A Review of the Structural Geology of the Cape Fold Belt and Challenges Towards Future Research

This review focuses on our understanding of the structural and tectonic setting of the Cape Fold Belt (CFB) based on contributions made by academics and professional geologists, mainly during the last two decades. Most of the research concentrated on the identification and mapping of thrust faults in the southern arm of the CFB, as well as seismic surveys which provided data for putting forward tectonic models to account for structural and stratigraphic features of the fold belt. Thrust stacking is a common characteristic in all three stratigraphic sequences of Palaeozoic Cape Supergroup rocks. A complex pattern of ductile and brittle deformation occurs in the Table Mountain Group whereas in the overlying Bokkeveld and Witteberg Groups there is a close association of folding with development of thrust faults. Thin-skinned characteristics are prevalent in the southern arm of the CFB, but give way to thick-skinned features in the southernmost central part of the fold belt where basement rocks have been thrusted northwards towards the foreland. A variety of tectonic models proposed for the CFB have generated some controversy among researchers. Currently popular are the Andean and the strike-slip (transpression) models. The former accounts for the northward vergence of structures in the southern arm of the fold belt, but thicknesses of crustal substrate obtained from recently carried out deep sounding seismic surveys across the fold belt do not entirely corroborate this model. Structural characteristics in cover rocks that favour the transpression model are en echelon folds and faults as well as flower structures which are commonly associated with strike-slip regimes.