Stratigraphy, geometry, and facies of a Middle Devonian ramp-to-basin transect (eastern Anti-Atlas, SE Morocco)

In the eastern Anti-Atlas (SE Morocco), a small sedimentary basin (Mader Ba sin) evolved during the late Palaeozoic. The Middle Devonian deposits consi st of shales and limestones with a thickness up to 700 m in the depocentre. Sedimentary structures and sole marks of Middle Devonian limestones indica te transport from the northwest and the south towards the basin centre, loc ated in the central Mader area. Lithostratigraphic, biostratigraphic, and d ynamic stratigraphic approaches were applied to correlate stratigraphic sec tions. Five correlatable large-scale base-level hemicycles were recognized in the Middle Devonian succession. Thickness trends of Middle Devonian depo sits, regional correlations, and facies-trends reveal the geometry of a car bonate ramp. The carbonate ramp was slightly inclined (< 1 degrees) to the NE. A sedimentary wedge, consisting of limestones and limestone/marl altern ations, was deposited during the Eifelian and marks the transition from the ramp to the adjacent basin. Middle Devonian water depths are estimated as close to and within the storm wave-base at the southern area of the ramp an d far below storm wave-base in the northeastern part of the ramp. Shallowes t conditions (inner-ramp environment), close or within the fairweather wave -base, existed during the early Givetian as documented by the abundance of reefal fauna (stromatoporoids, corals) and calcimicrobes (lumps, micritic e nvelopes) in the eastern and southeastern area of the ramp.