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The stratigraphy of the lower and middle Karoo Supergroup,
north of Paterson, Eastern Cape, South Africa
Dawn E. Black 1 , P.W.K. Booth 2 , M.J. de Wit 3
1. NMMU, South Africa, dblack@geoscience.org.za
2. NMMU, South Africa, peter.booth@nmmu.ac.za
3. UCT, South Africa, Maarten.DeWit@UCT.ac.za
ABSTRACT
Strata of the Karoo Supergroup (Karoo Basin) in an area north of Paterson, Eastern Cape, South Africa, are being
mapped in order to better define the litho and chrono-stratigraphy of the Ecca and Beaufort Groups. The southeast
Karoo Basin displays a thick section of Karoo Supergroup sediments that record deepening and shallowing of the
basin throughout the Permian.
Fieldwork to date has shown that mainly thinly-bedded deltaic deposits (Prince Albert, Whitehill and Collingham
Formations) are overlain by thick deltaic units of sandstone and mudrock (Ripon, Fort Brown and Waterford
Formations). Stratigraphically upwards the deltaic deposits of the Ecca Group give way to mudrock and lesser
sandstones of the Beaufort Group that represent fluvial sedimentation in an inland sea, with a provenance in the
south and east.
Once fieldwork is complete detailed lithostratigraphic columns will be constructed and geological sections drawn.
Features such as sedimentary structures, unit thicknesses and mineralogy will provide the basis for the
reconstruction of the palaeo-environment. The sections produced will form the basis for correlating Karoo strata
with the western part of the basin, albeit that such long range correlations may not be accurate.
Radiometric age dating especially of zircons in tuffaceous beds which occur throughout the Ecca and Beaufort
Groups will be determined by mass spectrometry (U/Pb isotropic method). Samples collected and analysed should
provide improved time constraints of the Permian-Triassic boundary in the south-eastern Karoo Basin, and will add
to the existing chronostratigraphic data base for the Karoo Basin. This approach should make for improved
interpretations of paleao-environments which previously relied on lithostratigraphy, but can now be modified or redefined
through the chronostratigraphy.
An additional aim of this project is to give a measure of the extent of deformation of the rocks, especially at their
southernmost outcrops, and thereby provide a better understanding of the relationship between Cape Supergroup
rocks and those of the overlying Karoo Supergroup.
KEYWORDS: Stratigraphy, Karoo Basin, ashfall tuffs.
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