Obisagawa Member

Obisagawa Member (Saito, 1960) Ando et al., 1995

Type locality: Ohisa river, Ohisa town, Iwaki city, Fukushima prefecture
Coherent formation
southern Yezo Forearc basin (Jobanoki basin)
Late Cretaceous, early? - middle Coniacian

Sedimentary facies: Marine
Sedimentary facies: Shoreface - Inner shelf
Sedimentary facies (Minor): Storm deposit
Lithofacies: Muddy sandstone, Sandy siltstone
Lithofacies (Minor): Conglomerate
Sedimentary structures: Bioturbation
Sedimentary structures (Minor): Hummocky cross-stratification, Low-angle cross-stratification, Parallel stratification

Upper limit: Conformity (Kasamatsu Formation), Unconformity (Shiramizu Group)
Lower limit: Bottom of the marine fine sandstone bed associated with trasgressive conglomerate
Lower limit: Conformity (Asamigawa Member), Abut unconformity (Ohisagawa Granodiorite)

Ashizawa Formation
[ Upper ]
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Obisagawa Member
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Asamigawa Member
~~~~~~~~~~~~~~
[ 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: Ohisa river, Ohisa town, Iwaki city, Fukushima pref.
Fossils: Nautiloids (Cymatoceras sp.), Brachiopods (Telebratula sp.)
Fossils (Vertebrata): Asterdontids, Basilemys sp., Hadrosaurids, Sharks (Teeth)
Fossils (Ammonoids): Anagaudryceras limatum, Baculites schencki, Baculites yokoyamai, Damesites sp., Eubostrychoceras indicum, Forresteria (Forresteria) alluaudi, Gaudryceras denseplicatum, Mesopuzosia yubarensis, Pachydesmoceras cf. mihoense, Phylloceras (Neophylloceras) subramosum, Polyptychoceras sp., Scaphites pseudoequalis, Yabeiceras orientale, Yezoites puerculus sp., Yokoyamaoceras sp.
Fossils (Shellfishes): Acila (Truccacila) hokkaidoensis, Amphidonte sp., Anomia sp., Apiotrigonia (Apiotrigonia) undulosa, Apporhais sp., Chlamys milleri, Dentalium otatumei, Didymotis akamatsui, Dosinioasis? sp., Eriphyla higoensis, Ezonuculaca mactraeformis, Glycymeris amakusensis, Gyrodes sp., Inoceramus uwajimensis, Leptosolen japonica, Limatula sp., Myrtea ezoensis, Nanonavis sachalinensis, Opis sp., Pholadomya sp., Pinna sp., Rostellaria sp., Turritella sp., Yaadia kimurai
Fossils (Trace fossils): Ophiomorpha isp., Anchonicus isp.

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.)