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Hachiisan Mudstone Member Ozawa et al., 1979

• Type locality: Mount Hachii, Omori town, Yokote city, Akita prefecture
• Coherent formation
• middle Miocene
• Contemporaneous heterotopic facies: Upper Sugota Formation

• Sedimentary facies: Marine
• Depth of water: Deep sea
• Lithofacies: Mudstone (Glauconite-bearing)
• Lithofacies (Minor): Acidic tuff

• Thickness: 300 m or thicker

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

• Distribution: Mount Hachii - Gokurakuji, Omori town, Yokote city, Akita pref.
• Fossils (Foraminifera): Anomalina globrata, Buccella cf. inusitata, Bulimina striata, Cassidulina norcrossi, Cibicides asanoi, Cibicides pseudoungerianus, Dentalina sp., Epistominella cf. naraensis, Epistominella cf. pulchella, Fissurina spp., Fursencoia mexicana, Globigerina spp., Globobulimina ovata, Globobulimina pacifica, Globorotaria cf. praefohsi, Guttulina sp., Gyroidina orbicularis, Hopkinsina sp., Lagena sp., Marginulina sp., Martinottiella communis, Nodosaria sp., Nonion cf. labradoricum, Planulina nipponica, Polymorphina sp., Pullenia bulloides, Pullenia salisburyi, Quadrimorphina sp., Rectobolivina sp., Sigmomorphina sp., Sphaeroidina bulloides, Sphaeroidina japonica, Stilostomella sp., Tosaia sp., Uvigerina probocidea, Valvulineria sp.

• Ozawa et al. (1979) Geology of the Asamai District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 53p. (in Japanese with English abstract 4p.)