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Ajiri Formation (Hanzawa et al., 1958) Ishii et al., 1982

• Type locality: Ojima town - Shintomi town - Teizandori, Shiogama city, Miyagi prefecture
• Coherent formation
• early Miocene (24.4 Ma, FT)
• Correlation (Lower): Oido Formation

• Sedimentary facies (Upper): Shallow marine
• Sedimentary facies (Upper): Tidal flat, Subtidal (Shellfish fossils)
• Sedimentary facies (Lower): Terrestrial
• Lithofacies (Top): Siltstone
• Lithofacies (Upper): Interbedde siltstone and sandstone
• Lithofacies (Upper, Minor): Tuff
• Lithofacies (Lower): Interbedde tuff and tuffaceous sandstone
• Lithofacies (Lower, Minor): Conglomerate, Pumice tuff, Silicified woods
• Sedimentary structures: Cross stratificaiton

• Thickness: 200 - 250 m
• Upper limit: Conformity (Lower Pumice Tuff Member), Unconformity (Hataya Formation, Toguhama Formation, Kameoka Formation)
• Lower limit: Bottom of pumice tuff-dominant horizon
• Lower limit: Conformity (Sauramachi Formation), Unconformity (Rifu Formation)

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

• Distribution: Ojima town - Shintomi town - Teizandori - Iboishi, Shiogama city, Miyagi pref.; Mount Anetori, Matsushima town, Shiogama city, Miyagi pref.
• Fossils: Desmostylus hesperus japonicus, Brachiopods (Terebratulina sp.), Echinoids
• Fossils (Shellfishes): Acesta sp., Acila (Acila) cf. divaricata, Anadara (Anadara) cf. ninohensis, Anadara (Anadara) watanabei, Ancistrolepis sp., Batillaria mizunamiensis, Batillaria tateiwai, Bittium sp., Calliostoma sp., Calyptraea tubura, Cancellaria hukusimana, Cancellaria aff. kobayashii, Cerithidea (Cerithideopsilla) minoensis, Chicoreus tiganouranus, Clinocardium (Ciliatocardium) cf. ciliatum, Clinocardium (Ciliatocardium) cf. shinjiense, Clinocardium (Clinocardium) cf. narusawaense, Cultellus izumoensis izumoensis, Cyclina japonica, Dosinia (Dosinella) cf. anguloides, Dosinia (Phacosoma) nomurai, Epitonium sp., Euspira meisensis, Fabulina? sp., Fissidentalium yokoyamai, Fulgoralia cf. densicostata, Fulgoralia cf. striata, Glycydonta itoigawae, Hiatula minoensis, Laternula sp., Limopsis osawanoensis, Lucinoma acutilineata, Macoma (Macoma) incongrua, Macoma (Macoma) cf. optiva, Megasurcula siogamensis, Mizuhopecten kimurai kimurai, Murex sp., Mya (Arenomya) aff. fujiei, Nassarius (Zeuxis) cf. kometubus, Neptunea sp., Nuculana sp., Oliva sp., Ostrea sp., Panomya simotomensis, Panope sp., Plicatula sp., Portlandia (Acilana) tokunagai, Saxolucina khatai, Siphonalia sp., Siratoria siratoriensis, Solen cf. strictus, Sprendrillia sp., Tateiwaia tateiwai, Tateiwaia yamanarii, Throcia sp., Turritella shataii, Vasticardium ogurai, Venericardia (Cyclocardia) siogamensis, Vicarya yokoyamai, Vicaryella aff. ishiiana
• Fossils (Shiogama flora): Carpinus sp., Cinnamomum miocenum, Comptonia naumanni, Dryophyllum sp., Fagus americana, Fagus antipofi, Ilex sp., Liquidamber formosana, Liquidambar miosinica, Metasequoia occidentalis, Parrotia fagifolia, Pterocarya protostenoptera, Pterocarya rhoifolia, Quercus miovariabilis, Salix sp., Sequoia sempervirens, Smilax trinervis, Sophora miojaponica, Zelkova ungeri
• Fossils (Diatoms): Actinocyclus ingens, Actinocyclus octonaris, Actinoptychus senarius, Actinoptychus undulatus, Cocconeis sp., Coscinodiscus endoi, Coscinodiscus marginatus, Coscinodiscus symbolophorus, Cymatosira sp., Delphineis penelliptica, Denticulopsis sp., Grammatophora sp., Goniothecium tenue (<= Ikebea spp.), Hemiaulus polymorphus, Hyalodiscus obsoletus, Ikebea sp., Isthmia sp., Kisseleviella carina, Liradiscus bipolaris, Mediaria splendida, Melosira sp., Neodelphineis? sp., Paralia sulata, Plagiogramma staurophorum, Porosira cfr. gracialis, Pseudodimerogramma sp., Raphidodiscus marylondicus, Rhaphoneis miocenica, Rhizosolenia cfr. praebarboi, Stephanogonia polyacantha, Stephanopyxis spp., Synedra jouseana, Synedra miocenica, Thalassionema hirosakiensis, Thalassionema nitzschioides, Thalassiosira spp., Thalassiothrix longissima, Triceratium condecorum, Trocosira spinosa

• Ishii et al. (1983) Geology of the Shiogama District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 112p. (in Japanese with English abstract 6p.)
• Ishii et al. (1982) Geology of the Matsushima District, Quadrangle Series, Scale 1:50,000, Geological Survey of Japan, 121p. (in Japanese with English abstract 9p.)