GLACIAL BEDS. 497 



Tlie Drift deposits of the Trent Basin have been divided as follows, by Mr. 

 R. M. Deeley :— 



Newer ( Later Pennine Boulder Clay. 

 Pleistocene ( Literglacial River Alluvium. 



M'rlHl ( Chalky Sand and Gravel. 

 -n^ ■ . I Great Chalky Boulder Clay. 



Pleistocene I at u c j 

 [ Melton Sand. 



Q, , / Middle Pennine Boulder Clay, 



p, . < Quartzose Sand, 



i-ieistocene | ^^^^^ Pennine Boulder Clay. 



The Early and Middle Pennine Boulder-clays, which closely resemble each other, 

 are composed of materials derived almost entirely from the Derbyshire hills, 

 but with a slight admixture (to the westward) of erratics derived from Scotland 

 and Cumberland. The latter were probably brought from those districts by an 

 ice-stream, the main materials of the deposits having been transported from the 

 Pennine chain by glaciers, and deposited in the partially submerged valley of the 

 Trent. The intermediate quartzose sand was deposited in the sea during a 

 milder interval attended by considerable submergence. The Middle Pleistocene 

 deposits, distinguished from the earlier beds by containing large quantities 

 of chalk and flints derived from the north-east, were apparently formed at a time 

 when the level of the Trent valley was lower than that of the Cretaceous 

 tracts in Lincolnshire and Yorkshire. The Chalky Boulder-clay was chiefly 

 a ground-moraine formed beneath an ice-sheet on land, but in places it presents 

 signs of aqueous origin. The Melton sand (of Melton Mowbray, etc.), in which 

 Cretaceous detritus first appears in abundance, consists of sands with occasional 

 beds of gravel or loam, and indicates a less extreme temperature. In West Stafford- 

 shire the gravels and sands probably represent the entire Middle Pleistocene deposits, 

 no Chalky Boulder-clay being found, and in this area fragments of marine 

 Mollusca are of frequent occurrence. The Chalky Gravel was also a marine 

 deposit, and, like the Melton Sand, was probably formed when the temperature 

 was rather milder than it was during the deposition of the Chalky Boulder-clay. 

 In the newer Pleistocene epoch re-elevation of the Trent valley and of the Pennine 

 chain appears to have again produced a change in the direction from which the 

 materials of the deposits were derived. The Interglacial Alluvium was of fresh- 

 water origin, but the admixture of Scotch and Cumbrian detritus with that derived 

 from the Pennine range indicates that glaciers from the north again reached the 

 Trent area. A colder age succeeded, during which the Later Pennine Boulder- 

 clay was formed, partly of local materials, partly of erratics from the Pennine 

 range, mixed with a few from Cumberland and even from Wales. This deposit is 

 almost entirely unstratified, and consists largely of moraine detritus, the ice-sheets 

 having disturbed and rearranged the earlier deposits and mixed them with rock- 

 detritus from the neighbourhood. To this later ice-sheet may be attributed the 

 contortions so frequently observed in the older and middle Pleistocene deposits, 

 disturbances which could not be accounted for by soil-cap motions.^ While Drift 

 occurs in the plains east and west of the Pennine chain, the higher grounds are 

 comparatively free from it." 



NORTH-EASTERN AND EASTERN COUNTIES. 



In the north-east of Yorkshire, the table-land of the Oolites is remarkably free 

 from Glacial Drift ; thus Boulder Clay extends to a height of about 800 feet in 

 some of the valleys, but the uplands appear to have formed an insular space round 

 which the ice-sheets swept, but which was not itself buried up. This is in 



1 R. M. Deeley, Q. J- xlii. 437. 



* Geol. N. Derbyshire, by A. H. Green, C. Le N. Foster, and J. R. Dakyns, 

 p. 127 ; see also J. Aitken, Q. J. xxxii. 184. 



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