Morphological reconstruction of the Kimberley-Elsburg series, with special reference to the Kimberley group of sediments in the East Rand basin

[摘要] ENGLISH ABSTRACT: The ideal geological column of the Kimberley-Elsburg Seriesin the East Rand Basin is described, with particular reference tothe IQrnberley group of sediments.A system of nomenclature has been devised, and it is suggestedthat it could'also be used in other parts of the large structuralbasin, stretching from Johannesburg'in the north to near Theunissenin the south,. and from .Klerksdorp in the west to Greylingstad in theeast.The stratigraphy of individual areas in the East Rand Basin isdescribed in detail, and it is shown that certain stratigraphic.unitsdisplay 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, theKlerksdorp area, and into the Orange Free State goid field.In the East Rand Basin the May Reef is the principal goldcarrier, and is of economic importance in certain mines. In theOrange Free State gold field the lowermost Kimberley reef is also ofeconomic importance.Three regional unconformities have been recognised in the partof the column extending from below the Kimberley Shales to above theMay Reef. The May Reef covers the upper one', and owes its existenceto this period of erosion. The history of this reef could be tracedback to its parent rock~ in this case, stratigraphically olderauriferous gravels. The author believes that the unconformity belowthe May Reef developed as a result of sub-aqueous erosion. The. oldesterosion surface probably developed in the same way. The middle onedeveloped largely on the land, but was subsequently submerged.It is concluded that the sediments of the Kimberley-ElsburgSeries were deposited in the marine neritic environment, i.e. ina sea of substantial but not excessive depth.A few remarks have been added on the metamorphism of theSystem. An interesting feature in this connection is the occurrenceof ubiquitous authigenic rutile in the form of minute needles andknee-shaped twins. It appears that the rutile developed as a stressmineral, ilmenite having been the original detrital constituent.

[发布机构] Stellenbosch University