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Oyana Formation Hatakeyama, 1954

• Type locality: Oyana, Yurihonjo city, Akita prefecture
• Volcanic rocks
• early Miocene
• Correlation: Monzen Formation
• Intruded by: Babame Dolerite

• Lithofacies: Acidic tuff, Lapilli tuff
• Lithofacies (Minor): Acidic welded tuff, Mudstone, Sandstone, Conglomerate

• Thickness: 200 - 400 m
• Thickness (Basal conglomerate): 0 - 30 m
• Upper limit: Conformity (Kanotsume Formation)
• Lower limit: Unconformity (Yamauchi Formation)

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

• Distribution: Oyana - Mount Kokuzo - Atarase, Yurihonjo city, Akita pref.
• Fossils (Aniai-type flora): Betula sp., Picea ugoana, Pinus sp.

• Nishikawa et al. (2008) Jour. Geol. Soc. Japan, vol.114, Supplement, pp.75-85 DOI
• Ozawa et al. (1988) Geology of the Yashima District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 87p. (in Japanese with English abstract 5p.)
• Ozawa et al. (1977) Geology of the Honjo District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 54p. (in Japanese with English abstract 4p.)