THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. III. 



No. IIL— MARCH, 1906. 



oiaioii^j^Xi .a.:rtic!les. 



I. — The Geological History of South Afeica.^ 



By Dr. F. H. Hatch, F.G.S., M.I.C.E., 

 President of the Geological Society of South Africa. 



THE subject of this address is a brief account of the succession, 

 thickness, and geological history of the South African, and more 

 especially of the Transvaal, formations. The information necessary 

 for such an account is of course very incomplete, but in broad outline 

 the succession is now known, and some speculation as to the physical 

 conditions that prevailed during the building up of the region may 

 perhaps be permitted. I propose to deal with the period of the 

 geological history of this country that came to an end with the close 

 of Karroo times. The Karroo period ends with the Stormberg 

 rocks (Ehsetic), and since that time South Africa has, with the 

 exception of a small coastal area, been a land surface, and the rocks 

 have consequently been exposed uninterruptedly to the forces of 

 denudation. 



1. Order of Superposition of the Stratified Bocks. 



As is well known, no determinable remains of organisms have 

 been found in the Transvaal below the Karroo Beds, and none 

 below the Bokkeveld Beds in the Cape Colony. In the absence 

 of fossil evidence, the succession can only be established by a careful 

 observation of the order of superposition and the lithological 

 character of the strata. The succession has already to a great 

 extent been determined by various workers, and the main dividing- 

 lines placed at the great breaks or unconformities that have been 

 found to exist. Thus we have, as natural dividing-lines, five 

 great unconformities, namely, that below the Dwyka Conglomerate 

 (which for future reference we will call Unconformity No. V), that 

 below the "VVaterberg Sandstone (Unconformity No. IV), that below 



1 Presidential Address delivered by Dr. F. H. Hatch to the Geological Society of 

 South Africa, 29th January, 1906. 



DECADE V. — VOL. III. — NO. III. 7 



