The Capo Rossello bore-hole (Agrigento, Sicily): Cyclostratigraphic and paleoceanographic reconstructions from quantitative analyses of the Zanclean foraminiferal assemblages

Cyclostratigraphy based on the quantitative analyses of planktonic foramini fera in the Zanclean segment (M Pl 1- base of M Pl 3 biozones) of the bore- hole drilled in the Capo Rossello area (Sicily, Southern Italy) allows us t o recognize that the calcareous plankton biostratigraphic events occur in t he same cycles as identified by previous authors. Exceptional thick cycles which are thought to represent two precession cycles show two fluctuations of Globigerinoides spp. Therefore the number of identified fluctuations is greater than the number of lithologic cycles. Between the base of the Plioc ene and the first occurrence of Globorotalia puncticulata thirty-five litho logic cycles and thirty-eight planktonic foraminifera fluctuations are pres ent. By comparison with relative abundance fluctuations of Globigerinoides spp., a clear relationship between the relative abundance fluctuations in the be nthic foraminifera and the astronomical record is recognized. In particular , the BN > 125 mu m and the Planulina ariminensis quantitative distribution s are related to the long eccentricity. Conversely, the relative abundance fluctuations of Siphonina re ticulata, Cibicidoides bradyi, Pullenia bulloi des and Uvigerina pygmaea appear to be generally forced by the precession p eriodicity, but in the intervals coincident with the eccentricity minima su ch a relationship is less clear. The very abundant and widespread distribution in several Mediterranean sire s of S. reticulata, which we consider a quasi-endemic species of this basin during the Early and Middle Pliocene is anticovariant with the quantitativ e distribution of Cibicidoides bradyi-robertsonianus, which is considered a characteristic species of the North Atlantic Deep Water (NADW). This relat ionship suggests that a peculiar, intermediate water mass was present in th e Mediterranean during this time interval. We propose for this water mass t he name of Early Pliocene Mediterranean Intermediate Water (EPMIW). Accordi ng to bibliographic data that report the sharp decrease in abundance of S. reticulata during the M Pl 5 biozone, EPMIW was present in the Mediterranea n basin until about 2.5 Ma.