334 THE GEOLOGICAL FORMATION OF GERMAN S.W. AFRICA. 



At intervals there are also intrusions of Dolerite, which often 

 stand out above the surface of the Granite and Gneiss. 



A very large number of Quartz reefs are met with in the Granite, 

 particularly just North of the Orange River, in the neighbourhood 

 of Warmbad, near Dreihoek and further North, All round 

 VVarmbad are a large number of reefs of compact white Quartz. 

 Some are of enormous size and form large white hills running for 

 considerable distances. The apex of these hills is seen to consist 

 of the Quartz reef in place, while the sides are composed of frag- 

 ments of Quartz (including great blocks) that have been broken 

 down from the reef. These reefs are particularly tree from metal- 

 lic contents, though a number of smaller ones near Warmbad and 

 elsewhere contain a little copper in the form of Copper Pyrites, 

 which is mixed with a considerable proportion of Iron Pyrites. A 

 little Galena is also noticed. Traces of Zinc were found near 

 Velloor. 



Just South of Dreihoek the first occurrences of younger sedi- 

 mentary rocks are met witli, namely a few small outliers of Dwyka 

 Conglomerate resting directly on the Granite. As far South as 

 Warmbad some Sandstone debris is observed — apparently the 

 remains of Table Mountain Sandstone that has been denuded. At 

 Dreihoek a considerable bed of Dwyka Conglomerate occurs, rest- 

 ing at its southern end on granite, and at the northern end on 

 Table Mountain Sandstone. This Conglomerate is well exposed, 

 forming the cliffs on a river bank. It exhibits spheroidal weather- 

 ing, and in places where the fine material preponderates, decided 

 cleavage planes have been developed. 



From here northward are a number of outliers of Table Moun- 

 tain Sandstone and about twenty miles north of Dreihoek more 

 Dwyka Conglomerate is found resting partly on Granite 

 and partly on the Sandstone. From this point to Kanghus similar 

 outliers of the Sandstone are seen at frequent interv^als. 



It is evident from the extensive distrfBution of the remnants of 

 Archaean rocks and the enormous extent of country over which 

 Table Mountain Sandstone is scattered in disconnected patches, 

 that a great amount of denudation has taken place previous to the 

 deposition of the Dwyka Conglomerate, and it is probable that the 

 other members of the Cape Series, namely the Bokkeveld Beds 

 and Witteberg Quartzites, may at one time have been extensively 

 represented. I have, however, no evidence of their existence. 



At Kanghus a considerable amount of Archaean Clayslate has 

 been preserved, being overlaid by Table Mountain Sandstone, 

 which in turn has a considerable amount of Dwyka Conglomerate 

 resting on it. Further north the Dwyka appears to be wanting 

 for a considerable distance, and right up to theTKaras Mountains I 

 have observed only numerous outliers of the same Sandstone rest- 

 ing on Granite. 



At the Gi'eat Karas Mountains the formation becomes more in- 

 teresting. The Southern hills are cappings of sandstone on great 

 upheavals of Granite, while the Northern hills consist of enormous 

 masses of typical Mica Schists, Quartzites, Clayslates and Lime- 

 stones that have been upheaved by the Granite into a nearly 



