Der passive und der gescherte Kontinentrand vor Mosambik: Früher Zerfall Gondwanas und der rezente Einfluss des ostafrikanischen Riftsystems (The passive and rifted continental margin off Mozambique: Early dispersal of Gondwana and the recent influence of the East African rift system) (PAGE-Four), Report of RV "Sonne" cruise SO-231, Project PAGE-Four, 20. February 2014 to 29. March 2014 (English)

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The main goals of the project are (I) an improved understanding of Gondwana break-up and (II) to analyze timing, structures and kinematics of ancient to modern extension along the East African continental margin. We acquired a total of 4300 km of geophysical profiles. In the northern Mozambique Basin, the transition from oceanic to the continental crust around Davie Ridge coincides with a fossil collision zone, dominated by compressive structures, while further north extensional structures predominate. In order to archive well control for seismic marker horizons, the position of DSDP site 242 was crossed twice. Both, in the northern and western part of our study area we will include correlations with published well information. So far there is no confirmation of an earlier proposed sharp boundary between continental and oceanic crust just east of the Davie Ridge. Rather we found evidence for a broad transition zone, more than 100 km wide and situated east of Davie Ridge. In this zone the basement reveals unusual weak reflectivity. Magnetic data are indifferent and there is no clear distinction between oceanic crust that formed during the Jurassic quiet period and continental crust. Evidence for neotectonic deformation is derived from seismic reflection data. In order to interpret the mainly extensional deformation in a regional framework we expanded the detailed swath bathymetry mapping performed during the previous cruise SO-230 father to the south.