CRYSTALLINE SERIES. 



19 



Hindu Kush in this part of Afghanistan. At the northern end of the ' 

 Paghman range, the ridges behind Charikar are composed of biotite- 

 gneiss and granite capped by crystalline limestone ; the latter contains 

 mica and coccolite and is overlain by a grey saccharoid marble with 

 lenticular patches of calcite, evidently a sedimentary rock altered by the 

 numerous veins of schorl-granite by which it is penetrated. These rocks 

 in some respects resemble those nearer Kabul, but the biotite-gneiss 

 appears fresher and more like the common foliated biotite-granite of the 

 Himalaya. Rock-types very similar to the limestones have been pro- 

 duced, only a few miles away across the Ghorband river and on the 

 same line of strike, by the action of the granite of the Hindu Kush 

 on an undoubted sedimentary series of post-Cambrian age. On this 

 basis the hematite of Masai might also be claimed as the representative 

 of the similar rock of the Koh-i-Baba and Ghorband {infra, p. 24). 



The advanced state of metamorphism of some of the sedimentary 

 beds in Ghorband and Parwan certainly led me at first bo regard them 

 as Archsean, but convincing evidence, subsequently obtained, proved 

 them to be comparatively young and not older than Lower Palaeozoic. 

 It must be admitted therefore that it is equally possible that the 

 crystalline rocks of Kabul are the result of an analogous set of pheno- 

 mena and merely a more advanced stage in the metamorphism of 

 similar post-Cambrian sediments. 



It is clearly impossible, on such facts as are at our disposal, to 

 attempt to estimate the age of the crystalline rocks of Kabul and the 

 Siah Koh. On the one side, we have penological evidence pointing to 

 the Indian Archaean group, whilst, on the other, pakeontological evi- 

 dence suggests the Palaeozoic. A third point of view is the tectonic, and 

 from this Mr. Griesbach (13, 6G) and Professor Suess (29, 291) have 

 assumed that an Archaean mass, lying between the Hindu Kush and 

 the Safed Koh, is accountable for the difference in trend between these 

 two regions. Mr. Griesbach writes : — "This was land, when the partly 

 littoral, partly fresh-water, beds of the trias (with coal) were laid down 

 in the basin of Kataghan and Afghan Turkistan, and formed a rigid 



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