QUANTITATIVE REGIONAL KINEMATICS MODEL FOR THE OPENING OF THE RED SEA

We present a quantitative regional kinematics model for the opening of the Red Sea in the past 22 Ma year driven from: (1) Remote sensing analysis aimed at matching the Red Sea shorelines and correlating Precambrian structures exposed in the Arabian Shield in the east and the Nubian Shield to the west. We focused on the analysis of Landsat Thematic Mapper (TM) band and band-ratio images of the Hafafit Shear Zone and Um Khariga Volcanic Belt in Egypt, and the Al-Wajh Shear Zone and Wadi Marawah Volcanic Belt in Saudi Arabia; (2) Published Global Positioning System (GPS) surveying which indicate that the Arabian plate is currently moving by ~15 mm/year in a north direction relative to the African plate; and (3) A published geological model which suggests that the Red Sea opened in two phases; an early phase (22-10 Ma) characterized by an orthogonal NE-SW extension followed by a late phase (10-Present) in which the Arabian plate started moving in a north direction relative to the African plate due to slab-pull under the Zagros Orogenic Front. Assuming a stationary African plate, no within plate deformation, and the motion of the Arabian plate remained steady during the two phases, our model predicts the following: (1) The presence of a ~20 km gap between the restored Red Sea margins suggesting minimal lithospheric attenuation before rupture. This is in good agreement with the observed sharp thinning of the Arabian plate lithosphere between the topographic escarpment and the Red Sea shoreline where depth to Moho shallows from ~37 km to ~15 km in this short distance. This predicts that much of the Red Sea is underlain by oceanic crust. (2) Between 22 and 10 Ma the Arabian plate moved by ~125 km in N66°E direction relative to the African plate at a rate of ~10.4 mm/year. This was accompanied by 5° anticlockwise rotation of the Arabian plate. This indicates that during this phase extension across the Red Sea was orthogonal and was dominantly driven by ridge-push. (3) Between 10 Ma and the present the Arabian plate moved by ~150 km in a north direction relative to the African plate at a rate of ~15 mm/year. During this phase extension across the Red Sea was oblique, and this coupled with the accelerated rate of movement of the Arabian plate suggest that extension is dominantly driven by slab-pull.