Rifting to spreading in the Gulf of Aden
Abstract
The Gulf of Aden margins systems are volcanic to the West, where they are influenced by the Afar hotspot, and non-volcanic East of longitude 46°E. The combined use of magnetics, gravity, seismic reflection, field observations (tectonic and sedimentological) allowed us to obtain better constraints on the timing of continental rifting and seafloor spreading. From the Permo-Triassic to the Oligocene, the Arabian-African plate was subject to distributed extension, probably due, at least from the Cretaceous, to tensile stresses related to the subduction of the Tethysian slab in the north. In Late Eocene, 35 Ma ago, rifting started to localize along the future area of continental breakup. Initially guided by the inherited basins, continental rifting then occurred synchronously over the entire gulf before becoming localized on the northern and southern borders of the inherited grabens, in the direction of the Afar hot-spot. In the areas with non-volcanic margins (in the East), the faults marking the end of rifting trend parallel to the inherited grabens. Only the transfer faults cross-cut the inherited grabens, and some of these faults later developed into transform faults. The most important of these transform faults follow a Precambrian trend. Volcanic margins were formed in the West of the Gulf, up to the Guban graben in the south-east and as far as the southern boundary of the Bahlaf graben in the North-East. Seaward dipping reflectors (SDRs) can be observed on many oil-industry seismic profiles. The influence of the hotspot during rifting was concentrated on the western part of the gulf. Therefore, it seems that the western domain was uplifted and eroded at the onset of rifting, while the eastern domain was characterized by more continuous sedimentation. The phase of distributed deformation was followed by a phase of strain localization during the final rifting stage, just before formation of the Ocean-Continent Transition (OCT), in the most distal graben (DIM graben). About 20 Ma ago, the emplacement of the OCT started in the east with exhumation of the subcontinental mantle. Farther west, the system was heated up by the strong influence of the Afar hot-spot, which led to breakup with much less extension. In the Gulf of Aden (s.str), up to the Shukra El Sheik fracture zone, oceanic spreading started 17.6 Ma ago. West of this fracture zone, oceanic accretion started 10 Ma ago, and 2 Ma ago in the Gulf of Tadjoura. Post-rift deformation of the eastern margins of the Gulf of Aden can be seen in the distal and proximal domains. Indeed, the substantial post-rift uplift of these margins could be associated with either the continental break-up, or activity of the Afar hotspot and related volcanic/magmatic activity. The Afar plume is therefore important for several reasons. It allows the localization of deformation along the Red Sea/Aden system and the rapid opening of the Gulf after the continental break-up.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.T23A2368L
- Keywords:
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- 3005 MARINE GEOLOGY AND GEOPHYSICS / Marine magnetics and paleomagnetics;
- 3015 MARINE GEOLOGY AND GEOPHYSICS / Heat flow;
- 8105 TECTONOPHYSICS / Continental margins: divergent;
- 8120 TECTONOPHYSICS / Dynamics of lithosphere and mantle: general