A reappraisal of legacy reflection seismic data from the western margin of the Kaapvaal craton, South Africa, with implications for Mesozoic-Cenozoic regional tectonics

Abstract

The 150 km long, 6 s TWT, 2D seismic profile KBF03A, which was acquired in 1994 and lies near the western edge of the Kaapvaal craton in South Africa, has been reprocessed using standard reflection seismic processing methods. The results exhibit a significant improvement in the imaging quality of the subsurface features and an evident boost in the signal-to-noise ratio. The improved seismic data, combined with application of seismic attributes, integration with surficial geological and geophysical maps, and computation of velocity tomograms, has revealed previously undetected structural features within the supracrustal sequences underlying the profile. In particular, the Phanerozoic sediments found along the profile, comprising exclusively Kalahari Group and Dwyka Group deposits, are disrupted by multiple folds of varying wavelengths (~1–10 km) and variably oriented normal and thrust faults. Additionally, the effect of the Moshaweng fault, previously characterised as a listric fault extending to depths of >10 km, on the Phanerozoic sediments has been further constrained to suggest repeated extensional reactivations and a more recent (<1 Ma) inversion. Considerations of the eastern end of the profile have suggested links between some of the observed structural features and the nearby ~146 Ma Morokweng impact structure, the lateral expanse of which is poorly constrained in the literature. The collection of these newly imaged features is interpreted as evidence for multiple Late Mesozoic to Cenozoic tectonic events, including polyphasic reactivation of basement structures, under both extensional and compressional stress regimes. By analysing these newly detected features, our study not only provides new insight into the neotectonic evolution of the Phanerozoic sediments along the western margin of the Kaapvaal craton, but also demonstrates the utility in reprocessing legacy data and reveals its untapped potential.