Choanji Formation

Choanji Formation (Onuki, 1956) Tazawa and Niikawa, 2018

Previously interpreted as the lowest part of Carboniferous Hikoroichi Formation.

Type locality: Lower reaches of Kogayo creek, Choanji, Hikoroichi village, Ofunato city, Iwate prefecture
Coherent formation
late Devonian, Frasnian - Famennian

Lithofacies (Main): Sandstone, Shale
Lithofacies (Minor): Tuffaceous sandstone, Conglomerate, Tuff, Limestone

Thickness: 295 m or thicker
Distribution (East - West): 200 m
Distribution (North - South): 850 m

South Kitakami Belt (Hikoroichi - Setamai, Iwate pref.)
[ Upper ]
?--?--?--?--?-
Choanji Formation
~~~~~~~~~~~~~~
Nakazato Formation
--------------
Okuhinotsuchi Formation
~~~~~~~~~~~~~~
[ Lower ]

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

Distribution: Choanji - Shimokogayo, Hikoroichi village, Ofunato city, Iwate pref.
Fossils (Trilobites): Brachymetopus sp., Phillibole sp., palaeophillipsia sp. Linguiphillipsia sp., Phillipsia sp.
Fossils: Bivalves (Lithophaga sp.), Brachiopods (Desquamatia (Seratrypa) sp.), Conularia tyoanjiensis, Fenestella sokolskayae, Rhombopora exigua

Tazawa and Niikawa (2018) Jour. Geol. Soc. Japan, vol.124, no.2, pp.111-116 DOI