Simultaneous folding in the western and southern branches of the Cape fold belt

Abstract

Historically, the Western and Southern Branches have always been considered different entities of the Cape Fold Belt with regard to both their origin and mechanism of formation. Deformation in the Western Branch was generally considered to be the older of the two. A review of the sparse evidence that led earlier authors to the above conclusions has indicated many shortcomings : the Witteberg-Dwyka unconformity in the western Karoo does not imply an early phase of folding in the west ; and evidence of pre-Dwyka folds is clearly lacking. The monoclinal folding in the Western Branch obviously originated from horizontal compression. This, together with indications that the NW-trending folds do not die out westwards, eliminates the need for a vertical tectonics model for the Western Branch. Soft sediment tectonic structures in outcrops of the Witteberg Group in both branches indicate similar states of diagenesis during the main fold phases