PRE-CAPE ROCKS OF THE NORTH OF THE COLONY 85 



Near Vryburg the limestone near the base of the 

 series contains fragments of lava like many of the Pniel 

 lavas and those in the Black Beef series. 



In a paper already referred to in a footnote, Prof. R. 

 B. Young shows that the dolomitic limestones may be 

 changed into rocks which have the appearance and com- 

 position of quartzites, but in addition to quartzites which 

 have such an origin there are others which are certainly 

 sandstones converted into quartzites by the usual process 

 of the deposition of quartz in the interstices. These 

 rocks, however, are not abundant in the Campbell Band 

 series. 



Some of the chert interbedded with the limestone was 

 probably formed during the deposition of the beds- on 

 the sea- floor, for it lies in thin bands parallel to the 

 bedding of the rock ; but a much larger part of the 

 chert has been formed subsequently, as shown by its 

 irregular distribution through the limestone beds and its 

 filling joints. Thin sections through the bedded cherts 

 have not revealed traces of radiolaria or other organisms. 

 Such grey or black cherts are always abundant and well 

 developed in the upper half of the series ; this feature is 

 characteristic of the formation not only in the Colony 

 but in the Transvaal as well. 



Towards the upper limit of the limestones of this 

 group layers of ferruginous chert or jasper occur, similar 

 in all respects to those which form the balk of the suc- 

 ceeding Lower Griqua Town beds. 



The chief area formed by the Campbell Band series 

 is called the Kaap Plateau and it lies between the 

 Asbestos Mountains and the Harts- Vaal Bivers. It is 



