90 Reports and Proceedings — Geological Society of London. 



including the towns of Leicester, Loughborough, Coalville, and 

 Hinckley. As has been shown by Professor Watts, the Charnian 

 rocks project through a mantle of Triassic deposits which once 

 completely covered them. In numerous quarry-sections the relation 

 of the Keuper to the pre-Cambrian rocks is well exposed. 



The quarries generally have been opened in the summits of the 

 more or less completely buried hills. A quarry is so worked that 

 its outline follows the contour of the buried hill; consequently, the 

 section presents but a dwarfed impression of the irregularity of the 

 rock-surface. Nevertheless, considerable undulations are observed, 

 and wherever there are any sections at right angles to the contours, 

 the rock-slopes are seen to be remarkably steep. Contoured maps 

 have been prepared, showing the features of some of these covered 

 peaks. 



On the buried slopes and in the gullies are screes and breccias, 

 and bands of stones and grit are present in the adjacent beds of marl. 

 All these stones, in every case, are derived only from the rock 

 immediately at hand. They never resemble pebbles, but often are 

 fretted into irregular shapes. Where exposed to the present climate, 

 the Charnian igneous rocks are deeply weathered and disintegrated. 

 But the same rocks beneath the Keuper are fresh right up to the top, 

 as also are the rock-fragments in the marls. 



The Keuper marls lie in a catenary manner across the gullies, 

 and probably across the large valleys also, for they dip away steeply 

 in all directions around each buried peak. 



There has been almost no post-Triassic movement in Charnwood. 

 Nevertheless, the beds must have been originally laid down horizontally, 

 for they are in no way peculiar, and contain the normal seams of 

 shallow- water sediment. All the points of contact of any one bed 

 with the Charnian rocks lie on one horizontal plane. The inclination 

 of the strata must, therefore, be due to subsequent sagging. 



The Upper Keuper deposits accumulated in a desert basin, of which 

 parts were dry and parts Avere occupied by ever-shifting salt lakes and 

 pools. In these waters the red marls were laid down. The red 

 marls are of several different types, and are usually well-bedded. The 

 principal ingredients are a certain aluminous mineral in very small 

 particles and a much smaller proportion of very fine quartz-sand. 

 There is generally 20 or 30 per cent, of dolomite present, in the form 

 of minute rhombs. 



The grey bands include various kinds of rock. Each band usually 

 contains one or more seams of well-bedded sandstone or quartzose 

 dolomite, and may safely be relied upon to indicate the bedding. The 

 irregularities are due to irregularity in the bleaching above and below 

 these porous seams. 



The abundant heavy minerals are garnet, zircon, tourmaline, stauro- 

 lite, rutile, magnetite. These are found in every sediment — marls, 

 sandstones, grits, breccias, etc. The grains are intensely worn. 



The quartz-grains are sometimes evidently wind-worn. The sand 

 in the grey bands is coarser and more abundant than that in the red 

 marls. Each grey band marks the introduction of coarser sediment 

 into the basin. The false bedding is mainly from the south-west. 



