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Yamaya Formation

• Type locality: Upper - middle reaches of Yamaya river, Kakunodate town, Senboku city, Akita prefecture
• Volcanic rocks
• Miocene (7.9 Ma, U-Pb; 9.2, 8.3 Ma, FT)

• Lithofacies: Biotite rhyolite lava, Biotite rhyolite volcaniclastic rocks
• Lithofacies (Minor): Siliceous mudstone, Mudstone
• Sedimentary structures: Graded bedding, Parallel stratification, Cross stratification, Ripples

• Thickness: 100 - 200 m
• Lower limit: Unconformity (Yamayakawa Formation, Katsurabuchi Formation)

• Distribution: Yamaya river, Kakunodate town, Senboku city, Akita pref.; Hinokinai river, Takano, Nishiki town - Wakamigo, Kakunodate town, Senboku city, Akita pref.
• Fossils: Trace fossils
• Fossils (Pollen): Sequoia sp., Pinus sp., Fagus sp., Abies sp.

• Hosoi et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.4, pp.279-295 DOI