74 



HAYDEN : GEOLOGY OF NORTHERN AFGHANISTAN. 



into the overlying beds. At the same time the axes of their folds in the 

 Khurd Kabul hill are almost at right angles to those of the younger 

 beds and it is evident that they represent an old, probably pre-Carboni- 

 ferous land-surface. 



The Khingil series is peculiar to this one area so far as we know. It 

 is apparently different to the Upper Paleozoic facies of Bamian and 

 the Hindu Kush, but related both to the Productus Limestone of the 

 Salt Range and to the Trias of the Himalaya. Between Kabul and the 

 Salt Range, the Productus Limestone has been found in the Bazar 

 valley on the northern flanks of the Safed Koh (15, 111) and the same 

 formation almost certainly forms part of the main range between the 

 Bara valley and the Khyber. The presence of the Khingil series to 

 the north of Tangi Grharu has been referred to above (page 14), but 

 nothing is known of its extension beyond the range bordering the 

 Kabul plain and even this has not been visited. The unconformity at 

 the base of the series between Butkhak and Khurd Kabul inevitably 

 suggests a comparison with the Aryo-Dravidian (Upper Palaeozoic) 

 unconformity of the Himalaya and one is tempted to see in these 

 limestones proof of the extension as far as Kabul of the transgression 

 characteristic of the Carboniferous Indian marine province. 



At a comparatively short distance away, to the west and north-west 

 of Kabul, the older sedimentary series are developed in a different facies, 

 and in the Koh-i-Baba and Hindu Kush we find evidence of the exist- 

 ence of marine conditions at least as early as the Devonian period and 

 probably much earlier. The Kalu series, Hajigak limestone and the 

 Helmand series represent, no doubt imperfectly, the Dra vidian group 

 of the Himalaya and indicate shallow-water marine conditions extending 

 throughout almost the whole period of their deposition. The hematite 

 bed and the graphitic slate suggest a temporary interruption and the 

 prevalence of terrestrial conditions towai'ds the end of the Silurian or 

 beginning of the Devonian period. This was followed by re-submer- 

 gence, and the formation of a coral limestone probably at no great 

 distance from a coastdine, for the (?) subsequently-formed slates and 



