sec also vol. xxxviii. 
 p. 411 (1882). 
 
 T I'roc. Cottetw. Club, vol. viii. p. 2.14 (1SS.~>). 
 
 $ Qwirt. Journ. <1>1. Hoc., vol. xl. p. ;J7.~> (LSS4) ; .see also Proc. Cardiff 
 Xat. -W-., vol. iii., pp. 30 (52 (1872). 
 
63 
 
 o d 
 
 10 
 
 ft 
 
 P3 
 
 i 
 
 8 
 
 PQ 
 
 m 
 
 m 
 
64 Lias. 
 
 easterly direction in outlying tracts partly covering the core of the 
 anticline. The succession agrees closely with that given by Mr. 
 H. B. Woodward * for the Penarth district. 
 
 General Section of the Coast of South Glamorgan. 
 
 FT. IN. 
 
 Zones of / Blue and brown limestones, in beds up to 2 feet, 
 
 A. semicostatus, averaging 1 foot or less, with shale part- 
 
 A. Bucldandi, ings ; Gryphcea arcuata, Lima, etc. At 
 
 and / least - 200 
 
 A. anguiatus ] Grey marls and shales with occasional nodules 
 
 [ = Bucldandi- and bands of limestone (Lavernock Shales). 
 
 group.] 1^ About - - 40 
 
 Limestones and shales, alternating. A. plan- 
 
 Zone of J orbis. About 22 
 
 A. planorbis. ^Limestone-flags (Ostrea-beds) with shale-part- 
 
 V ings. Ostrea liassica - - - - - 15 
 
 The superposition of the relatively hard beds of the zone of A. 
 planorbis upon the Rhsetic marls and shales gives rise to a low 
 escarpment ; while the limestones of the A. Bucklandi- group over- 
 lying the Lavernock Shales produce a bolder scarp which forms the 
 edge of the Liassic plain of the coast-tract. The steep clayey slopes 
 leading up to the scarp are occupied by hanging woods, such as Coed 
 Garn-lwyd north of Llancarfan, Coed Arthur and Coed-y-Colwn 
 near Llantrithyd, the woods south-east of St. Hilary, and Draenog 
 and Arglwydd Woods at St. Mary Church. 
 
 The Lias of the coast shows no indications of having been laid 
 down near a shore, but farther northwards it develops an oolitic 
 structure, and includes small rounded fragments, usually of Carboni- 
 ferous Limestone and chert, occasionally in such size and number as 
 to constitute a coarse conglomerate or breccia. At the same time 
 shale -par tings disappear and the rock becomes massive and hard, 
 while bands of Sutton-stone often make their appearance. The 
 breccias are well-marked in the Os^rea-beds and also in the overlying 
 beds of the Bucklandi-gTonp. It has been already pointed out 
 (p. 59) that the Sutton-stone type of limestone occurs in both Rhsetic 
 and Lias, and as it rarely yields recognisable fossils, the determina- 
 tion of the age of an isolated exposure of the rock is often difficult. 
 
 The Osrea-beds enter the map near Blackland, south-east of 
 Bonvilston, as a low escarpment in which are several small old 
 quarries. They can be traced along the south side of Coed-yr-Aber 
 to a large quarry near Greendown. 
 
 The extreme western end of a small outlier of Ostrea-beds just 
 enters the map at Redland. There is a larger outlier of the same 
 beds south of Bonvilston, the thin-bedded limestones and alternating 
 shales being well-shown in some shallow old quarries north-east of 
 Langlon Wood. The eastern limits of this outlier are obscure ; 
 there are some indications of a prolongation of the beds eastwards, 
 or there may be a small separate outlier north of Coed-yr-Aber. 
 
 * 
 1893. 
 
 The Jurassic Rocks of Britain, vol. iii., p. 121 (Mem. Geol. Survey), 
 \ t 
 
Eastern Part. 65 
 
 Towards Leige Castle and around Castell-ar-foel the O^rea-beds 
 are thin, and indeed at the latter locality they may be absent 
 altogether, if we are right in identifying as Lavernock Shales some 
 buff shales exposed in a pit 100 yards north of Carmel Chapel. 
 
 South-west of Castell-ar-foel the Ostrea-beds and the Lavernock 
 Shales are faulted out, but the former reappear south-east of Wren 
 Castle, and may be seen in quarries south of Tre-gyff, also south-west 
 of Green, and in cuttings on the Cowbridge-Aberthaw railway a little 
 farther west (pp. 42, 43). They have been quarried also at Ystum- 
 elaid and near Cross Barn, and are well-exposed in a railway-cutting 
 north of St. Mary Church Koad (p. 41). West of Ty-fry they are 
 evidently closely approaching their original margin. 
 
 The Lias north of the Pentre fault consists of the Osfrea-beds 
 alone, except perhaps for a few feet of nodular limestones seen at 
 Coed Hills ; it is generally more or less pebbly and impure, and 
 contains bands of Sutton-stone, composed of the comminuted shells 
 of Ostrea and other fossils. It has been quarried 250 yards south- 
 east of Tair Onen ; and near a kiln several feet of white Sutton-stone 
 rest on flags of a more than usually shelly character. Towards 
 Garn also the Lias presents much the same aspect, and inasmuch as 
 in the direction of Tair Onen it overlaps the Rhsetic Beds we infer 
 that the shell-beds and Sutton-stone have been formed close to the 
 original shore-line. Occasional traces of galena occur in these rocks, 
 and have given name to two of the fields. 
 
 An old quarry 250 yards south by east of Eastdown shows flaggy 
 limestones with a few specimens of Ostrea and Modiola, and several 
 thin bands of light-coloured limestone containing small pebbles of 
 dark limestone. This Lias is possibly faulted down against 
 Rhsetic sandstones on the north. About 150 yards south-west of 
 St. Hilary Cross a wedge of Lias, only a few yards broad, has been 
 let down along the line of the Pentre fault. 
 
 The Ostrea-bQds of an outlier at Old Beaupre are somewhat sandy ; 
 they are exposed by the side of the river under the walls of the old 
 castle. The same beds in another outlier east of How Mill have been 
 quarried along the edge of the valley north of the mill. 
 
 West of the Dawen Valley the Os^rea-flags are exposed at Sandpit 
 near Gigman Bridge, and can be traced thence along the west side 
 of the valley to a quarry in the fields north of The Herberts Farm. 
 Mr. F. T. Howard in his paper on the " Geology of the Cowbridge 
 District " * gives the following section, in descending order : 
 
 Section at The Herberts, Llandough-juxta-Cowbridge. 
 
 FT. IN. 
 3. Hard limestones, containing many specimens of Lima, 
 
 Pentacrinus, and gasteropoda, much calcified - - - 5 
 2. Coral-limestones in three bands, the lowest being the 
 richest. The corals are in the position of life. A few fossils 
 of other genera, principally Ostrea and Modiola 1 ft. to 1 2 
 1. Typical Ostrea -limestones full of Ostrea liassica - 40 
 
 * Trans, Cardiff Nat, tioc., vol. xxx, (1807-8). 
 7665. F 
 
(iii /, nil-: 
 
 The coral max be Thecoftmilia irmjuhiris, Duncan (7\ Duncani, 
 Tomes), according to Mr. rC. T. Newton. 
 
 Thin-bedded blue limestones with shale-partings, somewhat higher 
 in the series, are exposed in a quarry on the south side of the road ; 
 here Mr. Howard observed Lima, Cardinia, and A. [Arietites] 
 BucMandi. 
 
 West of Llandough the lowest Lias exposed in the Llannhangel 
 Valley contains corals but few oysters. North of the village the 
 0,s-/Vm-beds are well exposed in a quarry o(JO yards S.S.lv of New- 
 house. This is probably the quarry referred to by Mr. Howard* 
 as showing below the Os/ f ea-beds " from two to three feet of yel- 
 lowish impure limestones and dark blue shales, differing widely from 
 the very fossiliferous Ostrea limestones above," and he surmised 
 that these lower beds might be a portion of the White Lias. 
 
 South-west of Xewhouse there is a working quarry in what appear 
 to be chertv 0,s7/vv/-f1ags ; due west of the same farm there is an old 
 quarry in ihiggy limestone, and a few yards south of Bryn-hyfryd 
 is a third. Some or all ol these are probably "the quarnes at 
 Llanbethian " described by Moore."!* 'The following 
 rnarised foini of his section, taken in descending order 
 
 Quarries at Llanbleiddian. 
 
 Limestones containing .1. jJanorln's, Nerito'ims <.</</ i/n, 
 M< l/r/iia. ( 'lif'iu n//~;/n, ('nrditn, l.tnin, PtcJin yW///.r, He. 
 
 Limestones containing Oxtrca liaxxicn, Cnrdinin, Limn 
 
 (/>'</'> nfcd, Thf'.Cafinnlut, Mmttlicnltin, etc. - 7 > 
 
 Lime stones \\ith Mix/t'iifd Indium, I*UUKI f;< tinxl/'Hihtx. Teiq., 
 
 /'</( i -a [>/>llii.r. I'lirntnln nrii ini nntn , Limit //it/ti >/(<'<!, He. - \ 1 O } 
 
 The middle group of limestones was supposed by Moore to re- 
 present the 0,sf/'eY/-beds. The fossils do not support this view. 
 
 From Bryn-hyfryd the edge of the Lias descends rapidly into the 
 village of Llanbleiddian, overlapping the Rhsctic Beds (p. 44) and 
 Trias (p. '\\) and then resting directly on the Carboniferous Limestone, 
 which is exposed in the road immediately south of Llanbleiddian 
 Cottage. We have here evidence of post-Liassic folding along an 
 east and west axis, for since the overlap proceeded from south to 
 north up an inclined plane of Carboniferous Limestone, we should ex- 
 pect to find the edge, of the Lias, where in direct contact with thr 
 Carboniferous Limestone, at a greater altitude than where under- 
 lain by Kh;ctic and Trias, and not at a lower, as is actually the case. 
 Several exposures west of Bryn-hyfryd, however, show northerly 
 dips which prove the post-Liassic movement and explain the cir- 
 cumstances. They mark th - northern side of the post-Liassic 
 anticline shown in Kig. '2. 
 
 Some of the Liassic rocks here contain pebbles of dark limestone. 
 Without these they would be difficult to distinguish from the 
 Carboniferous Limestone, as, for example, along the southern slope 
 of Llanbleiddian Hill. 
 
 * O] t . elf. 
 
 t Quart. Jaiirti. (!<-<>L ,W-.. xxiii. (1S07), pp. "> IS- ">!!, 
 
Eastern Part. 67 
 
 Along the north side of this same hill alternating limestones and 
 shales, probably of a higher horizon than the Ostrea-beds, are thrown 
 down by the Cowbridge fault against the Carboniferous Limestone. 
 From below this normal type the literal variety emerges and is 
 well-exposed in quarries on the Llantwit Major road 350 yards 
 from the Westgate Inn, Cowbridge. The quarry at work in 1898 
 on the north-west side of the road shows a blue-hearted brown 
 oolite, flaggy in the upper part and containing Carboniferous Lime- 
 stone pebbles in several of the bands. An old quarry a few yards 
 nearer Cowbridge in lower beds yielded a few specimens of Ostrea, 
 probably 0. liassica, ranging up to T6 inches in length. All these 
 rocks may be referred to the Ostrea-beds, though their aspect is 
 somewhat abnormal, and they are perhaps thickened by detritus of 
 the Carboniferous Limestone. The junction of the two formations 
 can be seen in the Llantwit road 50 yards from the Westgate Inn, 
 where it was sketched by De la Beche,* and a minute outlying 
 patch of the same pebbly Lias caps Gibbet Hill near by. 
 
 The junction is better exposed in a large quarryf 200 yards south- 
 west of Llwyn-helyg House, where 4 or 5 feet of nearly horizontal 
 Lias lie on Carboniferous Limestone dipping at 25. On the south 
 side of the valley and 90 yards south of this quarry the basal crags of 
 the Lias consist in part of the Sutton-stone variety containing shell- 
 fragments and small cubes of galena. The basement-beds are well 
 exposed along the Bridgend road, and irregularly- bedded well 
 developed oolite has been quarried in a coppice 250 yards beyond 
 the first milestone from Cowbridge. Much of the Lias east of 
 Llwyn-helyg House is more or less conglomeratic. 
 
 The Cowbridge Lias outlier, so far as it has been opened up in 
 the fine railway-section, has been already described on p. 46. The 
 Ostrea-ftags and overlying A. planorbis limestones and shales, and 
 also part if not the whole of the Lavernock Shales of the A . Buck- 
 landi-zone, are all represented by hard and massive limestones, but 
 it is doubtful if any of the overlying limestones of this zone are 
 present. This agrees with the opinion of Moore,} who was dis- 
 posed to assign the Cowbridge Lias to a lower horizon than that of 
 either Sutton or Brocastle on account of the general absence of the 
 coral-fauna of those localities. It must not be overlooked however 
 that corals occur at the Herberts and also s:uth-west of Llandough 
 in or immediately above the Ostrea-beds. 
 
 Moore gives details of a quarry which was being worked about 
 the year 1867 " immediately opposite the railway-station " ; this 
 was probably a deep quarry 180 yards south-west of the entrance 
 to the old station in the High Street, and just behind the school in 
 the Broadway. In it he saw compact crystalline limestone to a 
 depth of 30 feet ; the lower beds were somewhat thicker-bedded and 
 contained ' flint ' layers or nodules. The fossils recorded were 
 
 * Mem. Geol. Surv., vol. i., Fig. 36, p. 274 (1846). 
 
 t Figured by Mr. Howard, Trans. Cardiff Nat. Soc., vol. xxx. (1897-8). 
 
 + Quart. Joum. Geol. ,SYx?., vol. xxiii. (1807), pp. 517-8. 
 
 7665. F 2 
 
68 Lias. 
 
 Plicatula acuminata, Ostrea intusstriata, 0. liassica, Pecten pollux y 
 Lima gigantea, Cardinia, Astarte, etc. Close to this quarry he 
 mentions another in somewhat higher, thinner, and more rubbly 
 beds ; this was probably one on the north side of the Broadway a 
 few yards west of the school. The coral ThecosmUia Michelini, 
 Terq. and Piette, was abundant in one of the beds here, and num- 
 bers of Entomostraca were present in the matrix between the corals. 
 Ostrea intusstriata, Em., and Neritopsis exigua, Terq., are recorded 
 also. Moore failed to find ammonites in any of the Cowbridge Lias 
 and realise i the resulting difficulty of fixing its horizon. "Small 
 sections in different parts of the outlier show that oolitic structure 
 and bands of Sutton-stone type are frequent ; in the Cardiff road 
 south of Slade this latter type of rock rests on Triassic breccia. A 
 similar junction may be found in the road at Porth-y-green east of 
 Llanbleiddian Castle, the Triassic breccia here being only a few 
 inches thick. 
 
 A small outlier on the north side of the dry valley north of Slade 
 consists of light-coloured obscurely oolitic limestone, and a faulted 
 strip of grey oolite is well exposed in an old quarry 250 yards south 
 of Aberthin. Both outliers have been referred to the Lias, with 
 some doubt, however, in the absence of fossils. 
 
 At the western end of Cowbridge the Lias extends north-east- 
 wards across the Dawen Valley, being faulted on the south 
 against Carboniferous Limestone, Trias, and Old Red Sandstone. 
 North - west of Aberthin it is overspread with glacial gravel, 
 and consequently its limit is conjectural ; but at that village 
 it can be seen to rest directly on the Carboniferous Limestone 
 and Lower Limestone Shales. Here the prevalent type is Sutton- 
 stone, more or less pebbly and frequently containing specks 
 of galena, as, for instance, in the lane near Court Farm. A minute 
 outlier of the same type of rock occurs south of the Welsh St. Donats 
 road about half-way between that village and Aberthin. North of 
 Aberthin this literal type gives place to normal limestones and 
 shales which, being evidently higher than the Ostrea-loeds and pro- 
 bably than the Lavernock Shales also, may be assigned to the A. 
 BucJdandi-gToup. Here and there the Lias presents its normal 
 characters even close up to its margin, as for instance in the fields 
 north-east of Aberthin. Between Prysc and Maendy the rock is 
 normal, but west of the Llantrisant road at the latter place a deep 
 quarry shows flaggy blue limestones, some of which are pebbly, 
 while there are also pebbly whitish rocks of the nature of Sutton- 
 stone ; chert-nodules also occur in some of the bands. These being 
 probably the O^rea-beds, the normal type seen at Prysc at a higher 
 level may be referred to iheA.BiccJdandi-loeds. The adjacent railway- 
 cutting shows a small exposure of thin-bedded grey faintly- oolitic 
 rock under a few feet of gravel. This may be an exposure referred 
 to by Moore.* 
 
 * Quart. Journ. Oeol t Soc,, vol. xxiii, (1867), p. 519, 
 
Eastern Part 69 
 
 At Bodlonga also flaggy limestones, probably the Ostrea-beds, 
 have been quarried, but both here and at Maendy it is possible that 
 some of the limestones and shales overlying the Ostrea-beds are 
 represented also. The small outlier at Pen-y-lan south-east of 
 Llansannwr consists chiefly of limestones resembling Sutton-stone. 
 
 The direction of dip at Bodlonga suggests that the Lias extends 
 eastwards under the drift-covered ground at Bwlch-gwyn and 
 Llwyn-du to join that at Cwm now to be described. In a brook 
 bounding the south side of the field at Ty-du on the Cwm Farm 
 (p. 27), some thin-bedded limestones, which may be either high 
 Rhoetic or low Lias, are just visible at the mouth of a small runnel 
 issuing from Ffynnon-yr-hebog, a strong spring just inside Coed 
 Leyshon. A few yards farther up the main stream there are over- 
 grown workings probably in the same rocks. On following up the 
 edge of the wood several small swallow-holes will be noticed, and 
 finally thin-bedded Lias limestones and shales under gravel are 
 exposed in a dingle on the edge of Coed Leyshon, 200 yards east- 
 by-south of Cwm Farm. These beds lie probably just above the 
 horizon of the Lavernock Shales and presumably belong to the 
 lowest part of the A. BucJdandi-group. They present no indications 
 of literal conditions. This exposure necessitates the conclusion 
 that the drift-covered escarpment ranging north-west and south- 
 east of Cwm must be the edge of a Lias plateau occupying the heath- 
 covered ground of Mynydd-y-glew. Two small trial-pits, said to 
 have been for coal, were made many years ago on this plateau ; 
 one just within the western edge of Coed Leyshon directly west of 
 Ty-fry farm, the other on the heath just outside the south-west 
 angle of Coed-y-marlau ; at both pits nothing but gravel is now 
 to be seen. % 
 
 The boundaries of this Liassic plateau are largely conjectural, 
 except at one point, where they are defined by an outcrop of Car- 
 boniferous Limestone at Welsh St. Donats. Wherever exposed, 
 except at Cwm, the beds are conglomeratic and of the literal type. 
 Thus, a roadside quarry 300 yards north of Pwll-y-daren shows 
 nine feet of white conglomeratic Sutton-stone, while at a pond near 
 the farm-house a band full of angular fragments of Carboniferous 
 Limestone appears among otherwise normal clays and limestones. 
 South of the Cowbridge fault, which crosses the road between the 
 pond and the farm-house, Sutton-stone with traces of galena re- 
 appears, while a little farther east, and 200 yards west of Pen-y- 
 ffordd-fawr, flaggy blue limestone containing abundant Ostrea 
 liassica but associated with Sutton-stone and breccia have been ex- 
 tensively quarried. Farther to the south-east there are several 
 sections in similar limestones, all of which may be referred to the 
 Ostrea-beds. 
 
 Tawney* records PlicatuLa intusstriata, Emm., Ostrea multicos- 
 tata, Miinst., Pecten suttonensis, Tawn., and Lima tuberculata, Terq., 
 from the ' Sutton Series ' of Welsh St. Donats, which he then 
 regarded as Rhsetic. 
 
 * Quart. Journ. Geol. Soc., vol. xxii. (1866), p. 69, See p. 80. 
 
70 Lias. 
 
 How far to the east the Lias extends is very uncertain ; a large 
 swallow-hole a few yards north of Cwrt-newydd, and another, 
 named Trial Shaft on the six-inch map (Glamorgan 42 S.W.), with 
 a small stream flowing into it, near the roadside at Ffald-wen, in- 
 dicate the presence of limestone beneath the gravel, but whether 
 Lias or Carboniferous cannot be stated. 
 
 On the small Lias outlier at Plwcau-Dafydd, Pendoylan, thin- 
 bedde I limestones and shales, the former containing ossicles of 
 Pentacrinus, are exposed in the road, and in the fields 150 yards 
 south-east of the house there are some old workings in the Ostfrea-beds. 
 
 On the western edge of the Peterston outlier the O^rea-beds are 
 poorly exposed ; thin-bedded limestones and shales, probably 
 belonging to a higher horizon, crop out in a lane east of Gwern-y- 
 cae-uchaf ; the Lavernock Shales are doubtfully present, and cherty 
 more massive limestones, probably of the BucMandi-zone, have been 
 quarried at Allt-las. 
 
 The western edge of the Castell-y-mynach outlier is concealed 
 by drift. The Rhsetic is recognisable at Ty-nant, but the junction 
 with the Lias is not exposed. 
 
 The Lavernock Shales can be easily recognised, wherever the Lias 
 retains its normal characters, round the northern margin of the 
 Liassic plain bordering the coast, as a wood-clothed slope between 
 the Ostrea-beds below and the plateau of the A . BucJdandi-beds above. 
 Good sections are rare ; the best being those afforded by the Cow- 
 bridge-Aberthaw railway in two cuttings, one south of Nant Tre- 
 gyff, the other south-west of Coed-y-colwn. Brown shales and 
 marls with nodules, and occasional thin bands, of limestone are ex- 
 hibited in both. 
 
 The overlying thicker-bedded limestones of the A. BucJdandi- 
 group of zones occupy the greater part of the area bordering the 
 coast ; they gently undulate in all directions and a dip of more than 
 5 is exceptional. Sections are numerous, as the limestone was 
 formerly burnt for lime and used as building-stone. Now it is 
 quarried chiefly for road-metal. It forms a soil which is suitable 
 for the plough, and much of the district is still in an arable condition. 
 Good sections are exposed on the Cowbridge-Aberthaw and 
 the Vale of Glamorgan railways, but the magnificent coast-section 
 affords the best view of the beds. The limestones are generally 
 about eight inches, but occasionally as much as two feet thick, with 
 shale-partings ; they belong chiefly to the zone of A. Bucklandi. 
 
 East of Roose Point the beds dip south-west at angles ranging up 
 to 25, but the effect of this dip is counteracted by numerous small 
 faults trending about W. 10 N., and throwing down N. 10 E. 
 At the Point the beds dip south, and farther west this changes 
 to south-east, the Point thus marking a synclinal axis. Joints are 
 conspicuous on some of the rock-platforms on the foreshore. Gry- 
 phcea arcuata, Lima gigantea, and ossicles of Pentacrinus abound. 
 The genera] south-easterly dip continues as far as a gentle anticline 
 at Andrew's Pant near Pleasantharbour, beyond which it becomes 
 south-westerly. 
 
Western Part, 71 
 
 The limestone for making Aberthaw Lime was gathered from the 
 shingle on the shore near Watch-house Point, and not from quarries. 
 Of late years the works have greatly declined.* Pebbles are shipped 
 to be used as a flux in the iron -works (see also p. 87). 
 
 Limestone is quarried and burnt at St. Athan Road Station, and 
 quarried half-way between Lower Porthkerry and Tre-Dwgan. At 
 Limpert Bay the coast is formed of an alluvial flat bordered on the 
 seaward side by an old beach of limestone-pebbles, which, at the 
 Ocean House, are burnt for lime. West of this bay the cliffs 
 reappear ; between Summerhouse Point and Stout Point a slight 
 seaward dip has caused them to slightly overhang at several places ; 
 and near the latter they attain an altitude of 160 feet. 
 
 Western Part. 
 By A. STRAHAN. 
 From Notes by R. H. TIDDEMAN. 
 
 South of Coity the Lias,'] where it rests on the Rhsetic sandstone 
 described on p. 51, is oolitic in its lower bands and contains chert. 
 North of St. Mary Hill village the O^raz-beds follow the Rhsetic in 
 normal sequence, but south of the village the Lias overlaps the 
 Rhsetic and passes on to the Carboniferous Limestone. It then 
 assumes the condition of Sutton-stone. Fragments of black chert, 
 small pebbles of white quartz and specks of galena occur in it accord- 
 ing to Bristow,f and it yielded to Mr. Woodward Cardinia suttonensis, 
 Lima, Modiola, Ostrea liassica, Pinna, and Pecten suttonensis. 
 
 Thence southwards bedded and shelly conglomerate forms the 
 local basement-bed, superimposed on Lower Limestone Shales at 
 Pen-llin, but on the Main Limestone elsewhere. A shaft sunk in an 
 unsuccessful search for lead at Gelli-araul, near Llangan, proved a 
 greater thickness of conglomerate than might have been anticipated. 
 The following account of it is given by Moore. J " At the surface 
 were regularly bedded, but finely conglomeratic dense lime- 
 stones with thin intervening beds of marl. ... In the marls, 
 Potticipes rhomboidalis, Moore, and Pentacrinites are frequent. 
 Following the above limestones, the Sutton Stone was passed through, 
 from which were obtained Patella Dunkeri, Terq., and Pecten pollux, 
 Tawn. 
 
 " Immediately below the Suttonstone unstratified conglomerates 
 were found, and passed through to the depth of 150 feet, and still 
 continued when the mine was abandoned. In the stratified 
 
 * H. B. Woodward, " The Jurassic Rocks of Britain,'' vol. iii. (1893), pp. 
 117-118 (Mem. Geol. Survey). 
 
 t Quart. Journ. Geol. Soc., vol.- xxiii. p, 204 (1867).: 
 + Ibid., p. 533. 
 
72 Lias. 
 
 beds above the Suttonstone, there are many species of Cardinia arid 
 Pentacrinus ; and I also obtained the following : 
 
 Ammonites angulatus Orthostoma avena, Terq. 
 
 Lepidotus -scales Pleurotomaria lens, Terq. 
 Pollicipes rhomboidalis, Moore Turbo rotundatus, Terq. 
 
 Entomostraca, 2 spp. Trochus Juliani, Terq; 
 Astarte irregularis, Terq: Langanensis, Moore. 
 
 Ostrea arietis.- Trochotoma clypeus, Terq; 
 
 Anomia irregularis, Terq. Astrocoenia gibbosa, Martin* 
 
 Gardita tetragona, Terq. Thecosmilia Michelini, Terq. 
 
 The conglomerates were considered by Moore to be of Liassic age. 
 Mr. Woodward compares the section to that in the ravine of Pant- 
 y-Slade (p. 76), where also the conglomerate was locally thick. 
 
 At Colwinston the marginal Lias consists of conglomeratic and 
 gravelly limestone, much of it consisting largely of shell-debris. 
 The regular run of these litoral rocks suggests that the Carboniferous 
 peninsula of Pen-llin corresponds in form to a Liassic promontory at 
 one stage of the subsidence. The description is continued by Mr. 
 Woodward in the " Jurassic Rocks of Britain " (vol. iii, p. 118), as 
 follows : 
 
 " At Bridgend the limestones of the Lower Lias have been exten- 
 sively quarried for building-stone and for Blue Lias lime, which has 
 been put on the market under the name of ' Aberthaw lime.' The 
 railway-cutting also shows fine sections of the beds, and these were 
 described in detail by Charles Moore, who recorded an alternation 
 of 476 beds of limestone and marl. The lower portion of the series 
 is worked in the quarry, but we do not see the base of the Lias ; 
 blue earthy limestones were the lowest beds to be seen, and they 
 are overlaid by compact and earthy bluish-grey and yellowish lime- 
 stones. Altogether upwards of seventy-six beds of limestone 
 were exposed in the quarry, for the most part in thick beds with 
 comparatively little clay. The fossils which I obtained, included 
 Gryphcea arcuata (and broad varieties), Ostrea irregularis, Lima 
 gigantea (large specimens), Pholadomya ambigua, Homomya, Uni~ 
 cardium cardioides, and Pleurotomaria. By the entrance to the 
 quarry from the railway, the Lias contains lenticular nodules of chert 
 or siliceous limestone, in which Dr. Hinde (to whom I sent specimens) 
 found rod-like sponge-spicules. Ammonites BucHandi occurred 
 here, and I obtained also a large specimen of Cerithium nodulosum 
 at the base of the railway-cutting.* 
 
 " Moore published a list of the fossils obtained by him, including 
 Ammonites angulatus, A. Conybearei, and (in the higher beds) A. 
 semicostatus and A. sauzeanus.\ He also noted a number of Gaster- 
 opoda. The beds correspond with those seen in the cliffs between 
 Dunraven and Aberthaw, and, like them, include portions of the 
 zone of A. angulatus, the zone of A. BucJdandi, and that of A. 
 semicostatus" 
 
 * The fossils were named by Messrs. Sharman and Newton, 
 f Quart* Journ. Geol. Soc., vol. xxiii., pp. 513-517. 
 
Western Part. 73 
 
 The Lias here is much disturbed. In the Great Western Railway- 
 cutting a southerly dip of 10 to 30 prevails, and is accompanied by 
 some crushing. A new cutting on the Aberthaw railway shows 
 that this dip forms part only of several sharp undulations. The 
 folds range generally east and west. 
 
 From Bridgend westwards the Lias is of the normal type, and the 
 O^rea-beds can be recognised wherever opportunity occurs. Near 
 Tythegston, however, where the Lias overlaps the Rhsetic group, 
 this ceases to be the case, there no doubt being a progressive overlap 
 also among the Liassic zones. The lowest bed is a hard oolitic 
 limestone, creamy or dark -grey, and by no means easy to distinguish 
 from Carboniferous Limestone, on to which, moreover, it is often 
 welded. Grypncea arcuata occurs not far from the local base near 
 Merthyr-mawr, and proves that the Lias sequence is not complete. 
 
 At Brocastle the Lias crosses the Carboniferous massif, much of 
 the rock apparently being of the normal type. The shore -deposits, 
 however, reappear along the road to Corntown. Here, in an old 
 quarry now much obscured, on the north side of the road 700 yards 
 west of Brocastle House, Moore found Liassic conglomerate resting 
 on Carboniferous Limestone. 
 
 The succeeding pages of this chapter, with the exception of the 
 passages in square brackets, are taken from the Jurassic Rocks of 
 Britain, vol. iii. (The Lias of England and Wales), chap, iv., by 
 H. B. Woodward. 
 
 Western Partcontinued. 
 BY H. B. WOODWARD. 
 
 At Brocastle, again, there is a rich Coral fauna, containing in 
 fact more species than have been found in the Sutton-stone, 
 although a certain number are common to the two deposits. 
 From this locality Moore obtained a very rich collection of 
 fossils, but, as he remarks, most of these proved to be new, 
 and therefore they afford but little evidence for correlating the 
 beds with other zones in this country. However the presence 
 of Gryphcea arcuata, Lima gigantea, Ostrea liassica, together 
 with several species'of Cardinia, recorded by Moore, suggest an early 
 stage of the Lower Lias, and agree generally with his grouping of the 
 beds in the zone of Ammonites angulatus, a position also assigned 
 to the mon the evidence of the Corals.* Mr. Tomes has expressed the 
 opinion that the "Brocastle bed has been to some extent re-assorted, 
 and this is not improbable : f undoubted evidence of the recon- 
 struction of beds is met with in the Lower Lias of the Radstock 
 district. Among the Corals (which have been worked out mainly 
 by Prof. Duncan) are species of Astrocosnia (Stylastrcea), Isastrcea, 
 Montlivaltia, Thecosmilia, etc. 
 
 * Moore, Quart. Journ. Geol. Soc., vol.- xxiii., p. 521 (1867) ; Duncan, Ibid.; 
 p.- 17. See also Rev. H.- H. Win wood, Proc. Bath Nat. Hist. Club, voL vL, 
 p. 218. 
 
 t Quart; Journ. Geol Soc., vol. xl, p. 357 (1884): 
 
74 Lias. 
 
 The quarry is practically disused, and the conglomeratic beds of 
 Lias are mostly obscured. It is however, possible, to trace these 
 beds abutting irregularly against the Carboniferous Limestone, as 
 represented by Moore. The older rock is a dark blue crystalline 
 and compact limestone, containing Spirifers and Encrinites. The 
 Lias beds comprise greyish-brown granular limestones, and con- 
 glomeratic layers having a matrix of pale and compact limestone. 
 Cherty masses here and there occur in the weathered soil on top 
 of the Carboniferous Limestone. 
 
 West of Longland, about eight feet of coarse pale grey 
 granular and brecciated limestones have been opened up by the 
 roadside, and at the lime-kiln to the south, beds of conglomeratic 
 Lias abut against the Carboniferous limestone. 
 
 [The existence of an outlier of Lias at Pyle village is evidenced by 
 small exposures in a tramway, 450 yards west of St. James Church. 
 
 The Stormy outlier of Lias is faulted along its southern margin and 
 not well exposed along the north side where it rests upon Rhsetic beds, 
 but has been laid open at the Cement Works, where the following 
 section was measured by Mr. Woodward (Jurassic Rocks of Britain, 
 vol. iii, p. 114) : ] 
 
 Stormy Cement Works. 
 
 FT. IN. 
 
 ( Brown clay 
 Hard compact blue limestones and shales with 
 
 Unicardium, etc. ......36 
 
 Even beds of shaly limestone and shales - - 20 
 
 Lower Lias. 
 Zone of 
 .1 mmonites 
 
 plauorbis. 
 
 Dark-blue shaly limestones ; near their base beds of 
 blue limestone and shale containing Ostrea lias- 
 sica and Modiola minima, about - - - 18 
 
 Conglomeratic bed ; pale-grey and bluish brecciated 
 \ and shelly limestone, about - - - - 10 
 Rhajtic Beds. See p. 56. 
 
 Bristow, who regarded the conglomerate as the attenuated repre- 
 sentative of the Sutton Series, noted its thickness as two feet, and des- 
 cribed the bed as a " hard, siliceous, and shelly blue conglomerate."* 
 
 From the Lower Lias here I obtained Ostrea irregularis, and poor 
 specimens, identified somewhat doubtfully with Ammonites Jokn- 
 stoni and Pholadomya glabra. Moore recorded A. [Psiloceras] plan- 
 orbis, Lima gigantea, L. tuberculata, Ostrea arietis, and Pecten pollux 
 (suttonensis)."\ These fossils compare well with those from the 
 beds at Sutton and Southerndown. 
 
 Coast Section, Sutton to Aberthaw. 
 
 The Sutton Stone has been extensively quarried near Sutton, 
 more especially between Sutton and Sealawn, on both sides of the 
 road, and again on the slopes facing the Black Rocks near Pant-y- 
 
 * Quart. Journ. Geol. Soc., voL xxiii. p. 204 (1867)g 
 j- Quart. Journ. Geol. Soc., vol. xxiii. p. 520 (1867), 
 
Coast Section. 75 
 
 Slade. The principal working in 1887, was immediately south of 
 Tusker Cottage, and the section was as follows : 
 
 FT. IN. 
 
 /Hard grey and white shelly limestones, with 
 occasional pebbles of Carboniferous Lime- 
 stone, and near the base a band of tolerably 
 compact blue limestone ..-GO 
 
 Les ' ^ Massive bed of white more or less tufaceous stone 
 of variable character, with fibrous structure 
 here and there, and much jointed and broken 
 \ up in places. (Sutton Stone proper) 7 or 80 
 
 The more abundant fossils are Ostrea multicostata, Plioatida in- 
 tusstriata, Pecten suttonensis (or pollux), and Cardinia suttonensis ; 
 but these are not very common, and in many instances the shells 
 have been dissolved away, leaving the rock in a cavernous con- 
 dition. I also obtained Gryphcea, Hinnites, Lima hettangiensis, 
 Astrocc&nia gibbosa, and lignite. 
 
 Galena has been observed in several places in the Sutton Stone 
 and overlying conglomeratic beds. De la Beche remarked that it 
 occurs not only in the mass of the stone, but in joints of jet-like 
 plants, and in cavities left by the dissolution of shells. He noted 
 also that in some localities the stone is dolomitic, a specimen having 
 been obtained at " Pare, two miles north-west of Bridgend." * 
 
 Along the coast west of the Black Rocks near Sutton, we come 
 upon the Sutton beds, resting directly on the Carboniferous 
 Limestone ; and the general dip of the newer beds being in a south- 
 easterly direction, the stone which at Sutton rises to an elevation 
 of 200 feet, gradually descends to 50 feet and less above sea- 
 level. 
 
 On the coast here (west of Pant-y-Slade), the beds consist of 
 white ^shelly conglomeratic and tufaceous stone, containing Ostrea, 
 corals, etc. ; they are variable in character, being in places coarsely 
 conglomeratic ; they show honey-combed weathering, and they 
 rest irregularly on the Carboniferous Limestone. The basement- 
 bed is generally the more conglomeratic, containing often large 
 boulders of Carboniferous Limestone in a creamy limestone-matrix ; 
 but bids with no pebbles lie in places directly on the older 
 rock. The conglomeratic series contains curious sparry veins, 
 sometimes tinged with a greenish colour. Corals derived from 
 the Carboniferous Limestone, as well as fragments of chert and 
 limestone also occur. 
 
 The connection between the white Sutton beds and overlying 
 bluish-grey conglomeratic limestones of the Southerndown Series, 
 may be traced in the ravine known as Pant-y-Slade, that descends 
 to the coast from a point north-west of the farm buildings of West. 
 (See Fig. 5, p. 63). Forming the higher ground here, and exposed 
 in three scarps at successively lower levels along the borders of the 
 
 * Mem. GeoL Survey, volg i.: pp.: 272, 273 ; see also Bristow, Quart i_ Journ. 
 Geol. Soc., vol.- xxiii. p. 199 ; and " Catalogue of Rock Specimens in the 
 Museum of Practical Geology," Ed. 3, p. 123. 
 
vfi Liaa. 
 
 ravine, there may hi 1 seen a series of blue ilaggy compact and 
 crystalline limestones, more or less conglomeratic or brecciatecl, 
 and containing angular fragments of Carboniferous Limestone 
 and chert. Some of the bi'ds indeed are not unlike Carboniferous 
 Limestone in texture,* and intercalated with them are thin shaly 
 beds. The sequence in these upper beds is not sufficiently clear 
 for detailed measurements, and it is quite possible there may be 
 some repetition by faults. It is, however, probable that we have 
 here a thickness of 70 or 80 feet (if not more) of conglomeratic 
 Lias above the Sutton Beds : a view that coincides with the evidence 
 obtained elsewhere along the coast, that the conglomeratic scries 
 thickens towards the west, and this agrees with the observations of 
 Charles Moore. f 
 
 The lower beds in ihe coast section, merge downwards into the 
 white Sut ton-stone Series, as seen i i the following section of the 
 cliff east of the Pant-y-Slade ravine : 
 
 ( .Bluish brecciatcd chert)' limestones with veins Pr. IN. 
 ( of calc -spar - - (3 
 
 /Palo brecciatcd limestone with fibrous structure ,'5 U 
 .Bluish-grey and pale, brecciated limestones 3 
 
 Compact bluish limestone more or less conglomer- 
 atic, passing into white tut'aceous and shelly 
 limestone, with iibrous structure: Pc'icn. 
 siuttonensis - [) U 
 
 Thick beds of pale tufa ceo us limestone with 
 iibrous structure, and with conglomeratic 
 bands here and there - 10 to lii 
 
 Massive beds of pale brecciated limestone, 
 passing down into conglomerate of irregular 
 thickness: Pcclcn sultonensis, Oxtrca mu.Hi- 
 , costata, Corals - 5 to 10 
 
 ( 'arbonifrrous Limestone. 
 
 It may be questioned whether the top 6 feet of strata, here 
 included with the Sutton Series, should be so grouped ; the evidence 
 obtained at Witches Point favours the view adopted, but the 
 question is of no importance. We have, however, near Sutton, 
 a thickness of from 25 to 40 feet of strata that may be assigned 
 to the Sutton Seri"S, as their thickness increases eastwards in places 
 according to the irregularities on the surface of the Carboniferous 
 Limestone. There can be no question of the intimate connection 
 between, the Sutton air I Southerndown Series ; and the higher 
 beds of blue conglomeratic limestone seen here, arc similar to those 
 seen above the white Sutton Beds on the southern side of Witches 
 Point, where the thickness of the Southerndown Series is much 
 reduced. 
 
 The higher beds in the Pant-y-Slade ravine have not proved to 
 be fossiliferous, so that we are not in a position to state whether 
 the greater thickness of the conglomeratic beds is due solely to an 
 
 * See also l)e la JJeche, Mtnt. (Jcnl. ,S'///r., vol. i., p. 272: 
 | Quart. Jour 11. G'eol. tioc., vol. xxiii., pp. 520, 5.'} I ; Tomes, LI>i<L, vol. xl. 
 p, 357. 
 
Count Section. 77 
 
 expansion of the Southerndown Series, or (as seems probable) to 
 the occurrence as we proceed westwards, of conglomeratic beds at 
 higher stages in the Lower Lias. 
 
 As we pass eastwards along the coast, over the irregular surface 
 of the Carboniferous Limestone, we find the pale Button Beds banked 
 up against the older rock (see Fig. 5), and at the base of the first 
 cave they occupy a large hollow eroded in that rock, and descend 
 to the beach-level. Here the Sutton Beds are 40 feet or more in 
 thickness, and it may be noted that the lowest bed of conglomerate 
 is very coarse, and of a bluish colour, similar to the basement-bed 
 on the further side of Witches Point. 
 
 Beyond this first cave the Carbcniferous Limestone again rises, 
 and we may readily follow the jale Sutton Beds, which appear in 
 marked contrast with the dark bluish-grey Carboniferous rock 
 beneath. Both groups have an easterly dip, and the stratification 
 in places is fairly conformable, but further east the Carbonif <. rous 
 Limestone rolls over abruptly in the same direction, ar.d the dis- 
 cordance between it and the overlying strata is great. 
 
 The Sutton Beds appear now as massive strata assuming a brown 
 aspect where weathered, and the lower layers are very irregular in 
 thickness. We can fix no divisional plane between them i nd the 
 overlying Southerndown Beds, for the cliffs, which rise to a height 
 of nearly 150 feet, are for the most part perpendicular. The 
 Sutton Beds, however, gradually descend to the sea-level by the 
 large " Fairy Cave."* To the east of this, their prolongation on 
 the foreshore is terminated by a fault ; but they are again upraised, 
 for a space, a little further on by another fault, being seen only in 
 ledges on the foreshore. Thence they do not reappear intil we 
 come to the cliffs on either side of the Witches Point at Dunraven, 
 as observed by Tawney and others. 
 
 From the Fairy Cavern eastwards, we can again note the upward 
 succession of the beds from the base of the Sutton Series into the 
 lower portion of the Sou herndown Beds, but the cliffs above are 
 inaccessible. Here we find on top of th3 Carbcniferous Limestone, 
 a thickness of 25 feet of pale conglomeratic limestones, alternating 
 with pale limestones like the Sutton stone. These, as at Sutton, are 
 surmounted by grey and bluish-grey limestones (4 feet 6 inches 
 thick), which form a connecting link with ihe conglomeratic lime- 
 ! tones of the Southerndown Series above. In these the limestones 
 become streaked with indurated shaly bands, whi h present a wavy 
 appearance. Here the highest bed we can reach is about 50 feet 
 above the Carboniferous Limestone ; it is a limestone with pro- 
 minent fucoidal markings, but bands of this nature occur at various 
 horizons in the Southerndown Series, and also in the ordinary beds 
 of Lias above. 
 
 Passing by the faulted tract to ihe east, where three great but- 
 tresses of rock with perpendicular faces are presented to view, we 
 
 * See Sections by Tomes, Quart. Journ. Geol. Soc., vol. xl., p. 357 ; and 
 , Proc, Cotteswold Club, vol, viii., Section D., p. 254, 
 
78 Lias. 
 
 come to what may be termed the main section of Southerndown, 
 for 1 he beds may be traced eastwards continuously, past Southern- 
 down beach to the cliff by the fault west of Dunraven Castle. That 
 in this division of the cliffs the sequence is clear, may be proved by 
 detailed measurements of the beds at either end of the beach ; and 
 by observing the continuity of a thick and prominent band of lime- 
 stones (with little shale), that occurs near the upper part of the 
 Southerndown cliff and appears again on the Dunraven side of the 
 little bay. (See Fig. 5). 
 
 In the entire section about 180 feet of ordinary Lower Lias lime- 
 stones and shales have been exposed, and of these beds about 100 
 feet are shown in the Southerndown cliff. These beds rest on a 
 series of hard and more massive beds of bluish conglomeratic lime- 
 stone and shale (Southerndown Series) that form the base of the 
 cliffs ; and, as the strata undulate, the sequence can be traced 
 upwards from the lowest bed exposed on the foreshore at the 
 western end of the bluff, and again further eastwards, where the 
 ledges and platforms of rock stretch out seawards for some distance. 
 Unfortunately in these exposures we do not find evidence of the 
 white Sutton Stone and conglomerate anywhere along the base 
 of the cliffs or foreshore. Bristow's section was evidently taken 
 from this portion of the cliffs, and consequently it did not show 
 the Sutton Stone that underlies the Southerndown Beds. He notes 
 the occurrence of an irregular layer of black chert, in addition to 
 the derived fragments of this rock ; and W. D. Conybeare noted 
 that specimens of Gryplicea, coated with chalcedony, were to be 
 found in the Lias of this area.* In order to make clear the 
 sequence we must carry our investigations further eastwards beyond 
 the Witches Point. 
 
 The section of the beds at Southerndown, traced westwards from 
 the fault seen in the cliffs east of Southerndown beach, and near 
 Dunraven Castle, is as follows : 
 
 FT. IN. 
 
 /Limestones and shales (mostly inaccessible). 
 Unicardium cardioides and Gryphcea arcuata 
 
 7 * in lower beds .... About 100 
 
 Thick and prominent mass of irregular limestones 
 
 Ammonites I -. r , if\ f\ 
 
 P , 7 ,. and marly clays 10 
 
 Alternate bands of earthy, compact, and shelly 
 limestone, and dark shale : yielding Ammon- 
 ites [Arietites] Bucklandi, Gryphcea arcuata, 
 Ostrea, Unicardium, lignite- - - - 05 
 
 Hard grey and conglomeratic limestones with 
 thin shaly beds. Gasteropods abundant in 
 different layers of limestone. Cerithium, Litto- 
 rina, Gryphcea arcuata - - - - 56 
 
 Hard grey limestones, conglomeratic, and with 
 
 obscure shaly layers. Ammonites, lignite - 43 
 
 Hard blue and grey limestones, with occasional 
 conglomeratic beds, cherty limestone, and in- 
 durated shale - - 24 3 
 
 Southerndown 
 
 Beds 
 
 * Conybeare and Phillips, Geol, Eng. and Wales, p. 265 ; see also J. J. Cony- 
 beare, Ann. Phil., 1822, p.- 336, 
 
Coast Section. 79 
 
 FT. IN. 
 
 Hard blue limestone, with chert fragments ; 
 Southerndown ) Gasteropods - 10 
 
 Beds. | Hard blue conglomeratic limestones, with in- 
 
 ( durated shaly bands. Seen to depth of - - 13 
 
 Tawney estimated the thickness of the Southerndown Series in 
 this section at 50 feet ; so that our measurements well agree. 
 
 In the south-eastern angle of the bay, on the western side of 
 Witches Point, there is a fault and much disturbance of the strata. 
 The Lower Lias limestones and clays on the north, are brought 
 abruptly against the conglomeratic beds of Lias, the Sutton Stone 
 and conglomerate, and the Carboniferous Limestone on the south : 
 and the downthrow on the north must amount to about 100 feet. 
 The beds on the northern side of Witches Point are for the most 
 part inaccessible, but their general arrangement may be studied 
 from the shore. The white conglomerate is seen to rest irregularly, 
 and with varying thickness, on the Carboniferous Limestone, 
 which here contains many nodules and lenticular bands of chert, 
 and exhibits an undulating anticlinal structure. (See Fig. 5.) 
 Beyond the Witches Point the beds are more accessible at low-tide, 
 and here the Sutton Stone inosculates with the older rocks, having 
 undercut it in places ; a feature also observable near Sutton. 
 
 The main mass of white stone and conglomerate forming massive 
 beds, here occurs at the base, as in the cliff at Panty-y-Slade ; it is 
 from 20 to 25 feet thick, but above are nearly 20 feet of blue, bluish- 
 grey, and pale-grey limestones that contain the same fossils and 
 cannot be separated from the Sutton Series. Higher still, we can 
 just trace the more decidedly bluish limestones, more or less con- 
 glomeratic (Southerndown Series), that underlie the ordinary beds 
 of Lower Lias. 
 
 Along this part of the coast the sequence is interfered with by 
 an occasional dislocation of the beds. On the eastern side of 
 Witches Point there is a cavern, excavated in the white Sutton 
 Beds which rest on the Carboniferous Limestone. The basement 
 Sutton conglomerate contains fragments of chert, and pebbles or 
 boulders of Carboniferous Limestone. It is here 9 feet thick, and 
 is overlaid by about 18 feet of pale limestones more or less brecciated. 
 We are unable to trace the sequence continuously from this point, as 
 a little further north there is a small fault or joggle, the precise 
 throw of which it is difficult to determine, but it appears not to 
 exceed about 4 feet on the further side towards Dunraven. It 
 suffices, however, to carry the Carboniferous Limestone out of sight. 
 From this point we are enabled again to trace the beds upwards 
 from the Sutton Beds to the ordinary Lower Lias ; for although there 
 is another fault that traverses the cliffs in an oblique direction, with 
 a downthrow of about 8 or 9 feet on the west or south-west, yet we 
 are at no loss in comparing the beds on either side of this displace- 
 ment. The beds adjoining the fault present a massive and wall-like 
 appearance, and some of the higher layers of the Southerndown 
 Series present, where weathered, a curiously ragged, cavernous, and 
 
80 
 
 Lias. 
 
 crinkly appearance, standing out in marked contrast from the softer 
 earthy limestones and marls of the Lower Lias above them. (See 
 Fig. 5.) 
 
 Section of the Cliffs from below the Flag Staff, Dunraven, to the 
 cavern near the Witches Point. 
 
 FT. IN. 
 
 /Hard limestones, much jointed, and dark bluish- 
 grey and blue-black shales, with Gryphcea 
 Zone of arcuata, Pholadomya ambigna, P. glabra; 
 
 Ammonites J Irregular and nodular pale earthy limestones, 
 Bucldandi, \ dark shales and marls, with Ammonites angu- 
 &c. lotus, Gasteropods, Gryphcea arcuata, Lima 
 
 gigantea, Unicardium cardioides. (Here and 
 { there we find bands crowded with G. arcuata.} 
 
 Hard and somewhat irregular bluish-grey lime- 
 stones, with sparry veins, shaly beds, fucoidal 
 markings, and occasional fragments of Car- 
 boniferous Limestone. Lima gigantea, LI 
 tuberculata, Ostrea - - - - - 59 
 
 Southerndown J Hard and irregular grey limestones with little 
 Series. ^ or no shale, with sparry veins, and occasional 
 
 fragments of Carboniferous Limestone - - 40 
 Compact grey limestones, with shaly layers : 
 conglomeratic in places. Ostrea liassica, O. 
 multicostata, Lima gigantea, spines of Echini, 
 lignite - .... 4 
 
 'Hard compact pale-grey and bluish-grey lime- 
 stones passing in places into a bed like Sutton 
 Stone. Pecten suttonensis, Ostrea multicostata 6 
 
 Hard bluish -grey and compact limestones, con- 
 glomeratic and brecciated : massive beds. 
 
 Pecten suttonensis 76 
 
 Sutton Series; \ Compact bluish-grey limestones, wedge-bedded 
 
 in places ....... 5 7 
 
 Compact blue limestones, brecciated in places ; 
 passing down into pale -grey brecciated lime- 
 stone, like Sutton Stone. Shelly in places - 5 
 
 Buff, pale-grey, and bluish-grey limestones, 
 
 ^ passing down into white conglomerate. About 15 
 
 It will be noted that beneath the ordinary limestones of the Lower 
 Lias, we come to, first, a series of hard and more or less conglom- 
 eratic limestones that yield Lima gigantea, L. tuberculata, 
 and other fossils. These are from twelve to fourteen feet 
 thick. They rest on a series of bluish-grey and pale-grey 
 limestones, more massive in appearance, that pass down 
 gradually into the white conglomerate. In the upper part 
 of this lower series, which is mainly bluish in colour, we may note 
 the horizontal change of a compact blue limestone into pale-grey 
 stone of the character of Sutton Stone, showing that the test of 
 colour is one not to be entirely depended upon. This, moreover, 
 is shown by the fact that the lowest bed of conglomerate, be- 
 neath the white Sutton Stone and conglomerate, is here and there 
 decidedly blue. Moreover, some of the compact blue limestones 
 yielding Pecten suttonensis, present characters resembling the highest 
 
Coast Section. 81 
 
 beds noted in the section at Pant-y-Slade, beds which there and 
 elsewhere along the coast, form a sort of passage from the white 
 Sutton Stone upwards into the blue conglomeratic Southerndown 
 Beds. 
 
 It is clear that wherever the base of the conglomeratic se ies is 
 exposed, we find the white Sutton Stone and conglomerate (of 
 varying thickness) resting on the Carboniferous Limestone. No 
 attempt is made to correlate particular beds in the Southerndown 
 Series of Dunraven with those under Southerndown, because of the 
 blending of these divisions, and the absence of any definitely marked 
 lithological or palaeontological horizons. 
 
 Undoubtedly the pale creamy and white colour of the Sutton 
 Stone and cmglomerate has led to the supposition that the beds 
 represent the White Lias. In texture, however, the Sutton Stone 
 differs very much from that rock. It should, moreover, be noted 
 that at Penarth the White Lias is i epresented mainly by grey shaly 
 marls, twelve feet or more in thickness, and does not exhibit a mass of 
 compact white limestones such as we find in Somersetshire. Again 
 at the Stormy Cement Works, between Bridgend and Pyle, the 
 White Lias is but feebly developed, and its probable representative 
 is overlain by a thin bed cf conglomerate that occurs at the bass of 
 the Lower Lias. In other localities in this district, as observed by 
 Bristow, the Rhaetic Beds are exhibited in close proximity to the 
 conglomeratic Lias. Bearing in mind the fact that in places the 
 Rhsetic Beds merge almost imperceptibly into the Lower Lias, it 
 would perhaps be wrong to state dogmatically that no portions of 
 th) White Lias are represented in the conglomeratic Lias of South 
 Wales ; but at Subton we have no evidence that this is the case. No 
 specimens of Protocardium philippianum, or Lima precursor have 
 been obtained, but the fossils that do occur include species elsewhere 
 obtained from the basement-beds of the Lower Lias. 
 
 Modifications of the Lower Lias have been noticed elsewhere 
 on Broadfield Down and near Shepton Mallet, where the strata 
 rest in similar situations on the Carboniferous Limestone. The 
 beds and the fossils found near Shepton Mallet are so like those 
 of the Sutton Stone that they could not be distinguished.* This is 
 remarkable, as there is no evidence of any original continuity over 
 the intervening area between beds of this character. The identity 
 is due to the similar origin of the strata, both being largely due to 
 the direct destruction of the Carboniferous Limestone, thus origin- 
 ating as shore-deposits of calcareous mud with which angular de- 
 tritus was occasionally mixed. In other cases where the Lower 
 Lias rests directly on the Carboniferous Limestone, and at the 
 same time presents its ordinary characters, we may infer that the 
 beds were probably laid down on submarine shelves or platforms 
 of the older rock. 
 
 The appearance of the beds in the cliffs of Sutton and Southern- 
 d:wn changes much, according as the layers come within the 
 
 * See also Moore, Trans. Cardiff Nat. Soc., vol. viii. 1877, p. 56. 
 
 7665. G 
 
82 Lias. 
 
 influence of the sea,* also where they are much weathered or present 
 joints or fault-faces. Where the Southerndown Beds have been 
 long exposed in the cliffs, they presant often a wavy or crinkly 
 appearance which is not exhibited on freshly cut faces ; the fact 
 being that softer shaly or marly partings are eroded, and the irregu- 
 larities of the limestone-bands are made more manifest. The 
 Southerndown Beds are more divided in some places than in others 
 by partings of shale. The surfaces of beds just uncovered by the 
 sea present a smooth appearance, and are blue or bluish-grey in 
 colour, while further on, the platforms, long exposed to the action of 
 the sea, have become brown, rough, and honeycombed. Many beds 
 above and below the chief Gryphcea-bed under Southerndown are 
 " fucoidal " at the base, and also here and there on the surface. 
 There is no definite horizon of Gryphsea, nor of Fucoidal beds, nor 
 even of Gasteropods. 
 
 Concerning the organic remains, fossils as a rule are not abundant, 
 and those that are present in the conglomeratic beds of Lias, are 
 difficult to extract, owing to the hardened nature of the rocks. In 
 the lower portions of the Sutton Stone and conglomerate, and especi- 
 ally in the conglomerate exposed above the Carboniferous Limestone, 
 on the coast near the Black Rocks and Pant-y-Slade, corals are not 
 uncommon. Some are identical with forms found in the Alpine 
 Trias. The most abundant species is Elysastrcea Fischeri, 
 which, according to Mr. Tomes, appears " in some places in great 
 masses, the corallites of which, either more or less closely packed, or 
 in disjointed branches, penetrate the stone through and through. "f 
 Many other species of corals have been obtained, and although in 
 Mr. Tomes's opinion many of them " must be assigned to a period 
 antecedent to that at which those beds were formed, "J yet the litho- 
 logical characters of the rocks, and the absence of clayey sediments, 
 suggest that favourable conditions for coral-growth may have 
 existed at the time. It is therefore possible that the peculiar 
 character of the Sutton Stone may have been due in part to the 
 waste of coral-beds : the calcareous mud being mixed with the 
 debris of corals. Higher up in the series, where clay-beds come in, 
 we lose the coral-fauna. The Southerndown Beds on the coast 
 contain but few corals, and the two species recorded are also 
 found in the Sutton Beds. 
 
 The development of coral-life seems to have been local, so that 
 wd cannot attempt definite correlations, based on the occurrence 
 of the many species, with beds in other parts of this country, for, 
 except in Skye, nowhere else in the basement-beds of the Lower 
 Lias have these organic remains been found in such abundance. 
 
 * That the induration of the beds is not to any extent due to the action of 
 sea-water, may be judged from the fact that where the ordinary beds of the 
 Lias pass down to the sea-level, they do not exhibit any marked differences. 
 
 t Quart. Journ. Geol. Soc., vol. xl. p. 368. 
 
 J Ibid., p. 354, and remarks by Prof. Bonney, p. 375. 
 
 See Duncan, Quart. Journ. Oeol. Soc., vol. xxii. p. 15 (1866). 
 
Coast Section. 83 
 
 Only one species (Thecosmilia rugosa) has been recorded from both 
 White Lias and Sutton Stone. 
 
 The evidence of the Ammonites is important. Moore indeed 
 included-^ .[Schlotheimia] angulatus in his list of Sutton Stone fossils, 
 but in his sectionof the strata he notes the occurrence of this species 
 on top of the Sutton Stone at least 18 feet 3 inches from the 
 base ; * and in considering its horizon it is necessary to bear in 
 mind the varying thickness of the beds where they rest in the 
 hollows of the Carboniferous Limestone. Of the two species recorded 
 from the Sutton Series by Tawney, the one named A. sutt r mensis (a 
 form which, according to Prof. Tatef, is allied to A. Johnstoni) 
 was found about 20 feet above the base of the series, both at Dun- 
 raven and at the Sutton quarries ; while the fragment named A. 
 dunravenensis was found about 30 feet above the base of the Sutton 
 Series at Dunraven. We have therefore no actual record of the 
 discovery of an Ammonite in the main mass of the Sutton Stone 
 itself. In many localities, however, Ammonites [Psiloceras] planorbis, 
 which characterise 5 the lowest zone of the Lias, is not found 
 in the bottom-beds ; and these have in places been separated under 
 the name of Ostrea-beds, being conspicuous for the prevalence of 
 Ostrea liassica. 
 
 The two above-mentioned Ammonites, however, evidently occur in 
 the beds which shade off from the white Sutton Stone and conglo- 
 merate into the bluish grey Southerndown series, and thus confirm 
 the view that the Sutton and Southerndown beds constitute one 
 palseontological series. 
 
 The bed with Gasteropods, that occurs at the base of the ordinary 
 beds of Lias at Dunraven, may correspond with that marked as the 
 top of the Southerndown beds under Southerndown. There are, 
 however, at least three distinct bands of limestone in the Southern- 
 down Series that yield Gasteropods. The more prominent bed, 
 about 1 foot thick, occurs about 18 inches below the highest con- 
 glomeratic bed (top of Southerndown Series) under Southerndown. 
 It is a greyish limestone containing conglomeratic seams, and is 
 well seen in ledges on the foreshore, becoming darker and rougher 
 in appearance away from the cliffs. It has been planed off at some- 
 what different levels and inclinations. Tawney noted a bed with 
 a great number of large specimens of Chemnitzia, about 16 feet 
 from the top of the beds which he grouped with the Southerndown 
 Series : his description well applies to the bed above noted, and, 
 as he remarks, it is not possible to extract specimens owing to the 
 toughness of the limestone. J 
 
 Pecten suttonensis of Tawney, which is one of the most abundant 
 fossils in the Sutton Stone, was regarded by Moore as the Pecten 
 Pollux of d'Orbigny, while Tate considered it to be the same as 
 P. valoniensis, Def ranee. It is a somewhat variable form. It occurs 
 
 * Quart. Journ. Geol. Soc., vol. xxiii. pp. 526, 530 ; see also notes by Sir W. 
 V. Guise, Proc. Cottesw. Club, vol. iv. p. 109 ; and Ibid., p. 84. 
 f Quart. Journ. Geol. Soc., vol. xxiii. p. 309. 
 t Quart. Journ. Geol. Soc., vol. xxii. pp. 75, 76. 
 
 7665. y 2 
 
84 Lias. 
 
 in the beds at Shepton Mallet and also in the peculiar cherty modi- 
 fications of the Lower Lias at Harp tree Hill. At the last-named 
 locality this species occurs together with Ostrea midticostata and 
 Cardinia suttonensis, two of the most abundant Button Stone fossils, 
 and in the same beds at Harptree there occur A. [Psiloceras] planorbis 
 and A. [P.] Johnstoni (torus), furnishing strong corroborative 
 evidence that the Button Stone should be included in the zone of 
 Ammonites planorbis* A. [Psiloceras] Johnstoni has been found 
 in beds like the Sutton Stone, at Shepton Mallet. 
 
 From the published lists of fossils it is difficult to decide what 
 were the precise horizons of all the species. Thus Tawney has given 
 lists from the Sutton and Southerndown Series at various localities ; 
 Prof. Tate has given a list of fossils from the Sutton Stone, with a 
 revision of Tawney's species ; and Moore has done likewise, although 
 his revisions differ in several respects from those of Prof. Tate. 
 Moore has also given lists from the conglomeratic Lias above the 
 Sutton Stone at Southerndown, and lists from Brocastle, &c.f So 
 much difference of opinion exists on the identification of some 
 species, that it is best only to give those about which no doubt has 
 been expressed. 
 
 The following fossils have been recorded from the Sutton Stone : 
 
 Ammonites (see p. 83). 
 
 Neritopsis exigua. 
 
 Patella. 
 
 Pleurotomaria. 
 
 Trochus. 
 
 JCardmia suttonensis. 
 jGryphsea. 
 JHinnites. 
 JLima hettangiensis. 
 
 J tuberculata. 
 
 JOstrea irregularis. 
 
 multicostata. 
 
 JPecten suttonensis. 
 JPIicatula intusstriata. 
 JAstroccenia (Stylastraea) gib- 
 bosa. 
 
 reptans. 
 
 Cyathocrenia incrustans. 
 JElysastreea Fischeri. 
 
 Montlivaltia. 
 
 Rhabdophyllia recondita. 
 
 Thecosmilia mirabilis. 
 
 rugosa. 
 
 suttonensis. 
 
 The following species have been recorded from the Southern 
 down Series : 
 
 Am. [Schlotheimia] angulatus. 
 Belemnites acutus. 
 Cerithium nodulosum. 
 Littorina ? clathrata. 
 Cardinia. 
 
 Gryphaea arcuata. 
 Lima duplicata. 
 
 Lima gigantea. 
 
 - tuberculata. 
 Ostrea liassica. 
 
 - multicostata (arietis). 
 Pecten suttonensis. 
 Plicatula intusstriata. 
 Echinodcrm spines. 
 
 * Geol. East Somerset (OeoL Survey Memoir], p. 108. See also Moore, Quart. 
 Journ. Geol. Soc., vol. xxiii. p. 492. W. W. Stoddart noted the occurrence 
 of Sutton Stone fossils in the Zone of Ammonites planorbis of the neighbour- 
 hood of Bristol, but unfortunately he included the White Lias in that zone. 
 Quart. Journ. Geol. Soc., vol. xxiv. p. 203. 
 
 t Tawney, Quart. Journ. Geol. Soc., vol. xxii. p. 79 ; Tate, Ibid., vol. xxiii. 
 p. 309 ; Moore, Ibid., pp. 530, etc. 
 
 * Specimens so marked were obtained by myself, and identified by 
 Messrs. Sharman and Newton, 
 
Coast Section. 85 
 
 The ordinary beds of Lower Lias above the Southerndown Series 
 at Dunraven, have yielded the following species : 
 
 *Am. [Schlotheimia] angulatus. 
 
 * 
 
 [Arietites] Bucklandi. 
 
 * [ ,, ] Gonybearei. 
 
 * [Aegoceras] laqueolus ? 
 
 [Arietites] semicostatus. 
 
 Belemnites acutus. 
 
 Cerithium. 
 *Turritella (cast). 
 *Gryphaea arcuata. 
 
 Lima duplicata. 
 
 gigantea. 
 
 Hermann!. 
 
 *0strea multicostata (arietis). 
 *Pholadomya ambigua. 
 
 * glabra. 
 
 *Unicardium cardioides. 
 
 Rhynchonella calcicosta. 
 
 Pentacrinus tuberculatus. 
 
 From Dunraven onwards to Aberthaw, the coast is bounded by 
 cliffs exhibiting the blue and brown argillaceous limestones, shales, 
 and marls that overlie the conglomeratic Lias of Southerndown. On 
 the eastern side of the Dunraven headland, the conglomeratic beds 
 dip away beneath the beach, being repeated for a short distance by 
 the oblique fault (before mentioned, p. 79.), and by another fault 
 a little further on ; beyond which they are not seen again along the 
 coast-sections.j 
 
 These cliffs exhibit, perhaps, the finest exposure of the Lower 
 Lias Limestones in this country. We have not the complete se- 
 quence of Lias visible at Lyme Regis ; but here in South Wales the 
 zones of Ammonites angulatus and A. Bucklandi (taken together) 
 are much more fully and continuously exposed. It is true that li 
 miles of cliffs, showing the same set of beds, dislocated here and 
 there by faults, seem a little monotonous ; and as fossils are neither 
 very varied nor very abundant, we cannot wonder that the cliffs for 
 the greater part of the distance are but little visited by the geologist. 
 The beds must attain a thickness of quite 200 feet, and for a great 
 part of the way the limestones stand out also in ledges and platforms 
 along the foreshore, so that our progress along these natural pave- 
 ments is a very happy one, excepting where it is diversified by faults 
 that modify the strike of the ledges, or by heaps of boulder-shingle 
 that lie here and there on the surfaces of the platforms. 
 
 The following general sequence is shown : and the upper beds 
 being more jointed and open, springs are thrown out at their 
 junction with the bluer beds : 
 
 Yellowish argillaceous limestones ; about 55 bands, on the 
 whole thicker than the beds below and with less clay 
 the limestones here and there exhibiting rhomboidal 
 
 Zone of 
 
 Ammonites 
 
 Bucklandi, 
 
 etc. 
 
 jointing. 
 
 Bluish-grey limestones ; about 80 comparatively thin 
 and on the whole irregular bands, alternating with thin 
 clays, shales, or marls. 
 Southerndown Series, etc.; 
 
 * Species obtained by myself, and identified by Messrs. Sharman and 
 Newton ; some of these and other species are recorded by Moore. 
 
 f [Except at Whitmore Stairs, where Mr. Tiddeman has found some lime- 
 stones full of fragments of chert and limestone brought to view in the fore- 
 shore in the crest of an anticline.] 
 
 J These beds are very similar in character to the Black Limestone locally 
 known as " Aberdo Limestone," in the upper part of the Carboniferous Lime- 
 stone of Flintshire. A. Strahan, Geol. Rhyl (Mem. Geol. tiurv., Sheet 79 t 
 N.W.), pp. 15, 16. 
 
86 Lias, 
 
 The lower division attains a thickness of about 80 feet esti- 
 mated from the top of the conglomeratic series ; and in the first 
 cliff beyond the angle formed by the Dunraven headland, the 
 lower beds are shown to a height of about 70 feet, and the upper 
 occupy about 50 feet above. The cliffs between the gullies of 
 Cwm-mawr and Cwm-bach, rise to a height of 200 feet, so that 
 the limestone-series here exceeds that thickness, though not per- 
 haps to any great extent. We do not however notice any beds 
 in the cliffs as far as Aberthaw, that indicate higher divisions of 
 the Lower Lias, and, judging by the fossils, the beds belong to the 
 zones of Ammonites angulatus, A. Bucklandi, and A. semicostatus, 
 and mainly to that of A. Bucklandi. 
 
 On the whole the beds are tolerably flat, but with a general inclina- 
 tion (interrupted by a gentle anticlinal) towards Nash Point. Ap- 
 proaching this point, a thick mass of limestones appears on the top 
 of the yellow beds in the cliffs, forming a conspicuous band as at 
 Southerndown, and this caps the buttress of Nash Point. Here, 
 then, the cliff is formed of a thick mass of limestones, resting en 
 tolerably thick beds of limestone, bluish and yellowish, and these 
 again on bluish limestones, on the whole even-bedded with here and 
 there crinkly layers and thin partings of shale. The limestones 
 form thick ledges and pavements of rock, varying in direction with 
 the inclination of the beds, and the changes produced here and 
 there by faults. Gryphcea arcuata, Lima gigantea, anl Ostrea, occur, 
 often in clusters, together with Pentacrinus, small ammonites and 
 occasionally lignite. Pholodomya appears not uncommon in the 
 higher jointed beds, fallen masses of which lie on the beach. 
 
 The cliffs below the Nash lighthouses, show the thick mass ot 
 limestones towards the upper portion of the cliffs, and this is let 
 down to lower levels here and there by faults which thus counteract 
 the influence of the dip. In one instance, not far from Dunraven, 
 a small fault, which displaced the upper beds 2 or 3 feet, was lost 
 towards the base of the cliff, the layers of limestone being just 
 separated, then simply bent, and finally no appearance of disturbance 
 was visible. (See Fig, 6.) I have seen similar faults in the Purbeck 
 beds near Swanage. They appear to be due to irregular com- 
 pression of the beds, and not to the effects of landslips. 
 
 Immediately east and west of St. Donat's Point, the beds are 
 somewhat faulted and tumbled. There is however no great displace- 
 ment, and the ledges display Gryphcea arcuata, Lima gigantea, A. 
 [Arietites] Bucklandi, and lignite. From the higher beds I obtained 
 A. [Arietites] Conybearei. There is a considerable accumulation of 
 coarse boulder-shingle here, and Jarge blocks are taken away for 
 building purposes, and occasionally to be burnt for lime. Some of 
 the beds exhibit fucoidal markings. 
 
 The beds south of Llantwit-Major are much jointed ; in fact the 
 beds showing rhomboidal jointing come down to the beach, and the 
 blocks are worked off by the sea in huge masses. These are readily 
 broken up and rounded, so that the ledges of rock are in many places 
 irregularly covered by accumulations of boulder-shingle. From 
 
Coast Section. 87 
 
 Dan twit to Stout Point the beds are tolerably level and unbroken 
 the highest part of the cliffs being 146 feet. There is a slight sea- 
 ward dip, and this continues towards Summerhouse Point, where 
 the cliffs overhang in places. A short distance east of the Camp, 
 the cliff ends, the last beds seen here being 8 or 10 feet of jointed 
 limestones and clays. 
 
 From a short distance east of Summerhouse Point to the east of 
 the River Daw, at East Aberthaw, there are no cliffs, the coast being 
 bordered by alluvial flats, hillocks of blown sand and a high beach 
 of boulder-shingle. It is this shingle, composed of rolled limestone 
 derived from the cliffs further west, that has furnished and still 
 furnishes the celebrated Aberthaw lime. All the " lime " shipped, 
 goes away in the form of pebbles (3 or 4 inches in diameter), and 
 those are reckoned the best that are taken between high- and low- 
 water mark, where washed by the sea. The trade has of late years 
 
 FIG. 6. Fault in Lower Lias, east of Dunraven Castle, 
 Glamorganshire. 
 
 considerably declined, in fact, since the introduction of railways, the 
 lime from places inland has come more and more into use ; but I 
 was informed that about seventy years ago (1827-1837) there were 
 sometimes twentyjvessels in the " Port," that had come to take 
 away the stone for lime. 
 
 It is curious that the stones gathered from the t higher part of the 
 beach, where they are sun-dried, are said to be not so good for 
 hydraulic lime ; but they are burnt for local purposes at the lime- 
 kiln near Ocean House, West Aberthaw, where " lump lime " and 
 " ground lime " are prepared. 
 
 East of the River Daw, by Pleasant Harbour, the platforms of 
 rock contain Gryphcea arcuata, and Lima gigantea. The cliffs for 
 some distance show hard blue limestones in tolerably thick beds, 
 dipping gently eastwards, and yielding the same fossils together 
 with Ammonites. 
 
 [To this account by Mr. Woodward we now add that evidence has 
 been obtained by Mr. Tiddeman that the Lias rests directly upon the 
 
88 . Lias. 
 
 Carboniferous Limestone at Wick. The older rock is shown in four 
 inliers referred to on p. 14. The Lias in the case of the inlier 
 half a mile west-north-west of Wick assumes a rag-like character 
 near its base, and corals become abundant in some bands. A fifth, 
 however, which is only doubtfully referred to a Carboniferous age, 
 lies half a mile north of the last, and consists of tufaceous limestone 
 with traces of conglomerate. These sections, taken in connection 
 with an exposure of conglomeratic limestones at Whitmore Stairs, 
 form the evidence for extending the dry land in Keuper times as far 
 south as is shown in Fig. 2.] 
 
CHAPTER VIII. 
 
 FAULTS AND DISTURBANCES 
 
 By A. STRAHAN. 
 
 Though frequent reference has been made in the preceding chap- 
 ters to the faults and disturbances by which the rocks have been 
 brought to their existing structure, it will be convenient now to 
 summarise our conclusions with respect to them. They may be 
 divided at once into two main principal groups, namely, those 
 which preceded the deposition of the Secondary strata, and which 
 therefore affect the Carboniferous rocks only, and those which were 
 of later age than the latest Lias represented in the district, and 
 which affect all the rocks. The first group belongs to the powerful 
 system of east and west folding which reached its greatest intensity 
 in Somerset and Devon. It began after the close of the Carbon- 
 iferous period and concluded before the Trias commenced. It 
 therefore coincided with what was in this part of the world a pro- 
 longed continental period. To it was due the stupendous denuda- 
 tion undergone by the older rocks, and the unconformity between 
 them and the Secondary rocks which is so finely displayed in the 
 Vale of Glamorgan. 
 
 Pre-Triassic Disturbances. 
 
 In the adjoining Sheet (263) we had evidence of a series of anti- 
 clines ranging through Cardiff, Cadoxton, and Barry.* One only 
 of these is exposed to view in this western part of the Vale of Gla- 
 morgan, namely, that which brings to the surface Silurian rocks 
 near Cardiff and Old Red Sandstone near Cowbridge. The evi- 
 dence of its pre-Triassic age is found in the fact that the Triassic 
 rocks did not share in the upheaval, but that, on the contrary, 
 they rest at low inclinations on the upturned edges of the deeply- 
 denuded Palaeozoic rocks. This relation is well shown in the haema- 
 tite-workings illustrated in Figs. 9 J.O and 11, pp. 108, 109, and can 
 be seen or inferred in a multitude of other places. 
 
 It is to be noticed also that pre-Triassic denudation was especially 
 active along the Cowbridge-Cardiff anticline. The crest was so 
 deeply eroded as far west as the neighbourhood of Cowbridge that 
 a valley was formed along the axis of upheaval. Further west, 
 however, where the anticline tends to die away, the arch remained 
 unbroken, and this surviving part of the crest, with what may be 
 
 * The Country around Cardiff (Geolt Survey Memoir), p 22| 
 
HO Fimlts >m<l Disturb me cs. 
 
 called the foundations of the ruined arch east of Cowbridge, subse- 
 quently formed the Triassic island shown in Fig. 2. The anti- 
 cline, as far west as Pendoylan, took the form of a single broad 
 arch, but in that neighbourhood became compound. The main 
 axis of upheaval runs by Pen-llin, where it brings the Lower Lime- 
 stone Shales to the surface, and thence to near Porth-cawl (p. 13), 
 but subsidiary anticlines branch off to the north and south, as shown 
 in Fig. 1. The folding was accompanied, no doubt, by some faulting, 
 and at Pen-llin a fault which throws the shales against the Main 
 Limestone passes under Lias apparently without affecting it ; 
 the fault on the south, of Stalling Down also has not been detected 
 in the Secondary rocks of Cowbridge. 
 
 To the north of the anticline the Upper Carboniferous rocks come 
 on in succession, all dipping north except in some local undulations. 
 But at a distance of about six miles from the axis we reach the 
 synclinal region of Ton-yr-efail and Llandyfodwg, which again 
 is followed by the anticline of Pontypridd and the Moel Gilau 
 Fault.* With these, however, except that they form part of the 
 same system of disturbances, we are not now concerned. To the 
 south of the anticline there lies a region of gently-undulating Second- 
 ary rocks, under which the structure of the Palaoozoic rocks is un- 
 known, but in which the possibility of the existence of a coal-field 
 claims attention. 
 
 The evidence available in the area described in this volume is 
 scanty. Near Wick the Carboniferous Limestone dips north, which 
 suggests that other anticlines lie south of the Cowbridge-Cardiff 
 anticline. In the adjoining Sheet on the east (2()3) the proof of 
 such being the case is more conclusive, for the existence of at least 
 two other anticlines is evidenced at Cadoxton and Barry, while a 
 fourth traverses Flat Holme, all of them trending east and west. 
 It would seem, therefore, that the Pala3ozoic floor under the Second- 
 ary tract is more likely to be formed of folded Lower Carboniferous 
 rocks than of a syncline of Coal Measures. 
 
 Post-Liassic Disturbances, 
 
 The later system of disturbances in this region takes a direction 
 somewhat unusual in South Wales. Generally the most prominent 
 faulting has been the north-north -westerly system which cuts 
 through the Coal Measures and, to a less degree, the Secondary rocks, 
 while the leading disturbances belong to the W.S.W. system, of 
 which the Vale of Neath furnishes a notable example. Here, on 
 the contrary, some of the faults run due east and west, and others 
 west-north-west ; north and south faults are exceptional, and the 
 Neath system is unrepresented. We arrive then at the fact that 
 there is some agreement in direction between the earlier and the 
 later disturbances, and it becomes of interest to determine how far 
 there may be coincidence in position also, in view of the theory 
 
 The Country around Pontypridd (Gc.nl . ^vrroj Mviwiir), Chapter V1J I. 
 
Post-Liassic. 
 
 91 
 
 that lines of weakness 
 once established have 
 proved lines of faulting 
 or folding at successive 
 geological periods. 
 
 Turning to the Cardiff - 
 Cowbridge anticline, we 
 are met with the fact 
 that it does not strictly 
 coincide with the axis of 
 upheaval of later times. 
 The Rhsetic base, which 
 forms a convenient datum - 
 line, lies at a lower level 
 on it than either to the 
 north or south of it. 
 Moreover, one of the 
 principal lines of post- 
 Liassic upheaval, which 
 runs through Bonvilston 
 to the south of Cowbridge, 
 keeps about three miles 
 north of the line of 
 principal pre-Triassic up- 
 heaval, and coincides with 
 no pre-Triassic anticline. 
 This post-Liassic anticline 
 is followed northwards by 
 a syncline at Llanbleiddian 
 (p. 66), which again corre- 
 sponds to no syncline in 
 the older rocks, but lies 
 partly over the site of the 
 Stalling Down anticline. 
 From this neighbourhood 
 a fault runs westwards 
 through the Lias to St. 
 Bride's Major, but, except 
 that it runs east and west, 
 it shows no connection 
 with the structure of the 
 older rocks ; on the other 
 hand the fault in the older 
 rocks near Pen-llin is not 
 recognisable in the Lias. 
 Again a post-Liassic anti- 
 cline crosses the Ogmore 
 considerably south of the 
 anticlinal axis in the 
 Carboniferous Limestone. 
 
 .19 
 
 i-O 
 
 S 
 
 O 
 
 o" 
 
 H 
 
Faults <(vd Disturbances. 
 
 X 
 
 s 
 
 -X <! 
 >< 
 
 00 
 
 d 
 
 I 
 
Post-Liassic. 93 
 
 The sections forming Figs. 7 and 8 have been drawn with a 
 view to illustrating the differences in the structure of the newer 
 and older rocks. In. Fig. 7 it will be noticed that the Keuper and 
 Ehaetic thin out from south to north and leave the Lias in con- 
 tact with the Carboniferous Limestone. Here, therefore, we can 
 fix a point on the Khsetic shore-line. But the surface of the 
 ilhsetic land, as thus determined, descends to a lower level than 
 the shore-line, obviously in consequence of the subsequent forma- 
 tion of a syncline. That syncline, however, is not situated over a 
 syncline in the older rocks, though, no doubt, the dip of those 
 rocks must have been slightly modified by it. Similarly Fig. 8 
 shows Triassic conglomerate on the shore south-west of Sutton, 
 but Lias resting directly on the Carboniferous Limestone at Sutton. 
 The Rhaetic shore-line therefore ran between the two spots. The 
 conglomerate comes in onOgmore Down and at Lalestoii, but between 
 the two, though the surface of the Carboniferous rocks sinks to 
 sea -level, there is neither Keuper nor Khsetic below the Lias. 
 Here again, therefore, we find what was Khsetic land lying lower 
 than what was Rhaetic sea, in consequence of post-Liassic move- 
 ments, and in this case the post-Liassic syncline is not situated on 
 a syncline in the older rocks. 
 
 These instances show that the disturbances in the Secondary 
 rocks cannot be trusted to indicate the structure of the older rocks. 
 There is certainly no correspondence in detail, and in view of the 
 fact that the Vale of Glamorgan is an anticlinal region as regards 
 the older rocks, but still part of a basin of Secondary rocks, there 
 would appear to be no correspondence in the broader features 
 either. 
 
 The tract of Secondary rocks, entending from St. Mary Hill to 
 Pyle, is traversed by a number of faults with a general west-north- 
 westerly direction, which run obliquely to the strike of the under- 
 lying Carboniferous rocks. In fact, no connection exists between 
 the superimposed structures of the Secondary and those of the Car- 
 boniferous Rocks. The later rocks lie in a trough eroded along the 
 northern limb of the Cowbridge-CardifT anticline, so as to rest partly 
 upon the Carboniferous Limestone and partly on the Millstone 
 Grit. Their existence is due mainly to the fact that pre-Triassic 
 denudation had led to the formation of a strait as shown in Fig. 2, 
 but their survival is due partly also to the faults. 
 
 One of these faults forms the Triassic boundary from Llanilid 
 westwards, while another, parallel to it, forms the Liassic boundary 
 north of Bridgend and the Triassic boundary thence westwards 
 to Kenfig. These are downthrows to the south, and though there 
 are intermediate faults with downthrows north, the generalisation 
 holds good that southerly downthrows characterise the northern 
 margin of the Secondary tract. The south side, on the contrary, 
 is characterised by faults with a northerly downthrow. One, for 
 example, bounds the Lias of Stormy on the south, while others throw 
 the Rhaotic and Trias against the Carboniferous Limestone towards 
 Laleston. The faults, therefore, may be said in a general way 
 
94 Faults and Disturbances. 
 
 to border the trough, which amounts in the present case to saying 
 that they tend to run along the original margins of the Secondary 
 rocks. A similar coincidence has been noticed in the neighbourhood 
 of Belfast, where it has been attributed to differential movement 
 having been set up between the older and newer rocks by the shrink- 
 ing and consolidation of the latter. 
 
95 
 
 CHAPTER IX. 
 GLACIAL DEPOSITS. 
 
 Introduction. 
 By T. 0. CANTRILF. 
 
 The glacial deposits which occur in the area embraced by this 
 map airi almost restricted to the northern parts of the district, and 
 do not extend to the south of St. Mary Church or of Merthyr-mawr. 
 
 Most of the material is of a gravelly nature, but locally it becomes 
 more clayey, as along the north-eastern margin of the map. There 
 appears to be no difference in age between the Gravel and the Boulder 
 Clay, for the one passes laterally into or give s place to the other in 
 such a way that no hard and fast line can be drawn between them. 
 As a general rule, however, the gravelly material prevails near the 
 outer margin of the glaciated region. 
 
 The Boulder Clay generally forms featureless slopes, whereas 
 the Gravel usually gives rise to hummocky ground, diversified by 
 numerous mounds and hollows, the latter often occupied by small 
 ponds or peat^flats. 
 
 That the present southerly margin of the glacial deposits approxi- 
 mately coincides with the original limit of the ice-flow may be 
 inferred from the remarkable absence of drift-material in the soil 
 of the coast-region, the only exceptions being a boulder of dark-green 
 brecciated felsite, 2 feet 6 inches across, by the roadside at Pentre 
 near Llantrithyd, half a mile south of the present drift-margin ; 
 another of quartz-felsite and of about the same size which lay in 
 the village of St. Athan, and was removed about the year 1897 to 
 Barry ; and lastly two small patches of sand and gravel in the 
 Dawen valley near St. Mary Church. 
 
 The materials of both the Gravel and the Boulder Clay are almost 
 wholly of local origin, the only known exceptions being the boulders 
 mentioned above ; another, 6 feet long, of quartz-felsite, which lies 
 in a field 620 yards S. 23 W. of Newton House near Cowbridge ; 
 and the boulders from Pencoed discussed on p. 100. To them may 
 be added the supposed chalk- flints which occur in many parts of 
 the Vale of Glamorgan, but the origin of which is not certainly 
 proved*. 
 
 With these exceptions the boulders are rounded or subangular 
 pieces of Pennant and other Coal Measure grits, Millstone Grit 
 and Carboniferous Limestone, together with pebbly grits derived 
 from the upper part of the Old Red Sandstone and some red 
 
 * The Country around Cardiff (Geol. Survey Memoir), p. 78. 
 
96 Glacial Deposits. 
 
 grits from the lower part of the same formation. These materials, 
 some of which have been transported from the north side of 
 the Coal Field, are mixed in van-ing proportion with fragments 
 of Trias and Lias of local origin. 
 
 Eastern Part. 
 By T. C. CANTRILL. 
 
 The Boulder Clay which extends along th northern margin of 
 the map as far westward as Llanilid presents few good sections ; it 
 may be seen, however, at the old haematite-workings at Mwyndy, 
 but gives place to gravel at Pont Clun in the Ely valley, where sand 
 and gravel have been proved to a depth of 64 feet (p. 103). Farther 
 west much of the Coal Measure ground of Coed Trecastell, Gwaun 
 Uanharry, and Mynydd Hywel Dico is covered with a stiff impervious 
 yellow clay-with-stones which appears to be a boulder-clay derived 
 largely from the Coal Measure shales and sandstones, but which is with 
 difficulty distinguished from those rocks in a weathered condition. 
 
 A similar deposit occurs to the east of Groesfaen, and to the north 
 of Peterston Station, but gives place westwards in the lower ground 
 to gravelly drift. Here and elsewhere the gravelly type of drift 
 often shows so clayey or loamy a matrix as to be inseparable from 
 the boulder-clay type. 
 
 In a gravel-pit on the north side of the valley west of Warren Mill, 
 near Welsh St. Donats, the pebbles consist chiefly of Pennant sand- 
 s one, but include some of Old Red grit, with a few of vein-quartz 
 and ironstone. In another, south-west of Mountain Lodge, Pennant 
 sandstone again predominates, and sandy gravel of the same char- 
 acter has been dug to a depth of 8 feet, 400 yards north-east of Taly- 
 garn. At Ty-draw, north of Bryn Saddler, on the west side of the 
 railway, a ballast-pit shows coarse gravel with Pennant pebbles 
 ranging up to 6 inches in length, and gravel has been dug also 
 farther north, between the railway and Tyle-garw. 
 
 Near Ystradowain there are old pits at Rhyd-halog, one in loamy 
 Pennant gravel by the roadside near the railway-bridge ; another, 
 400 yards south of the farm, has been opened on a terrace-like flat 
 some 20 feet above the stream ; it shows on one side yellow sand 
 with pebbles of coal, and on the other about 10 feet of gravel. At 
 Castell-y-mwnw 3 near Llanharry station the e is a small gravel and 
 sand-pit 7 feet deep in which similar pebbles occur in the sand ; and 
 in another pit, 200 yards farther to the north-east, clean Pennant 
 gravel with layers of sand is exposed for six feet. Farther west, at 
 New Forest House south of Llanharry, a roadside exposure shows a 
 few feet of subangular gravel chiefly of Pennant sandstone, but 
 containing in addition several ironstone-nodules, one or two frag- 
 ments of red sandstone, and several pieces of yellow g it and sand- 
 stone, probably derived from the Coal Measures. 
 
 The gravel assumes a markedly moundy form near its southern 
 limit, especially along the high ground extending westward from 
 
Eastern Part. 97 
 
 Cottrell past Welsh St. Donats and Ystradowain to Llanilid. On 
 the lower ground it sometimes loses this character, while becoming 
 more clayey and tending to assume the featureless surface associated 
 with Boulder Clay, as in the Ely Valley; but along the courses of the 
 streams it appears to become sandy. At Cae-rhingyll, however, 
 east of the river Ely, a large mound, standing up conspicuously from 
 the surrounding alluvium, appears to consist of gravel. A similar 
 mound lies east of Pendoylan village. 
 
 Yellowish clayey gravel is exposed to a depth of some 40 feet in a 
 deep dingle coming down from the west to Cae'r-wigau Mill south of 
 Pendoylan. Prof. Edgeworth David* gives the following percent- 
 ages of boulders in a brown sandy boulder-clay at Pendoylan : 
 Carboniferous sandstone 51, Lias 18, Rhaetic 9, red Triassic sand- 
 stone 9, Millstone Grit 5, Carboniferous Limestone 4, light-green 
 dolomitic conglomerate 4. In addition to these he records a few 
 chalk-flints. 
 
 South and west of Pendoylan the gravel rises up and over the 
 Carboniferous Limestone escarpment and Liassic plateau of Welsh 
 St. Donats, and becomes remarkably moundy a character well 
 exhibited on Mynydd-y-glew (north-east of Welsh St. Donats), and 
 on the high ground about a mile south-west of Llanharry. The 
 same character is noticeable about Llanilid. In all these localities 
 there lie between the mounds small hollows many of which are 
 occupied by peat. On Mynydd-y-glew one of these peat-bogs 
 named Fawnog on the map was evidently till recently a pool, and 
 there are two others, known as Megan-felin and Pysgodlyn-mawr, 
 which still contain water. This gravel offers no resemblance to a 
 terminal moraine along its southern margin, but thins off to a knife- 
 edge. 
 
 West of Welsh St. Donats the margin gradually descends into the 
 Dawen Valley near Cowbridge ; it forms the terrace of gravelly soil 
 on which the town is built and there terminates. Two outliers, how- 
 ever, near St. Mary Church, suggest that it may have extended 
 ,' everal miles farther down the Dawen Valley. In the more northerly 
 of these, which lies on some flat ground north-east of How Mill, the 
 only exposure is furnished by a small sand pit in a field on the north- 
 west ide of the road to St. Hilary, .300 yards from the mill. It 
 shows 6 feet of clean brownish-yellow sand containing a few pebbles 
 of quartz and other rocks, several chalk-flints, and a small block 
 of quartz-pebbly grit probably from the Old Red Sandstone. The 
 base of this outlier must be about 35 feet above the alluvium of the 
 Dawen at How Mill. 
 
 The second outlier caps some rising ground west of Gigman Mill, 
 the base of the deposit being about 30 to 40 feet above the alluvium, 
 and about 10 or 20 feet lower than that of the other outlier. It 
 has been opened up to a depth of 10 feet in a sand-pit 450 yards 
 west-south-west of Gigman Mill. The yellow sand therein ex- 
 hibited contains numerous pebbles of yellow sandstone, red sand- 
 
 * Quart. Journ. GeoL Soc;, vol. xxxix. (1883), p. 39.- 
 766S. H 
 
stone, vein-quartz, chert, black shale probably from the Coal Meas- 
 ure.-, and several (supposed) chalk-flints. In another small pit 
 north-west of this, and just on the edge of the wooded side of the 
 Dawen Valley, there is a small block of quartz-pebbly grit. Sub- 
 angular fragments of what appears to be chalk-dint occur in the 
 soil of the small tributary valley one-third of a mile east of Old 
 Beaupre. 
 
 These isolated patches seem to be relics of a tongue of sandy 
 gravel which once extended southwards along the Dawen Valley 
 for some distance beyond the main ma-s of drift. Not only, how- 
 ever, has the gravel been in great part removed, but the valley has 
 been considerably deepened by post-glacial erosion. The mass of 
 the material is such as might have been carried by effluents from 
 the ice-sheet, but the occurrence of a few larger boulders is difficult 
 to explain except on the supposition that ice in some form, for a 
 time at least, reached the spot. 
 
 North of Cowbridiie the high Carboniferous Limestone escarp- 
 ment of Pen-llin limits the drift-covered area. The part of the 
 Dawen Valley known as Pen-llin and Newton Moors is covered with 
 a gravelly deposit which presents the composition of glacial gravel, 
 while at the same time it has the form of an alluvial fiat. It may 
 be supposed that the river, before it was confined to an artificial 
 channel, meandered and smoothed down such irregularities of 
 surface as may have existed. Much of the material therefore might 
 equally well be regarded as drift or as alluvium. Along the foot of 
 the escarpment there lies some brown loam which may be nothing 
 but rain wash. 
 
 The onlv known far-derived boulders which occur within the 
 eastern part of the map-area are the Pentre boulder near Llan- 
 trithvd. the Newton boulder near Cowbridge. and the St. Athan 
 boulder. 
 
 The Pentre boulder lies at the corner of a short lane on the west 
 side of the road leading north from Pentre. and :2<X> yards north of 
 Tv-iu-haf : it rests on bare Carboniferous Limestone at an altitude 
 of -^L!~> feet above < 'runance Datum, and half a mile south of the 
 southern limit of the drift. IT is unaccompanied by any other 
 drifted material. It measures 2i-x:2xlJ feet. Under the micro- 
 scope a slice [E. iN'> s j of the rock is described by Mr. Teall as a 
 dark-re-?n brecriated felsite. composed of a few porphyritic crystals 
 of felspar :orthoclase) and fragments of crystalline felspar-rock in a 
 finely-crystalline matrix largely composed of felspar. It was pro- 
 bablv a tutt. The source of the boulder is not known. 
 
 The Newton boulder stands at the north end of a field at 6:20 yards 
 distance S. :2:3 : W. from Newton House between Cowbridge and 
 Llaiisannwr. at about 100 feet above Ordnance Datum. It rests 
 on glacial clayey gravel near the southern limit of the drift. It 
 measures 6 x 4J feet, and is partially embedded in the ground. 
 Under the microscope [E. 3-S26] it is described by Dr. Flett as a 
 riuanz-felsite \virh phenoerysts of quartz, orthoclase. and plagio- 
 cla?e, in a felsitic matrix which i? somewhat brerciateH. 
 
Wr.Nfr.rn /V/V. 99 
 
 The St. A than bouMc.r has a somewhat remarkable history. 
 According to tradition it once lay somewhere to the south of Giles- 
 ton, at or about sea-level. It was taken to the village of St. Ath&n, 
 where it remained for some time, and was thence removed about 
 the year 1897, under the superintendence of Mr. Storrie, to the 
 Romilly Park, Barry, where it now lies. It measures about 3 feet 
 10 inches x 2 feet 8 inches x 2 feet. A small fragment of the boulder 
 has been sliced [E. 3830] and examined under the microscope, 
 and is described by Dr. Flett as a quartz-felsite with quartz and 
 felKpnr phorioorysts. Dr. Flett adds that all three boulders are 
 very similar to one another and may without difficulty 1)6 believed 
 to have been derived from the same area. 
 
 Large blocks of Old Red pebbly grit and pebbly yellow sandstones 
 or grits from the Coal Measures occur not infrequently on the 
 drift-covered areas. The following list gives details of some of the 
 largest which have been noticed in the eastern part of the district : 
 
 Pencyrn, east of Llansannwr, pebbly brown grit, 4 ft. x 3 \ ft. 
 X 2J ft. ; Grippy, City, near Llansannwr, coarse yellow grit, 2J ft. ; 
 ' Careg-lwyd,' New Forest House, Ystradowain, Pennant, 3 ft. x 3 ft.; 
 500 yards S.W. of Ty'r-capper, Llansannwr, Pennant, 3 ft. ; Mur-y- 
 llengau, Ystradowain, Coal Measure sandstone, 3J ft. ; 300 yards 
 south east of Ty-chwith, Ystradowain, Old Red Sandstone, 2J ft. ; 
 200 yards N.W. of Ash Hall, Ystradowain, Pennant, 6 ft.x3J ft. ; 
 350 yards S.S.E. of Llwyn-y-penau, near Groes-faen, Pennant, 
 4J ft. x 4 ft. ; 300 yards S.S.W. of Allt-y-Cawri, near Miskin, Pen- 
 nant, 10 ft. x 7 ft. x 5 ft. ; 350 yards east of Rhyd-halog, near 
 Talygarn, Keuper conglomerate, 4J ft. ; one-third of a mile west of 
 Brigam, near Llanharry, Pennant, 3 ft. All have been derived 
 from ground lying to the north-east, north, or north-west. 
 
 Western Part. 
 By A. STRAHAN, from Notes by R. H. TIDDEMAN. 
 
 At Llanilid there is a great assemblage of gravel-mouuds. These 
 however give place towards the north-east to a boulder clay, which 
 it is difficult to separate from weathered Coal Measures. In its 
 western part the gravel appears to have been rearranged by the 
 Ewenny, and the material around Tre-groes is classed somewhat 
 doubtfully as a river- gravel. At Groes on the west side of _ the 
 Ewenny a well was sunk eighteen yards in clay to water. 
 
 Lower down the Ewenny Valley there is a mass of undoubted 
 boulder clay. It extends from near Coychurch south-westwards 
 along the north bank of the Ewenny and reaches over towards the 
 Ogmore Valley, where however it is partly covered up by gravel. It 
 consists of a reddish clay with small stones of which the greater part 
 are Pennant rock, but among which there occur foreign boulders 
 and yellow partly-rolled flints. The clay where most free from 
 stones has been much used for pottery, and is said to have been 
 7665. H ' 2 
 
100 Glacial Deposits. 
 
 worked for this purpose since Roman times. The clay is covered 
 in places by gravel which has a more or less flat surface, and is not 
 easily distinguished from a river-gravel. 
 
 In a pit 100 yards north of Pencoed Station a similar clay has 
 been worked for making bricks and tiles. It is overspread by a 
 gravelly drift which is nearly 20 feet thick at the north end of the 
 pit, but only six to 10 feet at the south end. 
 
 This gravel is packed with rounded boulders of Pennant, many 
 striated, with some pebbl/ grits. It is bluish or brownish and 
 contains lenticular bands of grey sand or nefi gravel with coal- 
 dust. Below it and separated clearly from it by a somewhat 
 undulating plane lies a deep-red and purple clay with few boulders 
 and extremely stiff. This is said to be 28 feet thick and to rest 
 on sand. This pit is abandoned. 
 
 A new pit opened 300 yards further north shows a similar red clay 
 containing many bands of fine sand much twisted and contorted, and 
 also small pockets of sand which appear to be disconnected relics of 
 crumpled-up bands of sand. A little of the gravelly drift with Pen- 
 nant lies here and there on top of the red clay, and over all there 
 is much rainwash containing prostrate tree-trunks. Possibly some 
 of the superficial disturbances are due to tree-roots, but those 
 evidenced in the red clay are too deep and large for such an origin. 
 
 It is clear that there are two drifts at Pencoed of different 
 origin. The newer is a Coal Measure drift of the usual South 
 Wales type, and has moved southwards. The older contains little 
 if anything from the Coal Field, but is made up largely of red 
 marl, probably from the Trias, and has been disturbed, not improb- 
 ably by the over-riding of the ice moving southwards. Its source 
 appears to have lain to the west on the following evidence : 
 
 In the pit near Pencoed Station fragments of marine shells, now 
 preserved in the Cardiff Museum, were obtained by Storrie from 
 some sand. Though too much broken and worn for determination 
 they were believed to be Cyprina, and their character as glacial 
 fragments was considered unmistakable. So far this constitutes 
 the only record of shell-fragments occurring in the South Wales 
 glacial deposits, though they abound in North Wales and in several 
 parts of England. Th3 explanation is not far to seek. The South 
 Wales ice-sheet had its birth among the hills in and north of the Coal 
 Field, and travelled southwards or south-westwards. Such material 
 as it carried was picked up on the journey. In all the regions 
 where shell-fragments occur there is reason to believe that th-3 ice 
 was advancing from sea towards land. It may be inferred that the 
 Pencoed drift was not the product of the main South Wales ice-flow. 
 
 In the same deposit Storrie also found a large number of igneous 
 boulders, now preserved in the Cardiff Museum. They have been 
 examined by Mr. F. T. Howard, by whom the following descrip- 
 tions a^e supplied. The specimens were divided into eight groups, 
 and slices from each group examined under the microscope. 
 
 1; Gabbro. Showing at places interstitial micropegmatitic structure.- 
 
 The lath-shaped felspars are enclosed by augite (ophitic structure), fairly 
 well developed, and somewhat decomposed. 
 
Pan. 101 
 
 The augite is in part fresh and presents definite crystal-faces and a very 
 characteristic basal striation. There are also serpentinous pseudomorphs after 
 the rhombic pyroxene, sometime intergrown with the augite ; crystals of 
 epidote, probably produced by the alteration of the felspar ; magnetite and 
 haematite. 
 
 2. Fdspathic Ash. This rock appears to be composed of very angular 
 fragments of felsite. Some include porphyritic crystals of quartz and felspar 
 (both orthoclase and plagioclase). The base is greyish in colour with portions 
 of a greenish tint. 
 
 One fragment shows rnicrospherulitic structure marked by the typical 
 black cross when the nicols are at right angles to one another. 
 
 Small grains of magnetite are scattered through the slide. The rock 
 originally was glassy, but subsequently became " devitrified." 
 
 3. Felsite. The ground mass originally glassy is now completely devitrified. 
 There are many porphyritic quartz-crystals usually rounded, some much 
 
 corroded and indentated, and possessing internal cavities. A few are broken, 
 probably subsequent to cooling. 
 
 Large porphyritic crystals of plagioclase felspar are present, the majority 
 being decomposed. They exhibit the characteristic polysynthetic twinning, 
 and occasionally the pericline type. 
 
 Small patches of a yellowish green chlorite occur throughout the slide. 
 
 4. Porphyritic Basalt. Much decomposed. 
 
 The large crystals of plagioclase felspar are tabular ; some are broken and 
 others much weathered. 
 
 The ground mass is also composed of minute lath-shaped felspars, dark 
 brown in colour without augite. This feature would place the rock near the 
 a ndesites. 
 
 There are greenish decomposition products (chlorite ?), which may have 
 entirely replaced the original augite. 
 
 Two oval vesicles are also filled with chalcedony. 
 
 5. Basalt. Containing large lath-shaped felspars, some well-preserved, 
 others decomposed. Few exhibit polysynthetic twinning. One crystal i.^ 
 broken, and the parts separated. 
 
 There are small grains and crystals of augite and magnetite. Larger- 
 crystals of augite or another ferro-magnesian mineral are replaced by a green 
 decomposition product (serpentine ?). 
 
 6. Brecciated Felstone. The slide exhibits flow-structure, and the crushed 
 appearance may have been produced during the cooling of the rock. 
 
 A few good orthoclase felspar crystals with the typical Carlsbad twinning 
 are seen, and small broken quartz -grains are scattered through the slide. 
 The rock contains regular oval spaces. 
 
 7. Altered Basalt. Once contained many vesicles now filled up by secondary 
 minerals, especially calcite and zeolites. Some are slightly greenish, polarising 
 from brown to red, others are dark green in colour under crossed nicols. 
 
 Viridite has replaced a ferro-magnesian mineral, probably a rhombic 
 pyroxene, and in part appears hi the cavities. 
 
 Some original porphyritic crystals remain which look like felspars, though 
 multiple twinning is not distinct. 
 
 8. Ash. Basic in character ; very green in colour. 
 
 The fragmental portions originally belonged to a glassy scoriaceous basalt. 
 The vesicles and cracks are rich in opacite. The palagonite portions contain 
 strings and aggregates of chalcedony. Small crystals of plagioclase occur 
 in the basalt, and the pyroxene is replaced by fibrous serpentine. 
 
 With respect to the source of these rocks, Mr. Howard remarks 
 that No. 1 is identical with the gabbro of St. Davids Head. No. 2 
 is a common type in North Wales. No. 3 somewhat resembles the 
 pre-Cambrian rocks of St.Davids. No. 6 is similar to the Bala rocks 
 of Pwllheli, but there is a group near St. Davids also with closely 
 allied characters. No. 7 is probably from West Pembrokeshire. 
 
102 Glaeicd Deposit*. 
 
 No. 8 resembles rocks of the Ueyn Promontory in Carnarvon- 
 shire, but has more probably been derived from Skomer Island. 
 " An andesitic boulder in its microscopic characters is extremely 
 like a rock on the north side of the Neck, while a boulder of 
 porphyritic basalt can be fairly matched in a bed at Skomer Head." 
 
 The same author in conjunction with Mr. Small writes : 
 
 " According to Mr. Storrie the sedimentary rocks found at Pen- 
 coed likewise indicate an ice movement quite distinct from the 
 general southerly one of the district, for whilst they include re- 
 presentations of the local Millstone Grit, Pennant Grit, and Car- 
 boniferous Limestone, as well as Keuper, Rhietic, and Lias rocks, 
 there are also a number of Old Red Sandstone pebbles and cleaved 
 rocks and grits belonging to the earlier Palaeozoic strata. 
 
 It appears then that in the similarity of the igneous rocks at 
 Pencoed to the rocks of Pembrokeshire, in the presence of shell 
 fragments, in the distribution of the flints, .... we have a set of 
 phenomena which can be best explained by an easterly movement 
 of the ice along the area of the Bristol Channel, and it may well be 
 that the curious mixture of granites, porphyritic rocks, and quartzites 
 to be found on the shores of Flat Holm is due to the same cause."* 
 
 It would be premature to enter here into the history of the glacia- 
 tion of Western Wales and the basin of the Irish Sea, but we may 
 add that the hypothesis put forward by Messrs. Howard and Small 
 has received support from facts observed lately in Gower and on the 
 Carmarthen coast. There also we obtain proof of an eastward 
 movement of the drift near the shore of the Bristol Channel, though 
 the ice-sheet generated in South Wales moved south-westwards and 
 southwards. 
 
 The flints referred to were discussed in a previous part of this 
 memoir.f As then explained they closely resemble chalk-flints, 
 but no positive proof that they are so has ever been furnished. 
 They occur in the Vale of Glamorgan, but, as remarked by Messrs. 
 Howard and Small, are most numerous in the area which would be 
 least affected by the Brecknock and Coal Measure drift, between 
 the valleys of the Ogmore and Taff. They are found sparingly also 
 in the raised beach in Gower, which is of earlier date than the local 
 glacial drift. 
 
 The gravel which lies on the eastern side of the Ogmore north of 
 Bridgend takes the form of a terrace, and is only separated from 
 the gravel below Bridgend by a slight break. The pebbles consist 
 chiefly of Pennant, but it is often covered with a foot or two of 
 loam. The terrace shows a general gradient corresponding in 
 direction and amount with that of the river, which gives it a re- 
 semblance to a river-terrace, but its composition and distribution 
 indicate that it was the work of an effluent from the ice-sheet 
 rather than that of the Ogmore, and it is accordingly classed among 
 the glacial deposits. 
 
 * Notes on "Ice Action in South Wales," by F. T. Howard and E. W. SmalL 
 Trans. Cardiff Not. Soc., voL xxxiL, 1899-1900. 
 f The Country around Cardiff (Gtol. Survey Memoir), pp. 78, 79 (1902). 
 
ioa 
 
 CHAPTER X. 
 
 POST-GLACIAL DEPOSITS. 
 By A. STRAHAN. 
 
 The post-glacial deposits include blown sand, estuarine mud and 
 alluvium, peat, calcareous tufa and river-gravels (terraces). 
 
 River Gravels. The southern end of the gravel- terrace between the 
 Ely and the Clun enters the northern margin of the map. A larger tract 
 borders the Ewenny near Pencoed, where, however, it is doubtfully 
 distinguished from glacial gravel. In several cases difficulty has 
 been experienced in deciding whether a gravel-flat bordering a 
 stream should be classed as glacial or alluvial. At Pen-llin, for 
 example, the origin of a broad expanse of gravel is doubtful (p. 98), 
 and the same difficulty arises at Pont Clun and south of Miskin 
 Manor. At Pont Clun the depth of the gravel was proved in the 
 shafts referred to on p. 17. Though forming what looks like an 
 alluvial flat, the greater part of the deposit is likely to be of glacial 
 origin. The surface of the ground is 150 feet above Ordnance 
 Datum. 
 
 Cardiff Navigation Colliery. 
 
 FT. IN. 
 Soil and clav ' 18 
 
 Rough gravel 
 
 Mixture 
 
 Quicksand 
 
 Rough Gravel 
 
 Clay mixed with fine gravel 
 
 Fine clayey sand 
 
 Coal Measures, p. 17 
 
 29 
 
 3 
 
 23 
 
 1 
 
 3 
 
 4 
 
 Estuarine Mud and Alluvium. The fluviatile alluvium of the 
 Dawen merges into brown Scrobicularia-cl&y at Marsh House, and 
 in this form extends eastwards to the old watch-house, as a turf- 
 covered flat. It is, however, being invaded by shingle. Westwards 
 from the river a flat of similar origin forms the Lays. This tract is 
 protected from the sea by dunes, and is in parts thinly overspread 
 by blown sand. Some years ago Mr. Woodward noted on the fore- 
 shore, half a mile west of Limpert, Scrobicularia-claky resting on 
 white calcareous tufa with Helix, this in turn lying on Lias. 
 
 Blown Sand. East of the Dawen a narrow strip of blown sand 
 accompanies the shingle at far as the old watch-house. West of the 
 river the dunes fringing the Lays rise to thirty feet in height. The 
 
104 Post-Glaeud Deposits. 
 
 source of the sand is not obvious unless the alluvial tract formerly 
 extended over Limpert Bay, as suggested by the observation refe red 
 to above. 
 
 There is doubt also whence came the sand of Newton Burrows and 
 Merthyr Warren, unless it be supposed that there has been some altera- 
 tion of the coast within the last one or two hundred years. Blown 
 sand occurs generally where there is a broad alluvial foreshore, exposed 
 to the south and west, as, for example, as Aberavan. No such alluvial 
 tract exists at Newton, and it must be supposed either that the 
 shore between tide-marks has yielded the sand, or that an alluvial 
 tract once existed, but has been destroyed by the sea. Two facts 
 rather favour the latter hypothesis. In the first place the quantity 
 of sand is too great for the source on the first hypothesis, and in the 
 second, it is stated that within the memory of living men the Tusker 
 Rock was a sheep-pasture, though it is now covered by every tide. 
 The subsoil of the pasture must have been some easily eroded 
 material, and was presumably an alluvial deposit such as occurs in 
 so many parts of the Bristol Channel. It may be inferred that 
 it formed the last relic of a wider alluvial tract. 
 
 The Kenfig Burrows form the southern end of a belt of blown 
 sand which borders the shore as far as Swansea, with interruptions 
 only where the principal rivers break through. The general drift 
 is eastward. That the sand has made great inroads since Roman 
 times might be inferred from the fact that the Roman Road known 
 in different parts as the Water Street and Heol-las was taken across a 
 tract now occupied by high dunes. It is possible, however, to date 
 its movements more precisely. 
 
 The Parliamentary and Municipal Borough of Kenfig is now 
 represented by a few scattered cottages with a population of about 
 300.* The charters are preserved in a room in a building known as 
 the Town Hall, the lower part of which has been used as an inn. The 
 earliest is a charter of Thomas, Lord le Despencer, dated 16th 
 February, 1397, but there were earlier charters which have been 
 lost. In 1232 the place was attacked by the Welsh. The town was 
 situated half a mile north-north-west of the Town Hall, as shown 
 upon the Ordnance Map, and is supposed to have been abandoned in 
 the fifteenth century on account of the encroachment of the sand. 
 It is the general opinion that the sand made great advances in the 
 sixteenth century. It is still encroaching upon the southern end of 
 the village. Kenfig Pool is a broad sheet of water ponded up 
 between the drift on which Kenfig village stands and the sand en- 
 croaching from the west. Its greatest depth is about eleven and a 
 half feet, and the water is fresh. It has existed in almost its 
 present form since 1876, but is smaller than, and slightly different 
 in outline to, the pool of 1814. 
 
 * This account is based on various papers in the Archceologia Cambrensis. 
 See also A Topographical Dictionary of Wales, by Samuel Lewis. 4to. 
 London, 1845. 
 
Post-Glacial Deposits. 105 
 
 Beneath the sand, where it has been blown off the original surface, 
 Mr. Tiddeman has found many chips of flint, together with arrows, 
 lance-heads, scrapers, awls, and disused flakes, and ocasionally 
 ancient pottery. 
 
 Peat. Many of the drift-hollows are occupied by peat ; notably 
 in the neighbourhood of Llanilid. A peat-flat, once a pool, named 
 Fawnog on the map, occurs about a mile east of Welsh St. Donats. 
 A small peat-bog, lying in a valley south-west of Hensol Park, gives 
 rise to two small streams which flow in opposite directions. Morfa 
 Ystradowain is an extensive peat-bog lying on glacial gravel. It 
 now drains by Nant Dyfrgi northwards into the Ely at Pont Clun, 
 but before the deposition of the gravel, the water may have equally 
 well turned southwards by Ystradowain and Maendy to the Dawen. 
 
 Calcareous Tufa. An irregular bed of calcareous tufa has been 
 deposited at Garn-lwyd north of Llancarfan by a calcareous and 
 slightly ferruginous spring which issues in front of the house. Gas, 
 presumably atmospheric air, is evolved. 
 
 On the coast a trace of tufa-cemented shingle sticks to the face of 
 the Lias cliff, six feet above the top of the present shingle, about 150 
 yards west of Font-y-Gary Cave near Aberthaw. Either the shingle 
 must once have been banked up higher against the cliff than now, 
 or the deposit may represent the raised beach which is shown in 
 many places in Gower, and is always cemented. In view of the 
 waste undergone by these cliffs the latter supposition is hardly 
 possible. Some tufa observed on the foreshore by Mr. Woodward 
 has been already mentioned (p. 103.) 
 
106 
 
 CHAPTER XL 
 ECONOMIC PRODUCTS. 
 
 Building Stone and Road Metal. 
 
 The Quarella Stone, described on p. 51, and the Sutton-stone 
 described on p. 60, are the principal building-stones. The former 
 was once quarried near Pyle also (p. 55). Lias limestone is 
 used for road-metal, but locally only, the Carboniferous Limestone 
 being more durable. The latter is worked for this purpose at 
 Llanharry. 
 
 Lime, Cement, and SUica. 
 
 Lias limestone is used largely for both lime and cement at Stormy 
 and Bridgend. The well-known Aberthaw lime was obtained by 
 gathering pebbles of this limestone from the beach at that place 
 (pp. 71, 87). The Carboniferous Limestone, and in fact all the other 
 limestones, were formerly burnt in a multitude of places, each 
 farmer preparing lime for his own use. Now all the kilns are aban- 
 doned save those on a line of railway, as at Llanharry. Rhgetic 
 sandstone has been used for making silica-bricks at Stormy. 
 
 The following analyses of Lias limestones are quoted from the 
 'Jurassic Rocks of Britain/ vol. iii., p. 292, by H. B. Woodward, 
 to which reference should be made for a general account of the 
 economic products of the L!as. 
 
 Aberthaw.* Bridgend. f 
 Carbonate of lime - - - 86-0 76-0 
 
 Carbonate of magnesia - 
 Alumina .... 
 
 Silica .... 
 
 Oxide of iron 
 Moisture, organic matter and loss 
 
 2O 4-0 
 
 1-0 2-0 
 
 80 10-0 
 
 20 4-0 
 
 10 40 
 
 100O 100O 
 
 Galena. 
 
 Traces of galena occur in veins associated with barytes in the 
 Lower Limestone Shales at Groes-faen. At Pentre, north of Llan- 
 trithyd, several veins of calcite cross the road on the line of the 
 fault shown on the map. Galena was worked here about fifty years 
 
 * Analysis published by Mr. H. Keid, Manufacture of Portland Cement 
 1877, p. 56 ; see also R. Phillips, Ann. Phil., ser. 2, vol. viii., 1824, p. 72 ; and 
 A. Voelcker, Journ. Bath and W. of England Soc., ser. 2, vol. vi., p. 228. 
 
 f Analysis published by Mr. H. Reid. 
 
Bcematite t 107 
 
 ago, and it is said to have yielded more silver than is usual in the 
 district. Some has been got also by shafts and levels on the south 
 side of the valley east of New Beaupre, where a few feet of Triassic 
 breccia overlie the Carboniferous Limestone. There are two old 
 shafts also 200 yards north of New Beaupre. The more ambitious 
 attempt to work galena at Llangan has already been mentioned 
 (p. 71). An east and west vein containing barytes and specks of 
 galena has been tried also near Twmpath, and there is a row of 
 deep shafts along the base of the Lias, west of Pen-llin Court. 
 The Carboniferous, Triassic, and Liassic limestones all contain 
 specks or threads of galena more or less abundantly, especially 
 near the uncomformable junction, but the ore has not been 
 found in paying quantity. 
 
 Hcematite. 
 By T. C. CANTRILL. 
 
 The haematite-deposits extend along the junction of the Mill- 
 stone Grit shales and Carboniferous Limestone from the north-east 
 corner of the map near Mwyndy nearly to Llanharry. Those 
 rocks, dipping steeply northwards, are unconformably overlain 
 by Keuper conglomerate, and over much of the ground there is a 
 coating of glacial drift which is said to have attained a thickness 
 of 120 feet at some of the workings. 
 
 The haematite at Llanharry was known and worked en a small 
 scale in very early ages, for Dr. Watson* records that at Llechau 
 had been found old workings which by their form seemed to be of 
 Roman origin, and that some small amphorae of coarse red pottery, 
 undoubtedly Roman, were found a few years before in the bottom 
 of an ancient stall-working at Ty-isaf, and he gives a section and 
 plan of one of the old workings. That the Romans worked the 
 haematite near Mwyndy seems certain from the finding of a coin 
 of Antoninus Pius (A.D. 138-161) and a piece of earthenware 
 charged with figures of greyhounds, hares, etc., near Miskin in 1752, 
 under some iron-cinders which were being re-smelted.f It is prob- 
 able that the cinders referred to are those still to be seen in heaps 
 in a field on the west side of the River Ely 100 yards above the bridge 
 at Miskin. There is a smaller heap at Hendy-isaf nearer to Pont- 
 Clun. Old beds of cinders have been met with at the Mwyndy 
 Mine ; and in old workings in the adjoining Bute Mine, reopened 
 in 1854, ancient tools and human remains are said to have been 
 found. Several masses of charcoal-iron cinder lie by the side of 
 the footpath 250 yards south-west of Fron-wen, Llanharry. 
 
 Leland, in the Itinerary (circ. 1540), refers to the making of iron 
 as being then in progress in a " park " named Glinog in the district 
 south of Llantrisant. This name is apparently not now known, 
 
 * Geologist, vol. ii. (1859), p. 241. 
 
 | The Rev. W. Harris, in Archceologia, vol. ii., p. 1. 
 
108 
 
 Economic Products. 
 
 but Dr. Watson conjectured that the mine referred to by Leland 
 might be the same as one then (1859) working at Cornel-y-parc, 
 Mwyndy. The word " pare " forms part of several place-names 
 in the immediate vicinity. 
 
 The position of the iron- ore relatively to the Triassic and Car- 
 boniferous rocks is shown in some sections by Mr. Stephen Vivian,* 
 
 FIG. 9. Transverse Section of Mwyndy Mine. 
 BY S. VIVIAN. 
 
 which are here reproduced by permission of the Council of the 
 South Wales Institute of Engineers. 
 
 The ore usually occurs as an alteration product, in the form of 
 irregular masses which have replaced the upper part of the Carbon- 
 iferous Limestone. Upon it rest the shales which constitute the 
 lower part of the Millstone Grit. It thus has a fairly regular roof, 
 
 FIG. 10 Transverse Section of Mwyndy Mine. 
 BY S. VIVIAN. 
 
 though downwards it shades most irregularly into, and includes 
 masses of, unaltered limestone. 
 
 Occasionally the Keuper conglomerate becomes so rich in iron 
 oxides as to be worth working, as at the Trecastell Mine, where a 
 
 * Trans. S. Wales Inst. Eng., vol. xiv., plates 24, 25, 26, 
 
Hcematite. 
 
 109 
 
 small patch of ore occurred between the conglomerates and the shale, 
 some forty yards north of the regular ore-bed. Ore has been found 
 also in small veins and fissures in the conglomerat 3. 
 
 The conglomerat 3 generally consists, as at Mwyndy, of a mass 
 of subangular and rounded pebbles, chiefly of Carboniferous Lime- 
 stone, but with some of sandstone, embedded in a red ferruginous 
 and calcareous marly matrix. Occavsionally the pebbles become 
 small, rare, or absent ; and the rock then takes the form of a hard 
 reeky calcareous marl. At its contact with the underlying lime- 
 stone or shales this rock becomes highly ferruginous, and at the old 
 Llanharry Iron Ore Works it contains streaks of haematite and 
 nests of calcite. There is a notable absence of magnesian 
 compounds. 
 
 A specimen of this red ferruginous and calcareous marl from the 
 disused workings at the Llanharry Iron Ore Works has been ex- 
 amined by Mr. H. H. Thomas. The insoluble residue after treat- 
 ment of the rock with acid was divided by specific gravity solution 
 
 FIG. 11. Transverse Section of Trecastle Aline. 
 BY S. VIVIAN. 
 
 jtsbjyyjtj&^^/j A vVi. *^? 
 
 i-.*.-rf 
 
 into two parts. The part with specific gravity less than 2'8 consisted 
 chiefly of impalpable marly sediment which, with a little detrital 
 quartz, made up the bulk of the rock. The other part consisted 
 almost wholly of a heavy sulphate, probably of barium. 
 
 A specimen of a red ferruginous limestone was taken from the 
 north side of the road from Llanharry Station to the village, at 
 twenty yards east of the junction of the road from Ystradowain, and 
 close below the base of the fine red breccia of the Keuper. Mr. 
 H. H. Thomas finds that the residue after treatment of the rock 
 with hydrochloric acid forms a very small percentage and is mainly 
 detrital quartz, the grains in some cases having a secondary growth 
 of silica completing the crystalline form. These crystals are beauti- 
 fully sharp doubly-terminated short prisms. Besides the quartz 
 there are a few grains of brown tourmaline and also of pale garnet. 
 
 That the Triassic water was the source of the iron here, as in so 
 other many regions,* seems certain. The replacement of the calcium 
 
 * The Country arounr] Newport (Geol. Survey Memoir], p. 25. 
 
Econom ic Product*. 
 
 carbonate by an iron-salt would be guided by the impervious shales, 
 which would hold the water up in the base of the conglomerate, 
 or cause it to circulate along the top of the limestone below, accord- 
 ing to local circumstances, while the depth to which the alteration 
 of the limestone proceeded was determined by fissures, bedding- 
 planes, etc. 
 
 The ore occurs as the hydrated purple-brown ferric oxide known 
 as limonite, and as the harder anhydrous ImMuatite. The latter, 
 which was more abundant at Mwyndy than at Trecastell, is gener- 
 ally more siliceous and is called k blue iron.' The chief points of 
 difference in the two varieties are as follows* : 
 
 Limonite. Hu-matite. 
 
 (Treeustell.) (Mwyndy.) 
 
 Peroxide of iron - 74-71 70-f>7 
 
 Silica 3-S(> 18-36 
 
 Lime ,">.">(> 3-56 
 
 Carbonic acid 4-1) '2-71 
 Water combined - 7 -64 
 
 The replacement has affected only the uppermost beds of lime- 
 stone ; and rarely extends far below the Triassic base, the greatest 
 depth hitherto reached being about 100 yards. At Mwyndy the 
 ore extended vertically downwards into the limestone in a deep 
 pocket, and both here and at the adjoining Bute Mine several gash- 
 veins cut southwards into the limestone for 100 or 150 yards, with 
 a width of 5 to 15 yards, and a depth of 20 to 50 yards. When 
 followed along the strike, the main ore-bed rarely persists more than 
 100 or 200 yards. 
 
 The ores are stated to have yielded '>0 to 50 per cent, of 
 metallic iron, the residue being largely siliceous or calcareous. Dr. 
 Watson remarks that botryoidal forms of haematite are notably 
 absent, while fine specimens of quartz-crystals are common. The 
 ( raddle' of the Ulverstone district is not found here. 
 
 It was found that the ore became less siliceous at the greater 
 depths, and that it changed much in hardness, so that in places it 
 could be got with the pick. In colour it varied from red and brown 
 to blue, grey, and yellow. A small quantity of yellow ochre was 
 sold for colouring purposes, and a little manganese ore was found 
 at the Trecastell Mine. Lead- and copper-ores occurred but rarely. 
 Messrs. W. Vivian and J. H. Collins t have described and figured 
 some crystals of calcite and quartz containing inclusions of iron- 
 oxides from the Mwyndy Mine. 
 
 Mines east of the River Ely. 
 
 The easternmost workings on this map occur north of Bro-fiscin- 
 fach, and old openworks and shafts can be found as far west as 
 Cefn-yr-Hendy, but the most extensive works were carried on at 
 
 * From The. Iron Ores of Great Hritain, and Ireland, by J. D. Kendall, 8vo., 
 London, 1893, p. 13. 
 
 J- 3/t'n. Mag. t vol. i., pp. 18, 19, and 117.- 
 
Hcematite. Ill 
 
 the Bute Mine on the west side, and at the Mwyndy Mine on the 
 east side of the Llantrisant-Cardiff Road. 
 
 The modern period of these mines appears to have commenced 
 in 1854 and 1855 respectively, and Dr. Watson probably referred 
 to them in 1859 when speaking of mines at Hendy and Cornel 
 Park. In 1884 operations appear to have stopped, and in 1896-7 
 all the works had been long abandoned. The ore was first got by 
 open-works, till the cover of drift and conglomerate became over 
 100 feet thick. Slopes or drifts were then opened, following the 
 ore down a dip of about 30 to 40 ; but after a time shafts were 
 sunk some distance to the deep, and horizontal adits driven from 
 them southwards to the ore. 
 
 The quantity of water encountered, which, at times, amounted 
 to 20,000 tons a day, proved a great hindrance to the success of 
 the mines. It is said that 1,500,000 tons of ore were won from the 
 Mwyndy, Bute, and adjacent mines, with average value of 12s. to 
 14s. per ton. 
 
 At Maes-y-felin, Pont-Clun, trials were made by the Dowlais 
 Iron Company in search of haematite, but the quantity met with 
 was not sufficient to be worth getting. One of the shafts lies about 
 200 yards south-west of Llantrisant Station ; the tip is composed 
 mainly of black shale, with apparently no Triassic deposits. The 
 absence of the Trias in this valley was inferred on other evidence 
 also, obtained while the mapping was in progress. 
 
 Mines west of the River Ely. 
 
 The Trecastell Mine at Ty-du, according to Mr. Vivian, was 
 opened up by the Mwyndy Iron Ore Company about the year 1884. 
 Thick glacial gravel overspreads the rocks, and much water was 
 encountered, amounting to a yield of about 6,000 tons a day, un- 
 affected by rains. All the ore was obtained from one large pocket, 
 60 yards long by 35 broad, by means of a pit sunk to the deep and 
 adits driven southwards to the ore. The beds dip a little west of 
 north at about 35. The ore is particularly rich, and is calcareous 
 rather than siliceous. An analysis of a picked sample showed 
 over 62J per cent, of metallic iron. Some of the limestone brought 
 up from the shaft, and now lying in heaps on the site of the works, 
 has been found by Dr. Pollard to be a ferriferous dolomite, compose^ 
 of carbonates of magnesia, lime and iron, with a little manganese 
 and some ferric iron. 
 
 The supposed Roman workings at Llechau and Ty-isaf have 
 already been mentioned. 
 
 The Llanharry Iron Ore Works, half-way between Llechau and 
 Llanharry, were opened some time prior to 1885, at which date they 
 were alluded to by Mr. Stephen Vivian as having yielded a few 
 thousand tons of ore worked on the crop. The deposit appears to 
 have proved to be of limited extent, but of good quality. All 
 operations had ceased previous to 1899. There are no mines west 
 of Llanharry. 
 
112 Water Supply. 
 
 The foregoing account of the mines has been based largely on 
 the following publications. 
 
 A list of works dealing with the South Wales Hccnuitite Deposits. 
 
 1859. WATSON, J. .1. W. The Haematitic Deposits of Glamorganshire. 
 
 Geologist, vol. ii. (1859), p. '241. 
 18(51. ROGERS, E., SALTER, J. W., ETC. The Iron Ores of South Wales. 
 
 being Part JIT. of " The Iron Ores of Great Britain." Mew. Gfol. 
 
 Surv. 
 1872. VIVIAN', W. The Mwyridy Mines. Trans. Cardiff Nat. Hoc., vol. Hi., 
 
 pt. i., p. 70. 
 187<>. VIVIAN, W. Note on Paragenetic Formations of Carbonate of Lime 
 
 and Oxide of Iron, and of Quartz and Oxide of Iron, at the Mwyndy 
 
 Iron Mines, Glamorganshire. With Note on the Specimens by 
 
 J. H. COLLINS. Min. Mag., vol. i., no. 1, p. 18. 
 1877. VIVIAN, W. Further Notes on the Oxides of Iron, enclosed in Quartz, 
 
 at Mwyndy. Glamorganshire. Ibid., no. 4. },>. 117. 
 1882. MEADK. R. The Coal and Iron Industries of the Tinted Kingdom. 
 
 8vo. Loud. 
 
 WETHERED, K. On the Origin of the Haematite Deposits in the Car- 
 boniferous Limestone. Geol. Mag., p. 522. 
 .884. VIVIAN, S. The Haematite Deposits of the Southern Outcrop of the 
 
 Carboniferous Limestone of South Wales. Proc. *S'. Wales InM. 
 
 Eng., vol. xiv., p. 164. [Discussion, p. 211.] 
 1893. KENDALL, J. D. The Iron Ores of Great Britain and Ireland. 8vo. 
 
 Land. 
 1895. HOWARD, F. T. The Haematite Deposits of South Wales and the 
 
 theories regarding their formation. Trans. Cardiff Nat. tioc. 
 
 vol. xx vi., pt. i., p. 47. 
 
 WATER SUPPLY. 
 
 Eastern Part. 
 By T. C. CANTRILL. 
 
 In the eastern part of the area surf ace -springs are chiefly utilised 
 for the source of water. There are no deep wells, and draw-wells 
 are exceptional. The best springs are those thrown out along the 
 junction of pervious and impervious strata, for example, between 
 the topmost pebbly grit of the Old Red Sandstone and the under- 
 lying more marly beds ; between the Lower Limestone and the Old 
 Red Sandstone ; and between the Main Limestone and the Lower 
 Limestone Shales. The Keuper conglomerates also, and some- 
 times the marls, yield some good springs. Faults, especially where 
 they bring pervious against impervious strata, generally throw 
 out water. 
 
 Many small springs issue along the edges of the drift-deposits, 
 but they are usually less reliable. Among these may be mentioned 
 the Silver Well and the Bowmen's Well at Cowbridge, which, 
 apparently, are fed from the gravelly terrace on which the town 
 i s built ; the former is much drawn upon by a pump in the High 
 Street. A strong but intermittent spring, in the valley between 
 Prysr- and Aberthin. bursts up through gravel, but probably has its 
 source in either the Lias or Carboniferous Limestone. 
 
n Pr1. ^ I - 
 
 With respect to the springs thrown out by the " solid rocks," 
 we find a little water issuing from the base of the pebbly grits of 
 Old Red Sandstone south-east of Llwyn-y-penau near Groes-faen, 
 and at Kennel Grove in Heiisol Park. The Lower Limestone throws 
 out water at Llan-chwian-fach east of Cowbridge, and south of 
 Crofftau near Miskin Manor, and a good spring issues from the base 
 of the Main Limestone a quarter of a mile north-east of Groes-faen. 
 A powerful issue occurs at about the same horizon at Pant Wilkin, 
 east of Cowbridge. Other strong limestone-springs are Adam's 
 Well at Talygarn ; another 350 yards north-east of Llwynau, Bryn 
 Saddler ; and another situated on the edge of the alluvium 200 
 yards north-west of Rhyd-halog, near Ystradowain. There is a 
 strong spring on the edge of the alluvium of the Ely between Hendy- 
 isaf and Miskin, and others near the river immediately west of 
 Miskin, all being situated close to the supposed course of the Miskin 
 fault. Another line of fault appears to account for the issue of 
 Ffynnon Elan from Carboniferous Limestone near Ystradowain, 
 and for two strong springs at Llwyn-nwydog farther north. A 
 slightly chalybeate water issues from Coal Measures, and probably 
 from the crop of the Drydedd Vein, north of Tyle Garw near Pont 
 Clun. 
 
 Two strong issues of water flow from the junction of the Keuper 
 conglomerate and the Carboniferous Limestone at Llechau near 
 Llanharry Station, and form Felin-fach Brook. The conglomerate 
 again, 200 yards west of Ty-du, yields a strong supply which is 
 utilised for the supply of Bryn Saddler, the water probably being 
 held up in it by the underlying shales of the Millstone Grit and Coal 
 Measures. Ffynnon Deilo south of Pendoylan issues from the same 
 rock, but Ffynnon Cattwg, east of the church, is thrown out by Keuper 
 Marl, and another, on the edge of the alluvium of the Da wen north 
 of How Mill, by brecciated tea-green marls overlain by Rluetic 
 sandstone. Whitewell, south of Bonvilston, issues from Keuper 
 breccia and evolves bubbles, probably of atmospheric air. 
 
 The base of the Lias throws out a strong spring 250 yards south 
 of Bonvilston, at Coed-y-Castell near Llandough, and at Ffyrmon- 
 yr-hebog at Cwm near Pendoylan. Another spring issues from a 
 slightly higher bed in the Lias south of Ystum-elaid near Llan- 
 trithyd. 
 
 The limestones of the A. BucMandi-zoue give egress to water along 
 the top of the Lavernock Shales and along the alluvial flats. Such 
 springs abound in the coastal region, and among them may be men- 
 tioned a highly calcareous and somewhat ferruginous spring at 
 Garn-lwyd, near Llancarfan (p. 105), and another at Pistyll-hill north- 
 west of the same place; St. Mary's Well and the slightly hepatic 
 Eye Well at St. Mary Church ; and several good springs on the west 
 side of the Peterston outlier. Lias faulted against Carboniferous 
 Limestone gives rise to the Brewer's Well at Llantrithyd. The 
 Good well atFlemingston and St. John's Well at St. Athan are situated 
 in valleys in the Lias. The Eagle's Well is utilised for the supply 
 of Boverton. 
 
 7665. T 
 
114 Water Supply. 
 
 The following records of well-sections in the eastern part of the 
 area .have been obtained : - 
 
 Peterston, 200 yards west of the station ; fifteen feet in brown sandy gravel 
 and quicksand. 
 
 Peters Urn, 350 yards south-west of Oroes-y-parc ; fourteen feet in clayey 
 gravel with flints. 
 
 Peterston, at Tre-rhedyn, on the Pendoylan road ; thirteen feet in gravel. 
 
 Pendoylan, 150 yards north-west of the church ; over fourteen feet deep, 
 commencing in black paper-shales (AvicuLa contorta-zone) and ending 
 in Keuper Marl (tea-green beds). 
 
 Prysc, Welsh St. Donats. Two wells at the top of the hill, said to be seventy- 
 eight and seventy-two feet deep respectively, and the latter said to 
 end in " dark shale ; " they probably commenced in Lias of the A. 
 Bucklandi-zone and failed to reach the horizon of the supposed 
 Ostrea-beds which crop out at Maendy (p. 68). 
 
 City, Llansannwr, 100 yards west of the rectory ; thirty-three feet in gravel 
 and probably some limestone -debris and eighteen feet farther in 
 Carboniferous Limestone. 
 
 Argoed-isaf, Llansannwr ; thirty -six feet in gravel. 
 
 Fforest-fawr, Ystradowain ; six feet in " gravel " (probably limestone- 
 debris), thirty-three or thirty-six feet farther in Carboniferous 
 Limestone. 
 
 Cowbridge, at the station ; twenty-six feet in gravel and more than four 
 feet farther in rock, probably Keuper breccia. 
 
 Western Part. 
 
 By A. STRAHAN, from Notes by K. H. TIDDEMAN. 
 
 Tn the western part of the map, mention may be made of the 
 following springs : 
 
 From the Lias. Ffynnon Fair, a good spring in a dingle west of Monk-nash. 
 Ffynnon y Grotto, and another close by, in Factory Brook, west of 
 Llanbleiddian. A large spring in Llysworney. Chwech Ffynnonau, 
 400 yards north-west of Sixwells south of Nash. Large springs at 
 Great Frampton, said to be polluted. Springs at Sigingstone. The 
 Wound Well and the Eye Well in Cwm Marcross, supposed to have 
 healing properties ; a thorn-tree close by is hung with votive rags. 
 Spring west of Capel near St. Donat's. Mid Well which forms the 
 supply for Llantwit-Major. Ffynnon-wen, at the base of the Lias, 500 
 yards east of Peran-pren, west of Cwrt Colman. 
 
 From Keuper. Large springs in the cliff on the south side .of Sker Point. 
 St. David's well and Ffynnon-fawr at Nottage. St. John's Well at 
 Newton Nottage (see also p. 115). Waun-y-mer, south of Kenfig 
 Burrows, strong in winter, but nearly dry in summer. Ffynnon -y-mer, 
 a good spring at Pen-yr-heol south-east of Kenfig Burrows. 
 
 From Carboniferous Limestone. Great issues of water 650 yards east of 
 Ogmore Castle, where it is pumped for the supply of Bridgend; and others 
 to the west of the castle. The Lias of this region is a massive limestone, 
 adhering to and much resembling the Carboniferous Limestone. The 
 two rocks are equally liable to swallow -holes and to underground water- 
 channels. Springs issuing from them may contain any proportion 
 of contaminated surf ace-water*. Ffynnon Tre-Brenin, south of Nottage ; 
 the water in a quarry close by is said to be affected in level by the tide. 
 Porth-cawl Dock, a large spring visible at low tide. Springs in fore- 
 shore south of Newton Nottage, see p. 115. 
 
 At Ty Maen, South Cornelau, there is a well sixty -three feet deep in Car- 
 boniferous Limestone ; a band of clay in the limestone, 200 yards north- 
 east of South Cornelau, throws out*water. A well 300 yards south-west 
 
 * Dr. Bulstrode's Report to the Local Government Board upon the Water 
 Supply of .... Bridgend, and upon the relation thereto of tlv prevalence 
 of Enteric Fever, 1903. 
 
Western Part. 115 
 
 of 'Grove commences in Keuper conglomerate and has been sunk to a 
 depth of sixty feet. A well at Heol-las in Keuper is twenty feet deep. A 
 shaft 370 yards west of Ty'n-y-cae, north of Newton Nottage, was 
 originally sunk in search of iron-ore, but has been re-opened in an 
 attempt to get water. A well 450 yards north-east of Nottage Court 
 has been sunk 140 feet, commencing in Keuper conglomerate ; a spring 
 at a depth of thirty -two feet yielded 700 gallons per hour. The height 
 of the surface above Ordnance Datum is about forty-eight feet. The 
 spring therefore is a little above the level of the water in St. John's Well. 
 
 St. John's well at Newton Nottage has long been known to ebb 
 and flow in sympathy with, but not simultaneously with, the tide. 
 It was described and the movements of the water observed in 1898 
 by H. G. Madan, from whose paper* the following account is taken. 
 
 The well is 500 yards from the shore and separated from it by 
 sand-dunes and a pebble-ridge. The sand rests on Keuper con- 
 glomerate and this on Carboniferous Limestone. Between the two 
 rocks a considerable body of water flows seaward, and bursts out 
 on the foreshore. It is this water which is tapped in the well. The 
 well is thirteen and a half feet deep and its bottom is eight feet above 
 Ordnance Datum. From a number of hourly and half-hourly 
 observations Madan ascertained that the movements of the water 
 in the well were as regular as those of the tide, but that they 
 lagged behind the tide almost exactly three hours. 
 
 The water contains the rather high proportion of 27 '2 parts per 
 100,000 of sodium chloride, but shows the same proportion when at 
 its highest as when at its lowest level. 
 
 The interpretation of these phenomena presents no serious diffi- 
 culty. The water contained in the Keuper conglomerate and 
 Carboniferous Limestone " is in free communication with the sea, 
 along the line where the conglomerate crops out below high-water 
 level on the shore. 
 
 The tidal wave, on reaching the outcrop, is taken up by the water 
 in the permeable strata and propagated landwards, but with a 
 greatly diminished velocity, owing to the resistance to its motion 
 offered by the solid, though porous, stratum of conglomerate. . . . 
 Hence we have high water in the well three hours later than high 
 water in the sea " (op. cit., p. 305). 
 
 Two other wells in the village are said to ebb and flow synchron- 
 ously with St. John's Well. There is said to be a similar well on 
 Flat Holm f (Sheet 263). 
 
 * Quart. Jo-urn. Geol Sot., vol. liv., p. 301 
 t Proc. Geol. AMOC., vol. xi., p. 214 (1890). 
 
116 
 
 INDEX. 
 
 Aberdo Limestone, 85. Cae'r-wigau, 5, 27, 28 ; glacial, 07. 
 
 Abernant, 3D. Cue Tori 51. 
 
 Aberthaw, 85 -87 ; lime, 71, 72, lot; ; Calcareous Tufa, 105. 
 
 tufa, 105. 
 Abortliin, 12, 32, os ; spring, 112. 
 Adam's Well lo. I 13. 
 Allt-isaf, 3'. 
 Allt-las, 70. 
 
 Allt-y-Cawri, ^laoial, 99. 
 Analyses, -1!), :2, IOC, llo. 
 Andrew's Pant, To. 
 Aimvltown Asylum, 14-10, 52. 
 Arglwydd \Vood, 04. 
 Argoed-isal I I I. 
 A .ill Hall ! 1 ; glacial, 99. 
 Aust Hour U,l:,2. 
 
 Candleston, II. oo. 
 
 Carboniferous Limestone, (5-15 ; 
 
 springs, 1 12-115. 
 Cardiff Museum, 34. 
 Cardiff Navigation Colliery, 17,103. 
 Carmel Chapel, 05. 
 Castell-ar-foel, 40, 05. 
 Castell-y-mwnws, glacial, 90. 
 Castell-y-mynach, 3!), To. 
 Cave, 13. 
 
 ( VI n-yr-li'Midy, 1 lo. 
 I 'ement' Works, 50, Y-l, 1 00. 
 Chalk- flints, 95, 9V, 98, 102. 
 Cherl, 5!), 72. 
 Cli \vech I'Yynnonau, 1 14. 
 Clemenston, 1 4. 
 
 City, 11 ; glacial, 99 ; well, 114. 
 Clawdd-coch, 20, 27. 
 Coal Measures, IT- 19. 
 Coal-trials in lxh;etic, 49 ; in Lias, 
 
 09. 
 
 Coed Arthur, 04. 
 Coed Garn-hvyd, 04. 
 Coed Hills, 41, 05. 
 
 iarry, 25 : anticline, - S 9, 9o. 
 
 Jarytes, 8, 100, 1 07. 
 
 '.lackland, 39, (J4. 
 
 >lack Kocks, 71, 75, 82. 
 
 Jlown Sand, 1O3 ]O5. 
 
 iodlonga, 12, 09. 
 
 >odwr Seams, 1 7, 19. 
 
 Jolu'oed. !>. 
 
 Joiiney, Ilev. Prof. T. C., 82. 
 
 )<>n vilston, 13, 25, 29, 30,39, 50, 59, Coed Leyshon, 49, 09. 
 
 04, '.! : spring, 113. Toed Llwyn-Hywel, 26. 
 
 'overtoil, \vater-supp]y, 113. Coed Mwstwr, 50. 
 
 loiilders, 95-102. Coed Trecastell, glacial, 90. 
 
 Moulder (.'lay, 95-97. Coed-y-Brain, 11. 
 
 lowman's Well, 112. Coed-y-castell, 44 : spring, 113. 
 
 >re\ver's Well, 113. Coed-y-Cohvn, 64, 70. 
 
 '.ridgend, 59, 72,73,75,93, loO: Coed-y-( Arabia, 31 . 
 
 glacial 102; water-supply, 114. Coed-y-llwyn, 32. 
 
 Jrigani Wood, 11 ; glacial, 99. Coed-y-niarlan, 09. 
 
 '.ristow, Mr. II. W., 36,37,61,71, Coed-yr-Aber, 39, 04. 
 
 74, 75, 7>\ si . (Joed-yr-Uondy, 17. 
 
 iroadlield Down, 81. ( 1 oity,'32. 33, 51, 71. 
 
 Jroc.a.stle, 73, s I. Colleuc, ( J. 
 
 Jro-iiscin-tach, 3o, llo. Colliii,-, Mr. .1. H., llo, 112. 
 
 3,'on.foiouiil Thn-ni<t*'i, 34 
 Jrynau-gwynion, 19. 
 Jryn-helygen, 20. 
 Jryn-hyt'ryd, <i<i. 
 
 >ryn Saddler, |o ; glacial, 90 ; spring, ( 'ornelaii, 33. 
 
 ( '.)! \\ i nst OH, , 2. 
 
 Conybeare, Jtev. W. D., 4 1, 78. 
 
 Conybeare, Hev. .1. .1., 78. 
 
 Coral -growth in Lias, Oo, 82, 88. 
 
 I 13. 
 
 I >ryn v cae, I s. 
 
 I'.n'ck la iid llev. I Vol. W., II, 44. 
 P.uililiim' S|i me, lot;. 
 Bnlstrode, Dr. II. T.. I I 1. 
 liilte Mine, 3D. 0!>, |O7, llo, 111. 
 
 i. :J3, -'..< . ,Ui1 icline, 8!), !( 
 
 'orm;l-y-parc, |os. 111. 
 ConitoNvn, 73. 
 ( 'ot ham St >1U', 53. 
 Cottrcll 5, 7, 13 : glacial, 97. 
 Court K.irin, 12, 08. 
 Co \vbrid-r, 5, 13. 25, 31,32, 35, 39, 
 I I 48, On, Oli 08 ; glacial 95, 97 
 ! ; springs, 113, 114. 
 (.'owhridge-Carditt' anticline, i, 2, 4, 
 
 7, 13, 89 93. 
 Coyphnivh, 32. 33, ">o, .)i ^i.tnial, 99, 
 
m 
 
 Crack Hill, 13. 
 
 (Jribbwr-fawr Coal, 17-19. 
 
 Crofftau (Miskin), 4, 6, 8, C. 
 
 Crofftau (Ystradowain), 10. 
 
 Cross, The, 41. 
 
 Cross Barn, 65. 
 
 Cwm, 69 ; spring, 113. 
 
 Cwm Farm, 49. 
 
 Cwm-gran, 18. 
 
 Cwm-mawr, 86. 
 
 Cwrt Colinan, 33, 52, 53; spring, 
 
 114. 
 
 Cwrt-newydd, 70. 
 Cwrt-y-carnau, 9, 28. 
 
 David, Mr. J., 57. 
 
 David, Prof. E., 47. 
 
 Dawen Valley, 2, 11, 24, 68, 103, 113 ; 
 
 glacial, 95, 97, 98. 
 De la Beche, Sir H. T., 55, 60, 61, 
 
 67, 75, 76. 
 
 Disturbances, 89-94. 
 Dolomite, 8, 14, 111 ; in Lias, 75. 
 Draenog Wood, 64. 
 Duncan, Prof. P. M., 37, 38, 61, 73, 
 
 82. 
 
 Dunn, Mr. F. W., 18, 19. 
 Dunraven, 23, 25, 59-63, T7-80, 83- 
 
 87. 
 
 Dyffryn, 25, 50. 
 Dyffryn-lloff, 26. 
 
 Eagle's Well, 113. 
 
 Earth-movements, 58, 59, 66, 89-91. 
 Eastdown, 41, 65. 
 Ebbing and flowing wells, 115. 
 Ely Valley, 2, 9, 24, 113 ; glacial, 96, 
 
 97 ; gravel, 103 ; haematite, 107. 
 Esgyrn Vein, 18. 
 Estuarine Deposits, 103. 
 Etheridge, Mr. R., 36, 37, 61, 62. 
 Evans, Mr, D., 18. 
 Ewenny Priory, 13. 
 Ewenny Valley, 2, 23, 50; glacial, 
 
 99 ; gravel, 103. 
 Eye Well, 113, 114. 
 
 Fairy Cave, 77. 
 Faults, 89-94. 
 Fawnog, 105 ; glacial, 97. 
 Ffald-wen, 70. 
 Fforest-fach, 10. 
 Fforest-fawr, well, 114. 
 Ffynnon Cattwg, 27, 113. 
 Ffynnon Deilo, 113. 
 Ffynnon Elan, 113. 
 Ffynnon Fair, 114. 
 Ffynnou-fawr, 114. 
 Ffynnon Tre-brenin, 114. 
 Ffynnon- wen, 114. 
 Ffynnon-y-cae, 40. 
 Ffynnon-y-Grotto, 114. 
 Ffynnon-y-mer, 114. 
 Ffynnon-yr-hebog, 64, 113. 
 
 Firebricks, 50. 
 
 Flat Holme, 90 ; glacial, 102 ; spring, 
 
 115. 
 
 Flemingston, 113. 
 Flett, Dr. J. S., 31, 33, 43, 53, 54, 56, 
 
 60, 98, 99. 
 
 Flint implements, 105. 
 Fron-wen, 30, 107. 
 
 Galena, 8, 34, 40, 60, 65, 67-69, 71 
 
 75, 106, 107. 
 Gareg-lwyd, 99. 
 Garn, 41, 65. 
 Garn-lwyd, 105, 113. 
 Gelli-araul, 71. 
 Gelli-wen, 28. 
 Gibbet Hill, 67. 
 Gigman Bridge, 41^ 65. 
 Gigman Mill, glacial, 97. 
 Gileston, glacial, 99. 
 Glacial Deposits, 95-102. 
 Glauconite, 35. 
 Glinog, 107. 
 Goodwell, 113. 
 Gower, 14, 102. 
 Gravel, glacial, 95-102 ; of rivers, 
 
 103. 
 
 Great Frampton, 114. 
 Green, 65. 
 Greendown, 64. 
 Grey Grits, 4. 
 Grippy, glacial, 99. 
 Groes, glacial, 99. 
 Groes-faen, 4, 7, 8, 28, 39, 106 ; 
 
 glacial, 96, 99 ; springs, 113. 
 Grove, 115. 
 'Guinea' bed, 62. 
 Guise, Sir W. V., 83. 
 Gwaun Llanharry, 18 ; glacial, 96. 
 Gwern-y-cae-uchaf, 70. 
 
 Haematite, 30,32,33, 107-112. 
 
 Ham Farm, 12. 
 
 Harptree Hill, 84. 
 
 Harris, Rev. W., 107. 
 
 Hendre, 33, 50. 
 
 Hendy, 30. 
 
 Hendy-isaf, 29, 107-111. 
 
 Hensol Park, 4, 7, 28, 29, 105, 113. 
 
 Heol-las, 104, 115. 
 
 Heol-y-Slough, 14. 
 
 Herberts, The, 44, 65, 67. 
 
 Hinde, Dr. G. J., 72. 
 
 Howard, Mr. F. T., 38, 44, 47, 49, 65, 
 
 67, 100-102, 112. 
 
 How Mill, 31, 44, 65, 113 ; glacial, 97. 
 Hutch wns Point, 15. 
 
 Infra-Lias, 61. 
 Jones, Mr J., 37. 
 
 Kendall, Mr. J. D., 112 
 Kenfig, 33, 34, 93. 
 
118 
 
 IS'DEX. 
 
 Kenfig Burrows, 104, 114. 
 Keuper, 20, 23-24 ; springs, 112-115. 
 Kirkaldy, Mr. D. 52. 
 Kitchin, Dr. F. L., 42, 48. 
 
 Laleston, 14, 54, 92, 93. 
 
 Langlon Wood, 64. 
 
 Lantern Vein, 19. 
 
 Lavernock Shales, 59, 65, 67, 70. 
 
 Lays, the, 103. 
 
 Leckwith, 25. 
 
 Lee, Mr. J. E., 37. 
 
 Leige Castle, 30, 31, 39, 65. 
 
 Leland, John, 107. 
 
 Lewis, Mr. S., 104. 
 
 Lias, 58-88 ; springs, 112-114. 
 
 Liassic geography, 58, 59, 88, 93. 
 
 Lilly pot, 1, 13. 
 
 Lime, 6, 71, 72, 8T, 106. 
 
 Limpert Bay, 71, 103, 104. 
 
 Llanbleiddian, 12, 31, 32, 66, 68, 91 ; 
 
 springs, 114. 
 Llancarf an, 39, 64 ; tufa, 1 05 ; spring, 
 
 113. 
 
 Llan Chwiau Castle, 13. 
 Llan-chwiau-fach, 5, 12. 
 Llan-cos-lech, 29. 
 
 Llandough, 31, 44, 65-67, 91 : spring, 
 113. 
 
 Llandyfodwg, 90. 
 
 Llanerch, 28, 29. 
 
 Llanfihangel, 66, 91 . 
 
 Llangan, 15, 71, 107. 
 
 Llanharry, 6, 10, 11, 16, 29, 30, 106 ; 
 iron ore workings, 30, 107-112 ; 
 glacial, 96, 97, 99 ; springs, 113. 
 
 Llanharry Colliery, 18. 
 
 Llanilid, 16, 30, 93, 105 ; glacial, 96, 
 97, 99. 
 
 Llansannwr, 7, 11, 12, 69 ; glacial, 99 ; 
 wells, 114. 
 
 Llantrisant, 16, 23, 107, 111. 
 
 Llantrithyd, 12, 13, 25, 31, 40, 64, 
 106 ; glacial, 95 ; spring, 113. 
 
 Llantwit-Major, 86 ; water, 114. 
 
 Llamvensan, 28. 
 
 Llechau, 107, 111 ; springs, 113. 
 
 Llwynau, 1 0. 
 
 Llwyn-celyn, 12, 13. 
 
 Llwyn-du, 12, 69 
 
 Llwyn-Gibbwn, 28, 29. 
 
 Llwyn Helyg, 67, 91. 
 
 Llwyn-nwydog, 4, 10 ; springs, 113. 
 
 Llwyn-y-ixmau, 4, 8, 9, 28 ; glacial, 
 99 ; spring 113. 
 
 Llysworney, springs, 114. 
 
 Local Government Board Report, 
 114. 
 
 Lock's Common, 34. 
 
 Longland, 74. 
 
 Lower Limestone Shales, 106. 
 
 Lucy, Mr. W. C., 38,62, 77. 
 
 Madan, Mr. H. G., 115. 
 
 Maendy, 12, 28, 39, 68, 9. 
 
 Maes-ma wr, 8. 
 
 Maes-y-felin, 111. 
 
 Maes-y-llech, 25.' 
 
 Maes-yr-haul, 28. 
 
 Manganese, 110. 
 
 Marcross, 59; spring, 114. 
 
 Margam Abbey, 55. 
 
 Marshall, Prof. T. R., 49. 
 
 Meade, Mr. R., 112. 
 
 Megan-felin, glacial, 97. 
 
 Merry, Mr. J. S., 52. 
 
 Melin Cwcw, 53. 
 
 Merthyr-mawr, 13,14, 25, 73 ; glacial, 
 95. 
 
 Merthyr Warren, 104. 
 
 M'Gaul, Mr., 51. 
 
 Michaelston-le-pit, 25. 
 
 Mid Well, 114. 
 
 Millstone Grit, 16. 
 
 Miskin, 6-10, 15, 28, 29 ; fault, 9, 17 ; 
 glacial, 99 ; gravel, 103 ; iron- 
 works, 107. 
 
 Miskin Manor, 4 ; spring, 113. 
 
 Moel Gilau Fault, 90. 
 
 Monk-nash, spring, 114. 
 
 Monotis-beds, 54. 
 
 Moore, Mr. C., 37, 54, 61, 66-68, 71- 
 74, 76, 81, 83, 84. 
 
 Morfa Ystradowain, 4, 7, 10, 105. 
 
 Mountain Hare, 19. 
 
 Mountain Lodge ; glacial, 96. 
 
 Mumbles Head, 14. 
 
 Murchison, Sir R. L, 44. 
 
 Mur-y-llengau, glacial 99. 
 
 Mwyndy, 9, 16, 29, 107-112 ; glacial, 
 96. 
 
 Mynydd-y-glew, 69 ; glacial, 97. 
 
 Mynydd Hywel Dico ; glacial, 96. 
 
 Nant Dyfrgi, 10, 105. 
 
 Nash, 31 ; springs, 114. 
 
 Nash Point, 86. 
 
 New Beaupre, 107. 
 
 New Forest House, glacial, 96. 
 
 Newhouse, 44, 66. 
 
 Newton boulder, 98. 
 
 Newton Burrows, 104. 
 
 Newton Down, 14, 33, 34. 
 
 Newton, Mr. E. T., 57, 66, 84, 85. 
 
 Newton Farm, 11. 
 
 Newton House ; glacial, 95. 
 
 Newton Moor (Cowbridge), 32; 
 
 glacial, 98. 
 Newton Nottage, 14, 33, 34 ; springs 
 
 114, 115. 
 
 Nine-feet Vein, 17-19. 
 North Fawr Vein, 17, 18. 
 Nottage, springs, 114, 115. 
 
 Ocean House, 71, 87. 
 Ochre, 110. 
 
 Ogmore Valley, 2, 23, 25, 34 ; 
 99, 102. 
 
Ogmore Castle, 13 ; springs, 114. 
 
 Old Beaupre, 65 ; glacial, 98. 
 
 Old Bed Sandstone, 4, 5. 
 
 Oolitic structure, in Carboniferous 
 Limestone, 6, 10-15 ; in Rhaetic, 
 41 --46 ; in Lias, 59, 64, 71, 73. 
 
 Pant Wilkin, spring, 113. 
 Pant-y-cwestau, 10. 
 Pant-y-Cwteri, 92. 
 Pant-y-Slade, 63, 72, 74-76, 79, 81, 
 
 82. 
 
 Peat, 105. 
 
 Pembrokeshire, boulders, 102. 
 Penartb, 20, 25, 48. 
 Pencoed, 50 : glacial, 95, 100-102 ; 
 
 gravel, 103 a 
 
 Pencyrn, 1 1 glacial, 99. 
 Pendoylan f 5-27, 29, 38, 49, 59, 70, 
 
 90 ; glac ; aJ, 97 ; springs and wells, 
 
 113, 114. 
 Pen-llin, 7, 12-15, 71, 72, 90, 91, 
 
 107 ; glacial, 98 ; gravel, 103. 
 Pentre, 40, 106 ; boulder, 98. 
 Pen-y-coed-uchaf, 30. 
 Pen-y-ffordd-fawr, 7, 69. 
 Pen-y-lan, 7, 11,69. 
 Pen-y-waun, 18, 30. 
 Persondy, 50. 
 Peterston, 25, 28, 38, 39, 70 ; glacial, 
 
 96 ; spring and well, 113, 114. 
 Physical features, 1, 2. 
 Pistyll-hill, 113. 
 Pleasantharbour, 70, 87. 
 Plwcau-Dafydd, 27, 49, 70. 
 Pollard, Dr. W., 111. 
 Pont Clun, 17, 29 ; glacial, 96 ; 
 
 gravel, 103; iron-ore, 107, 111; 
 
 spring, 113. 
 
 Pontypridd anticline, 90. 
 Porth-cawl, 13, 15, 34, 90; spring, 
 
 114. 
 
 Porthkerry, 71. 
 Porth-y-green, 68. 
 Pottery clay, 99, 100. 
 Prysc, 68; spring and wells, 112, 
 
 114. 
 
 P\vll-y-daren, 13, 69. 
 Pyle, 20, 25, 33, 35, 54, 55, 74, 81,93, 
 
 106. 
 Pysgodlyn-mawr, glacial, 97. 
 
 Quarella Quarry, 51, 52, 106. 
 
 Radstock, 73. 
 
 Raised Beach, 105. 
 
 Redland, 30, 39, 64. 
 
 Red Marl, 20-34 ; in Rhaetic beds, 
 21, 36, 51, 53, 55. 
 
 Rhaetic beds, 20, 21, 35-57 ; shore- 
 line, 24, 35, 36, 40, 49, 50, 93. 
 
 Rhyd-halog, 10; glacial, 96, 99; 
 spring, 113, 
 
 Rhyd-y-castell, 29. 
 
 Rhythm, 33. 
 
 Rivers, 2. 
 
 River Gravels, 103. 
 
 Road Metal, 6, 100. 
 
 Rogers, Mr. E., 112. 
 
 Roman iron-workinsrs, 107 ; pottery, 
 
 100. 
 Roose Point, 70. 
 
 St. Athan, glacial, 95, 99 ; spring, 
 
 113. 
 
 St. Athan Road Station, 71. 
 St. Bride's Major, 14, 91. 
 St. Bride's-super-Ely, 25. 
 St. Davids, boulders, 101. 
 St. David's Well, 114. 
 St. Donat's Point, 86. 
 St. Donats, spring, 114. 
 St. Hilary, 25, 31, 32, 41, 43, 50, 64, 
 
 65. 
 
 St. Hilary Down, 1. 
 St. John's Well, 113-115. 
 St. Lythans, 25. 
 St. Mary Church, 59, 64 ; glacial, 95, 
 
 97 ; springs, 113. 
 St. Mary Church Road Station, 41, 
 
 42, 43, 65. 
 St. Mary Hill, 20, 25, 33, 50, 51, 71, 
 
 93. 
 
 St. Mary's Well, 113. 
 St. Nicholas, 25. 
 Salter, J. W., 112. 
 Sandpit, 65. 
 
 Sandstones in Rhaetic, 40-44, 50, 51. 
 Saunder's Quarry, 50. 
 Scrobiculartct-dKy^ 103. 
 Sealawn, 74. 
 Sharman, Mr. G., 84, 85. 
 Shells in Drift, 100, 102. 
 Shepton Mallet, 81, 84. 
 Sigingstone, spring, 114. 
 Silica, 50, 55, 106. 
 Silver Well, 102. 
 Six-feet Vein, 17-19. 
 Six wells, 114. 
 Sker Point, spring, 114. 
 Skomer Island, boulders, 102. 
 Slade, 32, 48, 68. 
 Slatog Vein, 17, 18. 
 Small, Mr. E. W., 102. 
 Soils, 2. 
 
 Sollas, Prof. W. J., 34. 
 South Cornelau, well, 114. 
 Southerndown, 14, 25, 61-63. 
 Southerndown Series, 61-63, 75-85. 
 South Fawr Vein, 17. 
 South Llanharan Colliery, 18, 19. 
 Springs, 112-115. 
 Stalling Down, 5, 12, 90, 91. 
 Stoddart, Mr. W. W., 84. 
 Stormy, 15, 74, 81, 93, 106. 
 Stormy Down, 55-57, 62. 
 
1-20 
 
 1\DF\ 
 
 Storrie, Mr. J., 3?, 99. 100. l-.. Tv-ganol, 40. 
 
 Sniu Point, 71. 57. Tvle-^nv : : 
 
 Summerliou*e Point. 71. 87. Tv-i??.!, 107. 
 
 Sun-bed, 56. 
 
 Siuton. 2\ 31. 6U-63, ,4 i 7, 92. !3 
 
 Sutton- -tune. 3.\ .p, 41, 4.\ 47. i>. 
 
 Table f strata. 3. 
 
 TatT> Well. 23. 
 
 Tair On. MI. 1. 2\ 31. 4>. 41 
 
 Tal-y-garn. 7. 1^ : glacial, 
 
 >pring, 113. 
 
 Tate, Prof. K.. 36. 37. 61. 8; 
 Tawney. Mr. K. R. 3ri. 37. 
 
 Tea-given Mark 2<>. 
 Teall, Dr. .1. .1. H.. 98. 
 Terraces, of rivers, U>3. 
 Thomas. Mr. H. H.. 109. 
 'liddeman. Mr. K. H, 71-73. 85. 81 
 
 88. K>5, 114. 115. 
 Tilau. 30. 
 Tome-. Mr. P. F, 37. 38. 61. 62. 7: 
 
 Ton-yr-efail. 9". 
 Torgelli Colliery. 18. 
 Tre^Aubrey. 13.' 31. 4". 
 Tre-betin. 11. 
 Tivca^le Mine. K7 111. 
 Tre-castell Wood, 17. 18. 
 
 Tre-grof^ghu-ial. 99. 
 
 Tre-G\\ ilyrn. 2 V . 
 
 Tri'-gyrt'. 4". I',:.. 7". 
 
 Tre-rhingyll, 11. 
 
 Trias, 20-57. 
 
 Trydedd Vein. 17. IS. 
 
 Tu>ker L'ottage ,5. 
 
 Tusker l!ock._P>4. 
 
 Twmpath, 107. 
 
 T\\r l. iron. 13. 
 
 Ty-chwith. glacial. 9;*. 
 
 Ty-draw. 4M : glacial. !"'. 
 
 Ty-du (Llantri>ant). If.. 3". Ill 
 
 spring. 113. 
 
 Ty-du (PendoylanX 27. 4!'. f.n. 
 Tv-frv. 57. 65. 69. 
 
 well 1 1 ' 
 
 v-n.mt , 2 , 3', ,0. 
 \ u-y - cae, 2>>. 2 < . 
 y'n-y-caeau-tawr, 19. 
 y'n->'-coed. 31 . 39. 
 
 v 'r-eapper, glacial. M9. 
 'ythegston, 72. 
 
 Ty-uchaf. 40 : glacial. 98. 
 
 Vivian. Mr. S.. 108 112. 
 Vivian. Mr. W.. 110, 112. 
 
 Warren Mill, glacial. 9ti. 
 
 Watch-house Point. 71. 
 
 Water Street. 104. 
 
 Wator Supply. 112 1 15. 
 
 Watson. Dr. .!. J. W.. 107, 108, 110- 
 
 112. 
 
 Waun-y-iner. spring. 114. 
 Well-sections, 114, 115. 
 Welsh St. Donats. 5, 7. 9. 12. 13. 29, 
 
 38, 68. 69 : glacial. W. 97 : peat. 
 
 1U5 : wells. 114. 
 Wenvoe. 23. 
 West. 75, 
 
 Wethered. Mr. K.. 112. 
 Whitehall. 19. 
 
 White Lias. 39. 40. 48. 50, f.2. 66, SI. 
 White well, 113. 
 \Vhite\vell Farm. 31. 
 Whitmoir Stair-. 23, 85. 
 Wick. 14. 23. 60, 88, MM. 
 Wilson. Mr. K., 3;. 
 
 \\ in\N 1. Rev. 11. H.. 73. 
 
 Witches Point. 14. 153. 76 80. 
 Woodward. Mr. H. 1... 36. 38, 48. 56. 
 
 Hl-64. 71-87, 1"3. 105, PK;. 
 Wound Well. 114. 
 Wren Castle. 40. 05. 
 Wright. Dr. T.. 37. 
 
 V-tradowain. 7. H. 11. 2!. Hi : 
 ulacial. 96. H7, 9H : spring and 
 well. 113. 114. 
 
 Ystum-elaid, 65 ; Airing. 113. 
 
 Z-'iie- in the Lias "> v . "'- ( . t; i. 
 
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