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Hekikai Formation Machida et al., 1962

• Type locality: west of Sanage station, Sanage town, Toyota city, Aichi prefecture
• Coherent formation
• early Pleistocene (MIS 5e or MIS 5e - 5a; ca. 32 ka, ¹⁴C; 90 - 80 ka, ESR)
• Upper: Pleistocene (95 - 70 ka)
• Lower: Pleistocene (120 - 95 ka)
• Correlation: upper Atsuta Formation, Miai Formation

• Sedimentary facies: Marine
• Sedimentary facies: Bay
• Sedimentary facies (Upper): Fore set of delta
• Sedimentary facies (Lower): Bottom set of delta
• Water temperature: Warm ocean current (Shellfishes)
• Lithofacies (Upper): Sands, Gravels
• Lithofacies (Upper, Minor): Interbedded sand and mud
• Lithofacies (Lower): Mud (Marine clay)
• Sedimentary structures: Parallel stratification
• Sedimentary structures (Minor): Cross stratification

• Thickness: ca. 5 - 35 m
• Upper limit: Unconformity (Koshido Formation)
• Lower limit: bottom of a thick marine clay bed
• Upper limit: Unconformity (Yadagawa Formation, Koromo Formation, Younger Ryoke Granitoids)

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

• Distribution: Sanage town - Koshido town - Miyama town - Toyota town - Kamigo town - Miyoshi town, Toyota city, Aichi pref.; Shinonome - Anjo station, Anjo city, Aichi pref.; Yokohama, Takahama city, Aichi pref.; Nishio city, Aichi pref.; Toyoake city, Aichi pref.; Chikusa ward, Nagoya city, Aichi pref.
• Fossils: Shellfishes, Echinoids, Bryozoans, Barnacles, Decapods
• Tephra: K-Tz

• Nakashima et al. (2021) Geology of the Toyota District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, AIST, 91p. (in Japanese with English abstract 4p.)
• Makinouchi et al. (2011) Jour. Geol. Soc. Japan, vol.117, no.2, pp.79-94 DOI
• Sakamoto et al. (1986) Geology of the Nagoya-Nambu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 55p. (in Japanese with English abstract 3p.)