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Yamaya Formation (Onuki, 1956) Kawamura et al., 2013

• Type locality: Yamaya - Gyonindaira, Shiwa city, Shiwa county, Iwate prefecture
• Volcanic rocks
• Early Cretaceous
• Correlation: Ubaishi Formation

• Lithofacies: Rhyolite - andesite lava, Siliceous tuff, Tuff breccia, Sandstone, Mudstone
• Lithofacies (Minor): Conglomerate

• Thickness: 130 - 1,000 m or thicker
• Lower limit: Unconformity (Orikabetoge Formation)

• Distribution: Yamaya - Gyonindaira - Akazawa - Mount Eboshikata, Shiwa city, Shiwa county, Iwate pref.; Orikabe - Mount Ono - Orobetsu? - Narahana - Mount Kamiiwayama, Ohasama town, Hanamaki city, Iwate pref.
• Fossils: Plants
• Fossils (Limestone gravels): Crinoids, Foraminifera (Saccaminopsis sp.)

• Kawamura et al. (2013) Geology of the Hayachine San District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 101p. (in Japanese with English abstract 4p.)