Okuyama Formation

[ Top ] [ Japanese ]

Okuyama Formation Otsuka, 1947

Type locality: Okuyama, Kyonan city, Awa county, Chiba prefecture
Coherent formation
Miocene
Interfingered: Okuzure Formation, lower Nakaobara Formation

Sedimentary facies: Marine
Lithofacies: Sandstone
Lithofacies (Minor): Conglomerate, Interbedded conglomerate and sandstone

Thickness: 300 m
Lower limit: Transitional (Okuzure Formation)

(Invalid synonym) Sakuma Group
[ Upper ]
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Nakaobara Formation
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Okuyama Formation
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Okuzure Formation
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[ Lower ]

Awa Group (Western part)
[ Upper ]
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Annno Formation
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Kiyosumi Formation
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Amatsu Formation
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Kinone Formation
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Sakuma Formation
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[ Lower ]

Mineoka Belt (Boso peninsula)
[ Upper ]
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Awa Group / Minamiboso Group
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Hota Group
::::::::::::::
Mineoka Group
?--?--?--?--?-
[ Lower ]

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

Distribution: Okuyama - Nakaohara - Nakaigatani - Nakane - Okatabira, Kyonan city, Awa county, Chiba pref.; Tajima - Naakanuma, Futtsu city, Chiba pref.; Ohata, Kamogawa city, Chiba pref.
Fossils (Shellfishes): Chlamys akihoensis, Crassatellites cf. nanus

Takahashi et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.8, pp.375-395, DOI
Suzuki et al. (1990) Geology of the Nago District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 48p. (in Japanese with English abstract 3p.)