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Namegata Member Ooi and Yokoyama, 2011

Invalid synonym: upper Miwa Formation

• Type locality: Ishigami, Namegata city, Ibaraki prefecture
• Barrier island system in Old Tokyo bay
• Coherent formation
• Pleistocene

• Sedimentary facies: Marine, Brackish
• Sedimentary facies: Coastal plain with beach ridges
• Sedimentary facies (Northernmost): Tidal channel, Lagoon
• Sedimentary facies (North, East): Storm-dominated beach - foreshore at the ocean side of a barrier island
• Sedimentary facies (Center): Flood tidal delta, Washover, Lagoon at the land side of a barrier island
• Sedimentary facies (South): Inner bay near a mouth of barrier islands
• Lithofacies: Sandstone
• Lithofacies (Lower): Mudstone
• Lithofacies (Basal): Conglomerate
• Lithofacies (South): Silty sandstone
• Sedimentary structures (Tidal): Planar cross-stratification, Hummocky cross-stratification, Trough cross-stratification, Parallel stratification, Pipe rocks

• Thickness: ca. 10 - 20 m
• Thickness (Basal): 10 cm - 3 m
• Upper limit: Conformity or Unconformity (Joso Formation), Unconformity (Ibaraki Clay Formation, Nukada Terrace Gravels, Hinuma Terrace Gravels)
• Lower limit: Unconformity (Ajigaura Pumiceous Tuff Member, Hanareyama Formation, Tomobe Formation, Kasagami Formation, Kenjaku Member, Yabu Formation, Kamiizumi Formation, Oarai Formation)

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

• Distribution: Inashiki terrace, Higashi-Ibaraki terrace, Namegata terrace, Kashima terrace, Lake Hinuma, Naka terrace, Ibaraki pref.
• Distribution: Hongo, Ibaraki city, Higashiibaraki county, Ibaraki pref.; Ishigami, Namegata city, Ibaraki pref.; Ogoyama, Kasama city, Ibaraki pref.; Shimoirino, Mito city, Ibaraki pref.
• Fossils (Upper Miwa Formation, Shellfishes): Anadara (Scapharca) subcrenata, Anomia cytaeum, Batillaria zonalis, Cadella luburica, Cerithidea fluviatilis, Cerithidea rhizophorarum, Chlamys (Chlamys) farreri akazara, Chlamys (Chlamys) swiftii, Chlamys nipponensis, Crassostrea gigas, Diplodonta (Felaniella) usta, Dosinia (Phacosoma) troscheli, Fulvia mutica, Glycymeris (Glycymeris) yessoensis, Gomphina melanaegis, Hiatula (Nuttallia) ezonis, Joanisiella cumingi, Limopsis (Oblimopa) forskalii, Lucinoma concentricum, Macoma incongrua, Macoma tokyoensis, Mactra (Mactra) sulcataria, Mercenaria stimpsoni, Musculus (Musculista) senhousia, Mya oonogai, Neptunea (Barbitonia) arthritica, Panope japonica, Paphia sp., Pecten (Notovola) albicans, Peronidia venulosa, Pillucina (Pillucina) pisidium, Potamocorbula amurensis, Protothaca adamsi, Raeta yokohamensis, Solen krusensterni, Spisula (Mactromeris) voyi, Spisula (Pseudocardium) sachalinensis, Suchium sp., Sunetta menstrualis, Tapes (Ruditapes) japonicus, Tapes (Ruditapes) variegatus kioroshiensis, Theora lata, Trapezium (Neotrapezium) japonicum
• Tephra: KtP (Kaidani Pumice Bed), Miwa Tephra group

• Ooi et al. (2013) Jour. Geol. Soc. Japan, vol.119, no.7, pp.488-505 DOI
• Ooi and Yokoyama (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.103-120 DOI
• Suzuki (2011) Jour. Geol. Soc. Japan, vol.117, Supplement, pp.121-133 DOI
• Sakamoto et al. (1981) Geology of the Ishioka District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 50p. (in Japanese with English abstract 3p.)
• Sakamoto (1975) Geology of the Isohama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 55p. (in Japanese with English abstract 4p.)
• Sakamoto et al. (1972) Geology of the Nakaminato District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 94p. (in Japanese with English abstract 5p.)