Sedimentological and sequence stratigraphy analyses of the syn-rift Triassic series of the Mohammedia–Benslimane–ElGara–Berrechid basin (Moroccan Meseta)

Abstract

Sedimentological analysis has shown that during the syn-rift phase (Upper Triassic) the Mohammedia–Benslimane–ElGara–Berrechid basin (MBEB) is characterized by detrital and evaporite sediment filling. A gradual decrease of palaeoslope over time led to the evolution of paleoenvironments of proximal alluvial fans system to braided rivers and then to an anastomosing system. These environments evolve finally to an alluvial plain associated with a coastal plain where playa lakes, mudflats and lagoons had developed. We have identified fourteen genetic sequences which are included in four progradationalretrogradational minor cycles that are themselves grouped in one major cycle. These cycles are related to the variations of the base level. The dominance of the retrogradation phases giving an asymmetrical appearance to the cycles is related to the predominance of the base level rise. These variations are probably of allocyclic origin: tectonic and probably climatic, in relation with the Tethys and the Atlantic Ocean being opened.