Paleoclimatic implications of a paleoecological study on a Tyrrhenian calcarenite (Mar Piccolo, Taranto, Southern Italy)

This work shows the preliminary results of a study conducted on two bulk-samples from the Mar Piccolo of Taranto, collected in 1976 from a weakly cemented Tyrrhenian calcarenite, from P.ta della Penna (sample T13) and south of Masseria S. Pietro (sample T5). The study focuses on molluscan species with >1% dominance (representing about the 79% of the association in T13 and the 82% in T5). Autoecological data indicate a lower infralittoral location for both paleocommunities. According to this relatively shallow settlement, the biocoenosis of Fine Well Sorted Sands (SFBC) dominates, associated with those related to vegetated bottoms [biocoenoses of Photophilous Algae (AP) and of Posidonia Meadows (HP)]; representatives of the Heterogeneous Community (PE) are present as well, suggesting moderate instability conditions. In both samples, percentages of endofauna and epifauna are comparable and sand-related species are dominant, followed by those requiring a mixed substrate. The major differences between the two samples are: 1) the presence in T13 of species related to the biocoenosis of Coarse Sands under Bottom Currents (SGCF) along with taxa inhabiting the intermatte channels, denotes a relatively high energy level of the environment, whereas a small percentage of taxa exclusive of the biocoenosis of Superficial Muddy Sands in Sheltered Areas (SVMC), present only in T5, points toward a more protected area for this paleocommunity; 2) in addition to sand-related species which are dominant in both samples, in T13 gravel-related taxa are present whereas in T5 mud-related ones are detected; 3) suspension-feeders are dominant in T13 and detritus-feeders are prevalent in T5. It is also of note the presence in T13, even if < 1% of dominance value, of species referable to the so called "Senegalese fauna", such as Thetystromubus latus (= Strombus bubonius), Conus ermineus and Cardita rufescens, which are not detected in T5. In conclusion, both samples are indicative of a similar paleoenvironmental frame, i.e. an infralittoral sandy bottom, locally vegetated, characterized by a lateral transition from a relatively high-energy setting (T13) to more sheltered bottom conditions (T5). The subtropical to eurythermal character of all the identified bivalves, along with the presence of Senegalese taxa, suggests for the considered Tyrrhenian calcarenite a climate relatively warmer than the present one: in fact, the mean sea-water temperature required by T. latus is about 25 °C, whereas the one yearly measured during the time span 1918-2004 ranges from 17,3 to 19°C; geochemical studies on key-species skeletons are underway to better define this aspect.