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Okura Formation Yanagisawa et al., 1985

• Volcanic rocks
• Miocene
• Intruded by: Rhyolite
• Correlation: Daijima Formation

• Sedimentary facies: Terrestrial
• Lithofacies: Andesite lava, Lapilli tuff, Tuff breccia, Dacite vitreous tuff, Conglomerate

• Thickness: 70 m
• Upper limit: Unconformity (Hakkaisan Formation)
• Lower limit: Unconformity (Hanegawa Formation, Myogazawa Formation, Kamigongendoyama Group, Nakanotake Metagabbros)

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

• Distribution: Niigata pref.

• Takahashi et al. (2004) Geology of the Suhara District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 80p. (in Japanese with English abstract 4p.)
• Chihara and Komatsu (1992) Geology of the Hakkaisan District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 107p. (in Japanese with English abstract 8p.)
• Yanagisawa et al. (1986) Geology of the Ojiya District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 177p. (in Japanese with English abstract 6p.)
• Yanagisawa et al. (1985) Geology of the Tokamachi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 104p. (in Japanese with English abstract 6p.)