関東山地秩父帯北帯の砕屑岩ユニットからのジュラ紀放散虫

概要

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The northern part of the Chichibu Belt in the Kanto mountains, central Japan, comprises four lithologic units : alternation of clastic rocks, volcaniclastic rocks, mudstone including exotic blocks mainly of limestone and greenstone, and mudstone with chert blocks and chert breccia. Abundant Middle of Late Jurassic radiolarians have been found from the argillaceous part of those units, although the ages of limestone and chert blocks are Permian and Triassic, respectively. They are regarded as a part of Middle to Late Jurassic subduction-accretion complex. Older Jurassic radiolarians such as Laxtorum (?) jurassicum, Hsuum fukazawaense and Parashuum sp., which have been known from the central part of the Chichibu Belt, were newly found from the clastic rock unit of the northern part. It indicates that the Chichibu Belt includes late Early to early Middle Jurassic terrigenous rocks in the subduction-accretion complex formed in an active convergent margin.
国立科学博物館の論文
1993-09-22