Integrated Stratigraphy across the Neogene–Quaternary Boundary at the Monte San Nicola (Sicily) Type Locality – the SQS-ICS Supported International Program GELSTRAT

The Global boundary Stratotype Section and Point (GSSP) at Monte San Nicola, near Gela, Sicily, Italy, located in an undeformed section at the base of a marly layer overlying the microlaminated sapropelic Nicola bed (bed A5), ratified in 1996 and dated to 2.59 Ma, defines the base of the Gelasian Stage, Pleistocene Series and Quaternary System. High-resolution integrated climatic and stratigraphic studies had been lacking for the type section when it was first ratified. In September 2021, the INQUA-SQS-ICS-supported international program GELSTRAT was inaugurated to reanalyse the Gelasian GSSP interval using modern methods and a broad range of proxies. Sampling conducted in 2021 and continuing through 2025 has yielded: 1) a high-resolution multiproxy record across an ~18 m interval spanning the GSSP and ranging from the top of bed A1 to ~10 m above the top of the Nicola bed, 2) an ichnological record across a ~10 m interval from just below the top of A1 to 70 cm above A5, and 3) ultrafine resolution records from blocks of the Nicola bed taken throughout Monte San Nicola including the GSSP section. Our initial multiproxy record for the type section is based on stable oxygen isotopes, alkenones, foraminifera and calcareous nannplankton from MIS G4 to the onset of MIS 99 (2.7–2.5 Ma), which, along with geochemical and mineralogical data refine the climatostratigraphic framework and characterise each sapropelic level. Analyses of pollen, dinoflagellate cysts, palynofacies, macrofossils, ichnofossils, magnetostratigraphy, 10Be, and numerical modelling are in progress. Our dataset reveals the excellent correlation potential of climate signals recorded through the section and refines the position of the GSSP itself within MIS 103 allowing global correlation. Multiproxy analysis of the Nicola bed at ultrafine stratigraphic resolution using microstratigraphy, ichnology, palynology, calcareous plankton, X-ray tomography, micro-XRF elemental analysis (ITRAX), microprobe and spectral analyses, reveals a detailed history of bottom-water anoxia and high-frequency fluctuations in surface-water productivity.