Structure of the Central Atlantic conjugate passive margins and their associated sedimentary basins

Deep seismic data represent a key to understand the geometry and mechanism of continental rifting. The Central Atlantic conjugate passive continental margins pair is one of the oldest on earth, formed during the Upper Triassic-Lower Liassic. We present wide-angle and reflection seismic data from two study regions along this margin. Along the NW-African the thickness of unthinned continental crust decreases from 36 km in the North to about 27 km in the South. Crustal thinning takes place over a region of 150 km in the north and only 70 km in the south. The ocean-continent transition zone shows a variable width between 40 and 70 km and is characterised by seismic velocities in between those of typical oceanic and thinned continental crust. The neighbouring oceanic crust is characterised by a thickness of 7-8 km along the complete margin. Comparison to the conjugate margin off Nova Scotia shows comparable continental crustal structures, however 2-3 km thinner oceanic crust on the American side than on the African margin. Comparison to the Gulf of Lions - Sardinian margin pair shows symmetric structures comparable to those of the NE-Canadian - NW - African margin pair.