Deep structure of the North Tyrrhenian Sea from multi-channel seismic profiles and on land wide angle reflection/refraction seismic recording (LISA cruise): Geodynamical implications

Abstract

We present a lithospheric section of the northern Tyrrhenian basin based on principal observations along a transect from Corsica Island to Tuscany margin. Offshore, crustal structure observations come from the LISA deep seismic cruise, composed by Multi-Channel Seismic profiles and wide angle reflection/refraction seismic data. Other parts of the section are constrained by published data, from different geophysical sources. A great detachment between Alpine Corsica and Hercynian Corsica constitutes the base of the Corsica basin. The end of this detachment is probably located below the Elba Island in the ductile lower crust where we observed an east dipping reflector interpreted as ductile shear zone. Similar detachments have been observed beneath the Punta-Ala basin on the Tuscany margin. Our section shows a thin crust below Corsican Basin (15 km thick) and a thicker crust below the Pianosa ridge (25 km). Between Elba Island and the Tuscany coast the Moho reflections shallow to (23 km/depth) as identified on the MCS profiles and from the modelling of the wide-angle reflection/refraction seismic date. An asthenospheric mantle uplift produces a significant heat flow below the Tuscany margin. The base of the lithosphere is located at 75 km depth below the Corsica margin, at 50 km below the Corsica basin and as shallow as 30 km below the Tuscany margin. The shift observed between the Corsica Basin and the Tuscany coast suggests an asymmetric lithospheric thinning which involves a detachment fault located at the base of the Corsican basin.