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Koyanosawa Formation (Inoue, 1957) Ozawa et al., 1985

• Type locality: Koyanosawa, Koikawa, Mitane city, Yamamoto county, Akita prefecture
• Coherent formation
• Miocene
• Contemporaneous heterotopic facies: Koani Formation
• Correlation: Nishikurosawa Formation

• Sedimentary facies: Marine
• Water temperature: Warm
• Lithofacies (Main part): Mudstone, Acidic tuff
• Lithofacies (Main part, Top): Calcareous tuff, Calcareous shale
• Lithofacies (Main part, Minor): Tuffaceous sandstone, Tuffaceous conglomerate
• Lithofacies: Basalt lava, Pyroclastic rocks

• Thickness (Overall): 200 - 700 m
• Thickness (Main part): 100 - 300 m
• Upper limit: Bottom of hard shale overlying acidic tuff or mudstone beds (Onnagawa Formation, Ozawa et al., 1985)
• Upper limit: Conformity (Onnagawa Formation), Unconformity (Ishikurayama Formation)

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

• Distribution: Koyanosawa, Koikawa, Mitane city, Yamamoto county, Akita pref.; Yamane, Gojome city, Minamiakita county, Akita pref.
• Fossils: Plants, Echinoids (Echinoidea sp.), Radiolarians
• Fossils (Shellfishes): Adamnestia sp., Astarte sp., Dentalium yokoyamai, Fusitoriton sp., Palliolum peckami, Propeamussium tateiwai, Protothaca sp.
• Fossils (Foraminifera): Bathysiphon sp., Discorbis sp., Florilus kidoharaense, Globigerina cf. bulloides, Globigerina incompta, Globigerina woodi, Gyroidinoides sordanii, Haplophragmoides sp., Hopkinsina sinboi, Martinottiella bradyana tarukiensis, Miogypsina kotoi, Pararotalia tochigiensis, Pullenia bulloides, Sigmoilina sp., Sigmoilopsis schlumbergeri, Spirosigmoilinella compressa, Uvigerina sp.

• Ozawa et al. (1985) Geology of the Ugo-Hamada District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 57p. (in Japanese with English abstract 4p.)
• Ozawa et al. (1985) Geology of the Moritake District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 69p. (in Japanese with English abstract 5p.)
• Hase and Hirayama (1970) Geology of the Gojome District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 46p. (in Japanese with English abstract 6p.)