Yagen Formation

Type locality: Yagen hot spring, Yagen, Ohata town, Mutsu city, Aomori prefecture
Volcanic rocks
middle Miocene (Shellfish fossils)
Intruded by: Dacite

Sedimentary facies: Marine
Lithofacies: Andesitic - dacitic tuff, Tuff breccia
Lithofacies (Minor): Mudstone, Sandstone, Andesitic - dacitic lava
Lithofacies (Basal): Conglomerate

Thickness: 600 m or thicker
Upper limit: Unconformity (Ikokuma Andesites, Ohata Formation, Komena Dacite, Asahinadake Lava)
Lower limit: Unconformity (Sai Formation)

Yagen Formation (Sai, Aomori pref.)
[ Upper ]
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Yunokawa Green Tuff Member / Yunokogawa Sandstone and Mudstone Member
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[ Lower ]

Yagen Formation (Yagen, Aomori pref.)
[ Upper ]
~~~~~~~~~~~~~~
Yunomatagawa Dacitic Tuff Member
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Ohatagawa Green Tuff Member / Kamanosawa Tuff, Sandstone and Shale Member
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[ Lower ]

Sai - Ohata river, Aomori pref.
[ Upper ]
~~~~~~~~~~~~~~
Ikokuma Andesites
~~~~~~~~~~~~~~
Yagen Formation
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Sai Formation
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[ Lower ]

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

Distribution: Sai city, Shimokita county, Aomori pref.; Yagen hot spring, Yagen, Ohata town, Mutsu city, Aomori
Fossils: Plants
Fossils (Shellfish): Anadara cf. ninohensis, Barbatia sp., Cardita siogamensis, Chlamys arakawai, Chlamys kaneharai, Glycymeris vestitoides, Luciniscus cf. yokoyamai, Patinopecten kimurai, Taras ustus, Acmaea sp., Pecten swifti, Pecten paraplepejus, Pecten kaneharai, Lima goliath yagenensis, Lima sp., Saxidomus gigananteus

Uemura (1962) Oma and Sai, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 39p. (in Japanese with English abstract 6p.)
Uemura and Saito (1957) Ohata, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 31p. (in Japanese with English abstract 8p.)