Résumé
Quantitative analysis of radiolarian assemblages was conducted on sediment cores collected from the seafloor during Integrated Ocean Drilling Program Expedition 346. During Expedition 346, Site U1427 was cored in the shelf region of the Yamato Basin, southern Japan Sea, to 570 m core composite depth below seafloor (CCSF-A) in Hole U1427A. Radiolarian biostratigraphy conducted for this site identified four datum levels: last occurrence (LO) of Lychnocanomma sakaii (0.054 Ma), LO of Amphimelissa setosa (0.085 Ma), LO of Schizodiscus japonicus (0.29 Ma), and first occurrence (FO) of Amphimelissa setosa ( approximately 1.48 Ma). In addition, the abundance maxima of subtropical water species, which indicate migration of the Tsushima Warm Current from the East China Sea associated with eustatic sea level rise during interglacial periods, are most likely correlated with the marine isotope stages during the past 1.5 My.