Ashizawa Formation

Ashizawa Formation (Konno, 1938) Sukai, 1957

Type locality: Ashizawa, Ohisa town, Iwaki city, Fukushima prefecture
Coherent formation
southern Yezo Forearc basin (Jobanoki basin)
Late Cretaceous, Coniacian (Fossils)

Sedimentary facies: Terrestrial, Marine
Sedimentary facies: small scale alluvial fan facing the sea, Continental shelf
Sedimentary facies: Talus, Alluvial fan, Shoreface - Inner shelf
Lithofacies: Sandstone, Sandy mudstone
Lithofacies (Basal): Conglomerate

Thickness: 40 - 200 m
Thickness (Basal): ca. 30 m
Upper limit: Conformity (Kasamatsu Formtion)
Lower limit: Unconformity (Yaguki Metamorphic Rocks, Hornblende biotite granite)
Lower limit (West): Unconformity (Ohisagawa Granodiorite)
Lower limit (Southwest): Unconformity (Takakurayama Group)

Ashizawa Formation
[ Upper ]
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Obisagawa Member
--------------
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: Ashizawa, Ohisa town, Iwaki city, Fukushima pref.; Oriki hot spring - Kitazawa creek, Hirono city, Futaba county, Fukushima pref.; Asami river, Nihonkunugi, Hirono city, Futaba county, Fukushima pref.
Fossils: Ichthyosaurus sp., Turtles (Basilemys sp.)
Fossils (Ammonoids): Anagaudryceras limatum var. iwakiense, Baculites (Lechite) yokoyamai, Bostrychoceras indicum, Hamite sp. (aff. Glyptoxoceras subcom pressum), Puzosia kuratai, Scaphites puerculus, Yabeiceras himuroi, Yabeiceras kotoi, Yabeiceras orientale
Fossils (Shellfishes): Glycymeris sp., Inoceramus uwajimensis, Trigonia kimurai, Trigonia subovalis var. minor

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.)
Iwao and Matsui (1961) Taira and Kawamae, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 103p. (in Japanese with English abstract 17p.)