Benkeinai Formation

Benkeinai Formation, Jinbo, 1931

Invalid synonym: Sekkenai Formation

Type locality: Cape Yasui, Higahitaki, Hiranai city, Higashitsugaru county, Aomori prefecture
Coherent formation
Miocene (Nishikurosawa stage, Shellfishes, Foraminifera)

Sedimentary facies: Shallow marine
Lithofacies (Upper): Interbedded tuffaceous sandstone and tuff
Lithofacies (Middle): Lapilli tuff
Lithofacies (Middle, Minor): Tuffaceous sandstone
Lithofacies (Lower): Tuff breccia
Lithofacies (Basal): Conglomerate

Thickness: 100 - 150 m
Upper limit: Conformity (Higashidaki Formation)
Lower limit: Unconformity (Tateishi Formation)

Natsudomari peninsula, Aomori pref.
[ Upper ]
~~~~~~~~~~~~~~
Moura Andesites
--------------
Sasamoriyama Volcanic Rocks
--------------
Wadagawa Formation
--------------
Higashidaki Formation
--------------
Benkeinai Formation
~~~~~~~~~~~~~~
[ Lower ]

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

Distribution: Cape Yasui - Tateishi, Higahitaki, Hiranai city, Higashitsugaru county, Aomori pref.; Benkeinai creek - Shirasu, Higashitaki, Hiranai city, Higashitsugaru county, Aomori pref.
Fossils: Foraminifera
Fossils (Shellfishes): Terebrataia innaiensis, Coptothris sp., Caridita siogamensis, Cardium? sp., Lima sp., Pahia hirabayashii, Swiftpecten swifti, Venericardia ferruginea, Ostrea sp., Patella? sp., Anadara (Anadara) cf. ogawa, Mercenaria cf. yokoyamai, Panope nomurae, Venericardia (Cyclocardia) siogamaensis, Turritella (Lolaclla) tanaguraensis

Uemura (1983) Geology of the Asamushi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 40p. (in Japanese with English abstract 4p.)