The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Volume 120, Issue 9
Displaying 1-4 of 4 articles from this issue
Review
  • Jun Inoue, Akiko Murakami-Kitase, Takamoto Okudaira
    2014 Volume 120 Issue 9 Pages 287-298
    Published: September 15, 2014
    Released on J-STAGE: December 22, 2014
    JOURNAL FREE ACCESS
    Spheroidal carbonaceous particles (SCPs) are one of the types of fly ash particles produced by industrial fossil-fuel combustion. These SCPs are mainly composed of carbon, which enables them to be preserved in sediments for a long time; this preservation means that sedimentary SCPs have been used to study the distribution and history of environmental pollution. SCPs are used as a proxy for temporal and spatial atmospheric pollution, as a marker for sediment core dating, and as a proxy for the evaluation of transboundary pollution (i.e., the identification of the source of pollutants originating in one country but deposited in another country). The concentrations of sedimentary SCPs and their characteristics, such as morphology, size and chemical composition, provide useful information on past and present atmospheric pollution. This review provides a summary of the technique and its application, principally in Japan during the past decade.
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Articles
  • Akira Miyake, Kazuki Yokoe, Bungo Suzuki, Yukari Igarashi
    2014 Volume 120 Issue 9 Pages 299-312
    Published: September 15, 2014
    Released on J-STAGE: December 22, 2014
    JOURNAL FREE ACCESS
    Metapelite, metapsammite, and metachert of the Ryoke metamorphic belt are widely distributed in the Dando-san area, Aichi Prefecture. These rocks are intruded by the Kamihara tonalite (Older Ryoke granitoid) in the southwestern part of the area and by the Busetsu granite (Younger Ryoke granitoid) in the northern to northeastern part. The mapping of metamorphic zones, based on metapelite mineral assemblages, reveals two large-scale thermal structures unrelated to the distribution of granitoids in the area. The metamorphic grade increases from the central part of the area toward the southeast in the first structure, and from the center toward the northwest in the second one. The first thermal structure is considered to have formed during Ryoke regional metamorphism, on the basis of inter-tectonic growth of andalusite without K-feldspar, and from comparison with the metamorphic zonation in the Hongu-san area located in the south-western direction. In contrast, the occurrence of post-tectonic andalusite coexisting with K-feldspar in the northwestern part of the area shows that the second thermal structure was produced under lower pressure conditions after regional metamorphism. This metamorphic event may have produced finegrained, high-grade metamorphic rocks that formed during a rapid increase in temperature.
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  • Hiroyuki Hoshi, Satoshi Tanaka, Toru Usami, Ryohei Nakagawa, Yoshihiro ...
    2014 Volume 120 Issue 9 Pages 313-323
    Published: September 15, 2014
    Released on J-STAGE: December 22, 2014
    JOURNAL FREE ACCESS
    The stratigraphic position of the Gauss-Matuyama polarity transition was determined in an outcropping section of the Tokai Group in Mie Prefecture, central Japan. Fine-grained sedimentary rocks in the section were sampled at seven horizons for paleomagnetic and rock magnetic measurements. Site (horizon)-mean directions were computed from characteristic remanent magnetization components and demagnetization great circles, both determined by principal component analysis. Rock magnetic measurements suggest that two main magnetic mineral phases, magnetite and hematite, carry the site-mean directions. We found a normal-to-reverse polarity change, which is correlated with the Gauss-Matuyama boundary, within a ~3-m-thick zone that contains an anomalous site-mean direction of intermediate polarity within it. Our results provide an important stratigraphic datum for the magnetostratigraphy and chronostratigraphy of the Tokai Group and correlative Plio-Pleistocene sedimentary sequences.
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