STRUCTURE AND TECTONICS OF THE AGULHAS-FALKLAND FRACTURE-ZONE

The similar to 1200-km-long Agulhas-Falkland Transform developed durin g the Early Cretaceous break-up of West Gondwanaland. On the African P late, the continent bordering the Agulhas Fracture Zone extends betwee n the Agulhas Bank and the South Tugela reentrant. It is divided into four distinct parts: Mallory Trough segment (I), Diaz Ridge segment (I I), East London segment (III) and Durban segment (IV), from southwest to northeast. Each segment differs from the others in its physiography and in the nature of the continent-ocean crustal boundary. In segment I, a wedge-like, eastward-narrowing deep-water basin separates the st eep continental slope from a marginal fracture ridge of probable volca nic origin along the transform fault trace. Along segment II the South African continental slope is deeply embayed and a great thickness of sedimentary strata has been ponded behind a buried ridge along the nor thern side of the fracture-zone trace, above a probable fragment of oc eanic crust representing a northerly extension of the Jurassic Falklan d Plateau Basin. In segment III, the continental margin is steep, espe cially along the middle slope; it Lies directly along the transform tr ace, but conspicuously rugged along the continental slope, due to the effects of submarine canyoning and sediment slumping. In segment IV, t he continent-ocean boundary also lies directly along the transform fau lt trace, and the margin shows evidence of seaward tilting above landw ard-dipping faults along the middle or lower slope. The segmentation i s inherited from Jurassic structural fabrics formed prior to Early Cre taceous transform motion, when tectonic rotation of microplates caused rifting and partial oceanization along the future Agulhas-Falkland me gafault trajectory.