The Numidian of Sicily revisited: a thrust-influenced confined turbidite system

Understanding whether a system was unconfined, and deposited on a relatively unstructured basin-floor, or was confined by actively deforming substrate is important for the prediction of turbidite stratigraphy. Here we consider the Numidian turbidite system (Oligocene-Miocene) of Sicily - for many the type example of thick structureless submarine sandstones. New mapping and detailed sedimentology in the Nebrodi and Madonie Mountains (northern Sicily), allied to existing and new biostratigraphic data, challenge conventional interpretations for the Numidian system as a whole. Rather than having been deposited within an unstructured foredeep by relatively unconfined flows, we show that Numidian deposition was confined by active structures. These governed the routing of turbidity currents to create sand fairways and associated facies variations. The controlling structures include thrust-related folds together with inherited basin-floor faults. Existing models suggest that facies variations between adjacent outcrops on Sicily (and elsewhere) result from long-range stratigraphic variations being juxtaposed by later large-displacement thrusts. Our research reveals a much simpler tectonic structure but a more complex stratigraphic arrangement for the Numidian on Sicily - a characteristic of confined turbidite systems.