[ Top ] [ Japanese ]

Irisugaya Formation Sugawara, 1972 ex Kitamura et al., 1983

• Type locality: Sunaoshi river, Irisugaya, Rifu city, Miyagi county, Miyagi prefecture
• Coherent formation
• middle - late Miocene
• Correlation: Hataya Formation, Kashimadai Formation

• Lithofacies: Tuffaceous sandstone, Tuffaceous siltstone
• Lithofacies (Minor): Lapilli tuff, Pumice tuff, Tuff
• Sedimentary structures: Parallel stratification, Ripples, Bioturbation, Pipe rocks

• Thickness: 40 - 50 m or thicker
• Upper limit: Unconformity (Bangamoriyama Formation)
• Lower limit: Abut unconformity (Shiogama Formation, Sauramachi Formation)

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

• Distribution: Irisugaya - Miyanomae - Sawaoto, Rifu city, Miyagi county, Miyagi pref.
• Fossils: Pipe rocks
• Fossils (Bivalves): Buccinum? sp., Chlamys cf. kaneharai, Macoma sp.
• Fossils (Diatoms): Actinocyclus ingens, Actinocyclus undulatus, Cocconeis sp., Coscinodiscus endoi, Coscinodiscus marginatus, Coscinodiscus symbolophorus, Coscinodiscus yabei, Denticulopsis hustedtii, Denticulopsis nicobarica, Denticulopsis praedimorpha, Fragilaria sp., Goniothecium odontella, Goniothecium rogersii, Goniothecim tenue, Grammalophora sp., Mediaria splendida, Melosira sol, Navicula sp., Paralia sulcata, Rhaphoneis sp., Rhizosolenia barboi, Rhizosolenia cf. styliformis, Rouxia californica, Stephanogonia hanzawae, Stephanopyxis turris, Thalassionema hirosakiensis, Thalassionema nitzschioides, Thalassionema cf. schraderi, Thalassiosira sp., Thalassiothris logissima

• Kitamura et al. (1986) Geology of the Sendai District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 134p. (in Japanese with English abstract 9p.)
• Kitamura et al. (1983) Geology of the Yoshioka District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 50p. (in Japanese with English abstract 5p.)