70 



HAYDEN : GEOLOGY OF NORTHERN AFGHANISTAN. 



in all the disturbances to which the underlying Cretaceous rocks have 

 been subjected, whereas the red conglomerate and overlying beds are 

 comparatively little disturbed. For this reason I consider that the 

 inter-Tertiary unconformity represents a very considerable time-interval. 

 At the north-eastern corner of the Madar basin, the road to Haibak 

 leaves the Tertiary beds and, skirting a magni- 

 ficent dome in the Cretaceous limestone (Plate 19), 

 ascends, first, through a narrow gorge in the same rock ; subsequently 

 it passes over some small outliers of the Lower Tertiary beds, to 

 the Kara Kotal, where there is a large outcrop of dark green diabase. 

 The field relations of this rock were not ascertained, but it is probably 

 intrusive among the Cretaceous beds. From the Kara Kotal the Upper 

 Cretaceous limestone extends westwards forming the high snowy ridge 

 which separates Madar and Ilajar from Ao-Khorak. On the north, the 

 Red Grit series is exposed along the flanks of this ridge, and extends 

 down into the Khorak valley, where it is underlain by the Saighan 

 series. The latter is well exposed along the banks of the stream, and 

 the characteristic fossil plants occur in some profusion in shales on the 

 left bank about half a mile below the small village of Khorak-i-paian. 

 The hills on the northern side are capped by Cretaceous limestone, 

 which lies unconformably on the Saighan series, and descends here and 

 there into the valley ; the structural conditions are rather complicated, 

 and suggest the presence of an overthrust. 



The Saighan series extends to the top of the Kotal-i-Sabz (vulg. 

 Kotal-i-Saozak) and down the other side into Chahil, where it is over- 

 lain by Cretaceous limestone and underlain, presumably, by the beds 

 with Ualobia sp. (supra, p. 31). The Kotal-i-Sabz was the limit of my 

 tour, and I was unfortunately unable to visit either Chahil or Dara 

 Yusuf. From Mr. Griesback's description of the latter area, however, it 

 would appear that the sequence in this part of Turkistan is different to 

 that in Saighan, the volcanic element of the Doab series being appa- 

 rently absent to the north of the Kara Kotal. The base of the Saighan 

 series is not exposed in Ao-Khorak. 



