Continental sediments in South Africa

Abstract

In the central part of the Karoo Basin, South Africa, the Triassic fluviatile Molteno Formation forms a northerly thinning braided clastic wedge. In the eastern Karoo Basin it forms part of a thick sequence of upper Karoo sediments (Triassic-Jurassic) assigned to a meanderbelt facies, a fluvio-lacustrine facies and an aeolian facies. Two braided classic wedges occur within the succession, one in the meanderbelt facies, and the other (the Molteno) between the meanderbelt and fluvio-lacustrine facies. An upward-fining sequence of uranium-bearing Permian sandstones and mudstones in the southwesternn Karoo Basin has been dividedt into three facies associations, representing deposition in the parximal, intermidiate and distal parts of an extensive alluvial plain.Coal-bearing Permian Karoo sediments in the Nongoma graben, north of the main Karoo Basin comprise low and high sinuosity channel deposits, with the latter containing the best coals. The early Palaeozoic Cape Peninsula Basin contains a prograding sequence of arenites with subordinate interbedded shales and siltstones deposited on the proximal and distal parts of a marine influenced braidplain. Younger (Triassic-Jurassic) upper Karoo sediments in northeast Swaziland contain diamonds near the base of a fluvio-lacustrine ‘red bed’ sequence, overlain by aeolian deposite similar to those in the main Karoo Basin.