178 GRIESBACH : GEOLOGV OF THE CENTRAL HIMALAYAS. 



local faults, and the interpretation of which is not at all easy, but 

 which I will endeavour to illustrate further on. 



The ranges of Dharma and Byans. 



The hill-ranges which form the watershed between the Gangetic 

 drainage and Tibet, with the numerous parallel chains to the south 

 of it, all run in a more or less south-easterly direction from the head 

 water region of the Dhauli (Dharma) Ganga. It proved a most diffi- 

 cult ground to explore geologically, and much of it being almost 

 entirely inaccessible, besides which, one has to carry all one's sup- 

 plies along, as there is not a single inhabited place in that area. 

 I found that the structure of this part of the Himalayas is very simi- 

 lar to that of the area immediately north-west of it, of which it is a 

 continuation. 



A series of flexures may be observed between the crystalline base 

 south, and the Hundes frontier, but it will be seen from the sections 

 in pis. 8 and 9 they are much more compressed and disturbed than 

 has been the case in the Lissar region, and a succession of faults of 

 greater or less'er stratigraphical importance render the interpretation 

 of the structure still more difficult. Three features characterize 

 the Dharma and Byans area. First, the silurian system is only 

 seen along the margins of the belt of sedimentary rocks, namely, 

 accompanying the strip of haimantas along the southern margin, 

 whilst some patches of silurian rocks form part of the high range of 

 the water-parting between Tibet and the Ganges drainage. 

 Secondly, the largest portion of the ground is occupied by rocks be- 

 longing to the devonian and carboniferous systems. Thirdly, the 

 permo-trias forms only narrow strips crushed into synclinals of upper 

 carboniferous rocks. 



I have already described the structure of the flexures which 

 form the highly elevated region of the head waters of the Dharma 

 valley, which is represented in section 4, pi. 7. That is the 

 only section in this part of the Himalayas in which some remains 

 of the Jurassic Spiti shales were met with ; further south-east the 



( 178 ) 



