Pleistocene calcareous nannofossil biochronology at IODP Site U1385 (Expedition 339)

Abstract

During Integrated Ocean Drilling Program (IODP) Expedition 339, Site U1385 (37°34′N, 10°7′W, 2578m below sea level) was drilled in the lower slope of the Portuguese margin, to provide a marine reference section of Pleistocene millennial-scale climate variability. Five holes were cored using the Advanced Piston Corer (APC) to a depth of ~151m below sea floor (mbsf) recovering a continuous stratigraphic record covering the past 1.4Ma. Here we present results of the succession of standard and unconventional calcareous nannofossil biostratigraphic events. The quantitative study of calcareous nannofossils showed well-preserved and abundant assemblages throughout the core. Most conventional Pleistocene events were recognized and the timing of bioevents were calibrated using correlation to the new oxygen isotope stratigraphy record developed for the Site U1385. The analyses provide further data on the stratigraphic distribution of selected species and genera, such as the large Emiliania huxleyi (>4μm), Gephyrocapsa caribbeanica, Helicosphaera inversa, Gephyrocapsa omega and Reticulofenestra asanoi (>6μm) and other circular–subcircular small reticulofenestrids, resulting in new insights into the environmental control of their stratigraphic patterns. Finally, the comparison between nannofossil datums and oxygen isotope stratigraphy on the same samples has resulted in an accurate revision of timing of the events, providing valuable biochronologic information.