PRE-CAPE ROCKS OF THE NORTH OF THE COLONY 99 



These hills present their steepest sides to the east, 

 where their escarpment faces the Kaap Plateau. The 

 rocks have a tendency to break away in vertical kranzes 

 where deeply cut into by kloofs ; elsewhere the outlines 

 are remarkably smooth, though from the resistance of 

 the rocks to the weather the surface is always covered 

 with loose ,slabs of stone. It is only near the Orange 

 Kiver, where the gradients of the numerous stream 

 beds, dry except during heavy rain, are steeper than 

 usual that the forms assumed by the hills made of this 

 group are rugged. 



The Asbestos-Kuruman Eange is the eastern edge of 

 a group of syn dines which become narrower and are 

 formed by more steeply dipping beds towards the west 

 and south. The positions of the larger synclines are 

 marked by the outcrops of the Ongeluk beds. 



The Doornbergen are a range of hills in Prieska made 

 almost entirely of the Lower Griqua Town beds folded in 

 a rather complicated way, and in part bounded on the 

 south-west by thrust faults which in places bring the 

 Pniel lavas, and even the granite, into contact with the 

 Lower Griqua Town beds. The strike of the rocks is 

 north-west, and the Orange Eiver below Prieska cuts 

 through them along the belt of country where the strike 

 twists round from north-west to north-north-east. 



The Middle Griqua Town or Ongeluk Beds. 1 



This group consists almost entirely of volcanic rocks, 

 chiefly lavas of andesitic type, together with occasional 



1 Descriptions of these are to be found in G. C., x., 179, 90 ; xi., 44- 

 48 ; xii., 64-69 ; xiii. 



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