GEOLOGICAL DIVISIONS. 2CJ 



These considerations allow us to discuss at once both the age of 

 Age of the mountain the Siwalik hills and of the more important 

 ranges. ranges with which they are associated. 



Throughout a series of strata extending from upper cretaceous to 

 upper eocene there is nowhere any sign of erosion or unconformity* 

 Therefore we must admit that until the last stages of the eocene 

 the upheaval of the ranges had not commenced. On the other hand, 

 the last chapter in the history of the upheaval, as illustrated by the 

 Siwalik strata, had ended before the end of the pliocene. Therefore 

 the folding of this large area, the upheaval of all the ranges, the 

 metamorphism of shales into slates, the intrusion of great igneous 

 masses, the conversion of the sea into a land area, the denudation 

 which furnished the materials for the Siwaliks, and finally the uplift- 

 ing of these latter ranges, must have all taken place within a relat- 

 ively short period of the earth's history. The upheaval may have 

 commenced before the end of the eocene, it attained its maximum 

 during the miocene period and came to an end with the pliocene. 

 Whatever may be the date of upheaval of the Himalayas, whose age 

 has given rise to some discussion, the facts will not allow much 

 doubt so far as the Baluchistan area is concerned, as to the compara- 

 tively late period at which these mountains were upheaved and the 

 comparatively short period necessary for the process. 1 



The data available are perhaps hardly sufficient to say that the 

 tangential forces have entirely ceased to act. Observations are 

 far too scanty and extend over too brief a period to decide whether 

 any small changes of relative level are taking place. The undis- 

 turbed condition of thick deposits of recent gravel and of the vol- 

 canic cones may show merely that those areas where they have 

 been observed have not suffered folding, and we know that large 

 areas have been comparatively exempt from folding throughout 



1 " That the elevation of the Southern Persian mountains is of no high geological 

 antiquity, we may infer from the fact that ranges 10,000 feet high consist of nummulitic 

 rocks, that the gyposiferous beds, which are newer than the nummulitics, are found at an 

 elevation of 7,000 feet above the sea, and the Makran formations, which are probably not 

 older than pliocene, attain almost an equal height." W. T. Blanford. Quart. Journ. Geol. 

 Soc, Vol. XXIX, p. 501. 



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