SUCCESSION IN THE TKENT BASIN, 477 



Thougli the sides of the valley slope with a tolerably steep incline, 

 its bottom, with the exception of a Y-shaped " dumble," about 15 

 feet deep, due to postglacial erosion, is rounded. The lower portion 

 of the excavation, where it cuts into the hill about ten or fifteen 

 feet above the bottom of the old valley, enters a morainic deposit 

 of Boulder-clay which clothes the side of the hill to a height of 

 about fifty feet. In its thickest part it attains a depth of about six 

 feet. It contains boulders of Mountain Limestone, basalt, sandstone, 

 (fee. Sometimes it is a mere rubble of limestone chips with quartz- 

 pebbles and an occasional flint. One limestone boulder measured 

 5' X 3' X 3' ; and another, nearly as large, was finely grooved and 

 scratched on one face. Many of the boulders occur scattered over 

 the face of the section from two to three feet deep in clean marl. 

 At many other points in the neighbourhood of Burton-on-Trent, 

 both in Staffordshire and Derbyshire, boulders of Pennine rock 

 either lie on the surface or are imbedded in the marl a few feet 

 from the surface. 



In South Derbyshire and Nottinghamshire the Later Pennine 

 Boulder-clay is also well developed. 



One mile N.N.AY. of Sudbury, near Oak Green, about 9 feet of red 

 gravel with sand-beds has been greatly disturbed. It contains 

 pebbles of flint, quartz, quartzite, chert, toadstone, and gritstone. 



In addition to the more or less contorted Interglacial River-gravels 

 (fig. 4) which have been described as belonging to a previous period, 

 there are gravels and sands like those on the *' Hill Top," near Ash- 

 bourne, and at Oak Green, which, though originally aqueous deposits, 

 have been converted into Boulder-clay. It is difficult in many 

 instances to be certain whether many of these deposits were origi- 

 nally of marine or fluviatile origin ; they are now Boulder-clays or, 

 more properly speaking. Boulder-sands. 



High-level Boulder-clay is exposed in a shallow excavation at 

 Heath House Green, north of Tutbury, and again on the road south- 

 west of Sutton- on-the-Hill. 



ISTorth-west of Derby, along the course of the Markeaton brook, 

 there extends a long patch of gravel, probably washed down from the 

 Bunter Conglomerate and converted by Later Pennine ice into unstra- 

 tified moraine. North of Markeaton, on the west side of the brook, 

 there is a good exposure ; it is here an indurated, coarse, red, sandy 

 gravel, exhibiting little sign of original stratification, but containing 

 a few lenticular beds of sand. A few flints and angular pieces of 

 Keuper sandstone occur; but the mass of the gravel consists of 

 quartz and quartzite pebbles. Another exposure, about 11 feet deep, 

 of the same deposit, may be seen near the Ashbourne road, just 

 before leaving Derby ; the same almost entire absence of sand-beds 

 is here shown. Not far off, near Stretton's Brewery, a deep exca- 

 vation passes through Boulder-clay of the same age, and probably 

 continuous with this disturbed gravel. The moraine is here at least 

 10 feet thick, and consists of pebbles stuck at all angles in Keuper 

 marl. The Boulder-clay stretches, with a thickness sometimes 

 exceeding 10 feet, over the greater part of the northern and eastern 



