山梨県の新第三系について : 特にグリーンタフ変動地帯における層序と地質年代学的研究

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The stratigraphy and chronology of the Neogene formations in Yamanashi Prefecture are shown in Table 1, and are summarized as follows. A. Fujikawa group 1. Akebono formation. It is composed mainy of boulder conglomerates together with some inter-calations of sandstone. Marine molluscan fossils are abundant in the sandstone. It may represent a horizon between the zones N 16 and N 18 of BLOW's standard. 3,500 m thick. 2. Minobu formation. It is composed of conglomerate and alternation of sandstones and mudstones. Among the foraminifers from the mudstones and fine sandstones Globigerina nepenthes and Globorotalia menardii are noteworthy, and may indicate the zone N 15. 1.000 m thick. 3. Aimata formation. It consists mostly of tuff breccia and agglomerates ranging from pyroxene andesite to more basic rocks. Thin beds of mudstone are intercalated. This formation interfingers with the preceding Minobu formation. It may also be correlated to the zone N 15 from fossil data and K-Ar dating of 9.3 m.y. 1,500 m thick. 4. Shimobe formation. It is composed of rhythmic alternation of mudstones, sandstones and fine conglomerates. Foraminifers are abundant, and significant are Globigerina nepenthes and Orbulina universa. It is considered to be correlated to the zone N 14. 1,500 m thick. B. Misaka group 1. Kawaguchi formation. It is composed of dacite and acidic tuffaceous sandstones. Mudstones are intercalated, and lenses of limestone are found rarely. It may be correlated to the zone N 13. 800 m thick. 2. Onuma formation. It is composed of acidic pyroclastics, sandstones and mudstones. The occurrence of Globorolalia fohsi fohsi suggests the zone N 11 or N 12. 1,000 m thick. 3. Takahagi formation. It consists mostly of basic lavas and pyroclastics, but has thin beds of mudstone. Operculina complanata is found in the mudstone, and may indicate the zone N 10. 1,500 m thick. 4. Nishiyatsushiro formation. It is composed of dacite and pyroclastics. Thin beds of mudstone are intercalated. Orbulina universa is found in this formation. It may be correlated to the zone N 9. 1,500 m thick. 5. Momonoki formation. It is made up mostly of massive mudstones. Among many foraminifers from this formation Lepidocyclina japonica and Miogypsina kotoi are noteworthy. This formation may be referred to the Daijima, and may represent a horizon between N 7 and N 8. 1,000 m thick. 6. Kushigatayama formation. It consists mostly of basic lavas and pyroclastic rocks with thin beds of shale. It may be correlated to the Monzen, and to the zones N 3 to N 6. The base is unknown. 3,000 m or more in thickness. Among the formations introduced above, the Kushigatayama is considered to be late Oligocene to early Miocene, while the Momonoki seems to be early Miocene. The Takahagi, Kawaguchi and the Shimobe are considered to be middle Miocene, and the Minobu and Aimata formations belong to the upper Miocene. The Akebono ranges from the upper Miocene to the lowermost Pliocene.
日本地質学会の論文
1976-12-30

山梨県の新第三系について : 特にグリーンタフ変動地帯における層序と地質年代学的研究

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