64 THE WILGENHOUT DRIFT SERIES 



where they are separated by faults from the Kaaien beds 

 to the east and from the Koras beds on the west. And 

 intrusions of a glassy doleritic rock have risen along the 

 faults ; on the north-east they are apparently overlain 

 unconformably by beds which have been assigned to the 

 Matsap series. 



The sheared diabase lavas are often amygdaloidal, 

 but with them are some sheared intrusions of diabase 

 which also penetrate slates of sedimentary origin, and 

 it is difficult to separate the lavas from the intrusive 

 rocks. The quartzites are dark-coloured reddish rocks. 

 In the north-eastern part of Upington Commonage there 

 is an isolated patch of dark red quartzite with diabase 

 below it resting unconformably upon the Kaaien beds ; 

 so if these beds belong to the Wilgenhout Drift series 

 the latter must be younger than the Kaaien beds'. 



[Kecent work along the south bank of the river shows 

 that these beds overlie and partake in the folding of the 

 Kaaien quartzites. They are cut by granite veins, and 

 may ultimately prove to be the uppermost portion of 

 the Kheis series.] 



The Wilgenhout Drift series must be over 3,000 feet 



thick. 



4. THE GKANITE AND GNEISS. 



In Bechuanaland granite occupies an area of several 

 thousand square miles, though over wide stretches the 

 rock is only seen in wells ; now and again the granite 

 forms. low ridges, as at Kraaipan, but usually it only 

 crops out occasionally along the river beds and in pans. 

 The granite of this district is usually a pinkish or grey 

 medium grained rock containing microcline and mus- 

 covite or biotite ; hornblende and augite are seldom 



