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Hirayama Formation (Otsuka, 1932) Takano, 1994

Invalid synonym: Hirayama Sandstone Formation

• Type locality: Uchikoshi town, Hachioji city, Tokyo
• Coherent formation
• Fore-arc basin sediments (Kazusa trough)
• early Pleistocene (1.57 - 1.36 Ma, Calcareous nannofossils)
• Correlation: Hanno Formation?, Kasumi Formation, Bushi Formation, Komiya Formation, Fukushima Formation

• Sedimentary facies: Marine
• Sedimentary facies: A cycle of regression - transgression sequence
• Lithofacies (Upper): Sands
• Lithofacies (Middle): Sands, Silt
• Lithofacies (Lower): Gravels
• Sedimentary structures (Upper): Trough cross-stratification, Pipe rocks
• Sedimentary structures (Middle): Bioturbation, Pipe rocks

• Thickness: 70 m
• Thickness (Upper): 3 m or thicker
• Thickness (Lower): 80 cm or thicker
• Upper limit: Conformity (Oyamada Formation), Unconformity (Gotentoge 1 Terrace Deposit)
• Lower limit: Conformity (Oyabe Formation)

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

• Distribution: Uchikoshi town - Katakura town - Horinouchi - Yarimizu, Hachioji city, Tokyo; Naganuma park, Naganuma, Hachioji city, Tokyo; Hirayama, Hino city, Tokyo; Hirayama bridge, Toyoda, Hino city, Tokyo
• Fossils (Upper): Calcareous nannofossils
• Fossils (Middle): Vertebrata, Elephants (Stegodon aurorae), Bivalves (Shallow marine), Diatoms (Freshwater), Pollen (Metasequoia sp.), Foraminifera, Calcareous nannofossils, Trace fossils
• Fossils (Middle, Plants): Juglans cinerea, Cunninghamia sp.
• Tephra: Yarimizu

• 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