Sm-Nd isotope evidence for the provenance of the Skoorsteenberg Formation, Karoo Supergroup, South Africa

The Karoo Basin is a late Palaeozoic to Mesozoic epicontinental foreland basin in South Africa. In its western part the basin fill, the Karoo Supergroup, is composed of the glacigenic Dwyka Group at the base followed by the shallow marine to lacustrine Ecca Group and the fluvial Beaufort Group. The Dwyka Group originated from the contemporaneous glaciation centre in the north. Current direction data suggest that the upper Ecca and lower Beaufort Groups are probably derived from the south and southwest. Petrographical data including heavy minerals from high grade rocks (detrital garnets, biotite and tourmaline) suggest that the likely source is a late Palaeozoic thrust belt and a magmatic arc. New Sm-Nd data on six sandstone samples from the Skoorsteenberg Formation of the Ecca Group, representing five submarine fans, yield very homogeneous epsilon(Nd)-values of around -5 at the time of deposition (270 Ma). Corresponding T-CHUR model ages of 0.73-0.81 Ga, and T-DM model ages of 1.19-1.34 Ga, are interpreted to result from a mixture of recycled Archaean and Proterozoic material with more juvenile Palaeozoic components in unknown proportions. (C) 2003 Elsevier Ltd. All rights reserved.