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Matsushima Formation Ishii et al., 1982

Invalid synonym: Matsushima Tuff

• Type locality: Mount Sokan - Isozaki, Matsushima city, Miyagi county, Miyagi prefecture
• Volcanic rocks
• early Miocene (16.5 - 15.5 Ma, Diatoms)

• Sedimentary facies: Marine
• Sedimentary facies: Submarine pyroclastic flow deposit
• Lithofacies: Acidic pumice tuff
• Lithofacies (Minor): Siltstone, Tuffaceous sandstone

• Thickness: 150 - 400 m
• Upper limit: The boundary between siltstone-dominant horizon and underlying pumice tuff and tuffaceous sandstone-dominant horizon
• Upper limit: Transitional (Otsuka Formation), Unconformity (Hataya Formation, Mitsuya Formation)
• Lower limit: Conformity (Ajiri Formation)

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

• Distribution: Mount Sokan - Isozaki - Miyato island - Nono island - Mahanashi island, Matsushima city, Miyagi county, Miyagi pref.; Toguhama, Shichigahama city, Miyagi county, Miyagi pref.
• Fossils (Diatoms): Actinocyclus ehrenbergii, Actinocyclus ellipticus, Actinocyclus ingens, Actinocyclus ingens var. nodes, Actinocyclus octonaris, Actinoptychus senarius, Actinoptychus undulatus, Arachnodiscus spp., Aulacosira granulata, Biddulphia aurita, Cocconeis californica, Cocconeis costata, Cocconeis scutellum, Cocconeis vitrea, Coscinodiscus cfr. curvatulus, Coscinodiscus endoi, Coscinodiscus lewsianus, Coscinodiscus marginatus, Coscinodiscus aff. nodulifer, Coscinodiscus oculus-iridis, Coscinodiscus symbolophorus, Cymatosira aff. lorentziana, Delphineis penelliptica, Denticulopsis cfr. kanayae, Denticulopsis cf. lauta, Denticulopsis norwegic, Diploneis smithii, Grammatophora sp., Hemiaulus bipons, Hemiaulus polymorphus, Hyalodiscus ukaiensis, Goniothecium tenue (<= Ikebea spp.), Kisseleviella carna, Liradiscus bipolaris, Macrolla stella, Mediaria splendida, Melosira sol, Melosira sulcata, Navicula spp., Nitzschia challengeri, Paralia sulcata, Pleurosigma sp., Porosira cfr. gracialis, Pseudodimerogramma elegans, Pseudopodosira aff. hyalina, Pterotheca subulata, Raphidodiscus marylandiscus, Rhabdonema japonicum, Rhaphoneis elegans, Rhaphoneis miocenica, Rhizosolenia miocenica, Rhizosolenia cfr. praebarboi, Rhizosolenia styliformis, Rhizosolenia aff. praebarboi, Rouxia naviculoides, Stephanogonia aff. hanzawae, Stephanogonia polyacantha, Stephanopyxis spp., Synedra jouseana, Synedra miocenica, Thalassionema hirosakiensis, Thalassionema nitzschioides, Thalassiosira leptopus, Thalassiothrix longissima, Trochosira concava, Trochosira spinosa, Zygoceros quadricornis

• 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.)