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Umikawa Formation (Shimazu et al., 1976) Nagamori et al., 2010
Invalid synonym: Umikawa Volcanic Rocks, Awakura Agglomerate
- Type locality: Umikawadaini power plant - Ebikura, Umikawa river, Itoigawa city, Niigata prefecture
- Andesite submarine volcano
- Volcanic rocks
- Pliocene (3.92 - 3.16 Ma, K-Ar)
- Contemporaneous heterotopic facies: lower Nadachi Formation, upper Nechi Formation
- Intruded by: Basalt dykes, Rhyolite - Dacite dykes
- Sedimentary facies: Subaqueous
- Lithofacies: Andesite - Basalt lava, Volcanic breccia, Tuff breccia
- Lithofacies (Minor): Rhyolite -Dacite lava, Volcanic breccia, Lapilli tuff, Sediments
- Itoigawa, Niigata pref.
- [ Upper ]
- --------------
- Tanne Formation
- ~~~~~~~~~~~~~~
- Umikawa Formation
- ~~~~~~~~~~~~~~
- [ Lower ]
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Umikawa river - Tannegawa river, Itoigawa city, Niigata city, Niigata pref.
- Nagamori et al. (2018) Geology of the Itoigawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 75p. (in Japanese with English abstract 3p.)
- Nagamori et al. (2010) Geology of the Kotaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 130p. (in Japanese with English abstract 4p.)
- Takeuchi et al. (2010) Jour. Geol. Soc. Japan, vol.116, Supplement, pp.123-142 DOI