a Member

[ Top ] [ Japanese ]

a Member

Synonym: U-IIIa

Coherent formation
Late Cretaceous, late Campanian - Maastrichtian (Bivalves)

Sedimentary facies: Marine
Sedimentary facies: Tidal deposit
Lithofacies: Sandstone
Lithofacies (Minor): Mudstone, Interbedded sandstone and mudstone
Sedimentary structures: Cross-stratification, Parallel stratification, Lenticular stratification, Flaser stratification, Tidal bundles with double mud drapes, Current ripples (20 - 30 cm wavelenth), Bioturbation

Thickness: 300 m or thicker
Upper limit: Conformity
Lower limit: Conformity

U-III Formation
[ Upper ]
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c Member
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b Member
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a Member
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[ Lower ]

Himenoura Group (Koshikijima islands)
[ Upper ]
~~~~~~~~~~~~~~
U-IV Formation
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U-III Formation
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U-II Formation
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U-I Formation
?--?--?--?--?-
[ Lower ]

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

Distribution: Cape Kumagase, Shikashima, Shimokoshikijima island, Koshikijima islands, Satsumasendai city, Kagoshima pref.
Fossils: Crassostrea sp., Yaadia obsoleta, Corbula ushibukensis, Turtles (Shells), Thalassinoides isp.

Komatsu et al. (2014) Jour. Geol. Soc. Japan, vol.120, Supplement, pp.19-39 DOI
Tonai et al. (2008) Jour. Geol. Soc. Japan, vol.114, no.11, pp.547-559 DOI