Paleoenvironmental and paleoclimate reconstruction of a Pleistocene (MIS 5.5) fossiliferous shallow-water deposit (Mar Piccolo, Taranto, Southern Italy)

This work shows the preliminary results of a study conducted on two fossiliferous bulk samples (named T13 and T5), Tyrrenian in age (interglacial MIS 5.5), collected in 1976 in a weakly cemented calcarenite outcropping along the Mar Piccolo coastline (Taranto). The study focused on the autoecology of molluscan species, selecting those with > 1% dominance (representing about 79% of the association in T13 and 82% in T5). Both paleocommunities inhabited the lower infralittoral, dominated by the biocoenosis of Fine Well Sorted Sands (SFBC), associated with species related to vegetated bottoms [biocoenoses of Photophilous Algae (AP) and of Posidonia Meadows (HP)]; representatives of the Heterogeneous Community (PE) suggest moderate instability conditions. As indicated by the dominant biocoenosis (SFBC), sand-related species are dominant, followed by those requiring a mixed substrate; proportions of endofauna and epifauna are similar in the two samples. Despite similarity, the two samples differ in some aspects concerning the hydrodynamics of the bottom. On one hand, T13 species indicate a relatively major energy, due to the presence of the biocoenosis of Coarse Sands under Bottom Currents (SGCF) and species of intermatte channels; moreover, the presence of gravel related taxa and the dominance of suspension feeders is detected. On the other hand, T5 shows a small percentage of taxa exclusive of the biocoenosis of Superficial Muddy Sands in Sheltered Areas (SVMC), along with some of the deeper biocoenoisis of Coastal Terrigenous Muds (VTC); mud related species are more abundant and detritus-feeders dominate. It is also of note the presence in T13 (< 1%), of species referable to the so called “Senegalese fauna”, such as Persististrombus latus, Conus ermineus and Cardita rufescens, which are not detected in T5. In conclusion, both samples are indicative of a similar paleoenvironmental setting, within a locally vegetated infralittoral sandy bottom, characterized by a lateral transition from a relatively high-energy level (T13) to more sheltered bottom conditions (T5). Moreover, the subtropical to eurythermal character of all the identified bivalves along with the presence of Senegalese taxa, suggest for such MIS 5.5 interglacial calcarenite a relatively warmer climate compared to the present, as the mean of the sea-water range of the tolerance temperature of P. latus of circa 23° C is higher than the present-day yearly mean of temperature, that is circa 18° C in the interval 1918 -2004. Geochemical studies on skeletons of key species are underway to better define this aspect.