The role of fracture zones during early Red Sea rifting: structural analysis using Space Shuttle radar and LANDSAT imagery

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The structural pattern of the Red Sea region, an area where continental lithosphere is cut by a young oceanic rift, was studied by means of satellite and space shuttle radar imagery. The Space Shuttle Mission 2 made two passes over the Red Sea bracketing a region transitional between the southern Red Sea, where true seafloor spreading started about 5 Ma BP, and the northern Red Sea where crust is probably continental, though thinned and stretched. Structures on these passes define bands of shearing in the African and Arabian margins parallel to the Dead Sea Fracture Zone (000–020°). Combinations of these data with LANDSAT information reveal four shear bands along the margins of the Red Sea and one oblique to the Gulf of Suez. We have named the northern three Red Sea shear zones detected on the SIR-A data, the Brothers–Dead Sea Fracture Zone, the Zabargad Fracture Zone and the Shagara Fracture Zone. Two sets of normal faults were also detected, trending 330–340° (parallel to the northern Red Sea coastline) and 310–320° (parallel to the axial deeps in the Red Sea). A map of the 310–320° faults bordering the Red Sea resembles a V-shaped wedge narrowing to the north near the Gulf of Suez. These faults may have formed as a result of the most recent push of seafloor spreading. If this is so, then there may be a propagating tectonic wedge moving from south to north which thins the continental crust up to distances of 300 km from the axis of spreading. Following continental deformation, oceanic crust may be emplaced in 'hot points' along the rift axis. These 'punctiform' oceanic spreading centres should propagate in the same direction as continental rifting. During this episode palaeo-shear zones probably act as barriers ('locked zones') to the axial propagation. One such case is at the Zabargad Fracture Zone where the oblique impact of the propagating rift against the palaeo-shear may have placed the Red Sea's western side under compression and uplift while the eastern side may have been subject to oblique extension with the formation of pull-apart basins. The Space Shuttle imagery allows integration of some of the northern Red Sea morphotectonic features with structures on the continent.