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Abstract

Triassic through Lower Cretaceous deposition along the Moroccan continental margin was con-trolled by Triassic rifting and subsequent continen-tal drift associated with the formation of the Atlantic Ocean. During Triassic rifting, basement- involved normal faults formed half-grabens which filled with continentally derived shales and sand-stones. In northern Moroccan basins, early rifting intensity was mild to moderate. Distant highlands provided only minor clastic input to these subsiding Triassic-Lower Jurassic half-grabens; instead, evaporite sequences developed during the invasion of the proto-oceanic basin by the Tethys Sea. Evaporite precipitation kept pace with basin subsidence. In southern Moroccan basins, rifting intensity was moderate to strong. Thick Upper Triassic-Lower Jurassic terrigenous clastic successions were deposited into rapidly subsiding half-grabens. Movement along the South Atlas fault zone accommodated the extensional strain between northern and southern Morocco.

Postrift or passive-margin sedimentation charac-terized the Middle Jurassic through Cretaceous rocks along the Moroccan margin. Less restrictive marine conditions prevailed as drifting progressed, resulting in increased carbonate deposition during the remainder of the Jurassic. Middle to Upper Jurassic reefs and carbonate platforms developed both over and landward of the deforming evapo- rites. With further drifting, the rifted continental margin subsided, “drowning” the Jurassic reefs. With erosional base level lowered and onshore highlands exposed, large amounts of clastic material were shed into the offshore basins. At least two Lower Cretaceous depocenters received clastic sediments in southern Morocco. Growth faulting in the Lower Cretaceous deltaic elastics created the large offshore deep-water slope anticline. During the Late Cretaceous, pelagic limestones and shales were deposited over Lower Cretaceous deltaic and paralic sediments.

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