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Oyabe Formation (Otsuka, 1932) Takano, 1994

Invalid synonym: Oyabe Mudstone Formation

• Type locality: Utsunuki town, Hachioji city, Tokyo
• Coherent formation
• Fore-arc basin sediments (Kazusa trough)
• late Pliocene - early Pleistocene
• Correlation: Osoki Formation, Hanno Formation?, Onita Formation, Kasumi Formation, Bushi Formation

• Sedimentary facies: Marine
• Sedimentary facies: At least 3 cycles of regression and transgression
• Lithofacies (Upper): Gravels, Sands
• Lithofacies (Middle): Sands
• Lithofacies (Lower): Gravels, Sands
• Sedimentary structures (Upper): Trough cross-stratification, Hummocky cross-stratification, Pipe rocks
• Sedimentary structures (Middle): Bioturbation

• Thickness: 40 m
• Upper limit: Conformity (Hirayama Formation, Terrace deposit)
• Lower limit: Conformity (Terada Formation)

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

• Distribution: Utsunuki town - Terada town - Uchikoshi town - Katakura town - Ofune town, Hachioji city, Tokyo; Aihara town, Machida city, Tokyo
• Fossils (Middle): Juglans cinerea, Pollen (Metasequoia sp.), Diatoms (Freshwater), Shellfishes (Shallow marine)
• Tephra: Kamiofune

• Suzuki et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.7, pp.343-356, DOI
• Ueki et al. (2013) Geology of the Hachioji District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 137p. (in Japanese with English abstract 6p.)
• Suzuki and Murata (2011) Jour. Geol. Soc. Japan, vol.117, no.7, pp.379-397 DOI