Neogene-Quaternary Mediterranean calcareous nannofossil biozonation and biochronology: A review

The present study focuses on calcareous nannofossil biostratigraphy of the last 23 Myr in the Mediterranean region and is intended as a review paper in which an updated zonation is presented. This includes the improvements in biostratigraphic classification achieved in the last decades. The proposed biozonal scheme incorporates the biochronologic data derived from the integration of biostratigraphically useful events with radiometric datings, magnetostratigraphy and astronomically tuned cyclostratigraphy. This biochronology directly derives by previous compilations and includes improved data and ages derived from recent studies based on high resolution quantitative analysis of nannofossil assemblages. The presented zonal scheme consists of 21 biozones and 35 subzones spanning the last 23 Myr, named according to the well-established code-system MNN (Mediterranean Nannofossil Neogene) for the Miocene and Pliocene time interval and MNQ (Mediterranean Nannofossil Quaternary) for the Pleistocene and Holocene. In addition, a revision of the nannofossil biostratigraphy at the Oligocene/Miocene transition is given, with the introduction of Zone MNP26 (Mediterranean Nannofossil Paleogene), as a result of the different age assigned to the Oligocene/Miocene chronostratigraphic boundary. This zonation provides a significant bio-chronostratigraphic resolution of about 0.5 Myr, corresponding to a degree of precision functional for dating sedimentary successions and, therefore, useful for geological studies (e.g. geological mapping, temporal scanning of geological phasis). The biostratigraphic resolution can be furtherly improved through integration with the analogous scheme recently established for planktonic foraminifers.