476 Revieivs — Geology of the Transvaal, South Africa. 



overlies unconformably the Malmesbury Series and the massifs of 

 granite by which it is traversed. The Malmesbury Series being 

 part of the Primary South African System, this last must be 

 Pre-Devonian, viz. either Silurian or Pre-Cambrian. 



II. Cape System. 

 The Cape System is composed of the following divisions, 

 enumerated from above downwards : — 



5. Series of the Waterberg Sandstone. 



4. Plutonic Series of the Boschveld. 



3. Pretoria Series. 



2. Series of the Dolomites. 



1. Series of the Black-reef. 



The Bokkeveld strata of Cape Colony, corresponding to the 

 Dolomites of the Transvaal, are the only deposits anterior to the 

 Karroo System in which fossils — marine organisms of the Lower 

 Devonian — have been found. 



The physical features of the deposits where the Dolomites pre- 

 dominate offer a great resemblance to the Austrian Karst. Caves are 

 frequent, many of them being ossiferous ; the organic remains have 

 not, up to the present, been studied. In many places rivulets, 

 penetrating through fissures at the surface, form subterranean 

 watercourses and lakes, and reappear again in the form of 

 numerous and voluminous watercourses, which scarcely diminish 

 during the dry season. To these remarkable constant sources of 

 supply almost all the perennial rivers of the Western Transvaal 

 owe their existence. 



III. Karroo System. 



In the Transvaal the Karroo System rests unconformably on the 

 before - mentioned older formations, and generally in a horizontal 

 position. Two primary subdivisions are to be distinguished, the 

 Lower and the Upper Karroo. 



1. Lower Karroo, 



Generally speaking, the strata of the Lower Karroo are 

 horizontal, although following more or less the undulations of the 

 ground. In the whole of South Africa geologists have adopted 

 the subdivision of the Lower Karroo into two etages, viz. the 

 LwyTca Conglomerate and the JEcca strata. 



The author adheres to the opinion of those geologists (Sutherland, 

 Griesbach, Stow, Schenk, etc.) who consider these two etages as 

 deposits of undoubtedly glacial origin, probably of the Permian 

 period. We must be prepared to find all the phenomena of a pro- 

 longed glacial action in much larger and more imposing proportions 

 than the diluvium of the Northern Hemisphere. 



The problem of the glaciation of South Africa, during the Permo- 

 Carboniferous period, presents more than a local interest. The 

 geological researches in India and Australia have shown that in 

 these countries formations exist of striking analogy. In India the 

 ■Gondwana System may be identified with the system of the Karroo. 



