A HISTORY OF BERKSHIRE 



Corals are abundantly found in the topmost beds, and Messrs. Blake 

 and Hudleston, in their account of the quarry at Bradley farm north of 

 Marcham, describe those beds as ' about six feet of magnificent coral, the 

 massive portions growing in lenticular masses with bases not horizontal 

 and the intermediate spaces filled to a large extent with Thecosmiliae, 

 and they add that the reef corals there are in a more perfect state of 

 preservation than in any locality they know of.' 1 



Brachiopoda and bryozoa are not common in this district, and 

 echinoderms are far less abundant than in the Corallian of Calne and 

 other places. 



As in the Lower Corallian, there are in some of the beds numerous 

 pebbles of quartz, lydite, etc., and there are also rolled fragments of hard 

 limestone bored by Lithodomi and encrusted with Serpulas. 



The fossils of the Corallian are all marine, and the above evidence 

 points to a sea with shallow sand and coral banks or shoals. The pebbles 

 suggest that land was at no great distance. 



The late Mr. J. H. Blake stated that good supplies of water are 

 frequently to be obtained from the Corallian, but the amount varies 

 according to the circumstances of the locality. Sometimes it is met 

 with in the upper part of the formation being held up by clay seams 

 or chert bands but it is usually most abundant near the bottom, where 

 it is held up by the Oxford Clay. 2 



KIMERIDGE CLAY 



The calcareous beds of the Corallian are overlain by another clayey 

 series, the Kimeridge Clay, which like the older formations already 

 described forms a narrow east and west band across the country. The 

 town of Abingdon stands on it. It is a good deal hidden by gravel and 

 alluvium. 



It consists of dark-coloured clays and shales with septaria, and occa- 

 sionally nodules or bands of earthy, fossiliferous limestone. The bones of 

 the reptiles Campfosaurus, Ichthyosaurus and Pliosaurus have been found in 

 it as well as many marine shells. Ammonites biplex is characteristic of 

 the upper part and Exogyra virgula and Ostrea deltoidea of the lower. 

 Many other fossils occur and also driftwood. These fossils taken 

 together with the character of the strata show that it is a marine mud 

 accumulated at some distance from land and probably in fairly deep 

 water. Possibly there was land in the west, Cornwall, Wales, etc., 

 and Mr. H. B. Woodward suggests that there was a coast to the south, 

 south-east and east. 



In Dorsetshire bituminous shales occur in this formation, but have 

 not been recorded in Berkshire. Fruitless trials for coal have been made 

 at times. The soil is cold and stiff. Oaks grow well on it. 



It is according to Mr. J. H. Blake apparently 140 feet thick at 

 Denchworth, 1 1 1 feet at Goosey, 94 feet at Wantage, and less at Chawley. 



1 Quart. Journ. Geol. Soc. (1877), xxxiii. 307. 



'The Water Supply of Berkshire from Underground Sources,' Gecl. Survey (1902). 



6 



