Neoarchean-Paleoproterozoic tectonics of the Witwatersrand Basin revealed in the Vredefort Dome (South Africa)
Abstract
The 2985-2849 Ma Witwatersrand Basin, located in the central Kaapvaal craton and host to ~40% of all the world's gold, represents a 350x200 km structural remnant of a larger sedimentary basin preserved through the interaction of multiple, syn- to post-depositional, Neoarchean to Paleoproterozoic tectonic events and a giant impact at 2023 Ma. At its centre lies the 90 km wide Vredefort Dome, the deeply exhumed central uplift of the originally ~300 km impact crater. Whilst considerable structural information is available from the gold fields around the basin edge, relatively little is known of the detailed 3D structural architecture of the basin in the vicinity of the dome and beneath Paleozoic strata that covers its southern half. In this study we integrated high-resolution reflection seismic, surface mapping and borehole data from the vicinity of the Dome to map strato-structural features. These include: (1) a north-northeast trending syn-sedimentary normal fault in the lower West Rand Group (2985-2902 Ma); (2) an undulate, normal faulted unconformity, constrained as post-West Rand Group and pre-Central Rand Group (2909-2849 Ma); (3) local enhanced uplift leading to an angular unconformity constrained as pre- to syn-Ventersdorp Contact Facies (2729 Ma); (4) a north-northeast trending listric fault system, constrained as syn-Platberg Group (2709 Ma); (5) a regional erosional angular unconformity related to the Black Reef Formation (2642Ma); (6) folds, including a large asymmetric, gentle anticline constrained to post-Pretoria Group (2310 Ma) and pre-Vredefort impact (2023 Ma); and (7) a late to post-central uplift formation, north-northeast trending listric normal fault across the southeastern margin of the Vredefort Dome. The identification of these structural features allows Neoarchean-Paleoproterozoic tectonic reconstructions across the previously little-studied parts of the basin, notwithstanding the severe deformation accompanying the impact event.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T13E0239M
- Keywords:
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- 7205 Continental crust;
- SEISMOLOGY;
- 8103 Continental cratons;
- TECTONOPHYSICS;
- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS;
- 8159 Rheology: crust and lithosphere;
- TECTONOPHYSICS