Irimazawa Member

Irimazawa Member Kubo et al., 2002

Type locality: Irimazawa creek, Ohisa town, Iwaki city, Fukushima prefecture
Coherent formation
southern Yezo Forearc basin (Jobanoki basin)
Late Cretaceous, late Coniacian - early Santonian

Sedimentary facies: Marine
Sedimentary facies: Shoreface - Inner shelf
Lithofacies: Sandstone
Lithofacies (Basal): Conglomerate
Sedimentary structures: Low angle cross-stratification, Hummocky cross-stratification
Sedimentary structures (Basal): Cross stratification

Thickness: 60 - 80 m or thicker
Upper limit: Unconformity (Shiramizu Group)
Lower limit: Bottom of conglomerate bed
Lower limit: Conformity (Kohisagawa Member)

Tamayama Formation
[ Upper ]
~~~~~~~~~~~~~~
Irimazawa Member
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Kohisagawa Member
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[ Lower ]

Futaba Group
[ Upper ]
~~~~~~~~~~~~~~
Tamayama Formation
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Kasamatsu Formation
--------------
Ashizawa Formation
~~~~~~~~~~~~~~
[ Lower ]

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

Distribution: Irimazawa creek - Ohisa river - Jinba, Ohisa town, Iwaki city, Fukushima pref.
Fossils: Ammonoids, Trigonia, Futabasaurus suzukii
Fossils: Echinoids (Hemiaster sp.)
Fossils (Reptiles): Elasmosaurids, Futabasaurus suzukii
Fossils (Fishes): Cretolamna appendiculata, Enchodus sp., Ischyrhiza iwakiensis, Isurus? sp., Odontaspis sp., Scapanorhynchus sp.
Fossils (Ammonoids): Gaudryceras denseplicatum, Paratexanites? aff. australis, Plesiotexanites cf. pacificus, Polyptychoceras sp., Texanites cf. collignoni, Texanites aff. quinquenodosus
Fossils (Bivalves): Apiotrigonia (Apiotrigonia) minor, Dosiniopsis? sp., Inoceramus amakusensis, Inoceramus mihoensis, Phelopteria? sp.

Ando et al. (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.49-67 DOI
Kubo et al. (2002) Geology of the Kawamae and Ide District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 136p. (in Japanese with English abstract 6p.)