Asakawa Formation

Asakawa Formation (Suzuki, 1938)

Invalid synonym: Asakawa Mudstone Member, Shinkoji Formation

It had been treated as a member of Aoki Formation.

Type locality: Shinkoji, Nagano city, Nagano prefecture
Coherent formation
Miocene
Correlation (Upper): Aoki Formation
Correlation (Lower): Bessho Formation
Intruded by: Rhyolite dikes

Sedimentary facies: Marine
Lithofacies: Mudstone
Lithofacies (Minor): Sandy tuff, Sandstone, Glendonite

Thickness: 300 m or thicker
Upper limit: Conformity (Susobana Formation)
Lower limit: Conformity (Hitoeyama Member)

Togakushi (East), Nagano pref.
[ Upper ]
--------------
Ronji Formation
~~~~~~~~~~~~~~
Susobana Formation
--------------
Asakawa Formation
--------------
Nishikyo Formation
--------------
[ Lower ]

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

Distribution: Shinkoji - Asakawasaijo - Sansenji, Nagano city, Nagano pref.; Saikawa river - Takizawa, Saikuchi, - Nagano city, Nagano pref.
Fossils: Whales (Vertebra), Shellfishes, Plants (Broad-leaf trees)
Fossils (Foraminifera): Dorothia sp., Gyroidina sp., Haplophragmoides sp., Plectina sp., Uvigerina akitaensis, Uvigerina (Hopkissina) morimachiensis, Uvigerina (Hopkissina) cf. nanataniensis, Uvigerina proboscidea

Tanabe (2015) Jour. Geol. Soc. Japan, vol.121, no.8, pp.265-278, DOI
Nagamori et al. (2003) Geology of the Togakushi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 109p. (in Japanese with English abstract 3p.)