Isoura Formation

Isoura Formation Noda et al., 2010

Type locality: Isoura village, Niihama city, Ehime prefecture
Coherent formation
Izumi sedimentary basin
Forearc basin associated with strike-slip fault related to Median Tectonic Line
Late Cretaceous, middle Campanian (Bivalves)

Sedimentary facies: Main filling of the sedimentary basin
Lithofacies: Interbedded turbidite and mudstone
Lithofacies (Upper): Sandstone
Lithofacies (Upper, Minor): Mudstone, Interbedded sandstone and mudstone
Lithofacies (Middle): Conglomerate
Lithofacies (Middle, Minor): Sandstone
Lithofacies (Lower): Sandstone
Lithofacies (Bottom): Interbedded sandstone and mudstone
Sedimentary structures (Middle): Graded bedding

Lower limit: Transitional, Interfingered (Kussaki Formation), Conformity (Niihama Formation)

Main facies (Niihama region)
[ Upper ]
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Niihama Formation
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Isoura Formation
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[ Lower ]

Izumi Group
[ North ]
~~~~~~~~~~~~~~
Northern marginal facies
Main facies
Southern facies
~~~~~~~~~~~~~~
[ South ]

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

Distribution: Isoura village - Hoshigoe village, Niihama city, Ehime pref.; Funaya - Iwaidani, Saijo city, Ehime pref.
Fossils (Bivalves): Sphenoceramus schmidti, Sphenoceramus sachalinensis, Nucula? sp., Acila (Truncacila) aff. shimojimensis, Nanonavis brevis, Inoceramus (Cordiceramus) yuasai, Inoceramus (Endocostea) bulticus bulticus, Myrtea angularis, Periplomya sp., Yaadia japonica
Fossils (Ammonoids): Tetragonites cf. popetensis, Gaudryceras sp.

Noda et al. (2010) Jour. Geol. Soc. Japan, vol.116, no.2, pp.99-113 DOI