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Akaishi Formation (Shibayama, 1929) Yagi, 1942
Invalid synonym: upper part of Ajigasawa Formation
- Type locality: Hitotsumori - Yamako, Fukaura city, Nishitsugaru county, Aomori prefecture
- Type locality: Tsuchimoriyama forest road, Kuromori - Matsudai, Fukaura city, Nishitsugaru county, Aomori prefecture
- Coherent formation
- late Miocene - early Pliocene (7 - 4 Ma, Diatom, Funakawa stage)
- Intruded by: Rhyolite dike
- Sedimentary facies: Marine
- Sedimentary facies: Submarine pyroclastic flow
- Lithofacies: Mudstone, Siltstone
- Lithofacies (Minor): Acidic pumice tuff, Turbidite sandstone, Scoria tuff, Conglomerate, Graconite sandstone
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Akaishi river, Ajigasawa city, Nishitsugaru county, Aomori pref.; Hitotsumori - Yamako, Fukaura city, Nishitsugaru county, Aomori pref.; Tsuchikurayama forest road, Kuromori - Matsudai, Fukaura city, Nishitsugaru county, Aomori pref.; Kodoji river - Odoji river, Fukaura city, Nishitsugaru county, Aomori pref.; Doronosawa creek, Iwasaki, Fukaura city, Nishitsugaru county, Aomori pref.; Omagoshi, Fukaura city, Nishitsugaru county, Aomori pref.
- Fossils: Whales, Shellfishes (Chlamys akitana), Sponges (Makiyama chitanii), Diatoms (Coscinodiscus sp. A cfr. nodulifer, Denticulopsis kamitschatica), Radiolarians (Spongurus pylomaticus)
- Fossils (Foraminifera): Milliammina echigoensis, Cassidulina japonica, Eponides karsteni, Bulimina pyrula, Angulogerina kokozuraensis, Epistomina elegans, Elphidium subgranulosum, Gaudryina cfr. oga, Cibicides pseudoungerianus, Planulina mediterransis, Lagena sulcata, Polystomellina discorbinoides, Globigerina spp.
- Sakai et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.4, pp.297-305 DOI
- Hirayama and Uemura (1985) Geology of the Ajigasawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 86p. (in Japanese with English abstract 6p.)
- Ozawa and Hirayama (1970) Geology of the Goshogawara District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 25p. (in Japanese with English abstract 3p.)
- Moritani (1968) Geology of the Fukaura District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 57p. (in Japanese with English abstract 5p.)
- Ozawa (1963) Iwadate, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 14p. (in Japanese with English abstract 3p.)