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Sunagomata Formation

Synonym (Invalid, Upper): Hamada Formation

• Coherent formation
• Pliocene (Shellfish fossils)

• Sedimentary facies: Marine
• Lithofacies (North): Dacitic pumice tuff
• Lithofacies (North, Basal): Conglomerate
• Lithofacies (North, Minor): Tuffaceous sandstone
• Lithofacies (South): Tuffaceous sandstone
• Lithofacies (South, Minor): Conglomerate
• Sedimentary structures: Cross-stratification

• Thickness (North): 200 - 300 m
• Thickness (South): 400 - 480 m
• Upper limit: Unconformity (Tanabu Formation)
• Lower limit: Angular unconformity (Sarugamori Formation, Shiriya Group), Unconformity (Gamanosawa Formation), Conformity (Tomari Formation)

• Distribution: Mount Katamine - Iwaya, Higashidori city, Shimokita county, Aomori pref.
• Fossils (Omma-Manganji fauna):
• Fossils: Sponges (Spicules), Barnacles
• Fossils (Bivalves): Chlamys swifti, Chlamys kaneharai, Placopecten sp., Lima yagenensis?, Hiatella sp., Mya truncata
• Fossils (Gastropods): Turritella? sp., Natica sp.
• Fossils (North, Shellfish): Cerithium sp., Clinocardium ciliatum, Clinocardium sp., Mya cfr. truncata, Patinopecten aff. yessoensis, Neptunea sp., Turritella cfr. nipponica, Balanus sp.
• Fossils (North, Foraminifera): Cassidulina sp., Nonion sp., Elphidium sp.
• Fossils (South, Shellfish): Acila nakazimai, Astarte alaskensis, Clinocardium chikagawaense, Chlamys heteroglyptus, Chlamys cosibensis, Chlamys swiftii, Limopsis sp., Macoma oinomikadoi, Nuculana sadoensis, Patinopecten kurosawaensis, Patinopecten plebejus, Pandora sp., Venericardia ferruginea, Yoldia notabilis
• Fossils (South, Foraminifera): Cibicides pseudoungerianus, Elphidium sp., Cassidulina sp., Astrononion sp.

• Tsushima and Takizawa (1977) Geology of the Shiriyazaki District, Quadrangle Series, 1:50,000, Geological Survey of Japan, 32p. (in Japanese with English abstract 4p.)
• Imai (1961) Chikagawa, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 45p. (in Japanese with English abstract 4p.)