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Nijikai Tuff (Iwai, 1965) Muraoka and Hase, 1990

Invalid synonym: Nijikai Formation, Tobe Formation (a part)

Includes Shoheizugawa Pumiceous Volcaniclastic Rocks?

• Type locality: Nijikaishinden, Owani city, Minamitsugaru county, Aomori pref.
• Volcanic rocks
• Pliocene (2.4 Ma, K-Ar)
• Intruded by: Sorigasezawa Andesite

• Sedimentary facies: Marine
• Sedimentary facies: Pyroclastic flow deposit
• Lithofacies: Andesitic pumice tuff, Tuff
• Lithofacies: Many accidental fragments are included.
• Lithofacies (Minor): Siltstone, Sandstone

• Thickness: 40 - 80 m
• Source: Ikarigaseki caldera
• Upper limit: Unconformity (Tazawamoriyama Formation, Ikarigaseki Formation, Aoni Tuff)
• Lower limit: Unconformity (Obirakiyama Pyroclastic Flow Deposit, Mitsumori Andesite, Arakawa Dolerite)

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

• Distribution: Nijikaishinden, Owani city, Minamitsugaru county, Aomori pref.; Yachinosawa creek, Hirakawa city, Aomori pref.; Aseishi river - Aoni river, Kuroishi city, Aomori pref.; Arakawa river, Aomori city, Aomori pref.; Ose river - Tsuta river, Towada city, Aomori pref.

• Takarada and Muraoka (2004) Geology of the Hakkoda San District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 86p. (in Japanese with English abstract 4p.)
• Muraoka and Hase (1990) Geology of the Kuroishi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 124p. (in Japanese with English abstract 8p.)