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Nisatai Formation (Otuka, 1934) Tuzino et al., 2018

Invalid synonym: Nisatai Dacite, Nisatai Liparite

The bottom clastic rocks had been included in Yotsuyaku Formation.

• Type locality: Nisatai river, Tareyanagi - Ohagino, Ninohe city, Iwate prefecture
• Coherent formation
• Oligocene - Miocene (21.8 - 21.0 Ma, K-Ar; 22.8 - 22.3 Ma, FT, 22.2 Ma, U-Pb)

• Sedimentary facies: Terrestrial
• Lithofacies: Rhyolitic pyroclastic rocks
• Lithofacies (Bottom): Conglomerate, Sandstone, Mudstone

• Thickness: 200 m or thicker
• Thickness (Bottom): 50 m or thinner
• Upper limit: Onlap unconformity (Sikonai Siltstone Member), Unconformity (Yotsuyaku Formation, Kadonosawa Formation, Asanai Terrace Deposit)
• Lower limit: Unconformity (North Kitakami Belt)

• Distribution: Nisatai river, Tareyanagi - Ohagino, Ninohe city, Iwate pref.; Numanotai, Ninohe city, Iwate pref.
• Fossils (Bottom): Plants

• Tuzino et al. (2018) Geology of the Ichinohe District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 161p. (in Japanese with English abstract 4p.)