Il8 MIDDLEMISS: GEOLOGY OF HAZARA AND BLACK MOUNTAIN. 



separating the slates to the north from the younger historical rocks 

 of Sirban. Owing to the recent gravels which occupy the valleys to 

 the north of Sirban this fault cannot be actually seen, nor can it be 

 represented on the map, because its actual position cannot be fixed. 

 The evidence for the important nature of the fault is of course fur- 

 nished by the steady dip down of the Infra-Trias in the direction of 

 the slates as if it would pass under them, a condition which would be 

 unintelligible without a fault of no small dimensions coming between 

 them. An accurate estimate of its throw is impossible, but 4,000 feet 

 would probably be under the mark, provided, as seems likely, that the 

 fracture was complete and had entirely replaced the middle limb of 

 the generating sigmaflexure. 



The second fold-fault has been already referred to as the north 

 Sirban fault. It marks a second line of intense folding or tearing 

 and faulting of the rocks. Its throw varies at different points, 

 but must reach 2,000 feet near the centre of the mountain- 

 mass. 



The third important fold-fault cutting through the hill east of 

 Tanakki, and the two or three subsidiary faults in the neighbourhood, 

 are all of the same nature, and in many places furnish clear proof of 

 their origin in a sigmaflexure, by remnants of the middle limb of the 

 latter being still left in full view on the steep side of the Bazdar glen 

 (see Horizontal Section No. I). 



From the evidence before us, therefore, laid bare in the slopes and 

 precipices of Sirban by the chisel of time, it becomes very clear that 

 this part of the Slate zone has been the seat of immense disturbance 

 of the strata since the latter were deposited horizontally on their 

 varied sea-bottoms. The three unconformities indicated, one at 

 the base of the Infra-Trias, one at the base of the Trias, and the 

 third at the base of the Spiti shales, also inform us that the dis- 

 turbance of the area has gone on from primitive geological times ; 

 and that though the present folds and lines which dominate the 

 earth's crust at this point must date from post-Nummulitic times, 

 they are perhaps only the last phase of a continuing upheaval (with 



( us ) 



