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Nishikurosawa Formation (Ohashi ex Toyama, 1925) Shikano et al., 2011
- Type locality: Nishikurosawa fishport, Oga city, Akita prefecture
- Coherent formation
- middle - late Miocene (17 - 12.3 Ma, Diatoms)
- Correlation: Umanokamiyama Formation, Manzaemonyama Formation, Tomarikawa Mudstone Member, Koyanosawa Formation, Gongenyama Formation, Sugota Formation, Aosawa Formation, Tobishima Formation, Numazawa Formation, Nishikurosawa Formation, Tanashigawa Member
- Sedimentary facies: Marine - Brackish
- Sedimentary facies (Upper): Offshore, Mud floor, Cold sea (Bivalves)
- Sedimentary facies (Middle): Open sea, Shallow marine, Sands and gravels floor (Bivalves)
- Sedimentary facies (Lower): Brackish, Warm shallow sea (Bivalves)
- Sedimentary facies (Lower): Lavinement deposit
- Lithofacies (Upper): Porcelanite
- Lithofacies (Lower): Conglomerate, Limestone, Siltstone
- Lithofacies (Minor): Glauconite sandstone, Acidic tuff, Basaltic pyroclastic rocks
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Nishikurosawa, Oga city, Akita pref.; Daijima - Onnagawa, Oga city, Akita pref.
- Fossils: Calcareous sponges, Foraminifera, Diatoms
- Fossils: Paleoparadoxia sp., Isurus hastalis, Lagnidae (Astriclypeus mannii ambigenus), Brachiopods (Coptothyris sp., Terebratalia sp.), Balanus sp., Calcareous sponges (Aphrocallistes sp.), Diatoms, Trace fossils (Nerites isp.)
- Fossils (Upper, Bivalves): Nuculana sp., Halicardia sp., Cyclocardia sp., Thracia sp., Cultellus sp., Fulgoraria sp.
- Fossils (Middle, Bivalves): Chlamys sp., Placopecten sp., Mizuhopecten sp., Kotorapecten sp., Gloripallium sp.
- Fossils (Lower, Bivalves): Vicaryella sp., Cypraea sp., Anadara sp., Dosinia sp., Meretrix sp.
- Fossils (Bivalves): Acila submirabilis, Anadara makiyamai, Anomia chinesis, Bittium sp., Calliostoma sp., Chicoreus sp., Chlamys akitana, Chlamys cf. arakawai, Chlamys cosibensis hanzawae, Clathurella sp., Clementia papyracea, Clinocardium sp., Crassostrea sp., Cultellus izumoensis, Cyclina cf. lunulata, Dosinia nomurai, Glycymeris sp., Leukoma itoigawae, Macoma sp., Masudapecten iwasakiensis, Mercenaria yokoyamai, Mizuhopecten sp., Natica sp., Saccella cf. toyamensis, Sinum yabei, Siratoria siratoriensis, Teredo sp., Vasticardium ogurai, Veremorpha minoensis
- Fossils (Daijima-type flora): Carya sp. (Pollen), Cyclobalanopsis mandraliscae, Cyclobalanopsis nathorstii, Fagus sp. (Pollen), Glyptostrobus europaeus, Liquidambar (Pollen), Machilus ugoana, Quercus miovariabilis, Quercus sp. (Pollen), Zelkova sp. (Pollen), Cones
- Fossils (Nishikurosawa fauna, Foraminifera): Alabamina japonica, Ammonia tochigiensis, Ammonia cf. yubariensis, Amphistegina lessoni, Bolivina asanoi, Buccella akahiraensis, Buccella mansfieldi, Buccella tanaii, Elphidiella momiyamensis, Cibicides datensis, Elphidium cf. frigidum, Elphidium yumotoense, Fursenkoina honyaensis, Globorotalia (Turborotalia) birnageae, Globorotalia (Turborotalia) peripheroronda, Globorotalia cf. praescitula, Globorotalia (Turborotalia) scitula praescitula, Hanzawaia tagaensis, Miogypsina kotoi, Nonionella miocenica, Nonion kodharaensis, Operculina complanata japonica, Pseudononion subcostatum, Virgrinella miocenica
- Fossils (Calcareous nannofossils): Coccolithus pelagicus, Sphaenolithus heteromorphus
- Kano (2018) Jour. Geol. Soc. Japan, vol.124, no.10, pp.781-803 DOI
- Kano et al. (2012) Jour. Geol. Soc. Japan, vol.118, no.6, pp.351-364 DOI
- Kano et al. (2011) Geology of the Toga and Funakawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 127p. (in Japanese with English abstract 4p.)
- Kobayashi et al. (2010) Jour. Geol. Soc. Japan, vol.116, no.10, pp.552-562 DOI
- Sato et al. (2009) Jour. Geol. Soc. Japan, vol.115, no.1, pp.31-46 DOI
- Ohguchi et al. (2008) Jour. Geol. Soc. Japan, vol.114, Supplement, pp.17-32 DOI
- Fujimoto et al. (2008) Jour. Geol. Soc. Japan, vol.114, Supplement, pp.51-74 DOI
- 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.)