Abstract

A flat-plate subduction model is proposed for southwestern Gondwanaland for late Paleozoic and Triassic time, in an attempt to explain some of the anomalous features of the Cape Fold Belt of South Africa and its continuations in South America and Antarctica. This fold belt is located at distances of as much as 1,000 km from the continental margin of the time, and it is suggested that the descending slab of oceanic lithosphere being subducted along the Andean margin of the continent became coupled with part of the overriding continental crust of Gondwanaland. Thus, some of the plate convergence at the boundary may have been taken up by deformational shortening within the Gondwana plate rather than by normal subduction at its edge. The deformation was partly concentrated along the intraplate Cape Fold Belt, which may have been situated over the zone where the subducted oceanic plate finally separated from the base of the continental lithosphere. Geological and geophysical data support the hypothesis, which should be tested further.

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