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Otogawa Formation (Fujita and Nakagawa, 1948) Shimizu and Fujii, 1995

Invalid synonym: Otogawa Group, Ao Formation

Mita Formation and Tenguyama Formation had been included in Otogawa Formation.

• Type locality: south of Otogawa, Fuchu town, Toyama city, Toyama prefecture
• Coherent formation
• middle - late Miocene

• Sedimentary facies: Marine, Fluvial
• Sedimentary facies (Upper): Shoreface
• Sedimentary facies (Lower): Channel deposit of braided river
• Lithofacies: Siltstone, Conglomerate, Interbedded sandstone and tuff, Sandstone (with plant frangments)
• Lithofacies (Minor): Tuff
• Sedimentary structures (Upper): Trough cross-stratification, Wave-forming ripples
• Paleocurrent: to Northeast

• Thickness: ca. 0 - 900 m
• Upper limit: Bottom of conglomerate bed ca. 10 m lower than OT3 Tephra (Ravinement erosion surface or Sequence boundary)
• Upper limit: Unconformity (Mita Formation, Zukawa Sandstone Member, Hanyu Formation, Kamitako Gravel and Clay, Muroda Formation, Kurehayama Gravel Bed)
• Lower limit: Conformity, partly Unconformity (Shakusenji Formation), Unconformity (Anamizu Formation), Arayama Unconformity (Higashibessho Formation, Tenguyama Formation, Tochizu Alternation of Sandstone and Mudstone Member, Joyama Mudstone Member)

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

• Distribution: Wada river - Yatsuo - Jinzu river - Jono - Seto - Kurotani - Kumanogawa river, Toyama city, Toyama pref.; Kaidashin - Tsubono - Hiebatake - Kanayamadani, Uozu city, Toyama pref.; Zukawa, Takaoka city, Toyama pref.; Kawata - Tsuboike - Otani, Himi city, Toyama pref.; Tofukuji - Kamioura, Namerigawa city, Toyama pref.; Omatsushin - Oiwagawa river - Shiraiwagawa river, Kamiichi city, Nakaniikawa county, Toyama pref.; Kasayaburi, Kurobe city, Toyama pref.; Mount Yachiyama, Kahoku city, Ishikawa pref.; Torigoe - Azamidani - Yoshikura - Lake Mikadoike - Rengeji, Tsubata city, Kahoku county, Ishikawa pref.
• Fossils (Upper): Otogawa fauna II
• Fossils (Middle): Diatoms
• Fossils (Lower): Otogawa fauna I
• Fossils: Fishes (Scales), Echinoids (Linthia nipponica), Sponges (Makiyama sp.), Foraminifera, Pipe rocks
• Fossils (Shellfishes): Acila (Truncacila) sp., Acila insignis, Anadara amicula, Anomia sp., Babylonia sp., Buccium sp., Cardium? sp., Chlamys ingenosa, Cirripedia sp., Clinocardium sp., Concocele dasjancta, Coraeophos nakamurai, Dentalium sp., Dosinia ettyuensis, Dosinia (Kneharaia) kaneharai, Dosinia nomurai, Fulgoraria sp., Fusinus sp., Glycymeris matumoriensis, Lima sp., Limopsis sp., Lucinoma sp., Lyropecten kagamianus, Macoma calcarea, Macoma nipponica, Mactra sp., Megasurcula yokoyamai, Mercenaria chitaniana, Mya cuneiformis, Nassarius sp., Nassanus sp., Natica janthostomoides, Neptunea nomurai, Nuculana congiensis, Ostrea sp., Patinopecten kurosawaensis, Patinopecten tokyoensis, Patinopecten yessoensis, Peronidea janensis., Pholadidea sp., Polinices fissuratus, Portlandia sp., Propeamussium sp., Saccela sp., Solemya sp., Spisula sp., Striarca sp., Tellina? sp., Turritella oyasio, Turritella saishuensis, Venericardia ferruginosa, Volsella sp., Yoldia sp.
• Fossils (Foraminifera): Cibicides lobatulus, Hanzawaia nipponica
• Tephra: Ot1, Ot2, OT3, Ot4, Pt1, Pt2, Rt

• Nakajima et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.7, pp.483-516 DOI
• Goto et al. (2014) Jour. Geol. Soc. Japan, vol.120, no.2, pp.71-86 DOI
• Tamura et al. (2010) Jour. Geol. Soc. Japan, vol.116, Supplement, pp.1-20 DOI
• Kunugiza et al. (2010) Jour. Geol. Soc. Japan, vol.116, Supplement, pp.83-101 DOI
• Amano et al. (2008) Jour. Geol. Soc. Japan, vol.114, no.10, pp.516-531 DOI
• Sumi et al. (1989) Geology of the Isurugi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 118p. (in Japanese with English abstract 5p.)
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