Fault rate controls on carbonate gravity-flow deposits of the Liassic of Central High Atlas (Morocco)

The aim of this work is to describe and to explore linkages between fault activity and gravity-related sedimentary deposits during the early rifting of a carbonate depositional system. The study area, located at the southern edge of Central High Atlas (Morocco), hosts 900 m thick Liassic gravity-related sedimentary deposits, preserved at the hanging wall of one of the possibly inherited, reactivated Hercynian faults (Tizi n'Firest fault). This study documents gravity-flow deposits constrained by a high-resolution biostratigraphic framework (ca. 100 ka). These gravity-flow deposits evolve over time. Unstratified conglomerate beds are limited to the Sinemurian and are preserved near the fault. Incomplete, ungraded Bouma sequence beds are preserved preferentially at the transition between the Sinemurian and the Carixian while complete, graded Bouma sequences are recorded during the Carixian and Domerian. Fine-grained turbidite beds are observed dominantly during the Domerian. Incomplete, graded Bouma sequences are observed all along the section. Our work suggests that fault activity over time, associated to rifting, has led to this diversity of gravity-flow deposits. Fault activity plays a key role in the initiation of gravity flows, but also influences the type of gravity-flow deposits, by controlling the amount of sediment available, the sediment grain-size, the slope morphology and the basin deepening.

► We describe carbonate gravity-related deposits at the hanging wall of an extensional fault. ► We explore linkages between the diversity of deposits and the associated fault activity. ► The fault activity plays a direct key role on the initiation of gravity flows. ► The temporal grain-size evolution of the deposits is related to the fault rate.