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Kotsunagizawa Formation Kitamura, 1959

• Type locality: Kotsunagi creek, Nishiwaga city, Iwate prefecture
• Coherent formation
• Half-graben
• middle Miocene (14 - 11 Ma, FT; 13.5 - 11.9 Ma, Foraminifera; 13.6 - 11.8 Ma, Calcareous nannofossils, 11.1 Ma, FT)

• Sedimentary facies: Marine
• Depth of water (Top): Inner sublittoral
• Depth of water (Lower - upper): Middle bathyal
• Lithofacies: Mudstone
• Lithofacies (Minor): Sandstone, Tuff, Basaltic volcaniclastics

• Thickness: 100 - 400 m
• Upper limit: Conformity (Onnagawa Formation), Unconformity (Kurosawa Formation)
• Lower limit: Conformity (Oishi Formation, Kawashiri Tuff Member)

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

• Distribution: Kotsunagi creek - Kacchi - Koonigase river, Nishiwaga city, Iwate pref.
• Fossils: Bivalves, Sponges (Aphrocallistes sp.), Calcareous nannofossils
• Fossils (Foraminifera): Angulogerina sp., Bathysiphon sp., Bulimina kamedaensis, Bulimina pupoides, Bulimina striata, Cassidulina japonica, Cassidulina kashiwazakiensis, Cawidulina yabei, Cibicides malloryi, Cibicides pseudoungerianus, Cyclammina japonica, Cyclammina pusilla, Cyroidina cf. soldanii, Dorothia sp., Elphidium sp., Entosolenia sp., Epistominella cf. pulchella, Eponides umbonatus, Globigerina sp., Globobulimina perversa, Globorotalia fohsi barisanensis, Guttulina pacifica, Guttulina yabei, Guttulina yamazakii, Gyroidina orbicularis, Gyroidina soldanii, Hapkinsina sinboi, Haplophragmoides sp., Lagena sp., Lagenodosaria scalaris, Martinottiella communis, Miliammina? sp., Nodosaria sp., Nonion cf. japonicum, Nonion kidoharaense, Nonion nicobarense, Nonion pompilioides, Nonion subturgidum, Plectofrondicularia goharai, Pseudoglandulina laevigata, Pullenia bulloides, Pullenia quinqueloba, Robulus nikobarensis, Sigmoilina schlumbergeri, Sigmomorphina sp., Sphaeroidina cf. compacta, Spirosigmoilinella compressa, Trochammina nobensis, Valvulineria cf. sadonica, Virgulina ishikiensis

• Hosoi et al. (2018) Jour. Geol. Soc. Japan, vol.124, no.10, pp.819-835 DOI
• Hosoi and Amano (2013) Jour. Geol. Soc. Japan, vol.119, no.9, pp.630-646 DOI
• Hosoi and Amano (2012) Jour. Geol. Soc. Japan, vol.118, no.8, pp.493-498 DOI
• Ozawa et al. (1971) Geology of the Kawashiri District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 40p. (in Japanese with English abstract 5p.)