ABNORMAL GEOLOGICAL DEPOSITS EN THE BRISTOL DISTRICT. 



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7. On Abnormal Geological Deposits in the Bristol District. 

 By Charles Moore, Esq., E.G.S. (Read November 17, 1880.) 



In making excavations at Eedland, on the edge of Durdham Down, 

 about 45 years ago, some conglomerates, associated with Carboni- 

 ferous Limestone, were opened up, which contained the teeth and 

 scattered and broken bones of reptilia, described by Messrs. Biley 

 and Stuchbury in the ' Proceedings of the Geological Society ' for 

 1836 under the names of Thecodontosaurus and Palceosaurus. As 

 they were then the oldest known reptilia and of a high order, much 

 interest has always attached to them. A few years since, in drainage- 

 works at the same spot, this conglomerate was again crossed, and 

 some other bones added to the series deposited in the Museum of the 

 Bristol Philosophical Society. The collection has since been reviewed 

 and described by Professor Huxley, E.B.S. *, and an account of 

 the physical characters of the district given by Mr. Etheridge, 

 E.B.S. t 



Much uncertainty has prevailed as to the geological age of the 

 Durdham-Down conglomerate. At first it was supposed to be Per- 

 mian ; but we have as yet no conclusive evidence of true Permian 

 beds in the West of England. Mr. Etheridge has placed it on the 

 horizon of the Dolomitic Conglomerate of the Keuper ; whilst, owing 

 to the discovery by myself of the same genera of reptilia, under 

 somewhat similar physical conditions, in the Ehsetic deposits of 

 Holwell, and since then of true Ehsetic remains on Clifton Down, I 

 had referred them to the latter age — a point to be reviewed below. 



In my paper on the abnormal conditions presented in the Erome 

 district I especially described numerous Secondary unconformable 

 deposits and vein-fissures resting upon or passing down through 

 the Carboniferous Limestone, some of them having organic remains 

 whereby they could be referred to different geological periods. 

 Since then I have discovered several other features of interest at 

 Holwell ; and as the phenomena of this district will serve as a 

 key to unlock hitherto unnoticed physical conditions in the geo- 

 logy of the Bristol area and some of the palaeontology connected 

 therewith, it will be desirable first shortly to notice the special fea- 

 tures presented near Erome. 



The Carboniferous Limestone has here its last south-eastern ex- 

 posure before being entirely covered up by Secondary deposits, and 

 is to be seen in very narrow ravines at the Yallis, Elm, Mells, What- 

 ley, Nunney, and Holwell. The prettiest combe is that of the Yallis, 

 from which, at its northern end, bifurcates that which passes 

 to Elm and Mells. At the entrance to the Yallis at Hapsford the 

 first sections show irregularly bedded Ehsetic conglomerates resting 



* " On the Classification of the Dinosauria, with observations on the Dino- 

 sauria of the Trias," Quart. Journ. Geol. Soc. vol. xxvi. (1870) p. 32. 



t "On the Geological Position and Geographical Distribution of the Kep- 

 tilian or Dolomitic Conglomerate of the Bristol Area," Quart. Journ. Geol. 

 Soc. vol. xxvi. (1870) p. 174. 



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