Jurassic-Cretaceous Red beds of the southern Front of Moroccan Central High Atlas (Aghbalou N'Kerdouss-Tadighoust region): Sedimentological, lithostratigraphical and paleogeographical studies

Abstract

Sedimentologic and lithostratigraphic studies carried out along the southern Front of the Central High Atlas in a mostly terrigenous Jurassic-Cretaceous series (Red beds) allow specifying the paleoenvironmental and paleogeographic evolution of three units: Guettioua, Ifezouane and Aoufous formations. The Bathonian Guettioua Fm, composed of terrigenous deposits of a median-distal piedmont and a proximal alluvial plain, is arranged into a regressive mesosequence. A terrigenous Lower (Mbr1) and an Upper (Mbr3) members of the Ifezouane Fm (Albian?-Cenomanian) were deposited in a median to a distal alluvial plain. Paleocurrent analysis indicates a southern source area of the terrigenous material mainly resulting from erosion of the neighbouring or distant Precambrian and Paleozoic basement. The southern origin of the material is opposite to a northern source proposed by authors for the surrounding western areas. These terrigenous supplies are interspersed with a lagoonal-marine incursion that covered the region during the deposition of a Middle Member (Mbr2) of the Ifezouane Fm. Fossiliferous limestone layers have yielded a restricted euryhaline microfauna and macrofauna. This restricted lagoon, E-W oriented with a multi-kilometre extension, was probably opened towards the East. By lateral correlations, this lagoonal-marine event can be dated to the Albian? - Cenomanian interval. This Cretaceous transgression, well documented for the first time, belongs to an earlier mesosequence recorder before the widespread and well-known Upper Cenomanian-Turonian transgression.