Abstract

In this study of Cape Supergroup rocks at Port Alfred, the strata are classified as Witteberg Group rather than the Bokkeveld Group because their lithological characteristics and position in the stratigraphic sequence are similar to Witteberg Group rocks elsewhere in the Cape Fold Belt. Palaeozoic Cape Supergroup strata are unconformably overlain by Tertiary and Quaternary sediments of the Algoa Group. Rocks of the Witteberg Group were folded into asymmetric folds and thrust faulted during the late Palaeozoic. Bedding-parallel thrusting, duplexing, and piggy-back thrusting have disrupted strata, giving rise to variable bed thicknesses and stacking of beds one upon the other. Northwest-striking normal faults are commonly developed in the proximity of the Kowie River, forming horst and graben structures. Strike-slip faults occur approximately parallel to the strike of normal faults. Thrust faulting is interpreted to have taken place during the late Palaeozoic, whereas normal and strike-slip faults are products of Gondwana break-up during the Mesozoic. This study stresses (i) the significance of faulting, in particular thrust faulting, and its effect on rocks of the Witteberg Group at Port Alfred, and (ii) the importance of carrying out structural and stratigraphic studies in concert in the Cape Fold Belt.

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