Mesoarchaean-Palaeoproterozoic crustal-scale tectonics of the central Witwatersrand basin - Interpretation from 2D seismic data and 3D geological modelling

Abstract

The Witwatersrand Basin represents one of the largest exposures of Meso-Neoarchaean rock on Earth and hosts the Vredefort Dome at its geographic centre. The southern half of the basin is covered by thin Palaeozoic to early Mesozoic marginal sequences of the Karoo Supergroup. However, visualisation and analysis of this unexposed portion of the basin can be achieved in a 3D geomodelling environment through the integration of geophysical (2D reflection seismics) and traditional geological data. In this study, the 3D structural architecture around the Vredefort Dome in the Witwatersrand Basin is evaluated to establish strato-tectonic relationships, first-order scale structures, and a new model for the architecture of basement rocks. From the geological modelling, several strato-structural features have been identified in the seismic sections, including a well-developed listric fault system in the southwest, a prominent fold system observed in the Transvaal Supergroup, and a large listric fault in the east that offsets the aforementioned fold system. Integration of these geophysical and geological data (in 3D space) has provided 3D constraints on the volumes for the Witwatersrand Supergroup, Ventersdorp Supergroup and Transvaal Supergroup to the south, southeast and east of the Vredefort Dome.