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Kobinaizawa Formation Hirayama and Sumi, 1963

• Type locality: Kobinai creek - Fujikoto river, Fujikoto, Fujisato city, Yamamoto county, Akita prefecture
• Coherent formation
• Miocene

• Sedimentary facies: Marine (Shellfishes)
• Lithofacies (Upper): Interbedded siltstone and sandstone
• Lithofacies (Lower): Siltstone
• Lithofacies (Minor): Acidic pumice tuff

• Thickness (Northwest): ca. 200 m
• Thickness (Southeast): ca. 300 m
• Upper limit: Top of the uppermost siltstone bed of interbedded sandstone and siltstone
• Upper limit: Transitional (Usuizawa Formation), Transitional, partly unconformity (Maeyamagawa Formation)
• Lower limit: Unconformity (Fujikotogawa Formation)

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

• Distribution: Kobinai creek - Fujikoto river, Fujikoto, Fujisato city, Yamamoto county, Akita pref.; Yonaizawa, Kitaakita city, Akita pref.
• Fossils: Sponges (Makiyama chitanii), Diatoms, Foraminifera, Plants
• Fossils (Shellfishes): Callista brevisiphonata, Clementia sp., Clinocardium shinjiense, Conchocele bisecta, Conchocele disjuncta, Cryptomya? sp., Dosinia? sp., Limatula sp., Lucinoma acutilineatum, Mactra kurikoma, Mercenaria sp., Mya? sp., Nassarius? sp., Patinopecten sp., Serripes yokoyamai, Siphonalia sp., Turritella nipponica, Vasticardium cf. shiobarense

• Murakami et al. (2008) Jour. Geol. Soc. Japan, vol.114, Supplement, pp.111-120 DOI
• Sumi and Moritani (1973) Geology of the Yonaizawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 46p. (in Japanese with English abstract 4p.)
• Hirayama and Sumi (1963) Takanosu, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 90p. (in Japanese with English abstract 7p.)