関東山地北東部日野沢地域の秩父帯北帯の地質

概要

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The geology of the north subbelt of the Chichibu Belt in the Hinozawa area, Saitama Prefecture, is lithologically divided into two units : Unit I and Unit II. The former consists mainly of sandstone and mudstone including a number of chert blocks and its brecciated derivatives, while the latter consists of mudstone and siliceous tuff including blocks of greenstone, limestone and chert. Both units are bounded by thrust faults of E-W trend and the Unit II occupies a part surrounded by the Unit I. The radiolarian age of the argillaceous matrix of both units is middle to late Jurassic, though chert and limestone blocks are of Triassic and Permain. The mode of occurrence of rocks and the different geologic ages in blocks and matrix indicate that both units are melange formed after an accretionary process due to oceanic plate subduction.
1990-03-22