Evolution of the Western Mediterranean

The western Mediterranean is the younger part of the Mediterranean, being a basin formed during the period from late Oligocene to the present. The western Mediterranean consists of a series of sub-basins, such as the Alboran, Valencia, Provenc \u327al, Algerian and Tyrrhenian Seas (Figs. 12.1 and 12.2). These basins have mainly a triangular shape and they generally young from west to east. They are partly floored by oceanic crust (Provenc \u327al and Algerian basins, and two smaller areas in the Tyrrhenian Sea). The remaining submarine part of the western Mediterranean basin is made of extensional and transtensional passive continental margins. The continental crust is composed of Paleozoic and pre-Paleozoic rocks deformed by the Caledo- nian and Variscan orogenic cycles. In the following, the gross structure of the Mediterranean structure and geody- namics is reviewed. In particular, the present day lithosphere-asthenosphere system is analyzed using two S-wave velocity cross-sections and the litho- spheric structure of the area is shown by lithospheric scale cross-sections along two regional-scale geotraverses. The lithospheric geological cross-sections are based on the result of the TRANSMED project (Cavazza et al., 2004), and the cross-sections discussed in this work are a simplification of the TRANSMED II (Roca et al., 2004) and TRANSMED III (Carminati et al., 2004) sections. The S-wave velocity cross-sections run parallel to the TRANSMED II and TRANSMED III geotraverses