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Quaternary surface water conditions within the Japan Sea change with eustatic sea-level changes and fluctuations in the East Asian Summer Monsoon (EASM), influencing regional climate and vegetation through the delivery of heat and moisture. Our marine pollen data suggest overall cooling from the Last Interglacial (ca. 125 ka) to the Last Glacial Maximum (LGM), a cold climate during Marine Isotope Stage (MIS) 2, gradual warming from 12 ka and rapid warming after 10 ka. These stages are concordant with published palaeoceanographic changes in the Japan Sea. During mid MIS 5 to MIS 3, marine sediments in the Japan Sea are characterised by fine alternations of dark-and light-coloured layers that formed under the influence of fluctuations in the EASM, possibly correlated with Dansgaard-Oeschger cycles. During the deposition of dark layers, high levels of precipitation are inferred from the abundance of Cryptomeria. In contrast, a cool and dry climate is interpreted for the light layers, based on an abundance of subarctic conifer pollen. The palaeoclimate of the Japan Sea region appears to have been influenced by orbital-scale changes in global climate and millennial-scale fluctuations in the EASM.

In this paper, we discuss depositional process and sequence stratigraphy of the Pleistocene Kioroshi Formation, Shimosa Group beneath the Omiya Upland, central Kanto Plain, central Japan. On the basis of sedimentary facies and fossil data such as molluscan and diatom assemblages, the Kioroshi Formation can be subdivided into the lower and upper parts which were formed by a incised-valley system and a barrier-island system, respectively. Each part represents successive upward-fining and upward-coarsening units composed mainly of mud and/or thin-interbedded sand and mud. Based on the correlation between pollen zones, tephrochronology, and the MIS curve, the lower part is considered to have deposited during the sea-level rise of MIS to early MIS e and most of the upper part during the gentle sea-level fall of late MIS e. The sea levels suggest that the incised-valley system is interpreted as lowstand and transgressive systems tracts and the barrier island system as a highstand systems tract.

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