Sequence stratigraphy of the Pleistocene Kioroshi Formation, Shimosa Group beneath the Omiya Upland, central Kanto Plain, central Japan

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 6 to early MIS 5e and most of the upper part during the gentle sea-level fall of late MIS 5e. 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.