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Shirasu Formation (Hayakawa, 1930) Makimoto and Takeuchi, 1992
Invalid synonym: Ushikubitoge Formation, Ushikubi FOrmation
- Type locality: Motogo, Yoshida, Chichibu city, Saitama prefecture
- Coherent formation
- Half graben-fill deposit
- middle Miocene (16.7 Ma, FT)
- Correlation: Kozono Formation, Ushibuse Formation
- Sedimentary facies: Marine
- Lithofacies (Upper): Sandstone, Mudstone
- Lithofacies (Lower): Conglomerate, Coarse-grained arkose sandstone
- Sedimentary structures: Slump structures
------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown
- Distribution: Motogo, Yoshida, Chichibu city, Saitama pref.; Shiroku, Arakawa, Chichibu city, Saitama pref.; Moe - Ushikubi pass - Kanazawa - Otomo, Ogano city, Chichibu county, Saitama pref.; Maehara, Minano city, Chichibu county, Saitama pref.
- Fossils: Paleoparadoxia tabatai, Echinoids (Echinarachnius (Kewia) minor), Foraminifera, Plants
- Fossils (Shellfishes): Ampullina cfr. asagaiensis, Callista sp., Chlamys sp., Conchocele disjuncta, Cultellus otukai, Dosinia sp., Lucinoma columbiana, Lucinoma hannibali, Lucinoma kalayosensis, Macoma optiva, Mactra sp., Mercenaria sp., Nuculana sp., Ostrea sp., Portlandia (Megayoldia) thraciaeformis, Portlandia (Portlandella) watasei, Solen saitamaensis, Tellina vancouverensis, Thracia sp., Turritella mitagawensis, Venericardia araii, Venericardia chichibuensis, Venericardia (Cyclocardia) laxata, Venericardia hannidali, Venericardia pacifica, Venericardia yalsatagensis
- 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.)