Abstract

The integrated results of a facies analysis and provenance study of the Late Triassic to Early Jurassic Elliot Formation (Karoo Supergroup) provide some new insights into the development of the main Karoo foreland system of South Africa. Based on changes in the fluvial style, palaeocurrent pattern, provenance, isopach trends and fossil content, a regional lithostratigraphic subdivision of the Elliot Formation is proposed. In addition, the boundary between the Lower and Upper Elliot formations appears to be a second order sequence boundary. This unconformity was probably generated by the last stage of orogenic loading of the Cape Fold Belt, which interrupted the overall, first order orogenic unloading of the system, suggesting that tectonically controlled flexural subsidence existed in the main Karoo Basin until at least the end of Triassic. The magnitude of this pre-Upper Elliot tectonic event is signified by the presence of outsized quartzite pebbles and boulders, believed to have originated in the Cape Fold Belt. A number of tectonic structures, e.g. pene-contemporaneous normal faults and large-scale convolute bedding, coupled to sandstones with basement uplift/craton interior provenance, and easterly palaeocurrent direction for the Upper Elliot Formation suggest that the first stages of inversion from a compressional to extensional tectonic regime began only in the Early Jurassic.

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