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Downloaded from http://trn.lyellcollection.org/ at University of Auckland on March 22, 2015 V.—On the Geology of Tor and Babbacombe Bays, Devon. 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 Torquay, 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 Goodrington, 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 Brixham. 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.

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