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Maeyamagawa Formation Hirayama and Sumi, 1963

• Type locality: Maeyama river, Maeyama - Kurosawa - Bosawa, Kitaakita city, Akita prefecture
• Coherent formation
• Pliocene
• Correlation: Wakimoto Formation or Shibikawa Formation, Mitsukita Formation

• Sedimentary facies (Upper - Middle): Marine, non-Marine
• Sedimentary facies (Lower): Marine
• Water temperature: Cold ocean current
• Lithofacies (Upper): Lignite-bearing interbedded sandstone and conglomerate
• Lithofacies (Middle): Interbedded sandstone and conglomerate
• Lithofacies (Middle, Minor): Perlite
• Lithofacies (Lower): Sandstone
• Lithofacies (Bottom): Pumice tuff, Tuff
• Sedimentary structures: Cross stratification

• Thickness: 600 m or thicker
• Upper limit: Unconformity (Yuguruma Formation)
• Lower limit: Top of the uppermost siltstone bed of interbedded sandstone and siltstone
• Lower limit: Transitional, partly unconformity (Kobinaizawa Formation), Unconformity (Fujikotogawa Formation, Iwaya Formation)

• Distribution: Maeyama river, Maeyama - Kurosawa - Bosawa, Kitaakita city, Akita pref.
• Fossils: Plants
• Fossils (Omma-Manganji fauna): Spisula sachalinensis, Umbonium akitana

• Murakami et al. (2008) Jour. Geol. Soc. Japan, vol.114, Supplement, pp.111-120 DOI
• Sumi and Moritani (1973) Geology of the Yonaizawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 46p. (in Japanese with English abstract 4p.)
• Hirayama and Sumi (1963) Takanosu, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 90p. (in Japanese with English abstract 7p.)