Crossing the Neogene-Quaternary Climate Variability: Marine and Terrestrial Evidence from the Monte San Nicola Type-Section (sicily, Italy)

We present an integrated reconstruction of climate variability across the Neogene-Quaternary boundary (~2.7-2.5 Ma) in the Central Mediterranean. This interval encompasses a global climatic transition following the Mid-Piacenzian Warm Period (~3 Ma) and coinciding with the first significant intensification of Northern Hemisphere Glaciation (NHG) (~2.7 Ma). The Global boundary Stratotype Section and Point (GSSP) for the Gelasian Stage, located at Monte San Nicola (Sicily), currently defines the base of the Quaternary System and the Pleistocene Series. This stratigraphic interval represents a key archive for understanding the environmental and climatic processes associated with the onset of NHG. Within the framework of the SQS-ICS-GELSTRAT project, we performed a high-resolution multiproxy investigation of the Monte San Nicola type-section (MSNt-s), the reference section for the Gelasian GSSP. Sapropels were identified through detailed field observations and geochemical analyses providing a robust astrochronological framework, enabling precise temporal constraints on paleoenvironmental changes. Our study integrates marine and terrestrial proxies across the Plio-Pleistocene transition, including planktonic foraminiferal δ¹⁸O, alkenone-derived sea-surface temperatures (SSTs °C), calcareous plankton and pollen assemblages to describe the time and expression of climatic changes associated with the NHG from a Mediterranean perspective. The results highlight pronounced variability in both marine and terrestrial environments on orbital and suborbital timescales across the studied interval, spanning Marine Isotope Stages (MIS) G4 to MIS 100. Variations in calcareous plankton assemblages indicate that surface-water conditions in the Mediterranean responded strongly to precessional forcing, reflecting changes in surface-water dynamics linked to the complex interaction between the African monsoon system and North Atlantic climate variability. A progressive shift toward cooler conditions is recorded in the marine proxies. Heavier planktonic δ¹⁸O values, together with a marked decrease in reconstructed SSTs and an increase in the abundance of the subpolar planktonic species Neogloboquadrina atlantica, indicate significant cooling and enhanced influence of northern water masses. These signals are consistent with the southward migration of the Subarctic Front during glacial intervals, starting from MIS 104, just below the Gelasian GSSP. Above the boundary, the marine record indicates enhanced seasonal contrasts, while terrestrial proxies document the expansion of colder and drier conditions on land. Pollen assemblages reveal increasingly pronounced glacial-interglacial cycles characterized by shifts between forested landscapes and more open vegetation. Glacial periods are marked by the widespread development of steppe environments and the expansion of xerophytic taxa such as Artemisia and Ephedra, reflecting increased aridity and cooler temperatures across the Mediterranean region. The section even records millennial-scale climatic oscillations. These fluctuations appear correlated with North Atlantic Ice Rafted Debris events showing similarities with the pattern of Dansgaard-Oeschger variability of the Late Pleistocene. Comparison with coeval Mediterranean and North Atlantic reference records demonstrates that both paleoclimatic signals and stratigraphic markers are exceptionally well preserved at the MSNt-s. These results reinforce the value of this section as a key archive for reconstructing early Quaternary climate evolution and significantly improve the potential for correlating the Gelasian GSSP with records outside the Mediterranean region.