Paleoenvironmental remarks on the Caltavuturo Fm. cropping out at Portella Colla (Madonie Mts.)

Micropaleontological investigations on the Caltavuturo Formation, belonging to the Imerese domain and cropping out at Portella Colla (Madonie Mts., Northern Sicily), provide new evidence on upper Eocene-Oligocene foraminiferal assemblages. The formation consists of marly clays and several 2-30 cm thick breccia layers rich in larger foraminifers and is affected by prominent silicization and bioturbation. The clayey layers are dominated by deep-water agglutinated foraminifera (DWAF), with rare epibathyal and bathyal hyaline taxa such as Cibicidoides, which disappears in upper Rupelian sediments (Benedetti & Pignatti, in press). In the resedimented breccia layers several larger foraminiferal taxa occur: the assemblages are allochthonous but show no evidence of reworking and have been used therefore for dating the succession using the standard biozones of Serra-Kiel et al. (1998) and Cahuzac & Poignant (1997). Heterostegina reticulata italica Herb, 1978, Borelis vonderschmitti (Schweighauser, 1951), and Discocyclina dispansa dispansa (Sowerby, 1840) indicate SBZ 19 (early Priabonian); no SBZ 20 markers were found. Nummulites vascus Joly & Leymerie, 1848, Nummulites fichteli Michelotti, 1841, and Halkyardia maxima Cimerman, 1969 characterize SBZ 21, whereas Nephrolepidina praemarginata (Douvillé, 1908) and Eulepidina formosoides (Douvillé, 1925) mark the mid-upper part of the Rupelian (SBZ 22A). The smaller benthic foraminiferal assemblages in the clays are dominated by DWAF which allowed us to propose a paleobathymetric interpretation (Benedetti & Pignatti, in press). It is possible to recognise a deepening of the basin on the basis of faunal turnover, the transition from epibathyal to bathyal assemblages and oscillation of the mean value of the diameter of the protoconch of larger foraminifera such as Nephrolepidina praemarginata. Embrication of resedimented larger foraminiferal tests allows us to hypothesize a W-E direction of the flows.