A NEW INTERPRETATION OF THE WAGENDRIFT SECTION NEAR ESTCOURT, KWAZULU NATAL PROVINCE, SOUTH AFRICA

The South African Karoo Basin preserves a continuous continental record across the Permian/Triassic Boundary in which both plant and vertebrate fossil assemblages co-occur. The Upper Permian Beaufort Group spans this boundary, and the Estcourt Formation in this sequence has been interpreted to represent levee infill of a bay, with sedimentation occurring as a product of overbank deposits. This interpretation implies sedimentation occurred along the margins of a large, Late Permian intracontinental lake. Recent work in a series of outcrops at Wagendrift Dam, near the town of Estcourt requires a reinterpretation of this setting.

The three outcrops in this area consist of several different facies that can be grouped genetically into lithotypes. The basalmost lithotype consists of mm scale, fining upwards sequences of siltstone to mudstone that has been interpreted as background deposition in a lake. Bedding is undisturbed and bioturbation is limited, indicating deposition within a low oxygen zone. The second consists of a rippled/ball-and-pillow coarse sediment, overlain by a finer, massive siltstone. This has been interpreted as turbidite deposition, which is further supported by the presence of large, localized slump blocks, with internal bedding planes preserved. The third lithotype consists of mm-to-cm scale fining upwards sequences of planar/(small, isolated) ripple beds of coarse (fine sand, coarse silt) sediment overlain by finer siltstone. This again represents background deposition, although under shallower conditions than found in Lithofacies 1. The last lithotype consists of thick, ripple-bedded sandstone representing a major change in depositional setting. This suite of sedimentological features is consistent with deposition in a deep, intracontinental lake regime, rather than a shallow, marginal lake setting.