NEW DATA ON MIDDLE TO LATE MIOCENE CALCAREOUS PLANKTON BIOSTRATIGRAPHY IN THE MEDITERRANEAN AREA

Planktonic foraminifera from one Atlantic Ocean (Site 397) and five Me diterranean sequences of middle to late Miocene age were investigated. The aim of the research was to refine the biostratigraphy of the Serr avallian to early Tortonian interval and, since the recent literature provides no general consensus, to check the range of Neogloboquadrina acostaensis (Blow) and Paragloborotalia siakensis (Le Roy). Examinatio n of planktonic foraminifera identified a succession of events which i s, in part, new in the Mediterranean area, and documented an overlap i n the distribution of N, acostaensis and P.lia siakensis. Based on the new data, the zonal scheme for the Serravallian to early Tortonian in terval proposed by Iaccarino and Salvatorini (1982) and Iaccarino (198 5) was emended. In particular, it was ascertained that the first occur rence (FO) of N. acostaensis falls in the upper part of the Serravalli an, well before the last occurrence (LO) of P.lia siakensis. The new z onation was calibrated with the calcareous nannofossil zonation and th e geomagnetic polarity time scale. In light of these new data, the eve nts closest to the base of the Rio Castellania-Rio Mazzapiedi-Tortonia n type-section are the LO of P.lia siakensis, the first common occurre nce (FCO) of N. acostaensis, and the FO of Discoaster hamatus.. Theref ore, the use of these events in selecting the GSSP of the Serravallian /Tortonian boundary is recommended.