NEOGENE TUSCAN SHELF-WESTERN TUSCANY EXTENSION EVIDENCES OF THE EARLY POST-COMPRESSIONAL DEPOSITS (TYRRHENIAN SEA- NORTHERN APENNINES, ITALY)

Seismic data of the inland Volterra Basin and of the Tuscan Shelf (Northern Tyrrhenian Sea) have been analyzed to determine the tectono-sedimentary evolution of this part of the Northern Apennines from the Early Miocene (about 20 millions years ago) to the Present. The study area is characterized by a series of sedimentary basins separated by tectonic ridges. Similar environmental conditions existed both inshore and offshore as indicated by the occurrence of similar seismic units. The units are separated by major unconformities. Three main geometries characterize the basin fill of Neogene deposits: bowl-shaped (wide and small), triangular- and blanket-shaped. Small bowl-shaped basins are indicative in both the Tuscan Shelf and the Volterra Basin of pre-rift Burdigalian- Serravallian deposits (although in the Volterra Basin they could also be early Tortonian). Triangular-shaped basins are indicative of rifting and developed during late Tortonian-early Messinian in both the Tuscan Shelf and the Volterra Basin. Wide bowl-shaped basins are indicative of a post-rift regime. This occurred from the late Messinian on in the Tuscan Shelf, while during Early Pliocene the inland Volterra Basin was affected by a new period of rifting, with a well developed half-graben. From Middle Pliocene on, the post-rift phase was established over all the studied area. Blanket geometry of the Pleistocene deposits call for a fully developed post-rift phase.