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V.—On the Geology of Tor and Babbacombe Bays, .

BY HENRY THOMAS DE LA BECHE, ESQ. F.G.S. P.R.S. F.L.S., &c.

[Read November 16th, 1827.]

THE district to be noticed in this communication enables us to trace the dis­ turbance of the Exeter red conglomerate, carboniferous limestone, and old red sandstone of the coasts of Tor and Babbacombe Bays, to the intrusion of trap rocks, subsequent to the formation of the Exeter red conglomerate. The following is a general sketch of the coast. There is no beach to the cliffs from near the Ness-point, at the mouth of the Teign, to Hope's Nose, the northern point of Tor Bay, with the exception of the bottom of a few coves, and the Babbacombe-sands, and their continuation the Oddicombe- sands, both misnomers, for they are shingle beaches. The cliffs plunge di­ rectly into the sea, and are well seen only from a boat. The coast is equally bold from Hope's Nose to , with the exception of Meadfoot-sands, which are, however, backed by a high broken hill. After passing the hill between Torquay and Tor Abbey, the coast assumes a milder character: the cliffs, where they occur, are of no great elevation; and there are extensive sands both at Paington and , separated by Roundham Head. Further south, low cliffs intervene between Goodrington-sands and the Broad-sands. Beyond the low rocky land of Galmpton Point, the cliffs are bolder, and con­ tinue so to the Berry Head, being, in a few places, broken into coves, the most considerable of which is occupied by the harbour of . This range of coast is backed by hills, varying in height from 200 to 500 feet. Furland Hill, between Brixham and Dartmouth, is 589 feet above the sea, according to the Ordnance Survey. I shall now proceed to describe the stratified rocks of this district, com­ mencing with the uppermost.

EXETER RED CONGLOMERATE.—Rothe Todte Liegende. Gres Rouge. The red conglomerate of Babbacombe and Tor Bays is similar to that of Heavitree and the neighbourhood of Exeter. It consists, generally, of a fine­ grained conglomerate of small fragments of carboniferous limestone, old red VOL. III. SECOND SERIES. Y Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

162 Mr. DE LA BECHE on the Geology sandstone, shale, quartz, grauwacke, and red quartziferous porphyry, ce­ mented by a red paste, generally argillaceous, and frequently very compact ; so that the mass affords a very good building stone. This fine-grained con­ glomerate often contains small earthy crystals of felspar. Besides the preceding, there is a large-grained conglomerate containing fragments that are sometimes a ton or more in weight. In this the cement varies, being principally loose and sandy, and seldom containing crystals of felspar. Interstratified with these are red sandstones and marls. These con­ glomerates may, for more easy description, be divided into three small dis­ tricts : 1. That of St. Mary Church and Watcombe; 2. That of Tor Moham, extending up to King's Kerswell; and 3. That of Paington.

1. Red Conglomerate of St. Mary Church and Watcombe. The range of cliffs extending west from the Ness-point at Teignmouth, exposes a section of this rock, which varies from fine-grained to coarse, the latter greatly predominating : the most abundant fragments are pieces of the limestones, on which the conglomerate here frequently rests; pieces of red quartziferous porphyry are, however, by no means rare, as in the east of Teignmouth. These porphyritic fragments are most decidedly rolled pieces, derived from some other rocks than the conglomerate that now contains them. The only interruption to the continuation of these conglomerates to their termination at the fault at Oddicombe-sands, is caused by the carboniferous limestones of Petit Tor*. These limestones are nearly isolated, being bounded on all sides but the sea by red conglomerate. The conglomerate would appear to rise to the carboniferous limestone on both sides. A short distance further south, the conglomerate abuts against trapf. This fault seems to continue through the village of St. Mary Churchy where the conglomerate abuts against carboniferous limestone. The church stands on the latter rock, sections of which are seen in the village on the new road to Torquay; nevertheless, close to these places, a mason sunk a well 100 feet deep without going through the red conglomerate. A porphyritic conglomerate, resembling that of Heavitree, is seen on Hollo- way Hill, over which both the roads from Torquay to Teignmouth pass.

2. Red Conglomerate of Tor Moham. This portion is joined to that previously noticed by a kind of isthmus of the same rock, passing round from Holloway Hill by King's Kerswell. The con­ glomerate stretches from King's Kerswell south-west to Tor Abbey-sands, re- * Coast section, Plate XVIII. fig. 1. t Plate XVIII. fig. 1. Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

of Tor and Babbacombe Bays, Devon. 163 posing upon the limestone and old red sandstone, and attaining considerable elevation between King's Kerswell and Cockington. At the Corbons, a small cliff at the south extremity of Tor Abbey-sands, is a good section of this rock. It is generally fine-grained, and the cement con­ tains crystals of felspar. There is also a coarse variety with many fragments of carboniferous limestone; a fault is here observable in it. At the northern extremity of these sands, the red conglomerate suddenly abuts against the carboniferous limestone, its strata becoming vertical*. On the south side of the Corbons, the conglomerate is seen close to a fault, resting on red sandstone with green spots :—some of the strata have various tints, and some are greenish. The Livermead-cliffs are composed of the same conglomerate and sandstone as the Corbons, containing rounded pieces of quartziferous, red porphyry.

3. Red Conglomerate of Paington. This is connected with the former by a stripe in front of the cliffs between Livermead and Preston, or Paington-sands. Here the Exeter red con­ glomerate seems brought into contact with the old red sandstone, probably by a concealed fault, affording the appearance of the former underlying the latter, whereas it only mantles round it. Fortunately, the distinctive cha­ racters of these two rocks is very clear in this district; and moreover, the red conglomerate contains abundantly portions of the old red sandstone,—a clear proof that the latter was a pre-existing rock. The Exeter conglomerate of Paington resembles those previously men­ tioned, and is exposed in many good sections. At Rowndham Head, the strata dip north at about 10°. They are often of considerable thickness, contain rounded pieces, varying in size, of carboniferous limestone, old red sandstone, grauwacke, slate, &c. and are interstratified with red sandstone. At Collaton Kirkham the conglomerate rests on old red sandstone.

CARBONIFEROUS LIMESTONE.—Neuere Uebergangs-kalk. CalcaireaEncrines. The rocks to which I here give this title, have usually been referred to the transition limestone of English geologists, that is, a limestone which occurs beneath the old red sandstone; they, however, rest upon that rock, contain fossils that have been discovered in the carboniferous limestone of other places, and, though a matter of minor importance, mineralogically resemble it:—they are, moreover, separated from the old red sandstone by a shale, which maybe considered the equivalent of the lower limestone shale. * Plate XVIII. fig. 5. Y2 Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

164 Mr. DE LA BECHE on the Geology These limestones occur in beds from a few inches to several feet in thick­ ness; the usual colour is grey, varying in intensity; they are frequently traversed by calcareous veins, and, in texture, vary from compact to semi-cry­ stalline, the latter predominating- in the vicinity of trap, and when the strata are much disturbed. The semi-crystalline limestones afford a great variety of beautifully tinted marbles, not so well known, nor so much employed for ornamental purposes as they deserve to be. These limestones are, here and there, interstratified with shale : they also rest upon a considerable thickness of argillaceous shale, into which they seem to pass. The shale is usually reddish in the upper part, brownish grey in the lower and larger portion, and strongly reminded me of the shale similarly situated in Pembrokeshire. The most abundant organic remains are encrinites and corals. The lime­ stones at Daddy's Hole near Torquay, are so full of pieces of encrinites, as to resemble, in this respect, the Black Rock of Bristol. The following is a list of the organic remains which I met with in this rock, including those found at Bradley quarries near Newton Bushel: Corals. Encrinites. Trilobites. A very singular fossil*, specimens of which were collected in the vicinity of St. Mary Church. The sections which have been made of these specimens exhibit no internal structure which enables me to refer them to any known class of organic bodies. Cardium alaeforme Min. Con. T. 552. f. 2. Megalodon cucullatus Sow. Gen. & Sp. Nov. Min. Con. T. 568. Terebratula porrecta Sow. Sp. Nov. Ibid with 5 or 6 small plaits in front. Ibid with 8 or 10 ditto.

j, .1 ? ("Trigonal, depressed, with four large plaits on the elevated \ front, and as many on each side. Spirifer decurrens Sp. Nov. rotundatus ? Min. Con. T. 461. f. 1. Ibid '. Sp. Nov.

* Plate XX. figs. 1. & 2.—It is not improbable that the fossil here referred to may have belonged to the Tunicata. The structure of the external covering appears to have some resem­ blance to that of Chelyosoma MacLeayanum, a new genus and species of that group, brought home by Lieut. Belcher, R.N. presented by him to the Zoological Society, and described and figured in the Zoological Journal, vol. v. p. 46. Tab. III. figs. 4. 5. & 6.; but, in none of the specimens of C. MacLeayanum examined by the writer of this note, does the number of plates, which are coriaceous and confined to the upper surface, exceed eight.—W.J.B. Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

of Tor and Babbacombe Bays, Devon. 165

Natica ? small and indistinct. Euomphaius small and indistinct. Bellerophon tenuifascia Min. Con. T. 470. f. 2. 3. Turritella abbreviata Sow. Sp. Nov. Min. Con. 565. Turritella? small ill-defined species, found also in Ireland. Murex ? Harpula Sow. Sp. Nov. Buccinum spinosum Min. Con. T. 566. f. 4. breve Min. Con. T. 566. f. 3. . imbricatum Min. Con. T. 566. f. 2. Pleurotoma (Helix Min. Con.) like Helix carinatus. T. 10. Nautilus Orthoceras 1. Limestones of St. Mary Church, Babbacombe, and the Northern Side of Tor Bay. These encircle the old red sandstone, which extends from Meadfoot-sands towards Upham. The section on the south side of Meadfoot-sands shows the limestones resting on old red sandstone. The quarry at the south-west points, opposite a rock called the Shag Rock, is worked in grey and reddish, compact limestone, dipping south-west: beneath, is an argillaceous shale, reddish in the upper part and grey in the lower,—the latter is slightly micaceous. This forms the cliff from the point to a short distance east of the place where the road descends to the beach; and to this succeeds a red siliceous grit traversed by veins of quartz, and containing iron. The cliff composed of red grit is much concealed. The limestones in the vicinity of Torquay are much disturbed, as are also, more or less, all the stratified rocks of the district. These beds are observed to be contorted along the whole coast, from the town to the point opposite the Shag Rock; they seem, however, to have a general dip away from the old red sandstone, between which and the body of limestone the argillaceous shale is always interposed. I have selected two examples of contorted strata near Torquay*, because, though the sections are only about eighty yards apart,, and both across the range of the strata, they show the contortions that must have taken place in all directionsf. So much confusion exists in the vicinity of Torquay, that no regular dip of the limestones can there be determined. They dip S.S.W. at an angle of 35° near the turnpike, and at the quarry near the baths to the south-west. They are perpendicular, with a north and south direction, at the little hill near Tor Moham, at the Chapel Hill, and under Torwood House. At Stantaway * Plate XIX. f The birds marked in the two figures show the same points of the hill viewed from opposite sides. Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

166 Mr. DE LA BECHE on the Geology

Hill, between Tor Moham and Upham, the calcareous slate and limestones are much confused. At Butterhill quarry the limestones are much disturbed. On the new road from Torquay to St. Mary Church, at the entrance of the rocky defile, irregular, detached and arched strata, have a very picturesque effect, the arch appearing to be almost a work of art. The coast also from Babbacombe to the Black Head, exhibits confused strata of limestone and argillaceous shale; at the latter place we may observe a thick, bent stratum of limestone included in the solid trap* : this limestone is very crystalline. Hope's Nose, with the Leadstone, Oarstone, and Thatcher Rocks lying immediately near it, are composed of limestone much contorted at the cove north of the Thatcherf. This mass of limestone is detached from the limestones on the west, that is, above the level of the sea; and, beneath, they are probably connected with the Torquay beds, for the Thatcher Rock is composed of them. Kent's Cavern, lately celebrated on account of the remains of elephants, rhinoceroses, hyaenas, bears, deer, wolves, &c. found in it, is situated in these limestones J. From Barton the limestone extends along the hill to King's KersWell, where Exeter red conglomerate covers it for a short distance : but, at the lower part of the village on the old Dartmouth road, the limestones again come in, and are continued to the top of the hill, where a quarry exhibits their contortions §.

2. Limestones on the South of Tor Bay. Like those on the north of the same bay, these are greatly disturbed, as may be seen along the coast from the Berry Head to Saltern Cove, near Goodrington. At Marstink quarry near Paington, thin strata of semi-cry­ stalline limestone dip north about 20°. At Saltern Cove, limestones are mixed with, and disturbed by, trap, which has greatly altered the character of the limestone at the points of contact. In one of the projecting points the altered limestone does not effervesce freely with acids; it contains corals. Reddish shale resembling that on the north side of Tor Bay, and similarly situated beneath the limestone, occurs much contorted at the western point of Saltern Cove. In some places it is traversed by quartz veins.

OLD RED SANDSTONE.—Jiingere Grauwacke. Gres Rouge Intermediaire. The general character of this rock is best exhibited near Cockington. * Plate XVIII. fig. 1. f Plate XVIII. fig. 4. % The Rev. John McEnery, who has formed a very valuable collection of these remains, intends, I believe, to publish an account of them; and Professor Buckland will probably do the same in the continuation of his (i Reliquiae Diluvianae." § Plate XVIII. fig. 3. Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

of Tor and Babbacombe Bays, Devon. 167 Between this place and Livermead-sands are two quarries of chocolate- coloured, micaceous, siliceous, and very compact sandstone. In both a slaty variety, splitting easily in the line of the laminae, which are filled with mica, is mixed with compact and micaceous beds, which vary in thickness from a few inches to two feet. The strata are much confused, some are curved, and some dip in all directions. In its great hardness, in its colour, in being micaceous, and in general ap­ pearance, it differs entirely from the red sandstone associated with the Exeter- conglomerate of the Corbons and Livermead. After passing Livermead on the road to Paington, a new cut exposes a slaty variety of this rock, apparently passing into grauwacke. Among the strata are a few of the more compact and solid sandstones. Thick beds of old red sandstone are observable on the rise of the hill west of Cockington, on the old road to Totness, but they are quickly covered up by Exeter conglomerate, which latter continues to conceal it as far as a small rivulet about half a mile east from Ockham, where it again emerges. From the vicinity of Ockham to Westerland, this rock passes gradually into grau­ wacke slate, losing its red colour, but preserving its mica. At Collaton Kirkham, the same slaty and compact varieties are seen as in the Cockington quarries; their dip is E.N'.E. at an angle of about 20°, the beds being sometimes curved. They are much more highly inclined in the same vicinity. Exeter red conglomerate covers these rocks on the same hill, and contains rolled pieces both of its slaty and compact varieties. The old red sandstone passes into grauwacke on the high hill N.N.W. of Paington. The red compact sandstone beneath the argillaceous shale at Meadfoot- sands, very much resembles the Cockington compact old red sandstone. At Hope Farm the resemblance between the two will be found most striking; and there can be no doubt that the limestone shale rests upon it in the vicinity : in fact, the wedge-shaped mass of old red sandstone extending from Meadfoot- sands and Hope Farm towards Upham, is bounded by a mantle of argillaceous shale. Sandstone and Slate of Meadfoot-sands. These may almost be considered as the passage of old red sandstone into grauwacke, or they may be the old red sandstone strata altered by the vicinity of trap. Beneath the red grit of the Meadfoot-sands is a grey, compact, fissile, and very micaceous sandstone, resembling in every thing but colour, the semi- schistose varieties of the Cockington red sandstones. Their angle of dip varies considerably; it is at first towards the south-west at about 65° or 70°. These strata rest upon, and pass into a slaty rock resembling the old red sandstone Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

168 Mr. DE LA BECHE on the Geology schist of the vicinity of Ockham in every thing but colour. They are here dark-coloured. These rocks traverse the point of land, named at its extremity Hope's Nose; and upon them the limestone of that place appears to rest. Small trap veins are observable both in this rock and the red grit of Mead- foot-sands. GRAUWACKE. A very small portion of this rock comes within the scope of the present communication. The old red sandstones pass into grauwacke between Ock­ ham and Westerland, at which latter place there is a quarry of grauwacke rather micaceous. It contains the vertebral columns of encrinites, corals, and bivalve shells. The schist is used to line the interior of the neighbouring lime-kilns. The dip is E.S.E. about 45°.

TRAP ROCKS. On the east of Babbacombe, trap rocks advance into the sea and form a small headland. They consist principally of greenstone, varying in grain, and containing abundantly particles of iron pyrites; some of it approaches the cha­ racter of a reddish sandstone, and the whole is occasionally traversed by veins of quartz, jasper, and very rich iron ore. Between this headland and the compact, and sometimes semi-crystalline limestone of the main land, argilla­ ceous shale is interposed. Another small headland, on the west of Babbacombe, is formed of green­ stone and greenstone porphyry. Very often the rock assumes a porphyritic and amygdaloidal character at the same time, the amygdaloidal cavities being filled with carbonate of lime. In all cases, iron pyrites, often in cubical cry­ stals, is disseminated through the mass:—calcareous and quartz veins traverse the trap, particularly on the Babbacombe side. This trap has evidently been protruded into the argillaceous shale from beneath : the strata are cut off and twisted by it; considerable portions also of the shale are included in the trap. The limestones, forming the upper part of the cliff, rest on the shale, and are also disturbed. From hence north-west to Oddicombe-sands, the same kind of trap is ob­ served intermixed with the shale at the base of the cliff, and appears to have forced its way high up among it, and, probably, also among the limestones; the cliff is inaccessible, but presents the appearance of different rocks irregularly mixed. The trap becomes so altered in its character as it ascends, that the highest portions scarcely deserve the name, presenting, when in contact with the limestone, a base that effervesces and contains green specks and crystals of iron Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

of Tor and Babbacombe Bays, Devon. 169 pyrites. This may perhaps be an altered limestone. The general character of this mass of trap is the same as that of the small point previously mentioned, being only more porphyritic and less amygdalo'idal. Good greenstone also occurs. At the fault in Oddicombe-sands the trap attains greater elevation, forcing up the shale, and causing it to occupy the top of the cliff. This trap forms the eastern part of the fault to which the Exeter red conglomerate rises, as if also elevated by it. We here learn that the trap was intruded among, and caused disturbance in, the shale and carboniferous limestone after the formation of the Exeter red conglomerate; for the latter also appears affected by it. As this conglo­ merate contains rounded portions of the limestones and shales, the fault pre­ sents two distinct, geological epochs; one, when the limestones and shales were partially destroyed, affording some of the materials of the conglomerate ; and another, when the trap was intruded among, and disturbed all these strata*. A small portion of trap is also seen among the limestones between Babba­ combe and the northern head of Anstis Cove *j*. At the bottom of the cove, greenstone, traversed by veins of jasper, is observed among the shale situated between the base of the cliff and the limestones on its summit; the shales seem disturbed. The greatest mass of trap on the coast constitutes the Black Head near Usam J. The principal rock is a greenstone, varying much in grain, and containing iron pyrites ; a very abundant mineral in the trap of this coast. At the base of this head, a thick, arched stratum of limestone is included in the trap. This limestone cannot fail to remind the geologist of those situations where calcareous rocks have become hardened, and rendered more or less crystalline in contact with trappean rocks. The limestones of Ilsam are much disturbed, probably from their vicinity to the Black Head trap. No more trap of any importance is found on the north of Tor Bay, and little on the south. Saltern Cove near Goodrington, presents another instance of the limestones and their accompanying shale being altered and disturbed by this rock, which is very compact, fine-grained, and of a mixed greenish and chocolate colour. It sometimes has an arenaceous structure and a reddish tint. Pieces of limestone, much altered, seem in a few instances included in the trap. The only remaining trap that I shall here notice, is situated near the high road between King's Kerswell and Dartmouth, not far distant from the con- * No pebbles of greenstone are found in this conglomerate, f Plate XVIII. fig. 1. + Plate XVIII. figs. 1. & 2. VOL. III.—SECOND SERIES. Z Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015

170 Mr. DE LA BECHE on the Geology of Tor and Babbacombe Bai/s, Devon. torted limestones before mentioned, and is probably the cause of their present appearance. I consider that the whole disturbance of this district, is attributable to the causes that produced the trap,—causes which probably also occasioned all those faults and contortions here so common. What the geological date of this event may be, it would be difficult to say, as we have no stratified rock resting peaceably on the trap. That this rock was here intruded after the formation of Exeter red conglomerate, is probable from reasons before assigned, and I feel disposed to connect the disturbance of the Tor Bay district with the catastrophe that elevated the strata in the line of Weymouth and the , and caused the contortions and faults so common on the coast;—a catastrophe perhaps corresponding in date with that which raised the great range of the Alps. Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015 Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015 Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015