534 E. Wilson and J. Shipman — The Keuper Basement Beds. 



of contemporaneous erosion, the sands having heen apparently cut 

 through by channels and replaced by other sands or by marls, while 

 the marls have been broken up and their debris, in the shape of 

 flakes, and lumps, scattered plentifully through the surrounding 

 sediments. Notwithstanding their intimate association with the 

 coarser deposits, the marls keep remarkably fine and pure. These 

 rocks are succeeded by the regularly bedded sandstones and marls 

 of the Lower Keuper. The line of junction, which is sharply defined, 

 is pretty level, but the " Basement Beds" appear to have been trun- 

 cated by denudation prior to the deposition of the Waterstones. 



Other Localities. — The " Basement Beds " of the Lower Keuper 

 are very variable in thickness, and, except in their areas of typical 

 development, very irregular in distribution. Prof. Hull long since 

 showed that the sediments which compose the Keuper rocks of 

 England probably came from the west or north-west; for he 

 demonstrated that the Triassic rocks, along with other Secondary 

 formations, attenuate in a south-easterly direction. 1 It was there- 

 fore to be expected that this lowest member of the Keuper 

 would be found to thin away going east, and such is actually the 

 case. On the west, in Delamere Forest, and the Peckforton Hills, 

 Cheshire, the Basement Beds proper are from 50 to 150 feet thick, 

 but, with the overlying red and white freestones, attain a thickness 

 of 250 feet or more. 2 At Alton, midway to Nottingham, these rocks 

 are not more than sixty feet, while still further east, at Nottingham, 

 they probably do not exceed twenty feet in thickness. East of the 

 valley of the Dove, these rocks rapidly attenuate, and are soon lost 

 beneath newer members of the Keuper, which then repose directly 

 on the Bunter Pebble Beds. Nor do they appear to be present 

 between the Derwent and the Erewash. Crossing that stream, how- 

 ever, we again meet with them — at Bramcote, Notts — as a few feet 

 of calcareous sandstone cropping out from beneath the " Waterstones." 

 They are found at Highnelcls, two miles nearer Nottingham, resting 

 on an eroded surface of Bunter Pebble Beds. Here they consist of 

 about seven feet of thick-bedded cemented quartzose grit, with 

 bands of compact conglomerate. They are also exposed in a small 

 boss of rock, at their outcrop near Bough Hill Wood — the most 

 easterly point at which they are to be seen in this country. We 

 have not attempted to trace these rocks further south than Burton- 

 on-Trent, near to which they are to be seen at Bladon Hill, in the 

 Trent escarpment, as white quartzose false-bedded grits, with thin 

 grey micaceous sandstones. Bed grit and pebbly sandstone, ap- 

 parently belonging to this series, are exposed near Ticknall, South 

 Derbyshire, between Heath Wood and Seven-Spouts. These beds are, 

 however, absent further east at Melbourne and at Castle Donington. 



Conclusions. — To arrive at satisfactory conclusions as to the 

 physical conditions under which the Basement Beds of the Lower 

 Keuper were formed, is no easy matter. That these rocks are all of 



1 Hull, " On the South-easterly Attenuation of the Secondary Bocks of England," 

 Quart. Journ. Geol. Soc. vol. xvi. p. 66. 



2 Hull, " Triassic and Permian Rocks of the Midland Counties." 



