Morphological reconstruction of the Kimberley-Elsburg series, with special reference to the Kimberley group of sediments in the East Rand basin
Thesis (DSc.)--Stellenbosch University, 1952.
ENGLISH ABSTRACT: The ideal geological column of the Kimberley-Elsburg Series in the East Rand Basin is described, with particular reference to the IQrnberley group of sediments. A system of nomenclature has been devised, and it is suggested that it could'also be used in other parts of the large structural basin, stretching from Johannesburg'in the north to near Theunissen in the south,. and from .Klerksdorp in the west to Greylingstad in the east. The stratigraphy of individual areas in the East Rand Basin is described in detail, and it is shown that certain stratigraphic.units display a remarkable regularity, maintaining their lithologica~ characteristics bver large areas, persisting also into the Greylingstad- Balfour district, the Central Rand, the West and Far West Rand, the Klerksdorp area, and into the Orange Free State goid field. In the East Rand Basin the May Reef is the principal gold carrier, and is of economic importance in certain mines. In the Orange Free State gold field the lowermost Kimberley reef is also of economic importance. Three regional unconformities have been recognised in the part of the column extending from below the Kimberley Shales to above the May Reef. The May Reef covers the upper one', and owes its existence to this period of erosion. The history of this reef could be traced back to its parent rock~ in this case, stratigraphically older auriferous gravels. The author believes that the unconformity below the May Reef developed as a result of sub-aqueous erosion. The. oldest erosion surface probably developed in the same way. The middle one developed largely on the land, but was subsequently submerged. It is concluded that the sediments of the Kimberley-Elsburg Series were deposited in the marine neritic environment, i.e. in a sea of substantial but not excessive depth. A few remarks have been added on the metamorphism of the System. An interesting feature in this connection is the occurrence of ubiquitous authigenic rutile in the form of minute needles and knee-shaped twins. It appears that the rutile developed as a stress mineral, ilmenite having been the original detrital constituent.
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