BO 



HAYDEN : GEOLOGY OF NORTHERN AFGHANISTAN. 



rapidly thinning out westwards and southwards and dying out altogether 



in Khargin dara at about two miles above the junction of this valley 



with Begal (Plate 12). Figure 8 shows the conditions prevailing at 



different points in that valley. It will be seen that the Doab series, 



like the Saighan series, also thins out, and is completely overlapped by 



the Cretaceous limestone. 



In the Begal valley, at about a mile above the mouth of Khargin 



dara, a conglomerate occurs some little way up in 

 Begal and Kbargin. . 



the Doab series and extends into Khargin dara ; 



its thickness is very variable, sometimes dwindling from fifteen or 

 twenty feet to a few inches. Possibly it is an old river conglo- 

 merate. In Khargin dara it overlaps the lower beds of the Doab series 

 and lies on a massive grey saccharoid limestone occurring in thick beds 

 and resembling the limestone associated with the slate and graphitic 

 schist series in the hills between Saighan and Bamian j both are like 

 the limestones of Ak Robat and Ghorband, with which I have classed 

 them. A little way up Khargin dara, the conglomerate is composed 

 of rounded and angular blocks of all sizes from small pebbles up to 

 masses, two feet long, of the underlying limestone. Except where the 

 conglomerate lies immediately on the limestone, the latter rock has not 

 been observed among the pebbles, which consist chiefly of quartz and 

 various siliceous rocks, and are usually about the size of a hen's egg. 



In Khargin dara and Begal, there are thus two distinct overlaps, 

 one by the conglomerate of the Doab series and the other by the Upper 

 Cretaceous limestone (Plate 13). Each of these oversteps all older beds 

 down to the grey limestone. On the other hand, there is no trace 

 here of the unconformity noticed in lower Saighan between the Saighan 

 beds and the Doab series, the passage from the dark shaly beds of the 

 latter into the white sandstone and shale at the base of the former being 

 seemingly perfectly normal. This section certainly suggests the asso- 

 ciation in time of the Doab series with the Saighan series rather than with 

 the Fusulina limestone and therefore offers important evidence against 

 the correlation of the volcanics of Saighan with those of Darwaz. 



