part I | A. BIFT-YALLEl IN WESTERS PERSIA. 217 



figures being minimum estimates of the maximum downthrow in 

 each ease. The measurements were made by aneroid: — 



Feet. 



No. 1 fault (at the mouth of the canon) 500 



No.3foult 200 



No. 4 fault >150 



No. 5 fault >150 



Cross-fault >100 



In addition to these faults of large displacement, many minor 

 faults of small or insignificant displaeement exist in the limestone 

 north of the great escarpment. Some of them can he seen in the 

 walls of the canon presently to be mentioned, in the development 

 of which they may have played a part. 



The photograph (PL XII) was taken from a point x on the 

 south-western wall (see map, p. 240), looking northwards across the 

 valley. It shows the escarpments of Xo. I fault (the northern 

 boundary-fault, forming the cliff in the background), No. 3 fault, 

 and Xo. 4 fault. On the limestone-terrace between the two last- 

 mentioned escarpments there are rounded hillocks of gypsum, and 

 the trough between Xo. 4 fault and the observer (himself stand- 

 ing on the escarpment of the southern boundary-fault i is entirely 

 tilled by the gypsum series. 



Although a great deal of the gypsum has been removed in 

 solution, the eastern end of the valley still retains much of its 

 gypsum-filling, which rises in one place nearly to the top of the 

 bounding wall. PI. XIII shows the gypsum-beds in contact with 

 the limestone-wall, the trace of the fault being clearly discernible. 

 It has already been said that the fault-scarps preserve in their 

 lower portions the smoothed and fluted surfaces produced by the 

 friction of the sliding rocks. This is best shown by the northern 

 boundary-fault at the mouth of the canon, and is reproduced in 

 PI. XIV, the man who is seen standing against the clifE-face 

 serving to give the scale. 



The drainage of the faulted region is curious in several respects. 

 The only perennial stream that traverses the valley cuts sheer across 

 it from side to side. Kising in the gypsum-beds on the north- 

 eastern Hank of the anticline, the stream turns south-westwards 

 and cuts right through the limestone in a deep canon; the Latter 

 breaches the northern fault-scarp where the downthrow is greatest, 

 and from here the bed of the stream lies in the gypsum of the 

 valley-bottom, except for a short stretch between No. 3 and Xo. -I 

 faults, where the limestone-floor is again exposed to view. The 

 stream finally breaks through the southern limestone-wall, and so 

 makes its escape from the valley. 



In order to understand this curious behaviour, it is necessary to 

 consider the conditions that prevailed before the vallev was scooped 

 out. There was then a gypsum cover over the whole area, and the 

 stream in question assumed approximately its present direction 

 at that period. Cutting down through the gypsum cover, it 



r L' 



