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Nakahara Formation Hanzawa et al., 1958

Invalid synonym: Karuizawa Sandstone and Conglomerate Formation, Tamaniwa Formation

• Type locality: Kotaru river, Nakahara, Yonezawa city, Yamagata prefecture
• Coherent formation
• late Pliocene

• Sedimentary facies: Fluvial
• Sedimentary facies: Braided river
• Lithofacies: Conglomerate, Mudstone, Sandstone
• Lithofacies (Minor): Lignite
• Sedimentary structures: Cross stratification, Imbrication

• Thickness: ca. 200 - 250 m
• Lower limit: Bottom of the horizon intercalating thick conglomerate beds
• Lower limit: Conformity (Tenoko Formation)

• Distribution: Kotaru river, Nakahara, Yonezawa city, Yamagata pref.; Tamaniwa, Kawanishi city, Higashiokitama county, Yamagata pref.; Sugo bridge, Iide city, Nishiokitama county, Yamagata pref.
• Fossils (Lower, Tenoko flora): Comptonia kotoi, Menyanthus cf. trifoliata

• Yanagisawa and Yamamoto (1998) Geology of the Tamaniwa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 94p. (in Japanese with English abstract 4p.)