The crustal structure of the Kerimbas Basin across the offshore branch of the East African Rift System

SUMMARY The Davie Fracture Zone (DFZ) evolved during the Jurassic and Cretaceous breakup subsequent drift of Gondwana off East Africa. This old weak zone has been reactivated evolution African Rift System. Recent faulting Cenozoic sediments in Kerimbas Basin northern Mozambique shows that they are affected by neotectonics. question is if how crustal fabric our research area modified rifting process. We present two seismic refraction profiles acquired offshore to investigate its regional structure tectonic history. show a continent–ocean transition widens from around 40 km at 13°S more than 100 11°S. In west transitional crust up 12 thick. To east, 150 coast lies oceanic whose thickness varies 4.9 6.5 along line 7.5 southern one. latter presents an unusual high-velocity lower body (7.0–7.2 s−1), about wide 3.8 thick, underlying crust. may consist underplated melt with same source as nearby Paisley Seamount, which not yet reached isostatic equilibrium. Despite well documented recent seismicity margin, neither reveal significant modifications or reduced velocities might be related ongoing extensional tectonics part Neither profile reveals evidence for presence major fracture sheared continental margin parallel margin. Instead, profiles’ broad transitions consistent their formation early stage plate divergence oblique Later, after 157 Ma, azimuth relative motion between West changed parts have locally strike-slip sense. However, details on movements directional change seafloor spreading 144 Ma available. formed initial divergent extension became faulted/modified both plates. Instead narrow deformation zone, DFZ charcaterized broad, diffuse transtensional deformation.