224 GRIESBACH: GEOLOGY OF THE CENTRAL HIMALAYAS. 



Chapter VIII. — Summary. 

 The Himalayan region forms part of the vast structure of the 

 Limits of Himalayan Central Asian elevation ; it is so closely con- 



area. 



nected with the latter, both structurally and 

 geographically, that it is very difficult to decide its exact limits. 

 Native geographers and the Puranic scriptures define the Himalayas 

 as comprising only the chain of snowy peaks at the head of the 

 Ganges drainage. Modern views generally limit the Himalayas to 

 the system of mountain ranges which extend between the Brahma- 

 putra and Indus rivers. Of course, structurally, these ranges continue 

 beyond these boundaries, but there are distinct changes in the fea- 

 tures of the ranges which make these limits advisable. As regards 

 the lateral extension of the region, several views have been formed ; 

 but I consider it most convenient, and at the same time more in 

 accordance with the original significance of the term, to call Hima- 

 layas only the system of ranges which fringe the Tibetan highlands 

 along its southern margin, a view which is now most generally held. 

 That part of the system in which rise the headwaters of the Ganges 

 drainage, and extending north-westwards as far as the Sutlej gorge, 

 I call here the Central Himalayas, and within this area I divide the 

 Central ranges into (i) Northern range (watershed), (and 2) 

 Southern range (line of highest peaks). 



Whilst the Southern range of the Central Himalayas is formed 



chiefly of crystalline rocks, mostly gneissic with 

 metamorphic schists, it is shown that the North- 

 ern range is almost entirely composed of a vast sequence of sedimen- 

 tary strata, ranging from the lowest palaeozoic to tertiary and recent 

 age. The detailed description of these various formations I have 

 given in the preceding pages, and I will here only recapitulate the 

 following points. 



Immediately on the crystalline schists reposes an enormous thick- 

 ness of beds of very varying lithological charac- 

 ter, named haimantas by me, which are sharply 

 ( 224 ) 



Geological structure. 



Haimantas. 





