Monte San Nicola (Sicily): Gelasian GSSP and base Quaternary/Pleistocene

The Gelasian Stage, established in 1998 at Monte San Nicola (Southern Sicily) as the third Stage for the Pliocene Series above the Zanclean and the Piacenzian, was overlooked for years but regained global recognition in 2009, when the base of both the Pleistocene Series and the Quaternary System was lowered to match the Piacenzian/Gelasian boundary. In recent years, independent research groups have been collecting scientific data at Monte San Nicola from two sections, namely the “historical” GSSP profile and the nearby Mandorlo section. Evidence collected in the “historical” section prove that the current GSSP definition does no longer meet the standards for a modern formal chronostratigraphic boundary, and the relevant host section is affected by tectonic reductions that prevent achieving a continuous and reliable chronostratigraphic record. On the contrary, the Mandorlo section offers a pristine depiction of the geological and biotic events that are expected to occur from the Piacenzian/Gelasian boundary up to the base Calabrian, which possibly make it the best reference profile globally for investigating the Neogene – Quaternary transition. We provide a commented review of the current state of the scientific knowledge on the Monte San Nicola stratigraphy in the view of possible actions to be taken soon, such as the definition of the Astronomical Unit Stratotype and Astrochronozones for the Gelasian Stage.