Chronological and post-depositional insights from single-grain IRSL dating of a Palaeolithic sequence at Stelida, Naxos (Greece)

Since 2015, the Stelida Naxos Archaeological Project (SNAP) has excavated a prehistoric site on what today is the northwest coast of Naxos, the largest island of the Cycladic archipelago in the southern Aegean Sea (Greece). Survey and excavations at the site have produced artefacts spanning the Lower Palaeolithic through the Mesolithic periods based on their techno-typological attributes. These discoveries suggest that exploitation of Stelida began as early as the Middle Pleistocene, challenging the long-standing model that the Cyclades were not inhabited until the Early Holocene. Due to the site’s likely temporal depth and the lack of preserved organics, luminescence dating is the most appropriate method to scientifically date this activity. However, luminescence dating in this context is complicated by the site’s complex hillslope formation processes. Experiments upon the Stelida sediments have demonstrated a lack of luminescence sensitivity of quartz at the site. To evaluate the potential for post-depositional mixing of previously acquired dates yielded from a stratigraphic sequence first published in 2019, as well as to evaluate the efficacy of multiple luminescence dating models, we measured and compared different infrared stimulated luminescence [IRSL] measurements on K-feldspars, with IR50 and pIRIR290 multi-grain and pIRIR290 single-grain signals. The single-grain results confirm the multi-grain results and provide additional and more precise information on the site’s depositional and post-depositional events. The results of each approach demonstrate that feldspars were well-bleached, suggesting that in hillslope settings where quartz grains prove difficult to date, IR50 and pIRIR290 multi-grain, and pIRIR290 single-grain signals of feldspars can be used to achieve reliable results. Finally, when considered alongside field and laboratory observations of site stratigraphy, these results suggest that colluvial and aeolian (windblown) deposits at Stelida retain a degree of stratigraphic integrity characterized by minimal post-depositional alteration following their most recent deposition. These support previous estimates of the deposition at the site, the new earliest determination being 233 – 217 thousand years ago [ka], compared to the date of 198.4 ± 14.5 ka published in 2019. These dates represent the earliest – indirect – evidence for open sea crossings in the northern hemisphere, though it remains uncertain as to which species of the genus Homo was responsible for such maritime activity. These results also have implications for the preservation potential of similar deposits across the hillslope, as well as deposits preserved in similar geomorphic settings in Mediterranean landscapes.