Paleoenvironmental conditions at Core KC01B (Ionian Sea) through Oxygen Isotope Stages 13-9: evidences from calcareous nannofossil assemblage

Quantitative analyses on calcareous nannofossil assemblages on high temporal resolution (600-800 years) have been carried out from Core KC01B in the Ionian sea (Eastern Mediterranean) throughout Marine Isotope Stage (MIS) 13-9, between 500-300 kiloyears. This is an interval of considerable climate changes known as Mid-Brunhes event, which includes MIS 11, that is considered as a possible analogue for future interglacial conditions. At the Mediterranean core the interval is characterized by the dominance of Gephyrocapsa spp. as also known from ocean records. Calcareous nannofossil abundance fluctuations have been interpreted in terms of modification of sea surface primary productivity/water stratification and temperature. Specifically, increase in abundance of Gephyrocapsa caribbeanica and small Gephyrocapsa coupled with decrease of F. profunda, Syracosphaera spp. and Rhabdosphaera spp. suggests enhanced primary productivity/mixed surface waters during interglacial stages and at the Terminations which can be interpreted in terms of interaction between climate changes and mesoscale oceanographic circulation. On the other hand, distributions of Calciosolenia spp., Oolithotus spp. and Umbilicosphaera sibogae, which are in phase with 18O curve showing higher abundances at the lighter values of the oxygen isotope record,, are considered as warm-water indicators. Biotic proxies point to a peculiar climate dynamics through MIS 12-11 transition (i.e. Termination V). High productive, cool, low salinity and turbid surface waters characterize the early MIS 11 (421-408 ky) and likely reflect enhanced continental humidity/monsoon activity over North Africa and increased runoff into the basin. A late surface water warming with respect to Termination V is established at about 403 ky, during a period of low insolation forcing almost coeval with the deposition of sapropel S11. A climate optimum, lasting about 15 ky (403-389 ky), is then recorded during a period of low insolation forcing centred at 398 ky. The later part of MIS 11 is characterized by climate deterioration at about 389 ky. Comparison with results from subtropical to polar Atlantic records suggests a remarkable relation between Mediterranean and Atlantic climate regime.