16 DIENER : GEOLOGICAL STRUCTURE OF CHITICHUN. 



of which pass underneath them quite unchecked in their development 

 or direction. In the crags of Iberg the rocks are completely 

 squeezed and crossed so intensely by thrust planes that the true 

 stratification can be made out but exceptionally. In the Roggen- 

 stock crag the sequence of beds is totally inverted as has been shown 

 by Quereau. Every single crag seems to be separated from the 

 underlying flysch by a quaquaversal thrustplane, and may consequently 

 be considered as a relic of an ancient recumbent fold, the larger 

 portion of which has been carried off by subsequent denudation. 

 These crags, like those of le Beausset or of the Ubaye district ought 

 therefore rather to be classed among the lambeaux de recouvrement 

 (Bertrand), than among the true Klippen, of which those of the 

 Piennine chain must be regarded as the prototype. 



The Tibetan crags of the Chitichun area form a special type of 

 structural features, which differ both from the Piennine Klippen and 

 from the Alpine " lambeaux de recouvrement " of the Ubaye or Iberg 

 type. They are distinguished by five peculiar characters, which 

 must be taken into consideration by any theory that may be ad- 

 vanced for the explanation of their origin. These five characters 

 are the following : — 



1. The difference of the rocks, both in the crags of Chitichun 



and in the main region of the sedimentary belt of the 

 Central Himalayas. 



2. The almost semicircular direction of their strike, which is 



arranged diagonally to the direction of the Himalayan 

 folds outside the Chitichun area. 



3. Their occurrence within a synclinal region, consisting of 



Spiti shales and Gieumal sandstones. 



4. Their intimate association with intrusive igneous (basic) 



rocks of cretaceous or tertiary age. 



5. The absence of any distinct littoral deposits in their 



vicinity. 

 These points will be separately taken into consideration. 



( 16 ) 



