Published online by Cambridge University Press: 01 May 2009
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.
page 251 note 1 Hatch, , “A Geological Survey of the Witwatersrand and other districts in the Southern Transvaal”: Quart. Journ. Geol. Soc., vol. liv, 1898, p. 73.CrossRefGoogle Scholar
page 252 note 1 The particulars of this borehole were published in my report to the Directors of the East Rand Mining Estates, Ltd., and issued in the Annual Report to the shareholders for the year ending 30th June, 1905. The particulars of the other boreholes and a general summing-up of the results are given in my paper on “The extension of the Witwatersrand Beds eastward under the Dolomite of the Southern Transvaal”: Trans, of the Geol. Soc. of S.A., vol. vii, 1904, p. 57.Google Scholar
page 253 note 1 Corrected for deflection from the vertical.
page 253 note 2 See the plan accompanying my paper on “The Extension of the Witwatersrand Beds eastward, etc.”, loc. cit.
page 255 note 1 Rogers, , “The Geology of the neighbourhood of Heidelberg”: Trans. Geol. Soc. S.A., vol. xxiv, 1921, p. 17. It is to be noted that Dr. Rogers will have none of Mr. Bleloch's correlation of the conglomerate overlying the Kimberley Slates with the Van Ryn reef. See p. 47, et seq.Google Scholar