Presentation Information
[G-P-20]Relationship Between Radiolarian Biostratigraphy and Climate Evolution in the Central Northwest Pacific Over the Past 10 Million Years (ODP Site 1208)
*Kenji Matsuzaki1, Shin-Ichi Kamikuri2 (1. Atmosphere and Ocean Research Institute, The University of Tokyo , 2. Faculty of Education, Ibaraki University)
Keywords:
Radiolarian Biostratigraphy,International Ocean Drilling Program,Central North Pacific,Paleoceanography
Although radiolarian biostratigraphy has been pioneered at numerous ODP and IODP sites since the 1970s, the Central Pacific remains poorly studied. Yet this region is critical for paleoceanography, acting as a transition zone between major circulation regimes and recording global climatic shifts. To fill this gap, we examined 10 million years of sediment from ODP Site 1208 on Shatsky Rise and developed the first comprehensive radiolarian biostratigraphic scheme for the Central Northwest Pacific. We recognize eleven distinct Interval Zones and fifty key bioevents with three of which are newly defined and five of which involve the emendation or renaming of existing zones. Our framework reveals three principal faunal turnovers that coincide with major climate transitions: the Late Miocene Global Cooling Event (~8–5.5 Ma), which saw subtropical taxa retreat in favor to subarctic species; the Pliocene Warming Events (~5.3–3.0 Ma), marked by a rebound of subtropical forms; and the onset of Northern Hemisphere Glaciation (~3.0–2.6 Ma), characterized by the extinction of ancient lineages and the emergence of modern subarctic assemblages. Subsequent Pleistocene climatic fluctuations further refined these assemblages.