Nuove Osservazioni sui depositi esposti sul fianco sud-orientale delle Colline delle Cerbaie (Valdarno inferiore, Toscana)

Abstract

The paper reports on the lower deposits outcropping along the southern border of the "Cerbaie Hills" (Lower Valdarno). These deposits underlie Middle Pleistocene gravel sheets previously attributed to the Pliocene marine cycle. A new survey revealed the prevailing continental nature of these deposits. From the lithological point of view, sands are locally intercalated with sometimes very thick silts and clayey layers. In the central-western portion of the studied area, two thin marine-brackish layers are intercalated within the continental deposits; these can stratigraphically be correlated with the Arctica islandica marine deposits outcropping on the left side of the Arno river. Remains of fossil continental mammals and molluscs were recovered, in particular Stephanorinus cf. etruscus, Leptobos cf. etruscus, Equus cf. stenonis and Sus cf. strozzii and Viviparus cf. ampullaceus, Negulus villafranchianus, Gastrocopta (Vertigopsis) dehmi and Leiostyla gottschicki. The chronological position of the examined sequences has been determined using information from the whole basin. In the post-Pliocene marine fan deposits along the border of Montealbano Mt., on the eastern margin of the basin, remains of Equus stenonis cf. vireti and Sus cf. strozzii were recognized and Anancus arvernensiswas found in the basal layers of a Arctica islandica-bearing marine sequence in the area of Montecastello. These findings allow us to correlate, on the basis of stratigraphical considerations, the studied deposits - at least their basal portion - with the St.Vallier Fauna Unit.