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Hachikokusan Formation (Ikebe, 1940) Kobayashi et al., 1989

• Type locality: Kunisawa river, Oguni town, Nagaoka city, Niigata prefecture
• Type locality (Andesite lavas): Fudo fall, Zegon, Kashiwazaki city, Niigata prefecture
• Volcanic rocks
• early - late Pliocene
• Contemporaneous heterotopic facies: Nishiyama Formation, upper Tamugigawa Formation
• Correlation: Yoneyama Formation, Kurohime Formation

• Lithofacies: Andesite lava (Hyaloclastite), Pyroclastic flow deposit, Lapilli tuff, Volcanic sands
• Lithofacies (Minor): Mudstone, Sandstone

• Source: West side of southern Hachikokusan Mountains
• Thickness: 100 - 400 m
• Thickness (Pyroclastic flow deposit): 80 m
• Upper limit: Top of Hap Tephra
• Upper limit: Conformity (Suganuma Formation)
• Lower limit: Bottom of Haa-I Tephra
• Lower limit: Conformity (Hododaira Formation)

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

• Distribution: Kunisawa river, Oguni town, Nagaoka city, Niigata pref.; Zegon - Hirota hot spring - Mount Hachikoku - Morichika, Kashiwazaki city, Niigata pref.
• Tephra: Gos, Hap, Haa-I, Haa-II

• Kobayashi et al. (1995) Geology of the Kashiwazaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 102p. (in Japanese with English abstract 4p.)
• Kobayashi et al. (1989) Geology of the Okanomachi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 112p. (in Japanese with English abstract 5p.)