Rifted margin formation in the south Tyrrhenian Sea: A high-resolution seismic profile across the north Sicily passive continental margin

Abstract

A new, 150 km long seismic line across the continental margin of north Sicily has been acquired and interpreted. The overall structure of the margin is controlled by extension, which caused crustal thinning and widespread normal faulting. Two main thinned zones are observed in the south in correspondence with the Cefalù basin and farther to the north at the continent-ocean transition. Zones of thinned crust coincide with zones of intense normal faulting. Extension began in late Tortonian times and caused the opening of the Cefalù basin controlled by a northward dipping listric fault. Messinian stretching affected most of the future margin and provoked a widening of the Cefalù basin and normal faulting in the north. Following a phase of relative quiescence in the early Pliocene, renewed extension determined further opening of the Cefalù basin and subordinate normal faulting in the north. Here, however, the record is unclear because of the emplacement of the calc-alkaline Sisifo volcano with associated volcanoclastic deposits. Breakup took place in the late Pliocene and was followed by the deposition of postrift Pleistocene sediments. At the lithospheric scale the sites of extension/thinning did not migrate during rifting. On the smaller scale, on the contrary, the Cefalù basin displays a remarkably systematic pattern of migration toward the foot-wall of the listric fault, which controlled the opening of the basin. The spacing of 4-6 km between faults is also quite systematic. Elongation experienced by the continental part of the margin (presently 97 km) has been derived by comparing the present-day and the preextensional lengths and is 10 km. The corresponding strain rate is 5x10-16 s-1.