46 BALL : GEOLOGY OF THE RAJMEHAL HILLS. 



From the uneven character of the surface which there are good 

 reasons for believing existed at the commencement of the deposition of 

 these rocks, the thickness exposed at different places are exceedingly 

 variable. In many places these rocks are found resting immediately on 

 the gneiss, and occasionally they altogether thin out, the trap being found 

 in contact with the older rocks, either Damudas or gneiss. Denudation, 

 too, has not been without its influence in diminishing the thickness of 

 this group in several localities. 



Although, as a whole, these rocks present a striking contrast to the 

 Sharp demarkation of appearance of the lower beds belonging to the 

 boundary difficult. Damuda series, still when it comes to sharply 



defining the limits of ,each in the field, much difficulty is often experi- 

 enced. Throughout extensive areas the representatives of the two series 

 are found to exhibit a complete "parallelism and conformity, and in such 

 cases, in the absence of strongly marked lithological differences, a con- 

 siderable amount of doubt must attach to the exact position of the 

 boundary. It has been above shewn that the trap, in some cases, rests 

 immediately on the Damudas, and that the thickness of these rocks varies 

 so that the position of the boundaries cannot even be determined by refer- 

 ence to the position of the superimposed trap. 



The following is an account of the rocks referred to the Dubrajpur 

 group as they occur in our area from north to south. 



Proceeding north from the civil station of Suri, the first rocks we 



„. a . ,, meet with are pinkish and grey fine-grained sand- 



First outcrops m the L ° J ° 



soutl1 - stone, with some flaggy shales; which crop out from 



beneath the alluvium in the neighbourhood of the village of Rugonath- 

 pur. The general aspect presented by these rocks is somewhat suggest- 

 tive of the lower Panchets, but similar rocks have been observed in the 

 upper Panchets, or lower Mahadevas, to which latter, from other consi- 

 derations to be presently noticed, they more probably belong. 

 ( 200 ) 



