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Tamugigawa Formation Niigata University Research Group of Geology in Higashikubiki District, 1987

Invalid synonyms: Taihei Formation, Koarato Formation, Nabetachiyama Formation

Invalid synonyms (Siltstone facies): Shobu formation

• Type locality: Tamugi river, Itayama, Oshima ward, Joetsu city, Niigata prefecture
• Coherent formation
• Rift basin sediments
• early - late Pliocene (5.4 - 3.2 Ma, FT, Foraminifera)
• Contemporaneous heterotopic facies: upper Takegahana Formation, Kurohime Formation
• Contemporaneous heterotopic facies (Upper): Hachikokusan Formation
• Interfingered: Suganuma Formation
• Interfingered (Upper): upper Yoneyama Formation
• Correlation: Nishiyama Formation (Hamatsuda facies)
• Correlation (middle - lower): Hododaira Formation

• Sedimentary facies: Marine
• Sedimentary facies: Submarine fan (Trough-fill type)
• Sedimentary facies (Lower): Turbidite
• Depth of water: 200 - 500 m (Shellfishes), 150 m (Foraminifera)
• Lithofacies (Upper): Mudstone-dominant interbedded sandstone and mudstone
• Lithofacies (Upper, Minor): Sandstone, Mudstone
• Lithofacies (Middle): Interbedded sandstone and mudstone
• Lithofacies (Lower): Sandstone, Interbedded sandstone and siltstone
• Lithofacies (Minor): Lapilli tuff
• Sedimentary structures: Trace fossils, Current marks

• Thickness: ca. 250 - 1,500 m
• Thickness (Upper): 450 m
• Thickness (Lower): 500 - 800 m or thicker
• Thickness (Siltstone facies = Shobu Formation): 150 - 450 m
• Upper limit: Transitional (Shiroiwa Formation, Higashigawa Formation), Conformity (Uragawara Formation), Conformity, partly unconformity (Kurohime Formation), Unconformity (Higher Terrace Deposit)
• Lower limit (Sugawa Formation): Bottom of interbedded sandstone and mudstone overlying mudstone bed
• Lower limit: Transitional (Sugawa Formation), Conformity (Takegahana Formation)

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

• Distribution: Itayama, Oshima ward, Joetsu city, Niigata pref.; Yoshikawa ward - Uragawara ward, Joetsu city, Niigata pref.; Isonobe - Yamanaka, Takayanagi town, Kashiwazaki city, Niigata pref.; Kiriyama, Tokamachi city, Niigata pref.
• Fossils: family Odobenidae, Sus sp., Sharks (Teeth), Balanus sp., Sponges (Makiyama chitanii)
• Fossils (Shellfishes): Akebiconcha kawamurai, Anadara amicula, Buccinum sp., Calyptogena sp., Cardium sp., Glycymeris yessoensis, Malletiidae gen. et sp. indet, Mercenaria sp., Mercensis sp., Nucula sp., Ostrea sp., Paphia sp., Rapana thomasiana, Tindaria soyoae, Turritella sp.
• Fossils (Foraminifera): Alabamia? sp., Ammodiscus sp., Ammonia sp., Baggina sp., Bathysiphon sp., Bolivina decussata, Bolivina pacifica, Bolivina robusta, Bolivinita quadriratera, Buccella frigida, Buccella inusitata, Bulimina aculiata, Bulimina striata, Bulimina tenuata, Buliminella elegantissima, Cassidulina carinata, Cassidulina japonica, Cassidulina norcrossi, Cassidulina norvangi, Cassidulina sagamiensis, Cassidulina yabei, Cibicides aknerianus, Cibicides pseudoungerianus, Cibicides reflugens, Cibicides ungerianus, Cibicidoides sp., Cribrononion clavatum, Cribrononion subglanulosum, Cribrostomoides cf. evoluta, Cribrostomoides cf. subglobosum, Cyclammina cf. ezoensis, Cyclammina japonica, Cyclammina pusilla, Dentalina sp., Discammina sp., Discorbis sp., Dorothia sp., Eilohedra nipponica, Eilohedera rotunda, Elphidium sp., Epistominella exiqua, Epistominella levicula, Epistominella naraensis, Epistominella pulchella, Eponides sp., Fissulina cucurbitasema, Fissulina marginata, Furusenkoina complanata, Gaudryna arenaria, Glangulina sp., Globigerina bulloides, Globigerina decoraperta, Globigerina falconensis, Globigerina foliata, Globigerina incompta, Globigerina inflata, Globigerina praebulloides, Globigerina quinqueloba, Globigerina rubescens, Globigerina umbilicata, Globigerina woodi, Globigerinita glutinata, Globigerinita uvula, Globocassidulina subglobosa, Globobulimina auriculata, Globobulimina cf. pupoides, Globocassidulina depressa, Globocassidulina subglobosa, Globoquadrina aluspira, Globorotalia inflata, Globorotalia praeinflata, Globorotalia cf. orientalis, Globorotalia praeinflata, Globorotalia scitula, Goesella schenckii, Gryoidina soldanii, Gyroidinoides nipponicus, Haplophragmoides cf. trullissatum, Islandiella japonica, Islandiella nipponicus, Islandiella norcrossi, Islandiella norvangi, Islandiella yabei, Karreriella japonica, Lagena acuticosta, Lagena distoma, Lagena laevicostata, Lenticulina sp., Loxostoma bradyi, Martinottiella communis, Melonis nicobarense, Melonis pompilioides, Miliammina echigoensis, Neoconorbina sp., Neogloboquadrina asanoi, Neogloboquadrina blowi, Neogloboquadrina continuosa, Neogloboquadrina dutertrei, Neogloboquadrina eggeri, Neogloboquadrina humerosa, Neogloboquadrina incompta, Neogloboquadrina cf. kagaensis, Neogloboquadrina pachyderma, Nodosaria sp., Nonion sp., Nonionella stella, Nonionellina labradicum, Orbulina universa, Oridosalis tenerus, Oridosalis umbonatus, Plectina sp., Plectofrondicularia miocenica, Pseudoparrella takayanagii, Pullenia apertula, Pullenia bulloides, Pyrgo murrhina, Quinqueloculina agglutinata, Redtobolivina raphana, Reophax sp., Rotalia? sp., Saccammina fragilis, Silicosigmoilinella sp., Sphaeloidina austriaca, Sphaeloidina bulloides, Sphaeloidina cf. japonica, Sphaeroidinella bulloides, Sphaeloidinella dehiscens, Spiroloculina sp., Textularia agglutinaris, Trifarina cf. angulata, Trifarina hughesi, Trifarina kokozuraensis, Triloculina sp., Trochammina spp., Uvigerina akitanesis, Uvigerina peregina diruputa, Uvigerina subperegrina, Valvulineria sadonica
• Fossils (Diatoms): Actinocyclus octonarius, Actinoptychus senarius, Aulacoseira sp., Coscinodiscus marginatus, Coscinodiscus radiatus, Neodenticula koizumii, Nitzschia marina, Paralia sulcata, Rhizosolenia hebetata f. hiemalis, Simonseniella barboi, Stephanopyxis spp., Thalassionema nitzschioides, Thalassiosira antiqua, Thalassiosira convexa
• Tephra: Kotsunagi Tuff, Kamioka Tuff, Itayama Tuff, Azamihira Hornblende Tuff, Isg-c, Isg-e, Isg-f, Isg-g, Isg-h, Suga Tuff, Shimoebiike Tuff, Yoneyama Tuff, Iriyamagawa Tuff, Nabiro Tuff

• Takano (2011) Jour. Geol. Soc. Japan, vol.117, no.4, pp.238-258 DOI
• Takeuchi et al. (2000) Geology of the Matsunoyama Onsen District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 76p. (in Japanese with English abstract 5p.)
• Takeuchi et al. (1996) Geology of the Kakizaki District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 48p. (in Japanese with English abstract 5p.)
• Takeuchi and Kato (1994) Geology of the Takada-tobu District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 67p. (in Japanese with English abstract 5p.)
• Kobayashi et al. (1989) Geology of the Okanomachi District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 112p. (in Japanese with English abstract 5p.)