新潟平野北東織部の第四系と地殻変動
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概要
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This paper discusses the Quaternary stratigraphy and tectonic movements around the northeastern marginal area of the Niigata Plain. Representative Quaternary in this area is divided into the Shimokonakayama, Nashinoki, Kushigata, Yokooka, Oosawa, and Harukiyama Formations in ascending order. They are overlain by the river terrace and alluvium deposits. The Shimokonakayama Formation comprises gravels and sands, and is about 10m in thickness. This formation unconformably overlies the Pliocene. The Nashinoki Formation is composed mainly of silt and sands, with channel fill gravels and colluvial gravels. This formation with thickness of 30m unconformably overlies the Shimokonakayama Formation. The Kushigata, Oosawa and Harukiyama Formations are debris flow deposits which are composed of boulder gravels. The Yokooka Formation comprises well sorted fine sands. The stratigraphic correlations between the study area and adjacent areas are clarified. Representative correlations are follows. The Shimokonakayama and Nashinoki Formation are correlated with lower Pleistocene Yamadera and middle Pleistocene Sasagami Formations, respectively. The Kushigta and Yokooka Formations are correlated with middle Pleistocene Gozu gravel bed and "Ancient Sand Dunes on higher terraces" respectively. In the southern part of the study area, upper part of the Quaternary deposit includes a large amount of grvels derived from the Kushigata Range, and each Quaternary formation overlaps the older strata accompanying the uplifting of the Kushigata Range and subsidence of the basin. These geologic features are very similar to one of the Sasagami area, where situated on the Shibata-Koide Tectonic Line. In the northern part of the study area, however, the newer layers hardly overlap the older strata in the hilly land, and the Quaternary deposits have a small amount of gravels derived from the hills back of the basin. The northern part of study area is situated in the north end of the Shibata-Koide Tectonic Line. According to these Quaternary features, block uplifting and subsiding is generally obvious on the Shibata-Koide Tectonic Line, but the north end of the line is characterized by gentle folding instead of block uplifting and subsiding.
- 地学団体研究会の論文
- 1994-01-25
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