Fault-controlled base-of-scarp deposits

The term base-of-scarp is proposed for those submarine deposits controlled by a fault and physically disconnected from their more proximal counterpart located on the footwall, although genetically linked to it. These systems differ from conventional fault-controlled deltas, such as shoal- and Gilbert-type, because they are entirely subaqueous and lack equilibrium morphology — a steady-state in which the system grows in size without altering its shape. We present field examples of faut-controlled base-of-scarp deposits from the Crati Basin and the Messina Strait (southern Italy) consisting of clastic wedges with primary inclined bedding. Beds are composed of immature coarse-grained gravel and sand, lack structures representative of wave-action, and reflect gravity-driven processes such as debris flow, debris fall, and high-density turbidity currents. A diagram for fault-controlled deposits is presented, including their steady- and unsteady-states, and the conceptual conditions under which a base-of-scarp system might evolve into Gilbert-type or shoal-water systems.