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Suganuma Formation (Ikebe, 1940) Yasui et al., 1983

Invalid synonym: Itabatake Formation

• Type locality: Hakamazawa river, Suganuma, Chiyazawa, Nagaoka city, Niigata prefecture
• Coherent formation
• late Pliocene
• Interfingered: Tamugigawa Formation, Kurohime Formation
• Correlation: upper - middle Nishiyama Formation, Takegahana Formation, Kakuma Formation

• Depth of water: Bathyal
• Lithofacies: Mudstone
• Lithofacies (Minor): Interbedded sandstone and mudstone, Conglomerate

• Thickness: ca. 230 - 270 m
• Upper limit: Transitional (Hachioji Formation), Conformity (Higashigawa Formation), Unconformity (Kume Conglomerate)
• Lower limit: Top of Hap Tephra
• Lower limit: Conformity (Hachikokusan Formation)

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

• Distribution: Hakamazawa river, Suganuma, Chiyazawa, Nagaoka city, Kunisawa river, Oguni town, Nagaoka city, Niigata pref.; Niigata pref.; Okakuma - Yasuda - Arayashiki, Kashiwazaki city, Niigata pref.
• Fossils: Pollen
• Fossils (Shellfishes): Acila (Acila) divaricata, Acila (Acila) divaricata vigilia, Acila (Truncacila) nakazimai, Conchocele bisecta, Megacardita sp., Megayoldia thraciaeformis, Palliolum (Delectopecten) peckhami, Pandora sp., Portlandia (Portlandia) japonica
• Tephra: Fup, Sug a, Sug b, Sug c, Sug d, Sug e, Sug f, Tsp, Tgm

• Kobayashi et al. (1995) Geology of the Kashiwazaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 102p. (in Japanese with English abstract 4p.)
• 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.)