Triassic-Liassic Western Moroccan synrift basins in relation to the Central Atlantic opening

The Upper Triassic-Lower Liassic sequence of the Atlantic margin of Morocco is primarily composed of fine-grained detrital sedimentary rocks containing basaltic intercalations. Its age is Carnian to Hettangian. Well data, outcrop observations and seismic sequence analysis suggest that rifting started earlier (Carnian) in the eastern and southern parts of the margin, and later proceeded towards the west and the north, resulting in the formation of the Central Atlantic rift. On the Moroccan margin, the rift was composed of: (i) eastern basins, relatively narrow and bounded by E-dipping faults, which are reactivated Hercynian structures; (ii) a central horst; and (iii) western basins bounded by W-dipping faults. The 020 degrees trending basins are separated by W-dipping faults. The 020 degrees trending basins are separated by 070 degrees striking transfer faults. Estimations of the amount of lithospheric extension along the Moroccan external rift system show a thinning ratio decreasing northward and probably associated to a necking of the lithosphere. Rift evolution on the part of the Moroccan margin shows good correlation to the conjugate North American margin. (C) 2001 Elsevier Science B.V. All rights reserved.