Sedimentary and ichnofacies analysis of the epiligurian Ponsano sandstone (northern Apennines, Tuscany, Italy)

Several stratigraphic sections have bcen measured in the Rencine and Ponsano area to Define, trough sedimentary and ichnofacies analysis, the depositional paleoenvironment of the late Serravallian•early Tortonian Ponsano sandstone Formation. The section of Rencine is characterized mainly by medium•fine sandstones (Sm facies). Few and thin layers of conglomerate are interbedded with sandstones,.No sedimentary structures have been recognized except for few remnants of planar cross- eds. In the section of Ponsano, the Ponsano Sandstone can be subdivided into two parts. The lower part is characterized by marlstones (Ms facies) at the bottom and medium-fine sandstones (Sm facies) in the middle and upper parts. The upper part is characterized by Ms at the bottom, Sm in the middle, and an alternation of pebble conglomerates (Cp), coarse conglomerates (Cb) and coarse sandstones (Sc) at the top. Fossils concentrations (f) occur throughout. The sandstone faeics are highly bioturbated, and most primary sedimentary structures are obscurcd: only remnants of even lamination, cross bedding and hummocky cross stratificationcould be recognized locally. Trace fossils are indicative of the mixcd Cruziana-Skolithos and the Skolithos icnofacics. Sedirnentary and ichnofacics data indicate that the Ponsano Saodstone was deposited in Shallow water environment. The morlstone faeies are indicative inner shelf, the sandstone facies of shoreface. Conglomerates are referred to a fluvio- deltaic environment.