Geophysical study of the conjugate East African and East Antarctic margins

Abstract

New data on the conjugate African and Antarctic margins constrain the relative movements from Jurassic to Cretaceous times. Two seismic refraction profiles across the central Mozambique margin show southward thinning crust and a lower crustal high-velocity-body. New magnetic data image the continent-ocean-transition close to the coast. M41n is assumed to correspond to the oldest oceanic crust. New potential field data across the Mozambique Ridge and the Natal Valley point to mainly oceanic crust south of the Lebombo. Magnetic data give evidence for the Astrid Ridge being divided into two oceanic parts. The continent-ocean-transition in the Cosmonauts Sea is imaged in aeromagnetic data. The absence of spreading anomalies points to oceanic crust emplaced during the Cretaceous normal superchron. A resulting kinematic model postulates a tight Gondwana fit and a two-stage breakup with the Grunehogna Craton moving south to the east of the Mozambique Fracture Zone during the second stage.