78 



C. MOOEE ON ABNORMAL GEOLOGICAL 



The sections remaining to be noticed are along the eastern edge 

 and to the north of the Bristol coal-field. On the eastern side the 

 Carboniferons Limestone does not come to the snrface between the 

 Mendips and a very small ontcrop at Grammar Rock, nnder Lans- 

 downe, near Bath (which is not recorded on the Ordnance Map), and 

 others at Wick Rocks and Codrington. From Chipping-Sodbury 

 a narrow belt continues to Tate snd Wickwar, and entirely sur- 

 rounds the north of the coal-basin. 



At Wick, where the quarries are extensively worked, mineral 

 veins are to be seen having their usual vertical bands of barytes, 

 galena, &c. passing down them. In their softer pockets Tubutella 

 is abundant ; in one which has a marly infilling it is present in 

 great numbers. Occasionally small patches or pockets of grey marl 

 lie near the surface ; but I have not yet found any other organisms 

 in them. 



The Tate Rock Sections. — These are between Chipping Sodbury 

 and Wickwar. On the ragged surfaces of the limestone there are 

 here also pockets containing more mineralogical materials with 

 Tubutella. A vein passes down from the surface of one of the 

 quarries a foot in thickness, containing soft mineralized material in 

 which are myriads of these little tubes ; they are often attached to 

 the broken-up pieces of barytes and other minerals. 



Nettlebury Quarry, Tate, and Cleveclon. — The Nettlebury quarry 

 is a large one, nearest Wickwar, and is the last I shall refer to on 

 this side the Bristol coal-basin. A section of it has been given by 

 Mr. Etheridge *, in which are shown to the east horizontal step-like 

 beds, overlying highly inclined Carboniferous Limestone, whilst 

 on the west side equivalent beds dip at the same angle as the 

 limestone towards the coal-basin. At the present time it would be 

 difficult to recognize the locality from the above section, from the 

 almost entire absence of the beds on the eastern side, though 

 they are present from 12 to 14 feet thick on the west. Mr. 

 Etheridge considers these beds to be of the age of the Dolomitic 

 Conglomerates, and the representatives in lithological condition and 

 age of the supposed Magnesian Limestones of Clevedon. The latter 

 are thick, irregularly bedded, yellow limestones, used in the district 

 for building-purposes. It is apparently a local deposit, resting in 

 the quarry near the hotel on Old Red Sandstone, which crops out on 

 the beach and abuts against Carboniferous Limestone to the east, the 

 Old Red being fringed on a level with the Severn by a continuous 

 belt of Dolomitic Conglomerate, continuing north for some miles. 

 Almost every parting or crack between the blocks of Clevedon 

 stone shows the presence of galena, carbonate of copper, or other 

 minerals. In only one instance have I found a block of stone with 

 organic remains. This contained a few Encrinital stems, an im- 

 perfect Bhynchonella, and also several imperfect Strophomence. Were 

 it not that the specimens put on the lithological appearance of the 

 enclosing matrix, I should be disposed to think them redeposited 



* Quart. Journ. Geol. Soc. vol. xxvi. (1870), p. 179. 



