PALEOCEANOGRAPHIC CONDITIONS AT THE BASE OF THE PLIOCENE IN THE SOUTHERN MEDITERRANEAN BASIN

Detailed quantitative analyses of the benthic foraminiferal assemblage from the base of the Pliocene sections (M Pl 1 biozone) at Eraclea Mi noa and the Capo Rossello area (southern Sicily) documented fluctuatin g paleoecological conditions indicative of a dysaerobic bottom water e nvironment. In particular, we identify the Uvigerina pygmaea-peregrina Event, which in the area studied covers the upper part of the M pi 1 biozone. According to the integrated calcareous plankton biostratigrap hy and to cyclostratigraphy based on fluctuations in the relative abun dance of fauna in the planktonic foraminiferal assemblage, the base of the Uvigerina pygmaea-peregrina Event coincides with cycle ba and its top coincides with cycle 10 in the Sicilian sections. A similar tempo ral correlation is seen in the Tyrrhenian basin (ODP Site 652). On the contrary, the Uvigerina pygmaea-peregrina Event covers a longer time interval in the Jonian basin, where it is recognizable from cycle 4 to cycle 12. The Uvigerina pygmaea-peregrina Event is rime equivalent wi th an interval characterized by cyclically repeated sapropels in the e astern Mediterranean basin. As a matter of fact, 10 sapropels are pres ent in the deepsea sediments (ODP Site 969) and 10 Uvigerina pygmaea-p eregrina peaks are present in the Roccella Ionica - Capo Spartivento c omposite section in the M Pl 1 - lowest M Pl 2 biozones. The diachrono us termination of the Uvigerina pygmaea-peregrina Event may indicate t hat well-oxygenated bottom conditions were established earlier in the western than in the eastern Mediterranean basin. Both the sapropels in terval in the eastern Mediterranean and low-oxygen bottom conditions i n the Jonian basin occurred during a time interval which straddles a m inimum of eccentricity in the astronomical record.