Abstract
The East African margin between the Somali Basin in the north and the Natal Basin in the south formed as a result of the Jurassic/Cretaceous dispersal of Gondwana. While the initial movements between East and West Gondwana left (oblique) rifted margins behind, the subsequent southward drift of East Gondwana from 157 Ma onwards created a major shear zone, the Davie Fracture Zone (DFZ), along East Africa. To document the structural variability of the DFZ, several deep seismic lines were acquired off northern Mozambique. The profiles clearly indicate the structural changes along the shear zone from an elevated continental block in the south (14°–20°S) to non-elevated basement covered by up to 6-km-thick sediments in the north (9°–13°S). Here, we compile the geological/geophysical knowledge of five profiles along East Africa and interpret them in the context of one of the latest kinematic reconstructions. A pre-rift position of the detached continental sliver of the Davie Ridge between Tanzania/Kenya and southeastern Madagascar fits to this kinematic reconstruction without general changes of the rotation poles.
Highlights
The breakup of Gondwana commenced around 182 Ma ago with massive emplacement of flood basalts and subsequent rifting in the Mozambique Basin (Müller and Jokat 2019)
In the absence of such knowledge, questions remain: Did Madagascar’s drift away from Africa follow a path close to the present-day African coast, or even inland of it? Does the topographic expression of the Davie Fracture Zone (DFZ) reliably indicate its crustal affinity and, if yes, how? Can continental crust be confirmed by seismic refraction data under the Davie Ridge (DR)? If so, where was the DR continental sliver situated before Gondwana breakup? How does the crustal fabric change in comparison with that of the rifted margin of central Mozambique?
During this oblique phase of East Africa, we propose with the refined model that continental stretching and accretion of oceanic crust mainly took place between Africa and the DR, and only minor stretching between DR and Madagascar as part of East Gondwana (Fig. 3; 163 Ma, 157 Ma)
Summary
The breakup of Gondwana commenced around 182 Ma ago with massive emplacement of flood basalts and subsequent rifting in the Mozambique Basin (Müller and Jokat 2019).
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