14 THE GEOLOGY OF TYTHERINGTON AND GHOVESEND. 



The following table gives the thicknesses for comparison 

 with the Clifton Section. 



The Tytherington Section. 



Upper Transition Beds (in Station Field) . . . . ? 



Upper or Lithostrotion Limestone (in Mr. Hardwicke's quarry) 145 + 



Middle Transition {Mitcheldeania) Beds .... 160 



T -r. • -i. 1 T • t (-The Gully Oolite 150) n-r, 



Lower or Encrimtal Limestone J -' } . boO 



1 The Black Kock 500 J 



Lower Transition Beds 315 



1275 + 



4. The Basement Beds of the Keuper. 



It is well known that in the Bristol area, the Permian 

 Strata of other parts of England, and the Bunter beds of the 

 Trias, so well developed in Cheshire, are both wanting, while 

 the Keuper beds are much reduced in thickness. During 

 the long period in which the Permian, Bunter, and part 

 of the Keuper were being deposited in other parts of 

 England, the Bristol area was dry land, and was suffering 

 denudation. 



As the Keuper lake extended into the Bristol area, there 

 was formed, along its margin and round the islands which 

 broke its surface, a deposit known as the Dolomitic Con- 

 glomerate. The name is an unfortunate one ; for it is not 

 always markedly dolomitic, and the angular fragments it so 

 often contains give it rather the character of a breccia 

 than a conglomerate. And if we work over the patches 

 of rock marked Dolomitic Conglomerate on the survey map, 

 we cannot fail to be struck by the very variable nature 

 of the deposit, as, indeed, is to be expected from its mode of 

 origin. At times it is a very coarse breccia, with huge frag- 

 ments of Old Red Sandstone, Millstone Grit, or Mountain 

 Limestone (according to the nature of the Palaeozoics on or 

 near which it rests) cemented in a ferruginous and cal- 



