The Monte Falcone-Rio Riorzo composit section: biostratigraphic and ecobiostratigraphic remarks.

The ecobiostratigraphic study of the historical Piacenzian stratotype and in particular of the Monte Falcone - Rio Riorzo section supports a three-fold subdivision of the Pliocene, consistent with the introduction of a new stage representing the Upper Pliocene. The base of this new stage, the Gelasian, which was ratified by IUGS in 1996, just predates the onset of significant northern hemisphere glaciation (in the sense of Shackleton et al., 1984). In the M. Falcone-R. Riorzo section two of the more significant changes in the taxonomic diversity of the Mediterranean molluscan fauna are recorded. The older change, characterized by the sharp disappearance of tropical taxa, is well calibrated within the magneto-biostratigraphic framework of the Mediterranean Pliocene and appears just to post-date the very base of the Gelasian. The paleoecological analyses of the succession testify that this change is not due to edaphic factors but to paleoclimatic changes. In conclusion the Monte Falcone - Rio Riorzo section appears to represent an useful ecobiostratigraphic model for the evolution of the shallow water environments of the Mediterranean late Pliocene.