120 SUB-HIMALAYAN ROCKS OF N. W. INDIA. [ClIAP. IV. 



It seems not unlikely that the changes we have noticed in the distri- 

 bution of clay in the lower part of the group may be an early result of 

 the same cause that produced the different distribution of boulders in the 

 upper beds, namely, the influence of the great rivers ; yet, in opposition 

 to this view, it may be asked, owing to what change in these conditions 

 at a subsequent period could clays accumulate so freely in the topmost 

 strata, and cotemporaneously with coarse boulders, over the whole area. 

 The mode of formation of these latter deposits is to me a very puzzling 

 question, and seems to require the hypothesis of some diluvial agency. 

 The theory of glacial action is hardly admissible ; the thoroughly 

 rounded condition of the boulders and the regularity of the stratification 

 require some other explanation of the formative conditions of these beds. 



The state of disturbance of the Sivalik group exhibits considerable 



_. x \ , c . . local irregularities. This is even the case in the 



Disturbance of biva- ° 



lik group detached ranges where there is no very evident 



cause for such breaches of symmetry. In these cases we may, I think, 

 fairly attribute them to the internal conditions of the strata themselves. 

 The very unequal accumulation of great banks of conglomerate cannot 

 but result in the confusion of stratification in the more regular deposits 

 with which they are associated, when all come to be compressed together. 

 In the region between the Kyarda and Pinjore duns, we can generally 

 trace these variations of dip to the irregularity of the boundary with the 

 older rocks. The rule already noticed in the case of the Nahun group 

 • w\\ rt f N along the main boundary is equally well observed 

 hun » in the Sivalik strata at their contact with the 



Nahun group. There is a remarkable example of this just to the west 

 of the Markunda section : the boundary takes a sharp turn to the north- 

 north-west, and along it the boulder-conglomerates dip steadily at 80° to 

 east-north-east along the Shilani valley, nearly to Myndar hill, where the 

 strike bends round to north-west. There are of course cases in which 

 it would be vain to assign the immediate cause of the state of upheaval : 



