4 DIENER : GEOLOGICAL STRUCTURE OF CHITICHUN. 



a steep escarpment of limestones, which seem to overlie conform- 

 ably the sandstones at their base. In 1879 Griesbach visited the 

 Balchdhura and believed the limestone to be of upper-cretaceous age 1 , 

 corresponding to Stoliczka's Chikkim limestone, which in Spiti 

 follows immediately above the Gieumal sandstone. 2 



We shared in this view, when passing along the southern slope 

 of the range towards the head-waters of the Kiogadh river on the 

 12th and 13th of July, being likewise under the impression of an 

 apparently normal position of the limestone cap above the under- 

 lying flysch. It was only after our discovery of the permo-carboni- 

 ferous and triassic limestone crags near Chitichun encamping 

 ground, that we began to doubt the correctness of our former 

 opinion. We therefore resolved to revisit the Balchdhura on our 

 trip from Laptal encamping ground to the Shalshal cliff, and 

 succeeded in examining the most western of the limestone peaks 

 which form the high range of mountains, extending northwards 

 and eastwards into Tibetan ground, and culminating in the big 

 rocky mass of Ghatamemin (18,700 feet). 



This limestone peak overlooks the Balchdhura (17,590 feet) 

 and is accessible from Sangcha Talla by a deep ravine, leading 

 in an eastern direction. Its base is made up of Gieumal sandstones 

 which show a very complicated dip and are penetrated by numerous 

 veins of igneous rocks. In the upper portion of the mountain these 

 igneous rocks and the tufa associated with them predominate. The 

 limestone crag itself rests entirely on beds of a clearly igneous 

 character, without coming into contact with the sandstone formation. 

 The highest crag forms a steep scarp and is likewise traversed 

 by veins of a diabase-porphyrite. The limestone is of a white to 

 reddish-white or red colour, without any distinct stratification, semi- 

 crystalline and partially altered, especially so where surrounded by 

 intrusions of igneous rocks. 



1 Geology of the Central Himalayas,, Mem. XXIII, p. 179, 1891. 



2 Mem, Geo!. Sui v. of India, VI, p. 113. 



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