Chronostratigraphy and deformation of Middle terraces around Kashiwazaki Plain, Niigata, central Japan

概要

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Late Pleistocene Yasuda Formation distributed around the Kashiwazaki Plain in Niigata Prefecture is mainly composed of alternated beds of silt, sand, and sandy gravel, with intercalated beds of peat and volcanic ash. The Yasuda Formation is 12 meters in total thickness. On the basis of correlation of the volocanic ash layers with volcanic tephras distributed regionally, the Yasuda Formation is considered to have been deposited at the isotope substage 5c, and correlated with the Obaradai Formation distributed around Kanto Plain. Molluscan fossils and diatom ecological group show that the upper part of the Lower Yasuda Formation was deposited in a brackish environment. Spatial distribution of the altitude of this horizon implies fault movements after deposition of the Yasuda Formation.
日本堆積学会の論文