BH6T MAHALS OF KUMAUN. 1 55 



Lapthal and the Kiangur pass (see sections in pi. 2), which incloses 

 crushed Spiti shales in an inverted synclinal of rhaetic and liassic 

 beds. The feature is clearly seen on the naked hillsides near the 

 Chidarmu encamping ground, and about four miles south of it in the 

 Kiangur pass itself (see fig. 21). The structure is further compli- 

 cated by extensive denudation, which in some cases has exposed the 

 rhaetic down to its lowest beds. 



East of this inverted flexure the bedding is normal, and the Liassic 

 East of Chidamu Spiti limestone and shales are seen to be overlaid by 

 shales and cretaceous. t he black Jurassic Spiti shales > which are again 

 in turn followed by the cretaceous system (18 in the sections on pi. 

 2). The dip is from 25 to 30 due east near the Kiangur pass. 

 The crest of the high range which forms the boundary with Tibet 

 here, is formed by upper cretaceous white limestone with fossils. 

 The peaks of the Kungribingri No. 2 are formed of this rock, which 

 overlies the greyish-green lower cretaceous (18) conformably. 



A similar section is seen to the north-east of Lapthal. The un- 

 dulating downs, which form the grazing district 

 North»east of Lapthal, i . . 



of Lapthal, are mostly within the belt of Spiti 



shales which here also rest conformably on the liassic strata. They 

 have a rolling dip from 15 to 25 to the north and north-east, passing 

 upwards into the greenish-grey cretaceous sandstones, shales and 

 limestones of the Balchdhura. The boundary of the cretaceous sys- 

 tem may be seen where the ground rises towards the north, in the 

 neighbourhood of the Sangcha Talla and Sangcha Malla camping 

 grounds. The ascent to the Balchdhura pass (17,590') leads mostly 



over cretaceous rocks, which are here disturbed 

 Traps. 



by igneous rocks. They are clearly intrusive ; 



it is a basaltic trap, associated with serpentinous masses, and I 

 believe forms part of the younger eruptive rocks which are largely re- 

 presented in Eastern Hundes, and to which probably a middle tertiary 

 age must be assigned. Some of the traps seen in the cretaceous 

 might be contemporaneous, but during my short stay in the frontier 

 district I have not been able to separate them from the undoubtedly 

 intrusive ones. 



( 155 ) 



