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Ota Pumiceous Volcaniclastic Rocks Sakurai, 1931 ex Hokkaido University, 1954

Invalid synonym: Ota Tuff Member

• Type locality: middle reaches of Obetsu river, Nakadomari city, Kitatsugaru county, Aomori prefecture
• Coherent formation
• middle - late Miocene (13.9 Ma, K-Ar; 13.1 - 12.9 Ma, Diatoms, Nishikurosawa stage)
• Intruded by: Rhyolite

• Sedimentary facies: Submarine pyroclastic flow
• Lithofacies: Pumiceous tuff breccia, Lapilli tuff, Tuff breccia
• Lithofacies (Minor): Rhyolite lava
• Sedimentary structures: Graded bedding

• Thickness: 100 - 750 m
• Upper limit: Conformity (Genpachimori Formation), Unconformity (Fudotaki Formation)
• Lower limit: Bottom of Ota Pumiceous Volcaniclastic Rocks
• Lower limit: Conformity (Umanokamiyama Formation)

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

• Distribution: Ota river, Goshogawara (Shiura city), Aomori pref.
• Fossils (Diatoms): Actinocyclus ingens, Denticula hustedtii, Denticula nicobarica

• Nagamori et al. (2013) Geology of the Aomori-Seibu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 67p. (in Japanese with English abstract 4p.)
• Kamikuri et al. (2010) Jour. Geol. Soc. Japan, vol.116, no.8, pp.403-411 DOI
• Fujii (1981) Geology of the Aburakawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 38p. (in Japanese with English abstract 3p.)