Wrench-fault and half-graben tectonics in the development of the Palaeozoic Zambezi Karoo Basins in Zimbabwe — the “Lower Zambezi” and “Mid-Zambezi” basins respectively — and regional implications

Abstract

A study of the Karoo basins of Central Africa shows that they are formed as a result of rifting of continental mobile belt terranes surrounding cratonic masses. Two fundamental intersecting planes of weakness, controlling basin development, are recognized trending NE-SW and E-W. Normal faulting has occurred along the former, whereas it is proposed that dextral wrench faulting during the Palaeozoic has developed pull-apart basins along the latter. This wrench fault trend is considered to have an earlier Proterozoic sinistral history of movement. This interpretation is put forward as a result of reviewing geological and geophysical data for the Central African basins, but more particularly for the Mid-Zambezi and Lower Zambezi basins, for which we suggest half-graben and pull-apart basin models respectively to explain their evolution. Tentative evidence for a possible marine influence on the sedimentation of the Lower Zambezi basin is also suggested.