Formation processes and geochronology of San Bernardino cave, a Middle Pleistocene neanderthal site from the south-eastern Alp foothills (NE Italy)

This study presents a multidisciplinary analysis of the Pleistocene sedimentary sequence from the Grotta Maggiore di San Bernardino, located in the Berici Hills, a subalpine region of north-eastern Italy. A combination of sedimentology, micromorphology, mineralogy, and optically stimulated luminescence (OSL) dating is used to reconstruct depositional processes and palaeo-environmental conditions for the site. Stratigraphic and micromorphological analyses reveal that the sequence reflects an interplay of geogenic and anthropogenic processes, with frost action, solifluction, and aeolian inputs alternating with accumulations of hearths, bones, and lithic debris. The sedimentary environmental proxies, integrated with biological data from a molluscan assemblage, point to alternating moist and more arid episodes, consistent with wider climatic fluctuations. The single-grain OSL ages presented here provide an improved radiometric framework for these deposits, indicating that accumulation of Units VII–IV spanned the interval from Marine isotope Stage (MIS) 8 through MIS 7 and into MIS 6. The chronology is consistent with palaeo-environmental evidence for alternating cold and interglacial conditions recorded within the sequence. These new dating results complement and expand upon minimum age estimates obtained previously using electron spin resonance and uranium series (ESR-US) dating, as well as non-finite radiocarbon ages published for the top of the sequence (Unit II – deposited sometime prior to early MIS 3). The updated chronological framework not only refines the temporal context of the archaeological and palaeontological assemblages but also anchors local sedimentation patterns to regional paleoclimatic oscillations. Overall, the results suggest that the San Bernardino deposits preserve a complex interplay of natural sedimentation from slope and aeolian processes, karstic inputs, and anthropogenic activity, offering critical insights into both site formation processes and human presence during the Middle Pleistocene.