PRE-CAPE ROCKS OF THE NORTH OF THE COLONY 83 



and then south-west from Vryburg along the right flank 

 of the Harts-Vaal Valley. 



The Campbell Kand series consists mainly of blue 

 dolomitic limestones. With the limestone there is 

 frequently found grey or black chert in irregular layers 

 parallel to the bedding of the limestone or in veins 

 and along joint-like surfaces lying in various positions. 

 There are also occasional quartzites, and frequently beds 

 of shale, the latter being well represented near Schmidt's 

 Drift. The limestones are the characteristic rocks of 

 the group; they weather with a peculiarly channelled 

 surface, which is also found on limestones of the Malmes- 

 bury and Cango beds of the south, and of the Dwyka 

 series and many older rocks l in the north of the Colony. 

 The weathered crust varies in co'our according to the 

 amount of iron and manganese in the rock ; where the 

 iron or manganese is abundant, the surface has a deep 

 reddish- or blackish-brown colour, otherwise the colour 

 is greyish brown or grey. The country occupied by 

 these limestones is often very rough, though it is at the 

 same time very flat as a whole. The limestone is often 

 dissolved away along joints, which are then represented 

 by sharply denned depressions a few inches or a foot 

 wide and several inches deep. The chert, also, adds to 

 the roughness of the ground, for irregularly shaped 

 masses of it project from the surface after the more 

 soluble limestone has been removed. 



lu places the limestone is made up largely of oolitic 



1 The limestones of the Griqua Town, Black Reef, Wilgenhout Drift, 

 Kraaipan and Kheis series are indistinguishable in hand specimens from 

 those of the Campbell Rand group. 



6* 



