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Yabu Formation (Sakakura, 1935) Tokuhashi and Endo, 1984

Invalid synonym: Ishizaki Formation, Yokaichiba Formation, Hokota Formation

• Type locality: Yabu - Yado, Kisarazu city, Chiba prefecture
• Coherent formation
• Paleo-Tokyo bay fill deposit
• A cycle of marine transgression - marine regression
• Pleistocene (MIS 9.3)

• Sedimentary facies (Upper): Shallow marine
• Sedimentary facies (Lower): Fluvial, Brackish
• Sedimentary facies (Northernmost): Estuary
• Sedimentary facies (North): Storm-dominated beach - shoreface
• Sedimentary facies (East, Upper): Wave dominated bay
• Sedimentary facies (East, Lower): Flood plain
• Sedimentary facies (West, Upper): Transgressive lag, Lower shoreface, Upper shoreface, Backshore, Foreshore
• Sedimentary facies (West, Middle): Quiet inner bay, Sand spit
• Sedimentary facies (West, Lower): Fluvial channel, Flood plain
• Lithofacies (East, Upper): Sandy mud, Muddy sand
• Lithofacies (East, Lower): Mud, Sandy mud, Muddy sand
• Lithofacies (West, Upper): Sands
• Lithofacies (West, Middle): Sandy mud, Muddy sandsS
• Lithofacies (West, Lower): Sands, Gravels, Mud
• Sedimentary structures: Hummocky cross-stratification, Trough cross-stratification, Parallel stratification

• Thickness: 5 - 60 m
• Thickness (Upper): 6.7 - 17.8 m
• Thickness (Middle): 10.3 m
• Thickness (Lower): ca. 20 m
• Upper limit: Conformity or Unconformity (Kamiizumi Formation, Kiyokawa Formation), Unconformity (Kenjaku Member, Namegata Member, Hinuma Terrace Gravels, Joso Formation, Kioroshi Formation)
• Lower limit: Conformity or Unconformity (Jizodo Formation)

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

• Distribution: Inashiki terrace, Kashima terrace, Namegata terrace, Higashi-Ibaraki terrace, Tsukuba terrace, Ibaraki pref.
• Distribution: Yabu - Yado, Kisarazu city, Chiba pref.; Anegasaki, Ichihara city, Chiba pref.; Hitomi - Sakata - Koitooyatsu, Kimitsu city, Chiba pref.; Kamihataki, Hokota city, Ibaraki pref.; Lake Hinuma - Hinuma river, Hokota city - Ibaraki city - Oarai city, Higashiibaraki county, Ibaraki pref.; Tomoe river - Nanase river, Hokota city, Ibaraki pref.; Sonobe river, Omitama city, Ibaraki pref.; Koise river, Ishioka city, Ibaraki pref.
• Fossils (Upper): Echinoids (Schizaster sp.), Annelids (Ditrupa sp.), Trace fossils (Macaronichnus segregatis)
• Fossils (Upper, Shellfishes): Acila (Truncacila) insignis, Anomalocardia (Velemolpa) minuta, Aquipecten vesiculosus, Cadella alubrica, Cadella lubrica, Clementia vatheleti, Clinocardium californiense, Clinocardium (Fuscocardium) braunsi, Corbicula sandaiformis, Cryptomya busoensis, Cryptonatica janthostomoides, Diplodonta (Felaniella) usta, Dosinia (Phacosoma) sericea, Fabulina nitidula, Glycymeris pilsbryi, Glycymeris yessoensis, Granulifusus musashinoensis, Limopsis cummingi, Lucinoma concentricum, Macoma nipponica, Macoma tokyoensis, Mactra sulcataria, Mercenaria stimpsoni, Minolia subangulata, Mitrella bicincta, Modiolus (Modiolus) difficilis, Neptunea (Barbitonia) arthritica, Olivella fabula, Panopea japonica, Paratapes undulata, Patinopecten tokyoensis, Pecten (Mizuhopecten) tokyoensis, Pecten (Notovola) albicans, Peronidia venulosa, Poromia flexosa, Potamocorbula amurensis, Protothaca (Callithaca) adamsi, Raeta (Raetellops) yokohamensis, Siliqua alta, Solen grandis, Solen krusensterni, Soletellina olivacea, Soletellina usta, Spisula sp., Tonna luteostoma, Turbonilla (Paramormula) paucicostulata, Yoldia (Cnesterium) notabilis
• Fossils (Lower): Oysters, Plant roots, Plant fragments, Burrows
• Fossils (Lower, Shellfishes): Dosinia angulosa, Macoma incongrua, Tapes japonica
• Fossils (Foraminifera): Buccella frigida, Buccella nipponica, Cassidulina depressa, Cibicides refulgens, Elphidium advenum, Elphidium clavatum, Elphidium crispum, , Globigerina budboides, Globigerina eggeri, Globigerina pachyderma, Globigerinoides ruber, Globorotalia inflata, Hanzawaia nipponica, Lagenonodosaria scalaris, Pseudononion japonicum, Pulleniatina obliquiloculata, Quinqueloculina spp., Rotalia minuta
• Fossils (West): Plant roots
• Fossils (West, Shellfishes): Arca sp., Dentalium (Paradentalium) octangulatum, Dosinella angulosa, Fulvia mutica, Raetellops pulchellus, Reticunassa japonica, Ringiculina doliaris, Scapharca kagoshimensis, Turbonilla sp., Veremolpa micra
• Fossils (West, Ostracods): Bicornucythere bisanensis, Loxoconcha optima, Neomonoceratina delicata
• Fossils (West, Diatoms): Achnanthidium spp., Cyclotella spp., Cymatosira belgica, Diploneis smithii, Luticola spp., Navicula spp., Pseudostaurosira spp., Reimeria sinuata, Thalassiosira spp.
• Fossils (West, Pollen): Alnus sp., Betula sp., Fagus sp., Juglans sp., Pinus sp., Pterocarya sp., Quercus sp., Ulmus sp., Zelkova sp.
• Fossils (Kimitsu city, Shellfishes): Crassostrea gigas, Cryptonatica andoi, Glossaulax didyma, Glycymeris vestita, Glycymeris yessoensis, Gomphina melanagis, Homalopoma nocturnum, Neptunea arthritica, Patinopecten tokyoensis, Pecten albicans, Psudocardium sachalinense, Ruditapes philippinarum, Scapharca broughtonii, Tresus keenae, Umbonium costatum
• Fossils (Kimitsu city, Ostracods): Aurila munechikai, Howeina sp., Loxoconcha (Loxoconcha) laeta, Loxoconcha (Loxoconcha) optima, Pontocythere miurensis, Ruggieria (Keijella) bisanensis, Xestoleberis hanaii
• Fossils (Kimitsu city, Diatoms): Actinella brasiliensis, Actinocyclus ingens, Actinoptychus senarius, Actinoptychus splendens, Amphora ovalis, Arachonoidiscus ehrenbergii, Auliscus caelatus, Caloneis lauta, Campylodiscus spp., Coscinodiscus marginatus, Crammatophora macilents, Cyclotella stylorum, Cymbella cuspidata, Diploneis finnica, Diploneis yatukaensis, Eunotia spp., Gomphonema spp., Gyrosigma spp., Melosira ambigua, Melosira distans, Melosira granulata, Melosira sulcata, Navicula americana, Navicula pusilla, Nitzschia cocconeiformis, Nitzschia granulata, Pinnularia spp., Stephanopyxis spp., Surirella spp., Synedra ulna, Thalassionema nitzschioides,
• Fossils (Kimitsu city, Pollen): Abies sp., Betula sp., Cupressaceae, Fagus sp., Picea sp., Pinus sp., Tsuga sp.
• Tephra: OgA, Yb0, Yb1, Yb2, Yb3, Yb4, Yb5

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