*86 VREDENBURG: SKETCH OF BALOCHISTAN DESERT. 



the M scaly s-tructure n which has been often described in the case of 

 the Alps and Himalayas, and there are numerous examples of thrust- 

 planes and overfolds, the thrust being always towards the low-lying 

 area, whether that be north or south of the mountains. 



The contrast which exists between the structure of the parallel 

 ranges and that of the low-lying districts finds 



Rocks occurring in . 



either type of region are no correspondence in any difference of the 



not different. ... T 



rocks constituting them. In either type of 

 country, exactly the same strata were observed : they are shales, 

 sandstones, and limestones, often containing an enormous proportion 

 of volcanic material, and ranging in age from upper cretaceous to 

 upper eocene. In a great many instances the rocks are nearly or 

 quite unfossiliferous, but where fossils can be identified the above 

 are respectively the oldest and newest horizons. 



In most cases the volcanic strata appear to be especially abun- 

 dant amongst the upper cretaceous and earliest tertiary beds, but ash- 

 beds still occur amongst strata which their fauna shows to be of the age 

 of the "Ranikot" of Sind, and in one instance, at Saindak, strata 

 containing a typical " Khirthar " fauna rest, apparently with perfect 

 conformity upon a thick bed of volcanic conglomerate. 



In addition to these stratified rocks, both volcanic and sedimentary, 

 there are great igneous intrusions which are of eocene age at the 

 oldest, as they are found to cut through all the marine strata above 

 mentioned. They consist of granites, syenites, and diorites, with 

 some more basic dykes. 



Apart from the recent and sub-recent gravels, which naturally 

 s ... occur only in the valleys and plains, the only 



rocks that are restricted to particular regions 

 are the Siwaliks: these occur along the margin of the desert plains in 

 the neighbourhood of the tall ranges of older rocks, As in the case of 

 the Himalayas, they usually dip towards the range which they fringe, 

 the dip being, therefore, southerly, where they occur along the south- 

 ern edge of a plain ; it is not always northerly as in the case of the 

 Himalayas. 



( s ) 



