Crustal structures and geodynamic processes along the southern margin of Africa

The southern continental margin of Africa is a sheared margin in its post-shear stage and represents an excellent example for studying tectonic processes and resulting structures along sheared margins. It developed during the early Cretaceous break-up of Gondwana when the African and South American plates separated from each other during a shear motion along the right-lateral Agulhas-Falkland transform. We collected seismic refraction and reflection data along two profiles across the South African continental margin from the Agulhas Bank to the Agulhas Passage and Agulhas Plateau. These profiles are part of the Agulhas-Karoo-Geoscience Transect a component of the Inkaba ye Africa project. Our velocity-depth models image the structure of the continent-ocean transition zone at the AFFZ. We find evidence for a sub-vertical reactivation of the AFFZ and discuss uplift due to a buoyant structure in the mid-lower mantle. Analysis of the velocity-depth structure beneath the Southern Outeniqua Basin and the Diaz Marginal Ridge (DMR) reveals a structure which is interpreted as a metasedimentary basin and termed Pre-Outheniqua Basin. Compressive phases during the continent-ocean shear stage of the continental margin may have pushed material from this basin upwards forming the DMR