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Hirayama Formation Takada Plain Research Group, 1961

• Type locality: Onuki - Hirayama, Joetsu city, Niigata prefecture
• Coherent formation
• Hirayama Terrace Deposit
• middle Pleistocene (ca. 110 - 100 ka)

• Sedimentary facies: Marine
• Sedimentary facies: Innar bay
• Climate: Almost same as present
• Lithofacies (Top): Volcanic sands
• Lithofacies (Upper): Sandy clay, Silt, Sands
• Lithofacies (Lower): Gravels, Sands
• Sedimentary structures (Lower): Cross stratification

• Thickness: ca. 20 m or thicker
• Thickness (Upper): ca. 4 - 8 m
• Thickness (Lower): ca. 6 m or thicker
• Upper limit: Conformity, partly unconformity (Katamachi Sand Bed), Unconformity (Hirayama Loam)
• Lower limit: Unconformity (Kota Formation, Ainokaze Formation)

• Distribution: Onuki - Hirayama - Naoetsu - Gotenyama town - Ii - Yamayashiki, Joetsu city, Niigata pref.
• Fossils (Plants): Aesculus turbinata, Alnus japonica, Euryale ferox, Juglans sieboldiana, Magnolia kobus, Magnolia obovata, Phellodendron amurense, Pterocarya rhoifolia, Scirpus sp., Styrax japonica, Tilia maximowiczii, Trapa macropoda, Vilis sp.
• Fossils (Pollen): Abies sp., Alnus sp., Cryptomeria sp., Fagus sp., Gramineae, Picea sp., Pinus sp., Quercus sp., Tsuga sp.

• Takeuchi et al. (1996) Geology of the Kakizaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 48p. (in Japanese with English abstract 5p.)
• Akahane and Kato (1989) Geology of the Takada-Seibu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 89p. (in Japanese with English abstract 3p.)