SUCCESSION IN THE TEENT BASIN, 459 



but I would suggest as an explanation that the brackish state of 

 the water in the partial!}' land- and ice-locked sea was inimical to 

 marine life. 



The stratification met with inmost rocks resulted from intermittent 

 current- action and the consequent irregular supply and deposition 

 of material. On the other hand, in the aqueous Boulder-clays, owing 

 to the constant nature of the supply of mud brought down by sub- 

 glacial streams, and the absence of strong currents, the sedimentary 

 nature of the deposit is not so well marked. 



When the glacial conditions of this stage reached a maximum, the 

 greater part of the Trent basin was occupied by ice, the immense 

 weight of which ground up the subgiacial floor and converted much 

 of the earlier stratified Boulder-clay into unstratified moraine. !Not 

 only did it rearrange earlier Boulder-clays, but in many places it 

 formed its moraine almost entirely from the older rocks themselves. 



The most north-westerly outlier of the Chalky Clay with which I 

 am acquainted occurs at Abbots Bromley. In a pit south-west of 

 the town, about 15 feet of silty clay, with occasional sand-partings 

 or beds of strong clay, passes up into stratified sand with flints and 

 quartzite pebbles. This silty clay, which is almost free from 

 pebbles or boulders, covers a very considerable area in this neigh- 

 bourhood and is exposed at several other points. 



At Hanbury Woodend, north-west of Burton-on-Trent, typical 

 morainic Chalky Clay is covered by Chalky sand, and rests upon what 

 appears to be Quartzose Sand. The Boulder- clay lies unconformably 

 upon the lower sand and reaches a thickness of about 9 feet ; it 

 contains chalk and flint in abundance, together with quartz and 

 quartzite pebbles, Carboniferous limestone, &c. Mr. Molyneux* 

 has noticed what he describes as a remarkable trail of chalk-flints 

 '' stretching across the high grounds of Hanbury Woodend running 

 east and west." He also describes many other sections, now ob- 

 scured by talus, and traces the drift, which sometimes reaches 

 90 feet in thickness, over considerable areas. 



What appears to be Chalky Clay occurs in the Dove Valley at Oak 

 Green brick-yard, N.N.W. of Sudbury. It is here a blue clay, some- 

 what similar to that shown at Abbots Bromley, with seams of coarse 

 sand, occasionally gravelly. A few flints were found in it. 



The next outlier, and the largest I have found north of the Trent, 

 occurs near Chellaston (figs. 1 and 3), where it fills up an old valley 

 and caps the hill-top. In this sheltered spot the Chalky Clay is of 

 a decidedly sedimentary character, and has to a great extent escaped 

 the grinding- action of the ice. Though this sedimentary condition 

 of the deposit is very clearly shown in most of the sections near 

 Chellaston, traces (sometimes very obvious traces) of ice-action are 

 to be seen. 



At the south end of the main working, near the outcrop of the 



gypsum bed, and lying upon the sandy deposits which have been 



described, comes about 12 feet of purple silt containing glaciated 



boulders. The boulders, which generally lie with their longer axes 



* Burton-on-Trent ; its History, its Waters, and its Breweries. 



