A radiometrically-constrained reference record of Last Interglacial climate and vegetation changes from the Fucino Basin, Central Italy

The Last Interglacial (LIG) was characterised by a global mean temperature ∼1 °C warmer than the pre-industrial, a pronounced Arctic warming and an elevated sea level. Exploring the nature of LIG environmental changes in local contexts can improve understanding of regional responses to a warmer background state. However, a lack of high-resolution palaeoclimatic archives underpinned by an independent and robust chronological framework remains a primary limitation in investigating climate variability and relating it to changes in other records. This paper presents a detailed palynological, charcoal and bulk carbonate oxygen isotope record of a thick lacustrine sedimentary sequence retrieved from the Fucino Basin, central Italy, covering the period ∼139 to 107 ka at sub-centennial to centennial resolution. A key aspect of the record is its independent chronology based on direct ⁴⁰Ar/³⁹Ar dating and geochemical fingerprinting of several tephra layers. The highly-resolved multiproxy record reveals substantial environmental variability on long- and short-term timescales. The pollen sequence documents a succession of arboreal phases interrupted by centennial-to millennial-scale contractions in temperate vegetation. Comparisons between δ¹⁸O records from the Fucino Basin and a speleothem stack from Corchia Cave (northern Italy) suggest a strong hydrological seasonal contrast during the early LIG, corroborated by increased Mediterranean taxa abundance and elevated fire activity. The early LIG in Italy emerges as a time of high seasonality with arid summers and enhanced winter precipitation driven by strong Northern Hemisphere summer insolation. The detection of high-frequency interglacial climate variability points to an interconnected North Atlantic and Mediterranean climate regime.