26 DIENER : GEOLOGICAL STRUCTURE OF CHITICHUN 



the occurrence of the crags in association with the diabase porphyrites 

 in the following manner : — 



" We have seen, that this limestone (which forms Chitichun No. 

 I and the neighbouring crags) lies apparently on Gieumal beds in 

 one section and on Spiti shales in another ; further that the crags 

 are accompanied more or less along their entire line of strike by 

 igneous intrusive rocks, and in one instance at least the latter 

 penetrates the permocarboniferous limestone, which is partially con- 

 verted into a semi-crystalline limestone. 



u I advance therefore the theory that these older rocks have been 

 brought to the surface by faulting. The latter is not directly visible, 

 which, indeed, is rarely the case in a complex of soft shales, such as 

 the Jurassic beds are in this region, but a fault may be inferred not 

 only from the existence of palaeozoic rocks above Jurassic, but also 

 from the fact, that the former rest on different divisions of the latter 

 in adjoining sections. 1 The assumption of a fault explains also the 

 presence of intrusive rocks, which may have most probably intruded 

 along a line of fissure." 



According to Griesbach these Chitichun faults may belong to the 

 system of dislocations, which affects the Hundes plain in the vicinity 

 of the Mana*sarowar lakes and has enabled the basic rocks of Eastern 

 Hundes to intrude. This system of dislocation is however purely 

 hypothetical, being based only on Strachey's reconnaissances, which 

 though very meritorious in many respects, are of no value for a 

 discussion of the complicated question of our Tibetan crags. 



If I should be asked an explanation of the origin of these crags, 

 I could give no better than the above quoted, which has been ad- 

 vanced by Griesbach, at least for the present moment, although 

 positive proofs of the supposed faults are yet absent. After all, this 

 opinion may yield to reconsideration, when the details of the struc- 



1 1 his fact-, however, is equally well consistent with ths hypothesis of a fault or of a 

 recumbent fold or overthrust. 



( 26 ) 



