八溝山地鶏足山塊の中生界 Mesozoic Strata of the Keisoku Mountain Block in the Yamizo Mountains, Central Japan

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The Yamizo Mountains consist of four mountain blocks: the Yamizo, Torinoko, Keisoku and Tsukuba Mountain Blocks, from north to south. The northern three mountain blocks are composed mainly of Mesozoic sedimentary rocks such as chert, shale, and sandstone. The sedimentary complex in the Keisoku Mountain Block is subdivided into the following four lithostratigraphic units: the Kasama, Kunimiyama, Takatori, and Ayuta Units based on the lithology and geologic age. The Kasama Unit is composed mainly of alternations of sandstone and shale with a small amount of chert and tuff layers. The Kunimiyama Unit consists of massive sandstone and alternations of sandstone and shale. The Takatori Unit is characterized by the chert-clastic sequence comprising “Toishi-type shale, ” bedded chert, siliceous shale, and clastic rocks in ascending order. The Ayuta Unit is composed mainly of alternations of sandstone and shale. These units are in fault contact with each other.<BR>Bedded chert of the Takatori Unit yields Middle Triassic to Early Jurassic radiolarians belonging to the Triassocampe deweueri, Triassocampe noua, Canoptum triassicum, Parahsuum simplum, and Hsuum hisuikyoense Assemblages. Middle Jurassic radiolarians, which are comparable to the Tricolocapsa plicarum and Tricolocapsa conexa Zones, occur from siliceous shale of the Takatori Unit. Late Jurassic radiolarians belonging to the Tricolocapsa yaoi, Mirifusus baileyi and Pseudodictyomitra primitiva Assemblages are obtained from clastic rocks of the Keisoku Mountain Block. Furthermore, late Early Triassic conodont fauna referable to the Neospathodus homeri Zone was discriminated from the “Toi shi-type shale” of the Takatori Unit.<BR>Based on the lithological and chronological characteristics, Mesozoic sedimentary complex of the Keisoku Mountain Block is correlated to those of the Tamba, Mino and Kiso areas in southwest Japan. Mesozoic strata distributed in the Keisoku Mountain Block is regarded as an accretionary wedges formed mainly by of fscrape-accretion during Late Jurassic time.

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  • 地學雜誌

    地學雜誌 107(4), 493-511, 1998

    学術雑誌目次速報データベース由来

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各種コード

  • NII論文ID(NAID)
    10002238420
  • NII書誌ID(NCID)
    AN00322536
  • 本文言語コード
    JPN
  • 資料種別
    ART
  • ISSN
    0022135X
  • NDL 記事登録ID
    4548260
  • NDL 雑誌分類
    ZM41(科学技術--地球科学)
  • NDL 請求記号
    Z15-169
  • DOI
    10.5026/jgeography.107.493
  • データ提供元
    CJP書誌  CJP引用  NDL  NII-ELS  J-STAGE 
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