Iwaibukuro Formation

[ Top ] [ Japanese ]

Iwaibukuro Formation Kawakami and Shishikura, 2006

Type locality: Iwaibukuro seashore, Kyonan city, Awa county, Chiba prefecture
Coherent formation
middle - lower: late Miocene
upper: middle Miocene
Correlation (Middle - Upper): Nishizaki Formation

Sedimentary facies: Marine
Lithofacies (Upper): Siltstone-dominant interbedded sandstone and siltstone
Lithofacies (Middle): Sandstone-dominant interbedded sandstone and sandy siltstone
Lithofacies (Lower): Siltstone-dominant interbedded sandstone and siltstone
Lithofacies (Minor): Scoria
Sedimentary structures: Slump structures

Thickness: 500 m
Upper limit: Unconformity (Senbatake Conglomerate Member)
Lower limit: Conformity (Aokiyama Formation)

Minamiboso Group
[ Upper ]
~~~~~~~~~~~~~~
Kagamigaura Formation
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Hedate Formation
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Koura Formation
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Kohama Formation
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Haraoka Formation
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Ishido Formation
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Azuma Formation
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Iwaibukuro Formation
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[ Lower ]

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

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

Distribution: Iwaibukuro seashore, Kyonan city, Awa county, Chiba pref.
Fossils: Radiolarians, Calcareous nannofossils

Takahashi et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.8, pp.375-395, DOI
Kawakami and Shishikura (2006) Geology of the Tateyama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 82p. (in Japanese with English abstract 5p.)