112 M1DDLEMISS: PHYSICAL GEOLOGY OF SUB-HIMALAYA. 



I have here shewn Nahans and M. Siwaliks in a like succession. 

 But until they are so found it is safer to call the lower beds Nahans. 

 I think also that this classification best agrees with that which Mr. 

 Medlicott has adopted over the larger part of his area. 



Still, should there be a slight discrepancy between our two classi- 

 fications, I think it will be in this respect. My Nahan beds may 

 possibly be, as a whole, of slightly lower horizon than Mr. Medlicott's ; 

 that is to say, I may have included with the Nahans older beds than 

 he has, and drawn the line between them and the sand-rock stage 

 a little below his. 



If we refer to what has been written in the foregoing pages about 

 Source of material of the petrology of the Sub-Himalayan system, we 

 Sub-Himalayan rocks. s hall see that the mineralogical composition of 

 the strata suggests something about the area from which the material 

 forming them was derived. The presence of so much mica, in well 

 preserved plates ; of magnetite ; and of occasional fragments of 

 felspar ; not to mention the very granitic appearance of much of the 

 rock ; shews unmistakably that the area from which this detrital 

 material was drawn was one of crystalline schists or granitic rocks. 

 The freshness of the material also proves that it cannot have 

 travelled far. Every presumption is in favour of the belief that it 

 came from the higher Himalayan range. That being the case, we 

 cannot suppose that range plunged beneath the sea, or below the 

 general level of denudation at the time of the deposition of the 

 greater part of the Sub-Himalayan series. Apart from their geogra- 

 phical distribution and their fossil contents, there is this indication 

 afforded by their minerals that the schists and granites of the Himalayan 

 range were exposed at that time, though there is no proof here that 

 they were in their present greatly elevated position. That the same 

 minerals might have been derived from some other land is of course 

 a possible, though not a probable, hypothesis. But, besides the com- 

 moner minerals herein mentioned, General McMahon (Rec, G. S. L, 

 Vol. XVI, p. 1 86) has described several accessory minerals whose 

 presence still more convincingly points to the crystalline rocks of 



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