AbstractThis sedimentological and palaeontological analysis of the Aptian–Albian sedimentary succession of the Ait Ourir basin in the High Atlas Mountains of Marrakesh in Morocco provides new data from a previously poorly understood basin. The palaeoenvironmental evolution is deduced based on a facies analysis allowing the restoring of depositional environments and their stratigraphic architecture. Within the Aptian–Albian succession, we distinguish two sedimentary sequences separated by a

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... discontinuity. The first sequence is composed of calcareous and dolomitic marls with the rudist Pseudotoucasia catalaunica of the Tadhart formation (upper Aptian in age) and of strongly dolomitized limestones with corals (Eugyra sp., Thalamocaeniopsis sp., and Holocystis sp.) of the Lemgo formation (uppermost Aptian in age). These two formations were formed in an internal carbonate platform (the intertidal zone to the subtidal zone). The second sequence, Albian in age, is composed of sandy limestones of the Oued Tidzi formation and is represented by sediments showing terrigenous influence, with deposits of silt, sandstone, dolomitic sandstone, and limestone.