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Hatoyama Formation (Fukuda and Ishiwada, 1964) Majima, 1989

Invalid synonym: Hatoyama Sandstone and Siltstone Member (Ohashi Formation, Tokigawa Group), Hatoyama Sandstone and Mudstone Member, Okuda Formation

• Type locality: Okuda, Hatoyama city, Saitama prefecture
• Coherent formation
• late Miocene

• Sedimentary facies: Marine
• Sedimentary facies: Slump
• Depth of water: Shallower than Shogunzawa Formation?
• Lithofacies: Alternate sandstone and siltstone
• Sedimentary structures: Dish structures

• Thickness: 200 m
• Upper limit: Conformity (Imajuku Formation)
• Upper limit: Top of the siltstone bed (around 11.2 Ma)
• Lower limit: Conformity (Shogunzawa Formation)
• Lower limit: Bottom of the first sandstone above the I-12 Tuff Bed (around 115. Ma)

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

• Distribution: Okuda - Ohashi - Kumai, Hatoyama city, Saitama pref.
• Fossils: Shellfishes, Anadara sp., Lucinoma aculilinela (Conrad), Plants (Lignite)

• Takahashi and Yanagisawa (2004) Jour. Geol. Soc. Japan, vol.122, no.12, pp.625-635.
• Kurihara et al. (2003) Jour. Geol. Soc. Japan, vol.109, no.4, pp.215-233.
• Koike et al. (1985) Jour. Geol. Soc. Japan, vol.91, no.10, pp.665-677.