Biogeographic and paleoclimatic characterization of Tyrrhenian (MIS 5e) molluscan assemblage from the Mar Piccolo of Taranto

This contribute shows the preliminary result of a paleoenvironmental study achieved on three MIS 5e fossiliferous bulk-samples from the Mar Piccolo of Taranto (MPT), Ionian Sea. The sampled level, a weakly cemented calcarenite, is characterized by the presence of elements of the “Senegalese Fauna”, indicative of warmer climatic conditions, compared to present; four of these species have been detected in our samples, i.e. Thetystrombus latus (Gmelin, 1791), Conus ermineus Born, 1778, Cardita rufescens Lamarck 1819, and Hyotissa hyotis (Linnaeus 1758). The other 117 identified taxa are still present in the Mediterranean. The association, as a whole, indicates a lower infralittoral dominantly sandy-vegetated bottom, with lateral transition either to more exposed, or more sheltered conditions. Biogeographic distribution of all taxa have been checked on gbif.org (2022) and several checklists, in order to perform a climatic characterization of MIS 5e interval. Species have been grouped into two categories: those with cold affinity (i.e. living also in northern cool temperate seas) and those with warm affinity (i.e. living also in southern, tropical seas). Results show that percentage of warm affinity species during MIS 5e is twice as many as today, testifying the expected warmer conditions; however, percentages of warm and cold affinity taxa in the fossil assemblage are comparable, suggesting a local, relatively less warm than expected situation, possibly related to cold freshwater karstic inputs, as observed today in MPT. Minimal – rather than optimal - thermal constraints of T. latus were used to estimate how warmer the MIS 5e MPT was in respect to present. T. latus requires 1) an annual mean SST of at least 21.5°C, 3.5°C higher than that recorded in the last century; 2) a SST of at least 16°C in the coldest month (February), about 5°C higher than present; 3) 6 months with a mean SST>23°C, so that these conditions lasted three months longer than today.