VREDENBURG: SKETCH OF BALUCHISTAN DESERT. 



io. All these rocks are profusely injected with basaltic dykes and 



sills, it being often difficult to decide whether the latter are intrusive 



or truly interbedded,. and to what period they belong. Quite close 



to the Afghan boundary, to the N, W. of Amir- 

 Sam K6h. D " 



Ch£h, the low flat-topped hill called Sam K6h 



also consists of black tuffs, here quite horizontal. 1 



Tozgi and neighbourhood of Tozgi. 

 At Tozgi, south-west of Amir-Ch^h, the orientation of the 

 structural features has again changed. The dip is 25 to 30 W. of 

 N. at angles varying from 25 to 30 . The strata form a succession of 

 monoclinal ranges, consisting principally of bedded tuffs and breccias 

 together with intrusive sills (lig. 1). The breccias contain large 

 boulders of hippuritic limestone. In a south-west direction, the 

 ranges sink rapidly beneath recent deposits ; the last hillocks visible 

 at the edge of the alluvial plain dip in quite a different direction, 40 

 W. of S. They probably belong already to the region of regular 

 foldb further south, for their strike is the same. 



At Tozgi the strata are particularly free from any violent disturb- 

 ance ; not only is there no cleavage, but the rocks are remarkably 

 free from jointing, which permits the collecting of exceptionally 

 fine specimens. At the same time they exhibit an instance of the 

 difficulty experienced in interpreting the relative ages of some of 

 the igneous rocks. In the field all the rocks have at first sight the 

 appearance of a conformable series of strata; but while on the one 

 hand c is an andesitic lava, and g a quartz-trachytic breccia, 

 on the other hand the rock a appears under the microscope as a 

 finely crystalline porphyritic eurite, d is a granophyric diorite- 

 porphyry or dolerite, and h an augite-diorite-porphyry. The latter 

 rock exhibits a basaltiform jointing ; trie field evidence as to its 

 intrusive nature is not quite conclusive : it does seem that it is not 

 quite parallel to the stratification, but as the strata are slightly affected 



1 Judging from photographs taken by Mr. Tate, the historical K6h-i-Khwaja in Seistan 

 has a very similar appearance. It is also flat-topped, and consists no doubt of horizontal 

 strata. Like the Sam K6h, it illustrates the absence of folding which has been mentioned 

 above (page 7) as characteristic of the low-lying areas. 



( 72 ) 



