^8 ORIGIN OF RAND DANKETS. 



These conditions, applied to the Transvaal, would indicate 

 that the several groups of banket reefs are reduplications of one 

 and the same series. The Main Reef series contain nominally 

 some six separate reefs; then there are some 1.500 feet of 

 qnartzites ; then the i^ird and Livingstone groups of reefs, 400 

 feet thick; then another 1.500 feet of slates and quartzites ; then 

 the Kimberley group of reefs, containing over a hundred separate 

 reefs and often 2,000 feet in thickness; then another 1,500 feet 

 ■of quartzites, and finally the volcanic agglomerates. This is a 

 rough general review of the grouping of the bankets, but every 

 section gives a varying thickness to all the beds, both conglo- 

 anerates and quartzites. The beds of conglomerate also vary 

 in number along the strike; in fact, the conditions of the upper 

 portion of the Enon Conglomerate as it is seen along the Olifanis 

 River in ( )udtshoorn is closely paralleled. The three natural 

 grou])s of the banket reefs may be taken to represent the lines 

 of isoclinal anticlines of sandstones containing conglomerate beds 

 near their basal margin ; the lower W'itwatersrand beds may be 

 said to underlie disconformably the upper quartzites and con- 

 glomerates. The conglomerates are due to tluviatile or Huvio- 

 marine action ; the ordinary inshore sands derived from the 

 weathering of the old mountain land were periodically raised to 

 the level of the sea or above; the mountains, given a greater alti- 

 tude, were wrapped in torrents which carried down the debris 

 and spread it out as a layer of boulders over the sand ; the pro- 

 gressive sinking of the earth's crust at this ]:)articular place was 

 resumed, and the bankets w'ere covered by sand. The gold 

 weathered from the rocks of the old continent was carried do\vn 

 by the rivers and deposited in among the pebbles of the con- 

 glomerate. Only the conglomerates near the source of the supply 

 received a notable quantity of gold ; those further away received 

 •only a little; therefore the l^ankets of the first syncline only 

 would contain api)reciable quantities of gold, and are the only 

 ■ones which have l)een found worth working. The gold was 

 •originally patchy placer gold, but owing to the circulation of 

 water under great pressure, the banket became approximately 

 equally enriched in gold all throug'h. 



1 remarked at the beginning that conditions at the deposi- 

 tion of the South African beds were constantly being repeated 

 throughout the rock series ; for instance, in the banded iron- 

 stones of the Swaziland, Lower Witwatersrand, Pretoria and 

 Witteberg Beds, one and the same specimen of rock often may 

 do duty as an example from at least any of the first three sys- 

 tems. In the case of the Rand Banket we have another example. 

 The quartzites and conglomerate are repeated in a supposedly 

 younger series, the Black Reef, the lowest bed of the three-fold 

 Transvaal System. Hence Ave are justified in asking: Are not 

 the banket reefs of the Witwatersrand S}stem the same as those 

 of the lilack Reef, and are not the Witwatersrand beds as a 

 whole but the metamorphosed representatives of the Transvaal 

 •System ? 



