Okura Andesite Member

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Okura Andesite Member Yanagisawa et al., 1985

Volcanic rocks
Miocene
Intruded by: Quartz porphyry, Dolerite

Lithofacies: Andesite - Basalt lava, Tuff, Tuff breccia
Lithofacies (Minor): Hyaloclastite, Pillow lava

Thickness: ca. 100 - 450 m
Upper limit: Unconformity (Hakkaisan Conglomerate Member, Sakadoyama Sandstone and Shale Member)
Lower limit: Unconformity (Cretaceous granites, Kamigongendoyama Group, Nakanotake Metagabbros)

Okura Formation
[ Upper ]
~~~~~~~~~~~~~~
Ozuki Tuff and Shale Member
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Okura Andesite Member
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Shimonagasaki Conglomerate and Shale Member
~~~~~~~~~~~~~~
[ Lower ]

Jonai Group
[ Upper ]
~~~~~~~~~~~~~~
Hakkaisan Formation
~~~~~~~~~~~~~~
Okura Formation
~~~~~~~~~~~~~~
[ Lower ]

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

Distribution: Mizunashi river - Yamaguchi - Hirohori - Mount Kinjo, Minamiuonuma city, Niigata pref.; Byobuzawa river, Udazawa river, Minamiuonuma city, Niigata pref.

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. (1985) Geology of the Tokamachi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 104p. (in Japanese with English abstract 6p.)