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Nenokami Formation (Arai, 1960) Makimoto and Takeuchi, 1992
Invalid synonym: Nenokami Sandstone Formation, Chigaya Formation, Iwadonozawa Formation
- Type locality: right bank of Akahira river, Tomita, Chichibu city, Saitama prefecture
- Coherent formation
- Half graben-fill deposit
- middle Miocene (16.0 Ma, FT)
- Correlation: Upper Kozono Formation
- Sedimentary facies: Shallow marine
- Lithofacies: Tuffaceous sandstone
- Lithofacies (Minor): Sandy siltstone
- Lithofacies (Basal): Conglomerate
- Sedimentary structures: Cross stratification
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Akahira river, Tomita, Chichibu city, Saitama pref.; Ota, Chichibu city, Saitama pref.; Chigaya - Iwadonosawa - Mount Kannonyama, Ogano city, Chichibu county, Saitama pref.; Maehara, Minano city, Chichibu county, Saitama pref.
- Fossils: Sharks (Cetorhinus sp.)
- Fossils (Lower, Shellfishes): Acila iwadonozawaensis, Acila submirabilis, Aequipecten hataii, Ampullina cfr. asagaiensis, Chone (Guidiella) trigonia, Conchocele disjuncta, Crepidula auricula, Cultellus izumoensis jobanicus, Cultellus otukai, Cultellus rectangulus, Dosinia fujimotoi, Felaniella cfr. usta, Fulgoraria (Psephaea) striata, Laevicardium yoshidense, Lucinoma hannibali, Macoma arctata, Macoma asagaiensis, Macoma optiva, Macoma orbiculata, Macoma snohomishensis, Macoma sookensis, Mya (Arenomya) grewingki, Mya (Arenomya) grewingki elongata, Neptunea modesta, Ostrea sp., Panomya elongata, Securelia carmanahensis, Securelia cryptolineata, Securelia postostriata, Solen saitamensis, Tapes higuchi, Tectonatica sp., Tellina vancouverensis, Thracia chigayaensis, Turritella chichibuensis, Turritella mitagawensis, Venericardia chichibuensis, Venericardia (Cyclocardia) tokunagai, Yoldia laudabilis
- Matsui et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.6, pp.261-266, DOI
- Hara et al. (2010) Geology of the Mitsumine District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 110p. (in Japanese with English abstract 4p.)
- Takahashi and Yanagisawa (2004) Jour. Geol. Soc. Japan, vol.122, no.12, pp.625-635.
- Makimoto and Takeuchi (1992) Geology of the Yorii District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 136p. (in Japanese with English abstract 6p.)
- Okubo and Horiguchi (1969) Geology of the Mamba District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 65p. (in Japanese with English abstract 5p.)