Paleoclimatic meaning of a molluscan assemblage in a Tyrrhenian (MIS 5e) calcarenite (Taranto Gulf, Southern Italy)

This work shows a paleoclimatic characterization of a MIS 5e fossiliferous calcarenite from the Mar Piccolo of Taranto (MPT). Three studied samples returned 121 molluscan taxa, including 4 of the Senegalian fauna typical of modern tropical latitudes, and well known in the warmer than today MIS 5e coastal Mediterranean deposits. Mollusks indicate an infralittoral dominantly sandy/vegetated bottom, with a lateral transition from more exposed to more sheltered areas. Taxa biogeographic distributions were checked on available literature in order to identify cold affinity (i.e. living also in cool temperate seas) and warm affinity (i.e. living also in tropical seas) taxa, together with their percentages. Warm affinity species are twice as many as today, indicating warmer than today conditions, but – differently than expected - they don’t dominate over cold affinity ones. This can be explained by cold freshwater karstic inputs, today present in the MPT, that could have lowered mean temperatures. The minimal thermal requirements of the Senegalian species Thetystrombus latus were used to infer the paleotemperatures. This species requires an annual sea surface temperature (SST) of at least 21.5°C, an SST never < than 16°C in the coldest month (February), and an SST of 23°C for six months. In respect to the SST mean values recorded in the last century, the MPT water was at least 3.5°C warmer, about 5°C warmer during February, and the SST of 23°C lasted three months longer than today.