108 SUB-HIMALAYAN ROCKS OF N. W. INDIA. [CHAP. IV. 



districts this abnormal order of superposition is a feature of what some 

 authors understand by the fan structure, in which case inversion is 

 involved. In less disturbed regions, and generally as here, in the fringe 

 ing zone of mountains, such sections are usually supposed to necessitate 

 prodigious faulting ; for the younger beds at the contact are the topmost 

 of a series many hundreds (perhaps thousands) of feet in thickness, as 

 ordinarily measured, and the older ones are the bottom beds of a series 

 equally thick. This mode of explanation by faulting is a most con" 

 venient one, and seems to harmonize well with, or even to be suggested 

 by, the general facts of the case, especially that most prominent one, the 

 upheaval of the mountain area on the upthrow side of the supposed 

 fault. The idea of the very recent upheaval of great mountains has 

 been largely based upon analogous sections to these ; yet in the case 

 before us it will, I think, be evident from the following sections that no 

 fault at all has occurred. 



On both sides of the Markunda valley, along the junction, where the 



conglomerate band runs close up to the Nahun beds, in the narrow and 



steep gullies draining to the south, the contact is better seen than in the 



„,., L . main river. In this position, on the path leading 



The Tib section, an *■ 1 ° 



original contact. f rom Tib village to Kairwala, a section of the 



contact occurs as represented in Fig. 13, and it must, I think, be taken 



Fig. 13. 



Section of contact south of Tib. e. Nahun group, f. Sivalik group. 



as a type and a clue for the rest. The beds / are the actual con- 

 tinuation of those we have just seen in the Markunda ; and so are the 

 beds e. Here, however, it is palpable that they are nearly in their 

 original relations, and that the beds / were deposited against a steep 



