The Sapropelic Nicola Bed as a Stratigraphic Marker for the Gelasian Stage GSSP: Palynological Organic Matter from Monte San Nicola (southern Italy)

Sapropelic microlaminated A5 (Nicola bed), in the Monte San Nicola succession (Sicily, southern Italy), directly underlies the Global boundary Stratotype Section and Point (GSSP) for the base of the Gelasian Stage and the Quaternary System, and constitutes a key stratigraphic interval for the identification and correlation of environmental markers across the Piacenzian–Gelasian transition. Within the framework of the international GELSTRAT programme, promoted by the Subcommission on Quaternary Stratigraphy (SQS-ICS), we present high-resolution palynological data, including quantitative analyses of pollen and palynological organic matter, from the Nicola bed and sub- and superjacent marls at the Monte San Nicola type section (MSNt-s) as well as from two adjacent sedimentary successions located east (G1) and west (G6-Mandorlo) of the MSNt-s. This integrated dataset enables comparison of closely spaced sections and assessment of spatial variability in environmental response. The Nicola bed is characterised by high percentages of temperate deciduous vegetation, particularly deciduous Quercus suggesting warm and humid conditions during MIS 103, followed by a marked decline in the overlying marls. Palynofacies indicate predominantly suboxic to anoxic conditions during sapropel formation, consistent with the microlamination observed in the sapropelic Nicola bed. Dinocysts dominate the marls, pointing to more fully marine conditions, whereas freshwater algae increase within the sapropel. Distinct palynological events observed in all three sections provide potential stratigraphic markers, including a Cathaya peak at the base of the bed and a deciduous Quercus maximum near its top. The comparison among sections highlights overall coherence in vegetation dynamic and in the successions of palynological events, despite small-scale lateral variability, particularly in palynological organic matter preservation and terrestrial input. These results complement existing multiproxy datasets from the Monte San Nicola area, including high-resolution geochemical, micropalaeontological and sedimentological records, and refine the environmental and climatic reconstruction of the Piacenzian-Gelasian transition, especially useful in the MSNt-s. The Nicola bed thus emerges as a key interval in which climate-driven vegetation changes and basin-scale environmental processes converge, providing a robust set of palynological markers for high-resolution correlation at the Gelasian GSSP. The integration of pollen and palynofacies data with marine and cyclostratigraphic evidence demonstrates the value of the MSNt-s as an integrated stratigraphic archive, in which terrestrial and marine signals jointly constrain the environmental and stratigraphic expression of the Quaternary boundary.