Extensional tectonics during Maghrebides Chain building since late Miocene: examples from Northern Sicily

The Northern Sicilian-Maghrebian Chain courses W-E from the Trapani Mts to the Peloritani Mts and is composed by a set of tectonic units deriving from the Miocene-Pleistocene deformation of the Northern African Continental Margin. Inside it three main geotectonic elements ("external", Sicilide and "Austroalpine") are present and outcrop juxtaposed with a W-E trend. The external element composes the more western Trapani, Palermo and Western Madonie Mts, the Sicilide composes the Eastern Madonie and Nebrodi Mts, while the "Austroalpine" composes the more eastern Peloritani Mts. The orogen shows a culmination in the Trapani Mts and a depression in the Peloritani Mts. The main plicative stages are relatable to late Oligocene-early Miocene from the more internal sectors, while the deformation of the more external sectors starts from early-middle Miocene. The Sicilian chain body is re-involved in tectonism since late Tortonian, which persists until the recent time. During this interval, the deformation of the Sicilian Chain continued by activation of fault systems with different displacements. In the present paper, an important extensional tectonic stage is recognised, starting from the Tortonian; it is supported by structural data and shows through several geological sections across the northern sectors of the Sicilian orogen. This deformation is of exceeded wedge critical taper values, controls the early stages of the Tyrrhenian Basin opening, and is represented by low-angle fault system, producing tectonic omissions in the stratigraphic sequence. The detachment fault system is subsequently displaced by a complicated grid of Plio-Pleistocene net- and strike-slip fault system that controls the genesis of tectonic depressions in the northern off-shore areas of the Sicilian Chain. This neotectonic system may be reconnect to a W-E trending simple shear system, which controls the more recent Tyrrhenian Basin development.