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Omma Sandstone Member, Onma Sandstone Member (Yokoyama, 1927) Sumi et al., 1989

Invalid synonym: Omma Formation, Onma Formation, Okuwa Formation, Yamazaki Calcareous Sandstone Member

• Type locality: Okuwa, Kanazawa city, Ishikawa prefecture
• "Omma" is the old name of Okuwa
• Coherent formation
• early Pleistocene (2.02 - 0.99 Ma)
• Interfingered: Zukawa Sandstone Member
• Correlation: Chokeiji Sand Member, Anyobo Sandstone and Mudstone Alternation Member, Yada Sandstone Member

• Sedimentary facies: Marine
• Climate: Cold
• Depth of water (Upper): Upper sublittoral zone (20 -100m, Nannofossils)
• Depth of water (Lower): Lower sublittoral zone (35 -100m, Nannofossils)
• Lithofacies (Upper): Fine - coarse sandstone
• Lithofacies (Upper, Minor): Siltstone, Conglomerate
• Lithofacies (Lower): Fine sandstone, Siltstone
• Lithofacies (Bottom): Conglomerate, Tuff
• Sedimentary structures: Cross stratification
• Paleocurrent: to North-northest - Northeast

• Thickness: ca. 110 - 350 m
• Thickness (Tuff): ca. 2 - 20 m
• Upper limit: Conformity (Udatsuyama Formation), Unconformity (Hanyu Formation)
• Lower limit: Conformity (Takakubo Formation), Unconformity (Sunagozaka Formation)

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

• Distribution: Southern Kanazawa city, Ishikawa pref.; Kamo - Yachi - Nakatsubata - Hontsubata, Tsubata city, Kahoku county, Ishikawa pref.; Tada - Yochi - Uwadana - Kiya - Uchitakamatsu - Kasashima, Kahoku city, Ishikawa pref.; Tagawa - Hachibuse - Anrakuji, Oyabe city, Toyama pref.
• Fossils: Sharks (Carcalodon sp.), Calcareous nannofossils
• Fossils (Omma-Manganji fauna, Shellfishes): Acila (Acila) divaricata, Acila (Truncacila) insignis, Anadara (Anadara) amicula elongata, Angulus uenulosus, Antiplanes contraria, Astarte (Tridonta) alaskaensis, Cadella lubrica, Chlamys (Chlamys) cosibensis cosibensis, Chlamys (Swiftopecten) swiftii, Clinocardium fastosum, Cryptonatica janthostomoides, Dentalium sp., Diplodonta usta, Dosinia japonica, Felaniela usta, Fulvia muticum, Glycymeris (Glycymeris) rotunda, Glycymeris (Glycymeris) yessoensis, Heteromacoma sp., LIma sp., Limopsis sp., Lucinoma sp., Macoma calcarea, Macoma tokyoensis, Mercenaria stimpsoni, Mizuhopecten tokyoensis hokurikuensis, Mya cuneiformis, Myadora sp., Mytilus sp., Natica janthostoma, Nemocardium samarangae, Nucula sp., Nuculana (Thestyleda) sp., Ostrea sp., Paphia sp., Patinopecten kurosawaensis, Patinopecten (Mizuhopecten) tokyoensis hokurikuensis, Peronidia lutea, Perodinia zyonoensis, Portlandia (Megayoldia) thraciaeformis, Pseudoamiantis tauyensis, Searlesia japonica, Spisula sachalinensis, Spisula (Mactromeris) vogi, Turritella (Neohaustator) saishuensis, Venericardia ferrugines, Venericaldia nakamurai, Yoldia (Cnesterium) excavata, Yoldia (Cnesterium) notabilis
• Fossils (Echinoids): Clypeaster virescens, Echinarachnius mirabilis, Echinarachnius tsuda, Linthia nipponica
• Fossils (Foraminifera): Bolivina seminuda, Cassidulina subglobosa, Cibicides refulgens, Elphidium clavatum, Elphidium bartletti, Hanzawaia nipponica, Nonion japonicum, Pseudopolymorphina ishikawaensis, Pseudopolymorphina okuwaensis, Rotalia japonica, Sigmoidella kagaensis
• Tephra: Hi, Tagawa tuffaceous tuff (21 m thick), O2 tuff

• Kaneko et al. (2016) Jour. Geol. Soc. Japan, vol.122, no.5, pp.193-206, DOI
• Tamura et al. (2010) Jour. Geol. Soc. Japan, vol.116, Supplement, pp.1-20 DOI
• Sumi et al. (1989) Geology of the Isurugi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 118p. (in Japanese with English abstract 5p.)
• Sumi (1978) Geology of the Tsubata District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 55p. (in Japanese with English abstract 4p.)
• Inoue et al. (1964) Johana, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 32p. (in Japanese with English abstract 5p.)
• Imai (1959) Kanazawa, Explanatory Text of the Geological Map of Japan, Scale 1:50,000, Geological Survey of Japan, 27p. (in Japanese with English abstract 3p.)