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Ichijiku Formation Otsuka and Mochizuki, 1932

Invalid synonym: Ichijuku Formation

• Type locality: Ichijuku, Kimitsu city, Chiba prefecture
• Coherent formation
• Fore-arc basin sediments (Kazusa trough)
• Contemporaneous heterotopic facies: Kakinokidai Formation
• Correlation: Higashinagata Formation, Takigawa Formation

• Sedimentary facies: Shallow marine
• Sedimentary facies (The part eroding lower horizons): Caldron structure
• Sedimentary facies: Paleo-Kuroshio oceanic current -origin sand wave deposit
• Water temperature: Cold ocean current
• Depth of water: 50 - 130 m
• Lithofacies: Sands, Gravels
• Lithofacies (Minor): Mud
• Sedimentary structures: Trough cross-stratification, Planar cross-stratificaiton

• Thickness: 0 - 230 m or thicker
• Upper limit: Conformity (Chonan Formation), Unconformity (Nagahama Sand and Gravel Member)
• Lower limit: Conformity, partly unconformity (Kokumoto Formation), Unconformity (Umegase Formation)

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

• Distribution: Ichijuku - Mount Kanozan, Kimitsu city, Chiba pref.; Mount Kinadayama - Nagahama, Futtsu city, Chiba pref.

• Majima et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.9, pp.655-683 DOI
• GSSP proposal group (2019) Jour. Geol. Soc. Japan, vol.125, no.1, pp.5-22 DOI
• Nakajima and Watanabe (2005) Geology of the Futtsu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 102p. (in Japanese with English abstract 8p.)