STRATIGRAPHY. 12 



thickness must have been greater than this. The thickness seen 

 in the other exposures varies greatly and is always less than this, 

 the difference being in part due to the removal of the upper beds 

 by denudation. It is probable, in a series formed as this has, that 

 there were great original variations in the total thickness, as there 

 certainly are in the thicknesses of the individual stages. 



The basal stage, as has already been mentioned, varies from 20 

 to 500 feet within short distances. The middle stage too is subject 

 to great variations, the most striking case being near Ghurder. In 

 the scarp above that village there are only some 10 or 12 feet of shale, 

 representing the middle stage, the rest of the series being entirely 

 composed of sandstones ; about a mile to the north of this scarp the 

 shales have thickened to several hundred feet, but it is uncertain 

 how far this is a real thickening of the stage or due to horizontal 

 replacement of the sandstones by shales. 



The upper stage of sandstones is only represented in the two 

 easternmost exposures, and most conspicuously in that furthest east. 

 Near Ghurder it attains a thickness of about 300 feet and in the 

 Jungel outcrop there would seem to be at least 1,000 feet exposed, 

 according to Mr. Vredenburg. 



Following on the red shales in ascending order come the rocks 



Vindhyan system. °J. ** great Vindh y an system. These are 

 divided into upper and lower, the former consist- 

 ing of three divisions to which, on account of their thickness, the 

 word series might not inappropriately be applied, though through- 

 out the three there is a prevailing uniformity of character which unites 

 them in one great series of sandstones with subsidiary zones of 

 shales or limestone. The lower Vindhyans, on the other hand, are 

 sharply distinguished from the upper by the prevailing rocks being 

 shale or limestone, sandstones forming "but a small proportion of the 

 total thickness, and being usually more earthy and impure than 

 those of the upper Vindhyans. 



The subdivision of the lower Vindhyan series which is best 



LcWer Vindhyan series. ^^ ^ ** of M '- Mallet, published in his 



memoir « On the Vindhyan series in the North- 



( 11 ) 



