Koikegawa Member

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Koikegawa Member

Formerly included in Uonuma Group.

Type locality: Koike river, Tsunan city, Nakauonuma county, Niigata prefecture
Volcanic rocks
Pleistocene (1.76 Ma, K-Ar)
Correlation: middle Uonuma Group

Sedimentary facies (Minor): Mudflow deposit
Lithofacies: Andesite tuff breccia, Gravels, Interbedded sands and silt
Lithofacies (Minor): Lignite

Thickness: 250 m
Upper limit: Bottom of Tt-TB
Upper limit: Conformity (Sori Member)

Kamigo Formation
[ Upper ]
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Sori Member
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Koikegawa Member
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[ Lower ]

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

Distribution: Koike river - Ashidaki river - Nakajo river, Tsunan city, Nakauonuma county, Niigata pref.
Tephra: Om-SK110, Mpk, Tr-TB

Shimazu and Tateishi (1993) Geology of the Naebasan District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 90p. (in Japanese with English abstract 5p.)