The A.D. 472 eruption of the Somma volcano

The results of a detailed quantitative and statistical analysis on benthic foraminiferal assemblages from the Langhian Cretaccio composite section cropping out at Tremiti Islands (southern Adriatic Sea, eastern Mediterranean Sea) are presented. The distribution patterns of the species allowed us to estimate a paleodepth of about 600 m for the entire composite section. The abundance curve of the oxic species indicates relatively well-oxygenated conditions of bottom water masses with a weak but gradual decline which culminates at about 37-38 m after the First Occurrence (FO) of Orbulina suturalis. The discontinuous distribution of Cibicidoides wuellerstorfi is suggested to be indicative of alternating episodes of active and relatively sluggish circulation of bottom water masses. Two major changes in the benthic foraminiferal assemblages are recorded along the succession. The first one occurring in correspondence of the lithological colour change at about 15 m is characterized by the sharp decrease of Bulimina costata, Gyroidina spp., Hanzawaia boueana and Melonis barleeanum testifying a decrease in productivity. The second one is more gradual and it is characterized by the regular increase of Uvigerina semiornata and U. striatissima/rom 8 m to 37-38 m indicating a gradual change in oxygen content. A third, less pronounced change concerns the last meters of the section, suggesting an amelioration of the bottom conditions. These changes are interpreted as the first response to paleoceanographic variations related to the closure of the connections between Tethyan and Indo-Pacific water masses. In term of chronology the section is estimated spanning the interval preceding the Paracme End (PE) of Sphenolithus heteromorphus (estimated approximately at 15.65 Ma) and postdating the FO of O. universa (dated at 14.36 Ma).