THE ORIGIN OF THE RAND BANKETS. 



I'.v Professor Ernest H. L. Schwarz, A.R.C.S.. F.G.S. 



The origin of the gold-bearing conglomerates of the Wit- 

 watersrand is still a matter of controversy. The question is 

 being attacked from the petrographical side and from the strati- 

 graphical side, but so far no attempt has been made to read 

 the riddle from a comparison with occurrences similar in nature 

 in other parts of South Africa. It is one of the most marked 

 features in South African geology that, throughout the period 

 covered by the sedimentary beds, conditions of deposition have 

 recurred several times, producing similar deposits ; and as the 

 story of the younger formations is tolerably plain and that of 

 the older obscured 'by metamorphism and from other causes, 

 such as the formations being only partially exposed by denuda- 

 tion, it may be of use to see whether we cannot apply what we 

 know about the conditions which produced the younger beds to 

 account for the older, and whether observations confirm the 

 analogy or otherwise. 



There are three groups of facts connected with the Neo- 

 Afric beds in Cape Colony which I think have a distinct 'bearing 

 on the question of the Pal-Afric ibeds of the Transvaal, especi- 

 ally the Rand Banket. It is the purpose of this paper to des- 

 cribe them in detail and then to apply the principles to the 

 conditions which led to the laying down of the beds now existing 

 as the quartzites and conglomerates on the Rand. The three 

 groups of facts are : — 



The three-fold Cape System, consisting of two shore de- 

 posits (sandstones) with an intervening deep water deposit. 



The Uitenhage System, consisting of a great gravel series 

 at the base ; then a fresh-water and sub-aerial series, consisting 

 of marls and blown sands ; and a marine deposit on top. 



The System of Folds on the south coast, which has caused 

 the Table ^Mountain sandstone to be folded on itself several 

 times. 



The Cape System. 



The Cape System is made up of the three conformable 

 series: Table Mountain sandstone at base, non-fossiliferous ; the 

 Bokkeveld Series above, consisting of shale and a few sand- 

 stone bands, and containing lower Devonian fossils ; and the 

 Witteberg Series on top, consisting of fine-grained ferruginous 

 quartzites with subordinate shale bands, containing Lepido- 

 dendra, referred to the lower Carboniferous. As far as we can 

 make out. the land-surface which provided the sediments of the 

 Table Mountain sandstone lay to the north. There are con- 

 glomerates at Pakhuis Pass and on the w-est coast, but other- 

 wise the rock consists of coarse-grained sands markedly false- 



