MALLET,, VINDHYAN SERIES, 95 



presents the bold precipices which relieve the outline of the lower escarp- 

 ments. Bands of dark red shale are often interstratified^ and the sandstone 

 itself is often shaly through a large thickness. It is generally fine-grained, 

 red^ with small white spots (a very characteristic variety) ^ greyish white and 

 purplish red. In the fine white flags which are sometimes met with, den- 

 dritic markings are to be found. The neighbourhood of Dumoh furnishes 

 fair specimens of these in the magnificent flags which are quarried there. 



Ripple marking, which is common throughout the greater part of 

 the Vindhyans, occurs in immense profusion and variety in the upper 

 Bundairs. Sun-cracks and water channels are also not unfrequent, but 

 rain drops have not been hitherto observed, a rather remarkable fact, 

 considering how common they are in the lower Vindhyans and the abund- 

 ance of sun-cracks in the strata we are speaking about. 



The prevalence of rippling and such like marks shows how shallow the 

 water must have been in which the Vindhyans were deposited. We have 

 already seen that both in Bundelkund and the Sone valley there is reason 

 to believe that the present limits of the formation are also nearly those 

 of original deposition. Combining these observations with the fact, 

 that several members of the series thin out partially or entirely from 

 east to west, and with the increase in width of the area in the same 

 direction, it seems a plausible supposition to regard the eastern 

 development of the Vindhyans as the result of estuary deposition. In 

 such case the sediment would have been supplied at the head of the estuary 

 by some great river coming from the eastward, and which must have 

 flowed over the crystalline rocks of Bengal, from the wasting of which we 

 may suppose the eastern Vindhyans to have been in great part formed. 

 In the course of time the estuary may have been completely choked up 

 with sediment, and the mouth of the river have been advanced further 

 west, so that the absence of the higher groups in the extreme east, may 

 be due to their never having been deposited there, and not only to subse- 

 quent denudation. 



( 95 ) 



