New data on the Middle Pliocene sedimentation in the southern Valdelsa basin (Siena, Italy)

The Valdelsa basin, one of the widest Neogene-Quaternary extensional basins of central Tuscany, is filled by dominantly clastic deposits of late Miocene and Pliocene age. Within the new regional project of geological cartography, sedimentological, stratigraphic and micropaleontological studies of the Pliocene marine sediments cropping out in the south-western area of the basin have been performed. The most important results are: a) the recovery of Globorotalia crassaformis, which allows to refer these sediments to the Piacenzian G. aemiliana Zone; b) the migration, during the Piacenzian, of the deeper areas of the Valdelsa basin from the central sector towards the eastern one; c) the recognition, during the same period, of a rapid transgression on the eastern margin. The analysis of these data, integrated with previous work from the surrounding areas, allows to outline the sedimentary evolution of the south-western sector of the Valdelsa basin during the Piacenzian.