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Higashigawa Formation Noda, 1962

Invalid synonym: Fukushima Formation, Mizunashi Formation

• Type locality: Higashi river, Akakura, Matsunoyama, Tokamchi city, Niigata prefecture
• Coherent formation
• Rift basin sediments
• late Pliocene (ca. 3 Ma)
• Correlation: Nishiyama Formation, Hachioji Formation, Asojima Formation, Minagawa Formation
• Correlation (Upper): Uonuma Formation

• Sedimentary facies: Shallow marine
• Water temperature: Cold ocean current
• Depth of water: Lower sublittoral (50 - 200 m, Shellfishes, Foraminifera)
• Lithofacies: Interbedded sandy siltstone and siltstone
• Lithofacies (Minor): Sandstone, Volcanic ash
• Sedimentary structures: Channel structure

• Thickness: 50 - 600 m
• Upper limit: Interfingered (Uonuma Formation), Conformity (Karigamine Member)
• Lower limit: Bottom of the horizon mainly composed of silty mudstone
• Lower limit: Transitional (Tamugigawa Formation), Conformity (Kurohime Formation, Suganuma Formation)

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

• Distribution: Higashi river, Akakura, Matsunoyama, Tokamchi city, Niigata pref.; Ishiguro river, Takayanagi town, Kashiwazaki city, Niigata pref.
• Fossils: Baleen whales (Bones), Echinoids, Trace fossils
• Fossils (Omma-Manganji fauna): Macoma sp., Tectonatica janthostomoides
• Fossils (Foraminifera): Ammonia cf. beccarii, Ammonia japonica, Ammonia takanobensis, Baggina totomiensis, Bolivina robusta, Brizarina decussata, Buccella frigida, Bucella frigida carida, Bulimina marginata, Cassidulina norcrossi, Cassidulina yabei, Cibicides cf. reflugens, Cibicides ungerianus, Cribrononion clabatum, Cribrononion subglanulosum, Cribrostomoides cf. subglobosum, Discorbis spp., Elphidium advenum, Elphidium etigoense, Epistominella pulchella, Eponides nipponicus, Fissulina sp., Florilus japonica, Florilus manpukujiensis, Globigerina bulloides, Globigerina incompta, Globigerina pachyderma, Globigerina quinqueloba, Guttulina spp., Hanzawaia nipponica, Islandiella japonica, Lenticulina sp., Loxostomun bradyu, Miliammina echigoensis, Planulina wuellerstorfi, Polystomellina discorbinoides, Pseudorotalia gaimardii, Quinqueloculina spp., Sigmoilopsis cf. schlumbergeri, Uvigerina subperegrina
• Tephra: Isg-h, Chitose Tuff, Akakura Tuff, Kamiebiike Tuff

• Takano (2011) Jour. Geol. Soc. Japan, vol.117, no.4, pp.238-258 DOI
• Takeuchi et al. (2000) Geology of the Matsunoyama Onsen District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 76p. (in Japanese with English abstract 5p.)
• Kobayashi et al. (1989) Geology of the Okanomachi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 112p. (in Japanese with English abstract 5p.)