The geological structure of the Muizenberg Block, Cape Peninsula, South Africa

Abstract

The Muizenberg Block, is an outlier of the Table Mountain Group (Cape Supergroup) and lies to the west of the main occurrence of the Cape Fold Belt. Structural mapping of this outlier has identified a spaced cleavage in Peninsula Formation quartz arenites, and an exposure of dolerite that have not been previously documented. Monoclinal folding, an unrelated spaced cleavage, low-angle faults, and steeply dipping faults, that strike east-northeast – west-southwest, are similar to structures found in the syntaxis domain of the Cape Fold Belt and are therefore thought to have formed during the Late Permian – Early Triassic Cape Orogeny. However, as the Muizenberg Block lies outside the presently accepted boundaries of the syntaxis domain, those boundaries may deserve re-examination. Sub-vertical dilational quartz veining, jointing, cataclastic faulting and the intrusion of a sub-parallel dolerite dyke, that all strike northwest – southeast, are thought to represent a younger tectonic event. They are provisionally attributed to the Upper Jurassic to Cretaceous taphrogenesis that preceded the drifting apart of South America and Africa.