The Permian-Triassic transition and the beginning of the Mesozoic sedimentation in High Atlas of Marrakech and Argana basins, Morocco

Abstract : In the High Atlas of Marrakech and Argana valley, Early Triassic red beds rest unconformably on Late Permian strata. These consist of (i) braided, (ii) meandering and (iii) anastomosing river deposits with calcic vertisols formed under arid to semi-arid climate, with strong seasonality. Whereas, the Early Triassic red beds are deposited in (i) alluvial fan setting with very weakly developed calcic aridisols under arid climate, (ii) ephemeral saline lake-salt pan-saline mudflat under a hyper-arid climate and (iii) braided to moderately meandering river environments associated to gleysols indicating a high regional water table. The Late Permian and the beginning of the Mesozoic sedimentation in Moroccan High Atlas records climate oscillations, through detailed sedimentary and pedogenic studies of several stratigraphic sections.