Stratigraphic and paleopedological aspects from the Middle Pleistocene continental deposits of the southern Valdelsa Basin

E. Capezzuoli(*), S. Priori(*) & E.A.C. Costantini(**) , F. Sandrelli(*)
(*) Dipartimento di Scienze della Terra, Università di Siena, Via Laterina, 8 - 53100 Siena, Italy. Tel. 0577-233974; fax 0577-233938; E-mail: capezzuoli@unisi.it. (**) CRA-ABP, Centro di ricerca per l'agrobiologia e la pedologia, Piazza M. D'Azeglio, 30 - 50121 Florence, Italy.

A multidisciplinary approach on mainly continental carbonate deposits outcropping in the southern part of the Valdelsa Basin has allowed the recognition of two units, the Strove Synthem (STR) and the Campiglia dei Foci Synthem (CDF), both previously attributed altogether to a single indistinct sequence. The presence of a mammalian fauna suggests that the STR Synthem belongs to the Early-Middle Pleistocene, whereas the CDF Synthem is assigned to Middle Pleistocene because of its stratigraphic position. Lateral correlation with continental deposits cropping out in the adjacent Lower Valdarno Basin suggests an age not younger of the Stage 11 of the isotope scale. A paleopedological study of the soils on the synthems has distinguished two pedogenetic typologies: a Cutanic Alisol (Manganiferric) on Gleyic Vertisol for STR Synthem and a Haplic Cambisol on Rhodic Luvisol on Rhodic Nitisol for CDF Synthem. The different pedogenetic development corroborated the hypothesis of two distinct synthems. The attitude of the STR Synthem (tilted deposits) in comparison with the CDF Synthem (sub-horizontal bedding) shows that the former was affected by a tectonic phase which ended before the deposition of the latter synthem. The chronostratigraphic attribution of the two synthems allow us to tentatively relate this tectonic phase with the regional Middle Pleistocene tectonic uplift, which caused the present Northern Apennine mountain chain.

Valdelsa Basin, Stratigraphy, Middle Pleistocene, Paleosol.