8 DlENER : GEOLOGICAL STRUCTURE OF CH1TICHUN. 



examination of the ground is necessary to fix the boundary between 

 them. The intrusive character of the igneous rocks has been proved 

 by the following important observation, which I shall quote in 

 Griesbach's own words :— 



" The base of the south-eastern slope of Chitichun No. I is 

 covered with a mass of debris, and there is therefore no actual con- 

 tact seen with the Spiti shales. But north-east a low saddle leads 

 across the range between the crags of Chitichun No. I and the one 

 immediately next in succession. The saddle is seen to be formed of 

 the basic igneous rock, which also runs as a vein up the side of the 

 crag, whilst the crown of the latter, a small level space, is entirely 

 composed of that rock. The latter is therefore proved to be of 

 intrusive character penetrating in succession the Spiti shales and 

 the crag in question. " 



A distinct stratification has neither been observed in the limestone 

 cap of Chitichun No. I, nor in any of the other crags, which I have 

 personally visited. It is true that the limestone of Chitichun No. I 

 appears to be bedded almost horizontally, especially if seen from the 

 west or south-west, but the rock is crossed by so many planes of 

 cleavage and thrust faults in nearly every direction, that it is 

 extremely difficult to recognise its original stratification. So large 

 indeed is the number of cleavage planes, that there is scarcely a 

 fossil in our collection which is not traversed by one of them. 



Triassic crag. — There is still another very remarkable crag imme- 

 diately to the east of Chitichun No. I. It is about 130 feet in height 

 and of a quite regular, conical shape. Its western, northern, and 

 southern slopes are completely surrounded by intrusions of igneous 

 rocks. Unfortunately there was no opportunity of examining its east- 

 ern slope. The surface of this cone is entirely made up of slabs of a 

 yellow greyish limestone of a lithological character, which strongly 

 recalls the topmost beds of the upper triassic limestones (Griesbach's 

 rhaetic system), corresponding to the Dachsteinkalk of the Austrian 

 Alps. 



( s ) 



