366 



STRATIGRAPHICAL GEOLOGY 



As stated on p. 359, this area was land during the formation of the 

 Banter Beds, and it was not covered by the waters of the Keuper 

 lake until a late epoch in the period ; indeed, the Mendip Hills 

 were never completely covered by these waters, and the flanks 

 of these hills display an interesting arrangement of littoral deposits. 

 These deposits consist of breccias and conglomerates with a 

 calcareous matrix, and are known as the "Dolornitic Conglomerate." 

 They are mainly composed of pebbles of Carboniferous limestone, 



Fig. 120. GEOLOGICAL MAP OF BACKWELL HILL BETWEEN BRISTOL AND WRINGTON. 



(Surveyed and drawn by Professor S. H. Reynolds.) Scale 1 inch to a mile. 



d. Lias, 

 c. Keuper. 



5. Dolomitic conglomerate. 

 a. Carboniferous limestone. 



most of these being about the size of a hen's egg, but ranging up 

 to boulders of 2 or 3 feet in diameter, the whole being compacted 

 by a calcareous cement which is generally dolomitic. These beds 

 dovetail into calcareous sandstones and red marls (see Fig. 121), the 

 latter of which fill the wider spaces between the islands of older 

 rocks. Remains of Palceosaurus and Thecodontosaurus have been 

 found in the conglomerate deposits. 



The manner in which the conglomerates run up into the lime- 

 stone hills along the lines of the old valleys is illustrated in Fig. 120, 

 and, from the contours indicated on this map, it will be seen that 

 these old inlets have no relation to the modern valleys. 11 



