6533b7d3fe1ef96bd125fe6a

RESEARCH PRODUCT

Rift-controlled fluvial/tidal transitional series in the Oukai¨meden Sandstones, High Atlas of Marrakesh (Morocco)

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Abstract The Carnian formation of the Oukai¨meden Sandstones was deposited in the northwestern corner of the African craton along tectonic troughs grouped as a WSW-ENE rift system on the southwestern margin of the Tethys. Red sandstones represent mainly distal braided-stream deposits where very extensive sand flats with 3D dunes, 2D sand waves and high-regime horizontally laminated sandstones predominate. The similarities in orientation between current patterns and trough border faulting, the sudden large variations in the thickness of deposits and the occurrence of lateral alluvial fans along the marginal faults are all evidence of the tectonic control of sedimentation. The middle part of this clastic continental rift series includes finer facies containing marine-reworked or in situ fossils and tracks as well as sedimentary structures interpreted as being of tidal origin, especially overlapping S-shaped sets. The episodic marine influxes that occur within these continental rift deposits are thought to result from the substantial downdropping of tectonic blocks and the drowning of fluviatile facies by the Peritethyan marine domain to the northeast. The development of marine facies was of relatively short duration and figures little in the sedimentary record, butit is evidence of the earliest Mesozoic onlaps of the Tethys over the African craton in a Carnian rift.