Structure of the Central Atlantic Conjugate Passive Margins and their Associated Sedimentary Basins

Summary 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.