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Niranohama Formation Kurosawa, 1929

• Type locality: Niranohama seashore, Utatsu, Minamisanriku city, Motoyoshi county, Miyagi prefecture
• Coherent formation
• Early Jurassic, Hettangian (Shellfishes)

• Sedimentary facies: Brackish, Marine
• Sedimentary facies: Tidal flat, Beach, Lower shoreface
• Sedimentary facies (Upper): Upper shoreface, Storm wave base
• Sedimentary facies (Lower): Surf zone
• Lithofacies (Upper): Sandstone, Sandy mudstone
• Lithofacies (Upper, Minor): Conglomerate, Calcareous mudstone
• Lithofacies (Lower): Calcareous silty shale
• Sedimentary structures: Hummocky cross-stratification

• Thickness: ca. 25 - 200 m or thinner
• Upper limit (Hosoura Formation): Bottom of the sandstone-deficient horizon
• Upper limit: Transitional (Hosoura Formation, Mizunuma Formation)
• Lower limit: Bottom of the sandy shale-bearing horizon
• Lower limit: Transitional (Uchinohara Formation), Unconformity (Saragai Group)

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

• Distribution: Hinokuchi - Saragai - Niranohama seashore - Nakazai, Utatsu, Minamisanriku city, Motoyoshi county, Miyagi pref.; Jao river, Shizugawa, Minamisanriku city, Motoyoshi county, Miyagi pref.; Maezawa creek - Moza creek - Takihama creek, Zaigo, Minamisanriku city, Motoyoshi county, Miyagi pref.; Aikawa creek - Shirahama - Nakahara, Kitakami town, Ishinomaki city, Miyagi pref.; Mount Maginosu, Nakano, Ishinomaki city, Miyagi pref.; Nakairihata, Ishinomaki city, Miyagi pref.
• Fossils: Ichthyosaurs, Sharks (Asteracanthus sp.), Belemnoids (Sichuanobelus sp.), Ammonoids (Alsatites (Yabesites) onoderai)
• Fossils (Shellfishes): Astarte sp., Bakevellia trigona (<= Gervillia trigona), Burmesia japonica, Coelastarte cardiniiformis, Camptonectes inexpectatus, Cucullaea mabuchii, Cuspidaria? praenipponica, Eomiodon? giganteus, Eomiodon lunulatus, Eomiodon vulgaris, Geratrigonia hosourensis (<= Laevitrigonia hosourensis), Geratrigonia lata, Gervillia (Cultriopsis) shizukawensis, Grammatodon (Indogrammatodon?) nakanoi, Integricardium (Yokoyamaina) hayamii (= Cyrena elliptica), Isognomon rikuzenicus, Liostrea sp., Lopha? sp., Lucina? sp., Meleagrinella sp., Modiolus bakeveloides, Orthotrigonia midareta, Ostrea sp., Parallelodon niranohamensis, Plicatula sp., Pronoella sp., Protocardia sp., Pteria kitakamiensis, Thracia subrhombica, Trigonia senex, Vaugonia (Hijitrigonia) kojiwa, Vaugonia namigashira, Vaugonia niranohamaensis, Vaugonia yokoyamai, Yokoyamaina elliptica (= Cyrena elliptica)

• Ehiro and Morikiyo (2013) Jour. Geol. Soc. Japan, vol.119, Supplement, pp.47-67 DOI
• Takeuchi and Kaneko (1996) Geology of the Shizugawa District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 93p. (in Japanese with English abstract 5p.)
• Kamada (1993) Geology of the Tsuya District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 70p. (in Japanese with English abstract 6p.)
• Takizawa et al. (1990) Geology of the Toyoma District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 126p. (in Japanese with English abstract 8p.)
• Takizawa et al. (1984) Geology of the Ishinomaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 103p. (in Japanese with English abstract 7p.)