Paleoceanography during the last 150 kyr off central Japan based on diatom floras

The paleoceanographic history of the area above the northern boundary of the warm Kuroshio Current during the last two glacial–interglacial cycles was reconstructed based on high-resolution records of the diatom flora in core MD01-2421. Ecological categories of the diatom flora were extracted using Q-mode factor analysis. The four most prominent factors explained ∼91.4% of the total variance. Cross-spectral analyses were performed on temperature estimates derived from diatom data (Td′), the relative abundance of littoral–neritic diatom associations, and the oxygen isotope record of benthic foraminifera. Diatom-derived temperatures show a 50-, 23-, and 17-kyr periodicity, with only the 23-kyr band coherent with that of benthic foraminiferal oxygen isotope values. Littoral–neritic associations show a periodicity at 62 and 17 kyr coherent with Td′. Species composition and relative abundance of the diatom flora changed at the marine isotope stage boundaries, when cold-water and warm-water mixed over the core site, due to hydrographic disturbances by changes in transport trajectory of the Kuroshio Current transport and global climatic changes.