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Abstract: Triassic-Lower Jurassic Basins of Western Morocco : Markers of the Central Atlantic Rifting

Pascal Le Roy, Alain Pique, Bernard Le Gall, Jean-Pierre Rehault, A. Ait Brahim, A. Tahiri, A. Demnati

The Triassic-Lower Jurassic basins which fringe the Moroccan continental margin developed in response to the continental rifting and opening of the North Atlantic Ocean. Interpretation of seismic reflexion data issued from petroleum exploration across this margin allows us to define the deep structures of these rift-related basins as well as to precise kinematics of the overall rifting process.

Seismic lines recorded over Doukkala onshore basin, north of the studied area, reveal several NNE-SSW trending fault-bounded half-grabens. The border faults dip undifferently eastward or westward. They affect the whole Triassic sequence and they are therefore related to a Lower Jurassic extensional event. Additional basinal tectonic patterns are documented further west along the complementary offshore domain. There, asymmetrical basins occur in relation with a prominent northeast dipping listric fault system that merges at depth along an intra-crustal detachment level. The variation observed in extensional styles from east to west are also evidenced from north to south as shown by the southern Tarfaya basin which is a more recent half-graben, bounded by a major southeast dipping fault and filled with much thicker syn-tectonic deposits, including notably two distinct deltaic system tracts. Finally, from a kinematic point of view, the geometrical variations displayed by the Moroccan Mesozoic basins are the expression of a south-north migration of the Atlantic rifting process, and to a lesser extent, of some transfer faults development.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France