A HISTORY OF DERBYSHIRE 



large patch of Middle Pennine Boulder Clay. A well sunk in a brick- 

 yard proved it to be at least 60 feet thick. It rests upon a contorted 

 surface of Keuper Marl and skerry. The clayey matrix is composed 

 chiefly of Coal Measure clay with varying proportions of Keuper Marl, 

 and is wholly unstratified. Amongst the pebbles were nodules of iron- 

 stone, Millstone Grit, chert, Coal Measure sandstone, limestone, coal and 

 quartzites. Some of the larger erratics, one of which weighed at least 

 6 tons, were finely polished, striated and grooved. Another small patch 

 of Boulder Clay caps the hill north-east of Chaddesden and north-west 

 of Brushwood. Its junction with the upper Keuper Marl showed the 

 stiff blue clay with boulders, contorted and crushed into the marl below, 

 masses of the one being sometimes torn off and buried in the other. 



At Sheldon Wharf brickyard south of Derby, on the road to Chel- 

 laston, was an exposure excavated in Boulder Clay. The pit was worked 

 at two levels. The lower one showed a section of 9 or 10 feet of a 

 loose broken red clay with pieces of Keuper Marl and pockets of sand. 

 Small pebbles are distributed through the mass. Towards the top 

 quartzite pebbles and fragments of carboniferous rocks begin to appear 

 in tolerable abundance, and have their longer axes arrayed in a horizontal 

 position. About 5 feet of silty sand and pebbles separated the redeposited 

 red marl from the Boulder Clay above it. This clay was about 8 feet 

 thick and contained numerous pebbles and boulders well polished and 

 striated. 



The largest one seen was of carboniferous limestone and measured 

 20 by 1 6 inches. In addition to pebbles of quartz and quartzite were 

 fragments of coal, ironstone, marble, chert, Coal Measure sandstone 

 and Millstone Grit. There was no marked line of division between the 

 beds, and Mr. Deeley considers that they were deposited in quiet water, 

 the local rocks at the bottom, the foreign materials coming in greater 

 abundance as the glaciers approached and deposited sand, mud and 

 boulders in the quiet water. 



The deposits formed in the Trent basin during the Middle Pleisto- 

 cene epoch indicate that important physical changes had taken place 

 since the earlier period. These changes led to the advance of an ice 

 sheet from a north-easterly direction, which spread out over central 

 England the rocks it successively encountered. The abnormal direction 

 of this ice flow probably owed its existence to a period of intense cold 

 coupled with a considerable depression of the Pennine axis. The 

 Boulder Clay from this ice sheet is known as the Great Chalky Boulder 

 Clay, because of the large number of cretaceous rocks which it contains. 

 An indication of the direction of flow was, in one instance at least, ob- 

 tained by Mr. Teall, who found the Lias limestone south of Nottingham 

 striated in the direction from east-north-east to west-south-west. 



The presence of sand below the Chalky Boulder Clay on Chellaston 

 Hill was shown by some borings which passed through the chalky sand, 

 then through some 40 feet of Boulder Clay into running sand, which 

 was 6 feet deep. Under this were 10 feet of loam, sand and gravel, the 



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