Arakawa Formation

Arakawa Formation Fujimoto and Watabe, 1947

Invalid synonym: Shimokarako Formation (Iwadono hills), Kanizawa Formation, Iida Formation

Type locality: Arakawa river, Kozono, Yorii city, Osato county - Hanazono, Fukaya city, Saitama prefecture
Coherent formation
middle Miocene
Correlation: Oganomachi Formation, Obata Formation

Sedimentary facies: Marine
Lithofacies: Turbidite
Lithofacies (Upper): Diatomaceous siltstone
Lithofacies: Interbedded siltstone and sandstone
Lithofacies (Minor): Felsic tuff, Lignite

Thickness: 450 - 1,250 m
Upper limit: Fault (ca. 15.4 Ma)
Lower limit: Conformity (Kozono Formation)

Matsuyama Group
[ Upper ]
?--?--?--?--?-
Yagii Formation
--------------
Tsuchishio Formation
::::::::::::::
Ichinokawa Formation
::::::::::::::
Arakawa Formation
--------------
Kozono Formation
?--?--?--?--?-
[ Lower ]

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

Distribution: Kozono, Yorii city, Osato county, Saitama pref.; Arakawa, Hanazono, Fukaya city, Saitama pref.; Ogawa city - Ranzan city, Hiki county, Saitama pref.
Fossils: Sharks (Teeth), Foraminifera, Radiolarians, Plants
Fossils (Shellfishes): Acila sp., Conchocele? sp., Cultellus izumoensis, Dentalium sp., Dosinia cf. akasiana, Dosinia anguloides, Dosinia japonica nomurai, Glycymeris sp., Lucina borealis, Lucinoma cf. acutilineata, Macoma cf. incongrua, Macoma nipponica, Macoma optiva, Macrocallista brevisiphonata, Macrocallista pacifica, Mactra sp., Meretrix meretrix, Nutica sp., Neptunea sp., Ostrea cf. gravitesta, Pecten cf. kaneharai, Pelulroma sp., Polinices sp., Reticunassa? sp., Saccella minoensis, Siliqua pulchella, Soletellina minoensis, Spisula sp., Tellina sp., Thyasira bisecta, Thyasira nipponica, Thyasira cf. ozawai, Trapezium sp., Turritella sp., Yoldia scapha
Tephra: T-3 (Hatakeyama Tuff Bed)

Arai et al. (2009) Jour. Geol. Soc. Japan, vol.115, no.5, pp.223-241 DOI
Takahashi and Yanagisawa (2004) Jour. Geol. Soc. Japan, vol.122, no.12, pp.625-635.
Makimoto and Takeuchi (1992) Geology of the Yorii District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 136p. (in Japanese with English abstract 6p.)