354 T. 0. Bosicorth — Origin of Upper Keuper, LeicestersJnre. 



smoothed and pitted, and bear projecting carved knobs which are 

 often coated with a red crust. At Xarborough, where the rock is 

 fine-grained and contains no evident quartz, the surface has taken 

 a high polish. At the north-east corner of Croft Quarry a large 

 surface of rock bared for quarrying may now be seen. Part of this 

 was covered by Keuper Marl, and part had been denuded of Keuper 

 by glacial agencj' and covered by Boulder-clay. The two parts are 

 quite different : the former is comparatively very fresh, and from it 

 project knobs of fretted stone covered with red crust containing round 

 quartz grains ; the latter is undulating, bare, and striated (PI. XV, 

 Fig. 1). At Groby, in the Sheet Hedge Wood Quarry, a precipitous 

 slope was bared about a year ago, on which a vein of quartz projected, 

 wliose pitted and fretted surface looked very unlike the work of water, 

 but rather as though blown sand had played upon it, picking out 

 the druses and chloritic grains. 



Another curious example I unearthed at Croft, two years ago 

 (see PL XV, Fig. 1). It has since been quarried away. Along 

 the joints in this rock fissures had been formed, which widen 

 downwards, the undercutting being greatest on their south sides. 

 This suggests the action of dew. But there is a conspicuous line, 

 above which the surfaces are fretted and the crevices widen upwards. 

 It may be that the rock was subsequently buried in desert dust up to 

 the level of this line, while the part above it was exposed to the 

 wearing action of drifting sand. At Bardon, Shepshed, and generally 

 along the northern border of Charnwood, and also at Woodhouse and 

 Swithland, where the rocks are broken or cleaved, the floor beneath 

 the Keuper is rough and craggy, though the rocks are still com- 

 paratively fresh. 



Worn slopes occur facing all j^oints of the compass, and their dis- 

 tribution seems to depend most upon the nature of the rocks. Isolated 

 rocks would be more favourably placed for wind-carving, and they 

 would more easily be grooved by sand brushing through narrow gaps 

 between them. Again, only massive and homogeneous stone would 

 stand long enough to become carved, while rocks with cleavage or many 

 divisional planes would crumble too quickly, and would moreover 

 give rise to talus slopes. This may account for the possible wind 

 effects being almost confined to the granitic rocks of Mountsorrel, 

 Groby, and South Leicestershire. 



3. The Nature of the Keuper Depemta. — In the open country the 

 Keuper beds are almost horizontal, but around Charnwood they are 

 often steeply inclined, and dip everywhere in the direction of the 

 surface slopes on which they lie, the amount of dip depending on 

 the steepness of the slope. Thus there is a radial direction of dip 

 around the Charnian peaks, and where the Keuper is seen occupying 

 depressions in the ancient land surface catenary bedding often occurs, 

 e.g. at Croft and at Groby (PL XV, Fig. 2). And from the way 

 the Keuper dips away from the hills it seems probable that the large 

 valleys were filled in the same manner. This inclination of the beds 

 might to some extent be explained by great contraction of the marl on 

 solidification. But we should in that case expect the bending to 

 be accompanied by fractures and slickensides. This, however, is not 



