THE PATL1 DUN. 65 



part of the middle limb of a sigma-flexure into which the sand-rock 

 is thrown) is preserved almost in its entirety : the thickness north of 

 the axis of the fold is almost equal to that on the south ; and the 

 nature of the rock changes by becoming harder and more Nahan-like 

 as we diverge both north and south from that axis. The structure is 

 as far removed as possible from that in section V ; and warrants us in 

 believing that, immediately south of the reversed fault in the Rcim- 

 ganga, the sand-rock is of proportionate thickness beneath the thin 

 band of conglomerate, and ergo that, immediately north of the fault, 

 a similar thickness has been denuded away from the top of the Nahan 

 ridge. 



The only question that seems to me to need considering is whe- 

 ther we are to regard the position in the Rimganga as entirely a 

 modification by further faulting of that in the Sona N., or whether we 

 may accept a compromise between that and the position as shown in 

 section V. The two extremes will be seen to be exactly equivalent to 

 those drawn by Mr. Medlicott across the Una dun and the west end of 

 the Pinjor dun respectively. 1 I think on the whole the position in ques- 

 tion must be regarded as more nearly agreeing with that in the Sona 

 N. We must picture a sigma-flexure, as in the Sona N. section, suffer- 

 ing further compression and tearing along the middle limb ; resulting 

 ultimately in the formation of a thrust-plane, and almost complete obli- 

 teration of the middle limb. The magnitude of the result is, however, 

 somewhat startling. The uppermost beds of the sand-rock, or the lower- 

 most beds of the Siwalik conglomerate, on one side of the reversed fault 

 lie at the same height as the visible base of the Nahans on the other 

 side. If we go back along the section to the point where the Nahan 

 sandstone band, north of K^lagarh, dips conformably below the sand- 

 rock, and carry an imaginary junction line forward beneath the sec- 

 tion up to the reversed fault continued downwards, and if we then 

 go forward along the section to where the Nahans are again covered 

 by the sand-rock, at Gutua gcidh, (33) and carry the junction line back- 

 ward above the section up to the reversed fault, we shall find the two 



1 Manual of the Geology of India, p. 550. 

 E ( 123 ) 



