5fi HATDEX : GEOLOGY OF XOBTTIERX AFGHANISTAN. 



foot of the Ak Robat Kotal. The conditions here are rather ob- 

 scure and all the rocks much disturbed, but the general dip between 

 the Kotal and the massive limestone of the lower end of the gorge 

 is south-easterly and I believe that the limestone overlies the grits 

 and the quartzites. Taking the section in what I regard as ascend- 

 ing order and starting from the only horizon in which deter- 

 minable fossils have been found, riz., the Fusulina-bearing crinoid 

 limestone of Ak Kobat Kotal, we find this limestone, which is a dark 

 schistose rock, cropping out on the descent from the top of the pass 

 towards Bamiin. Similar limestone occurs again lower down in the 

 main valley at the foot of the pass and is overlain by a thick series 

 of slate, quartzite and grit, much folded, but dipping in the main at 

 high angles to the south-east. At the lower end of the gorge this is 

 overlain by massive limestone through which the river rushes in a 

 narrow channel between high vertical cliffs. The latter limestone is 

 the rock in which Mr. Griesbach noticed remains of brachiopods. It 

 is to a large exteat crystalline and is penetrated by a network of fine 

 veins of white calcite which has presumablv been deposited alonff 

 planes of fracture. Numerous small lenticular bodies scattered 

 throughout the rock are very suggestive of Fujitlina. but their struc- 

 ture has been so obscured by metamorphism that I have not been able 

 to confirm this. 



Between the top of the Ak Robat Kotal and the southern foot of 

 the Kotal-i-Katar sum 1 I have no observations, 



Ak Robat to Saraiak. 



but where the road to Saighan finally leaves the 

 valley above the caravansarai, beds of crystalline limestone and slate, 

 the former containing pebbles of quartz, flint and chert, dip to the 

 south and overlie grit, conglomerate and quartzite which extend up 

 to the top of the pass. All these have at first a southerly dip but the 

 crest of the range is an anticline and on the northern slopes the beds 

 dip away towards the valley of Saighan. I include the crystalline 

 limestone just mentioned in the Fusulina Limestone series. 



1 TLis is the name employed en our maps. Mr. Griesbach refers to this pass as 



the northern Ak Robat. 



