468 ME. E. M. DEELET ON THE PLElSTOCEIirE 



that not only have the Boulder-clays and associated deposits been 

 removed, but the old river-gravels which lay beneath them have 

 shared the same fate. 



The Interglacial Eiver-gravel occupies terraces at various heights 

 along the valley of the Trent and its tributaries. I have not traced 

 it in detail out of South Nottinghamshire and South Derbyshire, 

 but no doubt it occurs in equal profusion at other points. The 

 sketch map (fig. 1) shows the distribution of the deposit in sheet 

 71 S.W. 



The long period of submergence brought to a close at the end of 

 the Chalky-gravel stage, by the emergence of the area of the Trent 

 basin above the level of the sea, gave rise to the formation of river- 

 gravels, which at high levels are difficult to separate from the 

 previous marine deposits, owing to the absence of molluscan remains, 

 and also to the disturbance they have suffered by subsequent 

 glaciation. 



Unfortunately no freshwater shells have been found in the Intergla- 

 cial Eiver-gravels ; but these gravels present so many characteristics 

 common to river- deposits, and differ so markedly from the Chalky 

 Gravel, that there can, I think, be little doubt about their origin. 

 The main proofs of their interglacial age will be given when the Later 

 Pennine Boulder-clay presents itself for consideration. They generally 

 have a rusty-red, compact appearance, which gives them a look of 

 great age* From their upper surfaces contortions frequently extend 

 downwards, until the rock upon which the gravel rests is bent, 

 broken, or even torn up. Unlike the Chalky Gravel, which forms 

 banks or sloping beds of varying thicknesses, the interglacial alluvium 

 runs for miles in nearly flat terraces of considerable width at almost 

 constant heights above the more modern river-deposits. In many 

 instances the gravel or sand is finely false-bedded in a direction 

 indicating currents down the valleys. A close relationship also 

 subsists between the thicknesses of these deposits and that of the 

 alluvial gravel now being formed by the rivers. It would thus appear 

 that the interglacial rivers were nearly similar in volume and depth 

 to the modern streams ; for when the gravels have not been much 

 eroded by Later Pennine ice, the postglacial and interglacial deposits 

 are of similar thicknesses. 



In the Dove valley Interglacial Eiver-gravel occasionally over- 

 looks the river from considerable heights. 



Near the Yelt Farm, east of Uttoxeter, about eight feet of highly 

 contorted gravel, with flints and beds of sand, forms a terrace at a 

 considerable height above the stream. 



Still further to the east, Poston Hall stands on a similar terrace, 

 at a height of 30 feet above the modern plain. The gravel is exposed 

 in two pits, one to the east and the other to the west of the park. 



A high-level deposit of rusty-red gravel, with occasional seams of 

 sand, occurs to the east of Hilton. Two sections may be seen — 

 one to the north of the village, and another on the highroad to the 

 east. At this point the thickness exposed is about 10 feet. The 

 whole of the surface- portion is considerably disturbed, the confusion 

 frequently descending several feet. 



