SUCCESSION IN THE TRENT BASIN. 439 



The importance of ascertaining the succession in this area will he 

 evident when its central position is considered, for, this once 

 accomplished, we should be within measurable distance of corre- 

 lating the Pleistocene deposits on the west side of the Pennine Hills 

 with those to the east of the same range. 



As will be seen from the classification I have adopted and the 

 tracing of some of the deposits into adjoining areas, a basis at least 

 for a tolerably correct correlation of the Pleistocene deposits of 

 England is furnished ; but I have thought it wise to leave detailed 

 work in this direction alone for the present. 



I. Geneeal Description and Classification. 



The Pleistocene deposits of the Trent basin are chiefly remarkable 

 for the great development which the glacial beds obtain ; they con- 

 sist of Boulder-clays, gravels, and sands, of various kinds and ages. 

 The distribution of the Boulder-clay varies very much both as 

 regards area and thickness, for in some localities it occurs in great 

 masses occupying small areas, and in others it covers considerable 

 districts with a tolerably uniform veneer ; its greatest development 

 is on the plains to the south and east of the Pennine axis. 



In the Trent basin the oldest Pleistocene deposits are distinguish- 

 able from those of later age by their freedom from Cretaceous rock- 

 debris. Professor Judd, in his " Geology of Eutland and East 

 Leicestershire," recognizes the existence of sands and gravels 

 beneath the Boulder-clay. These sands and gravels he describes as 

 containing local rock-debris, " in this respect offering a very marked 

 contrast with all the gravels of Post-glacial age, which usually con- 

 tain abundance of chalk flints and rocks foreign to the district." JN ot 

 only are there, as Professor Judd points out, gravels and sands free 

 from chalk and flint, but there are throughout the Trent basin great 

 thicknesses of Boulder-clay also free from Cretaceous rock-debris, 

 but containing an abundance of Pennine erratics. This feature 

 obtains throughout the whole area, and whenever members of the 

 two series are seen in an undisturbed condition in the same section 

 they invariably occupy the same relative positions ; and so great is the 

 lithological difference between the two series, and so largely are 

 they deifeloped, that I have ventured to regard the formation of 

 these early Pennine deposits as marking a distinct epoch in the 

 Pleistocene period, the great physical changes which took place at 

 its close introducing an entirely new series of rocks into the 

 Pleistocene deposits of the Midland Counties, and marking the 

 commencement of a newer epoch. 



Another break has been shown by Mr. A. J. Jukes-Browne * to 

 occur at a much later period, between the Chalky Boulder-clay 

 and the Purple Boulder-clay ; and though in the Trent basin this was 

 rather a change in the physical conditions of the area than a break 

 indicating lapse of time, there are good reasons for adopting it as- 

 another important line of division. 



* Quart. Joum. Geol. See. 1885. 



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