Omatagawa Mudstone Member

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Omatagawa Mudstone Member

Coherent formation
Miocene
Intruded by: Dolerite (Sill, Laccolith)

Sedimentary facies: Marine
Depth of water: middle -lower Bathyal (Foraminifera)
Lithofacies: Mudstone
Lithofacies (Minor): Acidic tuff, Tuffaceous sandstone

Thickness: 300 - 400 m
Upper limit: Interfingered (Main part), Conformity (Hachimori Andesite, Junitaki Acid Volcanic Rock)
Lower limit: Interfingered (Main part)

Aosawa Formation (Shonai)
[ Upper ]
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Junitaki Acid Volcanic Rock
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Taizoyama Andesite
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Lower part
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[ Lower ]

Aosawa Formation (Shinjo)
[ Upper ]
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Hachimori Andesite
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Omatagawa Mudstone Member
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[ Lower ]

Kisakata - Yashima, Akita pref.
[ Upper ]
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Onnagawa Formation
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Aosawa Formation
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Yashiozawakawa Formation
?--?--?--?--?-
[ Lower ]

Shinjo basin, Yamagata pref.
[ Upper ]
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Furukuchi Formation
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Kusanagi Formation
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Aosawa Formation
?--?--?--?--?-
[ Lower ]

Sakata - Tsuruoka, Yamagata pref.
[ Upper ]
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Kitamata Formation
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Kusanagi Formation
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Aosawa Formation
?--?--?--?--?-
[ Lower ]

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

Distribution: Omata river - Shiratama river - Aizawa river, Sakata city, Yamagata pref.
Fossils (Foraminifera): Bulimina striata, Globigerina sp., Globorotalia quinifalcata, Gyroidina orbicularis, Martinottiella? sp., Melonis barlleeanus, Pullenia bulloides, Uvigerina proboscidea

Tsuchiya (1989) Geology of the Osawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 85p. (in Japanese with English abstract 6p.)