GEOLOGY 



this is very exceptional ; the bed, which is quite local, thins out in all 

 directions, and only covers a very small area. 



Water from these rocks is very hard owing to the presence of gypsum, 

 and consequently unsuitable for general purposes, although much appreciated 

 for brewing. 



The Keuper Marl overlaps unconformably the rocks beneath ; and 

 although along its junction with the Keuper Sandstone it succeeds that 

 formation quite regularly, in fact the one passes into the other by almost 

 insensible gradations, still, where the oldest rocks come to the surface, as 

 around Charnwood Forest, and at Enderby, Croft, Narborough, Sapcote, and 

 Mountsorrel, it abuts directly against them without any intervening beds of 

 Keuper Sandstone, showing that these older rocks must have stood up as 

 islands in Triassic times. 



Various opinions have been advanced by geologists as to the mode of 

 origin of the Triassic rocks. Ramsay considered that all the Red Sandstones 

 of the Midlands, including both the Trias and Permian, were deposited under 

 continental conditions, 1 and this is the view, with slight modifications, 

 generally adopted at the present day. There can be no doubt that the rocky 

 floor of this region upon which the Trias rests was most irregular in form. 

 It was probably broken by tracts of high land in the neighbourhood of the 

 Pennine Chain, the Welsh Hills, the Lickey Hills, the hills of North 

 Warwickshire, the Charnwood Hills, and others, from which the material 

 was derived, and which enclosed basins and lagoons in which beds of salt and 

 gypsum were deposited; while the surrounding land was desert, producing 

 the ever-shifting sands that have formed the false-bedded sandstones, and the 

 remarkable eroded surfaces that have been found on the granite at Mount- 

 sorrel.* 



RHAETIC 



At the top of the Keuper Marl there are a series of beds which, although 

 they are classed with the Trias, are in mineral character more closely allied to 

 the overlying Lias. They rest on beds of tea-green marl at the top of the 

 Keuper, which was at one time included with them, but there is a sharp line 

 of division which is usually occupied by a thin band of conglomerate or 

 coarse sandstone, having a peculiarly gritty feel, known as the Bone-bed. 

 This bed, although sometimes absent, generally varies in thickness from 

 | in. to 2 in., or rather more. When met with at a little distance from the 

 surface it is very hard and pyritic, but nearer the outcrop it becomes 

 decomposed and much more brittle. It is a highly pyritous and impure 

 sandstone, full of the fragmentary remains of saurians and fish, the teeth and 

 scales of Colobodus^ scales of Gyrolepis alberti, teeth of Saurichthys acuminates, 

 Acrodus minimus and Hybodus cloacinus, together with fragments of Triassic 

 sandstones, pebbles, and coprolites. The Bone-bed is succeeded by a thick- 

 ness of about 1 7 ft. of dark, finely laminated shales, containing Avicula 

 contorta, Protocardium phillipianum, and other bivalves in considerable 

 abundance. These beds pass up into a series of bluish or grey shales which 



1 Quart. jfourn. GeoL Soc. xxvii, 195. 



1 These were first described by Professor Watts, Brit. Assoc. Rep. for 1899, p. 747 ; Free. Geol. Assoe. 

 xvii, 379. 



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