J 56 GFOLOGV OF THE SON VALLEY, ETC. 



and sandstones from above, drawbacks of this description being 

 rather greater on the western parts of the area than on the eastern. 

 Still every endeavour was made to see what evidence could be 

 gathered under the circumstances. In the attempt to get at 

 evidence bearing on the nature of the junction I followed it (the 

 junction) with a special look-out for any indications of denudation- 

 unconformity, but T cannot say I succeeded in coming anywhere 

 upon a contact of the Rohtas limestone with the rocks above 

 No erosion-unconfor- indicating an erosion-unconformity, though the 

 mity observed. ground was pretty closely examined wherever 



and whenever the state of exposure allowed it. The shales (so 

 constantly seen, specially on the western parts of the area under 

 notice) immediately overlying the Rohtas certainly seemed thicker 

 in some places than in others, but whether this was due to the 

 original variability in the shaly deposit, or to denudation of the under- 

 lying limestone in places (where the accumulation of shales would 

 thus be greater than elsewhere) before the deposition of the shales, 

 or to local depression in the rim of the basin, which would thus take 

 out of sight some of the lower beds, it was difficult to make sure. 

 Should there have been denudation in the case, the contact 

 between the limestone below and shales above ought to show some 

 evidence of erosion somewhere or other, but I myself never 

 succeeded in rinding any exposures demonstrative of such erosion. 

 But this evidence, though of importance so far as relates to the 

 localities of the particular exposures explored, cannot be said to 

 prove and establish the absence of erosion of the Rohtas before 

 the deposition of the superimposed beds for the whole area, inas- 

 much as I was not able to examine the junction in its perfect entirety. 

 But as regards that much of the junction as could be examined, the 

 indications pointed to the absence of erosion. 



In reference to the relations of the Rohtas with the supra-Rohtas 

 beds as regards dip, no dip-unconformity was 



Perfect dip-conformity ° L ' r J 



with the Kaimurs. anywhere observed either; but wherever there 

 was a clear exposure, the uppermost Rohtas beds were found to be 

 perfectly parallel with the suprajacent Kaimurs. 

 ( iS^ ) 



