The Western Bredasdorp Basin is part of the southern South African continental margin that has undergone a combination of rifting and transform processes in Jurassic-Early Cretaceous times related to plate movements along the Agulhas-Falkland Fracture Zone. By integrating seismic reflection profiles, well-logs and cores, we develop a consistent 3D structural model of the Upper Jurassic-Cenozoic sedimentary basin fill comprising three syn-rift and three post-rift stratigraphic units. Combined isostatic and 3D gravity modelling provides information about the density structure of the entire crust, in particular about the distribution of a pre-rift meta-sedimentary unit.

The present-day thickness distributions of the sedimentary sequences, associated fault geometries, and the deep crustal thinning trend reflect the changing kinematic systems through syn-rift and post-rift times. A model explaining the present-day configuration of the basin involves (i) the syn-rift development of a mantle involved deep-seated flower structure and of (ii) post-rift thermal subsidence being strongest above the Moho high and the potential ancient thermal anomaly. Derived syn-rift sedimentation rates exceeding post-rift sedimentation rates are another indicator for a typical sheared margin setting. Subsidence analysis involving backstripping techniques will help further constraining basin history (including paleo-water depths) and causative mechanisms.

Based on the structural configuration of the main geological units and their lithology- and depth-dependent physical properties, we calculate the steady-state 3D conductive thermal field of the basin. The modelled present-day temperature and heat flow distribution which is consistent with locally available temperature measurements provides ideal basin-wide boundary conditions for subsequent petroleum systems modelling. In this way, we intend to assess the basin’s hydrocarbon potential in a more holistic way in terms of source rock maturity and hydrocarbon generation, migration, and accumulation.

Poster

Depositional Margin Evolution of Western Bredasdorp Basin (Southern Offshore of South Africa): Insights from a 3D Basin Model

Project Supervisors

Dr. Daniel Mikeš (Department of Earth Sciences, Stellenbosch University South Africa)

Dr. Magdalena Scheck-Wenderoth (Section 4.4 Basin Analysis, GFZ Potsdam Germany)

Prof. Dr. Rolando di Primio (Section 4.3 Organic Geochemistry, GFZ Potsdam Germany)

Prof. Ron Steel (School of Geological Sciences, University of Texas at Austin, USA)

Partners

Nelson Mandela University , South Africa

Funding

Inkaba ye'Africa (LINK! a German-South African Earth System Research Initiative) in collaboration with the Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences