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Ojo Formation (Ota, 1957)

Invalid synonym: Ojo tuff breccia

• Volcanic rocks
• Early Pleistocene (1.2 Ma, Lava; 0.9 Ma, Lava)

• Sedimentary facies: Terrestrial
• Sedimentary facies (Minor): under water
• Lithofacies: Andesite tuff breccia
• Lithofacies (Minor): Two-pyroxene andesite lava, Volcanic sands

• Thickness: 300 - 500 m
• Upper limit: Unconformity (Banki Lava, Takama Lava, Kusatsu-Shirane volcano, Asama-Eboshi volcanoes, Agatsuma Clay, Tsumagoi Pyroclastic Flow Deposit)
• Lower limit: Unconformity (Kuresaka Lava)

• Distribution: Mount Ojosan - Naganohara - Azuma river - Sukawa river, Naganohara city, Agatsuma county, Gunma pref.

• Nakamura et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.8, pp.397-412, DOI
• Ota (1957) Kusatsu, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 75p. (in Japanese with English abstract 8p.)