80 



HAYDEN : GEOLOGY OF NORTHERN AFGHANISTAN. 



consisting of conglomerates, grits and sandstones followed by red lime- 

 stones with hippurites, which indicate a gradual reversion to marine 

 conditions. Subsequent disturbance led once more to the retreat of the 

 sea and the formation of salt-lakes in which gypsum was deposited. 

 This was the third important break in Afghan geological history. It 

 was followed by the great Upper Cretaceous transgression, which resulted 

 in the submergence of vast tracts of Asia, including much of Afghanis- 

 tan, Baluchistan and adjacent parts of India, but no evidence has vet 

 been found of the extension of the Cretaceous sea into Eastern Afghan- 

 istan, although it undoubtedly extended far to the south into Baluchistan 

 and eastwards into Kurram and Tirah. 



The close of the Cretaceous period was accompanied by some oscil- 

 lations of the sea-level and gradual contraction of the submerged area. 

 Evidence of the suppression of marine conditions is seen in the gypsum 

 beds of the Lower Tertiary system in Saighan and Kahmard. After 

 this the sea gradually disappeared, and by the latter end of the Tertiary 

 epoch Afghanistan was a land of great rivers comparable, in the width 

 of their valleys and the extent of their deposits, to those of the 

 Himalaya in the Siwalik age. This constitutes the fourth and last 

 break in the stratigraphical sequence. 



V SUMMARY. 



The facts that we have now at our disposal with regard to the geology 

 of Afghanistan lead us to the conclusion that that country is divisible 

 into two stiatigiaphical provinces, one of which is represented only 

 in Eastern Afghanistan, whilst the other comprises by far the greater 

 part of the country and embraces most of the northern and western 

 districts. The affinities of the former province are with the Himalayan 

 area, whereas those of the latter are with Western Asia and also to 

 some extent with Europe. The mutual separation of the two provinces 

 seems to have taken place towards the end of the Carboniferous period. 



The eastern facies embraces a series of old crystalline schists and 

 limestones which recall Archaean types of the Indian Peninsula and 



