Calcareous nannofossil response to Holocene climatic events in the North Ionian Sea.

The ND14Mbis marine sediment core was analysed to investigate the climate variability over the Holocene in the North Ionian Sea. The core was collected at a water depth of 665 m below sea level during the Next-Data cruise in 2014, aboard the R/V Urania (CNR). In this work, we focused on the study of the calcareous nannofossil assemblages coupled with the analysis of carbon stable isotopes from Globigerinoides ruber white, X-Ray Fluorescence data (Ca/Ti, K/Al). The lower portion of the investigated succession records the Sapropel 1 interval, between 10 and 7.7 ky BP (Checa et al., 2020), which onset is marked by the increase of Florisphaera profunda pointing out the formation of stable stratified waters and Deep Chlorophyll Maximum (Cascella et al., 2021). Afterwards, increases in the Warm Water Group (WWG) abundance pointed to warmer periods chronologically correlated with the major archaeological subdivisions such as the Copper Age, Early and Late Bronze Ages, and the Roman Period. Conversely, declines in the WWG and rises in the Cold Water Group (CWG) marked cooler short events at 7.4 ky BP and 4.2 ky BP, and cool intervals like the Middle Bronze Age, Iron Age, Dark Age and Little Ice Age. Calcareous nannofossils also indicated mixed and cooler surface waters during the Medieval Climate Anomaly. Particularly, the spectral analysis of the CWG signal revealed a 1.6 ky periodicity, which resulted correlatable with the onset of some Bond events (Bond et al., 2001). Throughout the record, we noted a positive correlation between Syracosphaera pulchra and δ13C values and variations in XRF trends, which indicate riverine runoff, confirming the affinity of this taxon with freshwater inputs. The North Atlantic Oscillation (NAO) atmospheric mode impact on Central Mediterranean continental runoff was investigated over the last 7.5 ky BP, using the NAO index by Smith et al. (2016). Negative NAO phases, which characterize the development of wetter winters at site latitude, coincided with episodes of higher riverine discharge highlighted by higher K/Al, lower Ca/Ti ratio values and increases in reworked coccoliths. However, from 2.3 ky BP upwards the evidence of enhanced continental runoff during positive NAO phases (i.e., drier winters) could be attributed to anthropogenic pressure.