THE STRAIT OF SICILY RIFT-ZONE - FORELAND DEFORMATION RELATED TO THE EVOLUTION OF A BACK-ARC BASIN

A reappraisal of the seismic profiles available over the Strait of Sicily rift zone has been undertaken in order to unravel its tectonic evolution. Although the area presents great structural complexity, the motion along the basin-boundary faults appears to have been mostly dip-slip with extension directed roughly NE-SW. A wide N-S-trending belt characterized by localized uplifts and depocentres, alkaline volcanics and structural inversions, separates the Pantelleria Trough to the west from the Malta and Linosa troughs to the east. This belt presents evidence of strike-slip tectonics and acted as a transfer fault zone between two segments of the rift system. The rifting occurred mostly during the Pliocene and was followed by a post-rift phase, with no sign of extension within the troughs, that probably spanned the whole Quaternary. Only within the Pantelleria Trough has a recent contractional episode been observed. The origin of the rift system is hypothetically related to the opening of the Tyrrhenian back-arc basin which occurred at the same time. Roll-back of the subducted slab and lithospheric mantle delamination have been proposed as feasible mechanisms originating the Tyrrhenian back-arc basin and the coeval contraction in the Apennine-Maghrebian fold-thrust belt. Both these mechanisms can also produce a limited amount of extension in the Strait of Sicily due to slab-pull and secondary mantle convection, respectively.