Micropaleontological data and inferred paleoenvironment of Early Zanclean Piedmont area (Norwestern Italy)

New micropaleontological and stratigraphical analyses, still in progress, have evidenced a well preserved succession encompassing the Messinian/Zanclean boundary and the Early Pliocene in the central Piedmont, from the Turin Hill (Moncucco T., Bicchi et al., 2002) to the Astigiano (Irace et al., 2005) and along the Tanaro river (Albese). Previously, the M/Z boundary was only briefly described by Sturani (1978) in the Narzole (Alba, CN) borehole and the oldest Zanclean deposits were never recovered in outcrops. The Pliocene succession of Piedmont was widely know in literature for its rich fossil assemblages, allowing the identification of a marine sedimentation that spans the MPl2 - MPl4 foraminiferal zones (Violanti, 2005). In the Moncucco quarry outcrop and borehole and in the Narzole borehole, quantitative micropaleontological analyses were carried out on foraminifers, calcareous nannofossils and ostracods. In both these sites, many bioevents recognized at the Mediterranean scale progressively occurred at stratigraphic distances from the M/Z boundary similar to the ones recorded in southern Mediterranean areas: a basal abundance peak of Globigerina nepenthes, sinistral coiling shifts of Neogloboquadrina acostaensis, the Globorotalia scitula common occurrence (CO), the re-immigration of Siphonina reticulata and the Globorotalia margaritae first common occurrence (FCO). Rare specimens of Ceratholithus acutus have been recorded at the very base of the Zanclean. The MPl1 assemblages were characterized by very high P/(P+B) ratios, by mesopelagic planktonic foraminifers as Sphaeroidinellopsis spp., deep benthic foraminifers (Cibicidoides robertsonianus, Uvigerina peregrina), common bathyal ostracods (Argilloecia kissamovensis, Paijenborchella jocosa), rare discoasterids and ceratholiths, tropical open marine taxa (Amaurolithus primus, A. delicatus). Foraminiferal and ostracod assemblages document an epibathyal basin just from the Early Zanclean. Moreover, a deepening of the basin during the MPl1, from about 500 m to about 1000 m depth, is inferred by the increasing diversity of benthic foraminifers and of deep bathyal ostracods. All paleobiological data suggest open sea conditions and a deep bottom circulation during the MPl1-MPl2 Early Pliocene zones. References Bicchi E., Cavagna S., Clari P., Dela Pierre, Irace A. & Boano P. (2002). La cava di gesso di Moncucco Torinese. In Polino R. (ed.) Il Sistema Alpino-Appenninico nel Cenozoico, 81a Riun. Est. Soc. Geol. It., Guida all’escursione, 152-158. Irace A., Dela Pierre F & Clari P. (2005). «Normal» and «chaotic» deposits in the Messinian Gessoso Solfifera Formation at the north-eastern border of the Langhe domain (Tertiary Piedmont Basin). Boll. Soc. Geol. It., Vol. Sp., 4: 77-85. Sturani C. (1978). Messinian facies in the Piedmont Basin. Mem. Soc. Geol. It., 16: 11-25. Violanti D. (2005) – Pliocene Foraminifera of Piedmont (north-western Italy): a synthesis of recent data. Ann. Univ. St. Ferrara – Mus. Sc. Nat., Spec. Vol., 75-88.