Calcareous Nannofossils and Variation of the Kuroshio Current in the Okinawa Tro ugh During the Last 14000 Years


A quantitative census study on calcareous nannofossils from sediments of Site 1202 recovered by ODP Leg 195 and surface sediments from the East China Sea was carried out to obtain a high-resolution nannofossil record of the change of the Kuroshio Current during the late Quaternary. Two nannofossil ratio indices were designed and employed in this study: (1) ratio of Florisphaera profunda against F. profunda, Emiliania huxleyi and Gephyrocapsa oceanica (F-EG ratio) as a nannofossil proxy of the Kuroshio Current, (2) ratio of G. oceanica against F. profunda and E. huxleyi and G. oceanica (G-FE ratio) as a proxy of near-coast environment. Results from the 14 surface nannofossil samples demonstrate that the F-EG ratio is > 15% in the assemblage lying directly under the main route of the Kuroshio Current, whereas it is very low (< 10%) in sediments off the current. High ratios G-FE (> 30%) were seen from all samples on the East China Sea continental shelf or from near-coast cores.

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