Crustal-scale structures and tectonic domains of the Kheis Tectonic Province in South Africa from multimethod seismic analysis

Abstract

The Kheis Tectonic Province of southern Africa represents a key, yet under-constrained, component in the tectonic history of the Kaapvaal Craton and its surrounding terranes. The complex geological framework is masked by extensive sedimentary cover and limited outcrop, making geophysical investigations essential. In this study, we present an integrated seismic analysis using the combination of a legacy deep reflection data (GS-02), a shallower reflection profile (KBF-01), teleseismic receiver functions, and refraction tomography to refine the crustal architecture and major tectonic boundaries across the region. Prestack time migration of the GS-02 profile reveals significant improvement in reflector clarity, enabling the identification of thrust faults, fold structures, and previously unresolved reflective packages. Refraction tomography constrains the thickness of the Kalahari Group cover, averaging ∼ 250 m, while receiver function analysis at three broadband seismic stations yields new Moho depth estimates ranging from 32 to 46 km and delineates crustal stratification. Our interpretation supports a model in which the Kaapvaal Craton is underthrusting westward beneath the Kheis Province, with partial crustal imbrication. We find no strong seismic evidence for the Dabep Thrust as a major tectonic boundary, aligning with recent challenges to its significance. In contrast, the Blackridge Thrust and the Kalahari Line show coherent seismic and geophysical expression, supporting their role as first-order structures. Additionally, we image a deeply buried, high-reflectivity zone in the west, suggestive of a possible plutonic body or relict basin structure. This multi-method seismic investigation advances the understanding of the crustal-scale structure and tectonic evolution of the Kheis Province, providing new constraints for regional tectonic models and highlighting the value of reinterpreting legacy seismic data with modern techniques.