Early tectonic extension between the Agulhas Bank and the Falkland Plateau due to the rotation of the Lafonia microplate

Along the Southeast African continental margin, a deep sedimentary basin and marginal ridge bordering the Agulhas Fracture Zone formed coevally with South American counterparts underlying the Falkland Plateau. Extension in both the Southern Outeniqua and the Falkland basin is related to large-angle ( ∼ 100°) rotation of the Lafonia (Falkland Islands) block in Middle-Late Jurassic times, during attempted propagation of the proto-Indian Ocean across the active circum-Pacific margin of Gondwanaland. In the Early Cretaceous, the Jurassic microplate boundaries were partly reactivated, and partly transected by a right-lateral shear along the ∼ 1200 km long Falkland-Agulhas transform fault. Preceded by substantial vorticity of the surrounding crustal blocks, this boundary segment separating the South American and African plates was probably generated by complex geodynamic interactions between oceanic plate subduction, continental to back-arc rift propagation, and the impingement of deep mantle plumes on the lithosphere. © 1993.