78 



HAYDEN : GEOLOGY OF NORTHERN AFGHANISTAN. 



Turkistan towards the end of that period. The shales and sandstones 

 with which the fossils are associated, and the broken condition of most 

 of the shells, prove them to be littoral deposits. 



In Western Afghanistan, in the neighbourhood of Herat, and in 

 Khorasan, the rocks included by Mr. Griesbach under the term " Plant- 

 bearing series " are apparently the representatives of my Doab and Saighan 

 series and, like the former of these, are associated with volcanic beds. 

 It appears, therefore, that the Triassic period was, at least during its 

 latter part, one of volcanic activity over the greater part of Northern 

 and Western Afghanistan, which formed a barrier between the Indian 

 and European Triassic marine basins. Over this area terrestrial condi- 

 tions prevailed on the whole, giving place occasionally to marine, owing 

 to incursions of a shallow arm of the sea. Whether this sea was the 

 European or the Indian we have not yet sufficient evidence to show. 



In a comprehensive review of the Trias of the Himalaya (4, 91), Dr. 

 Diener has referred to Afghanistan as the western extremity of the 

 Indian zoo-geographical region during the Middle and Upper Triassic 

 periods. This assumption was based on the evidence of the Chahil 

 fossils referred by Mr. Griesbach to Daonella lommeli and Monotis 

 salinaria, and which have now been found to be Halobiee of doubtful 

 affinities and not, so far as we know, referable to any Indian Triassic 

 forms. West of the meridian of Kabul, therefore, there is no un- 

 equivocal evidence of the former extension of the Himalayan Tethys over 

 Afghanistan at this period. Freeh, on the other hand, includes Western 

 Afghanistan in the European province (Lethcea mesozoica, Bd. I, map), 

 which he separates from the Himalayan by a narrow meridional belt 

 embracing Eastern Afghanistan and N. W. Kashmir; this, however, he 

 believes to have been submerged by subsequent transgression of the 

 Triassic sea, which thus finally linked up the two marine provinces. 

 So far as the greater part of the Triassic period is concerned, Freeh's 

 view is supported by such additions as have recently been made to our 

 knowledge of the geology of Afghanistan, but we are still without 

 definite evidence of any direct communication between the European 

 and Himalayan seas in Upper Triassic times. 



