The Geology of the Far East Rand and the Heidelberg District, Southern Transvaal.—A Retrospect

Abstract

Heidelberg, a town of insignificant proportions, lies 30 miles due south-east of Johannesburg at the foot of the Zuikerboschrand, a range of hills running south-west towards the Vaal River and made up of the volcanic beds of the Ventersdorp System and of the Elsburg series at the top of the Witwatersrand System. Travelling south-east from the Zuikerboschrand, the whole of the Witwatersrand formation is traversed in descending order. The district, which extends south-west of Heidelberg to Goedverwachting, a distance of 20 miles, and south-east to Greylingstad, another 30 miles, has a complicated geological structure, the succession being disturbed by faulting, broken by numerous igneous intrusions and obscured by frequent outliers of the Karroo formation. It is well known to the mining community on account of the fact that a gold-bearing conglomerate bed has been worked profitably at the Nigel Mine since the earliest days of the gold-fields, while numerous other reef outcrops in different parts of the district have induced much active prospecting, which has continued to the present day.