Calcareous nannofossil assemblages and their response to the Paleocene-Eocene Thermal Maximum event at different latitudes: ODP Site 690 and Tethyan sections

A major change in calcareous nannofossil assemblages has been reported at the Paleocene-Eocene Thermal Maximum (PETM) on a global scale. To document the response of the nannoplankton communities below, within, and above the PETM, we studied in detail six successions, representing a wide range of environments and latitudes. Calcareous nannofossil response was different in discrete paleogeographic areas. Several classical Tethyan sections (Alamedilla, Caravaca, Zumaia [Spain], Contessa [Central Italy], and Wadi Nukhl [Egypt]), plus the high-latitude Ocean Drilling Program reference Site 690 (Weddell Sea) were re-investigated using high resolution calcareous nannofossil quantitative analyses. Five assemblage zones were identified: two before the onset of the Carbon Isotope Excursion (CIE) and three after it. Before the PETM, several changes were observed in both high and low latitudes that are characterized by well-defined increases of r-selected taxa (Biscutum and Prinsius). These changes probably were in response to an upwelling pulse that increased nutrients in surface waters. These events, which predate the geochemical and oceanic changes at the PETM, indicate that there were global events occurring before the actual CIE onset.