Il6 GRIESBACH: GEOLOGY OF THE CENTRAL HIMALAYAS. 



As I have described in the general chapter on this group, the 



relations of it to the underlying rocks varies in 

 Rests on partially ..„ . i-uti. • j 



denuded carboniferous the different sections which 1 have examined. 

 roc s * Whilst in Spiti a gradual passage was observed 



from the carboniferous white quartzite (8) into an overlying Product, 

 us limestone, which in a lesser degree I also noticed in the most 

 eastern sections of Kumaon. I found that in the Niti sections the 

 Productus shales (9), part of which are here missing, are resting 

 directly upon a partially denuded surface of carboniferous rocks. So 

 marked is this feature, that when I first visited the locality in 1879, 

 I failed altogether to notice that a zone of Productus shales exists at 

 the base of the lower trias. 



In the Niti area, i.e., south-west of the watershed between the 



Dhauli Ganga and the Hundes drainage, it is 



Silakank section. 



again the steep, but not inaccessible, south- 

 western slopes of the range, which runs from the Marchauk pass in a 

 more or less north-westerly direction towards the head-waters of the 

 Shanki river, and in which the Silakank peaks and the Niti pass are 

 situated, which offers the most complete sections through the entire 

 group. Viewing this range from the north-western slopes of the 

 Chango (Patalpdni, Gwelding, etc.), one may notice a black band of 

 not very great thickness, sharply contrasting with the rocks below it, 

 which are generally the white quartzite (8)' of the upper carboni- 

 ferous ; the latter, however, thins out towards the north-west, and 

 then the black band rests on the deep-red Crinoid limestone (7) of 

 the upper carboniferous. 



'Ihis black band may be traced far away into the ragged and 

 mostly snow-covered, and very difficult area of the Upper Ganes 

 Ganga. It is everywhere visible from afar off, more resembling the 

 outcrop of a coal-seam than any other rock. 



After my second season in the Himalayas, when I observed the 

 TT , . Productus shales resting conformably on the 



Unconformity. ° J 



upper carboniferous in Eastern Kumaun, I felt 

 inclined to look upon the apparent unconformity between the car- 

 boniferous and the Productus shales in the Niti sections as due to 

 ( 116 ) 



