New insights on Numidian of Sicily: a thrust-influenced confined turbidite system

Outcropping turbidite systems of the central Mediterranean-Alpine region are widely used as analogues for a variety of deep-water hydrocarbons reservoirs. Understanding whether the system is unconfined and deposited on relatively unstructured basin floor or confined by actively deformed basins is important for the prediction of sand distribution and therefore the applicability of analogues. Here we consider the Numidian turbidite system (Oligocene-Miocene) of Sicily - for many the type example of thick massive submarine sandstones. The tectonostratigraphic setting of the Numidian is analogous to the Angostura (Trinidad) - Scotland (Barbados) sand systems of the Caribbean and associated ultra-deep water exploration. New mapping and detailed sedimentology in the northern and central Sicily, allied to existing paleontology, challenge conventional ideas on the Numidian system as a whole and how it can be used to inform deep-water hydrocarbon systems. Rather than having being deposited within an unstructured foredeep by relatively unconfined flows, we show that Numidian deposition was strongly confined by active structures. The system was controlled by thrust related folds and their intrabasin submarine slopes, together with basin floor architecture inherited from the underfilled passive continental margin. Thrust-top basins filled diachronously implying a large scale tectonic control both on sand fairways and facies variations along their margins. Existing models wrongly 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.