The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
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Volume 113, Issue 9
Displaying 1-6 of 6 articles from this issue
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Articles
  • Permeability and porosity structures under isotropic pressure on the Katakai fault zone in Ojiya city, Niigata
    Yasutaka Aizawa, Toshihiko Shimamoto, Kenta Kobayashi
    2007 Volume 113 Issue 9 Pages 455-469
    Published: 2007
    Released on J-STAGE: October 10, 2008
    DOIhttps://doi.org/10.5575/geosoc.113.455
    JOURNAL FREE ACCESS
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    Permeability and porosity are important hydraulic properties to understand fluid flow in underground. In this study, we focused on fluid flow in sediments and fault rocks, and measured gas permeability and porosity under isotropic high pressure. The samples were collected from the Quaternary deposits (Uonuma Formation) and Katakai fault zone in Ojiya city, Niigata. The Uonuma Formation in our study area consists of several different layers which are sand gravel, coarse- to fine-sand and silt. The Katakai fault zone is composed of dark brownish gouge and deformed sand with many fractures.
    Gas permeability and porosity were measured using the constant pressure method and the gas expansion method, respectively. The measurements were conducted at confining pressures up to 120 MPa.
    At low confining pressure, gas permeability of sand samples showed 10-13~10-14 m2, those of samples of silt and fault zone were 10-14~10-15 m2. The permeability decreased with increasing confining pressure. The permeability of the fault gouge was most sensitive to pressure and reached to 1.71×10-18 m2 at 120 MPa, which was one order of magnitude lower than other samples (10-15~10-17 m2). As for porosity of sand and silt, although every sample ranged from 38.76 to 48.79%at 5 MPa, sand samples were maximum 9.78%smaller than silt at 120 MPa. The porosity of the fault gouge was sensitively affected by change of confining pressure and dramatically decreased with pressurization (4.72%at 120 MPa).
    We also compared our data with reference data and the Kozeny-Carman equation to confirm the accuracy. As a result, porosity data approximately corresponded to reference data which were measured using drilling core from Niigata Basin. Permeability data did not conform to the value obtained from the Kozeny-Carman equation because of heterogeneity of grain size composed sample.
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  • Red thermoluminescence dating of Toya pyroclastic flow using single-aliquot regenerative-dose (SAR) protocol
    Yoshihiro Ganzawa, Risa Usui, Hitomi Tanaka, Tsuyoshi Azuma
    2007 Volume 113 Issue 9 Pages 470-478
    Published: 2007
    Released on J-STAGE: October 10, 2008
    DOIhttps://doi.org/10.5575/geosoc.113.470
    JOURNAL FREE ACCESS
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    Luminescence dating method, single-aliquot regenerative-dose (SAR) protocol was employed for Toya pyroclastic flows using Red thermoluminescence (Red TL) of quartz grains. Red TL intensities were corrected by test-dose monitoring for sensitivity changes due to repeated heating and X-ray irradiations. The corrected Red TL ages of Toya pyroclastic flows using SAR protocol were well agreed with age estimation deduced from geological correlation.
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  • K-Ar ages of Cretaceous Kibe cauldron and related rocks in Yamaguchi Prefecture: spatiotemporal variation of Cretaceous volcano-plutonism in western Chugoku district, SW Japan
    Tsukasa Kishi, Teruyoshi Imaoka, Hiroshi Kochihira, Yujiro Nishimura, ...
    2007 Volume 113 Issue 9 Pages 479-491
    Published: 2007
    Released on J-STAGE: October 10, 2008
    DOIhttps://doi.org/10.5575/geosoc.113.479
    JOURNAL FREE ACCESS
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    K-Ar analyses of hornblendes and biotites separated from the Kibe cauldron that is a type locality of the Shunan Group and the associated intrusives (Iwagoyama granite) , and from the Yamaguchi cauldron and Shikuma plutonic complex that are correlated with the Kibe cauldron, are carried out to reveal temporal and spatial variations of Cretaceous volcano-plutonism in the western Chugoku district, SW Japan. The age results including the previous radiometric ages on the Shunan Group and the closely associated intermediate intrusive rocks have revealed that a series of volcano-plutonism of the Shunan Group occurred between 100 and 90 Ma in the restricted southern part of the Chugoku Mountain ranges (Setouchi side) . Volcanic rocks of the Kanmon Group predating the Shunan stage are inferred to be 110–100 Ma in age, being spreaded over the whole western Chugoku district from Japan Sea side to Setouchi side. The volcano-plutonism of the Abu Group and the related intrusive rocks following the Shunan stage is dated to be 90–80 Ma, and expands on the northern part of the Chugoku Mountain ranges (Japan Sea side).
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  • 380 Ma 40Ar/39Ar ages of the high-P/T schists obtained from the Nedamo Terrane, Northeast Japan
    Makoto Kawamura, Takayuki Uchino, Chitaro Gouzu, Hironobu Hyodo
    2007 Volume 113 Issue 9 Pages 492-499
    Published: 2007
    Released on J-STAGE: October 10, 2008
    DOIhttps://doi.org/10.5575/geosoc.113.492
    JOURNAL FREE ACCESS
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    The Nedamo Complex is an accretionary complex constituting the Nedamo Terrane located at the boundary between the Jurassic North Kitakami Terrane and the Paleozoic South Kitakami Terrane. The accretion age of the complex is Early Carboniferous. Uchino and Kawamura (2006) identified tectonic blocks of high-P/T glaucophane-bearing mafic schist in the Nedamo Complex. In this study, step-heating method in 40Ar/39Ar chronometry was applied to muscovite from the high-P/T schists, yielding an age of ca. 380 Ma age (Middle-Late Devonian). This age is at least 30 myr older than the accretion age of the Nedamo Complex. Accordingly, the schists are considered not to be a metamorphosed part of the Nedamo Complex itself but rather a part of a pre-Carboniferous metamorphosed accretionary complex.
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Short Article
  • Discovery of Late Jurassic rudist bivalves from the Torinosu-type limestone blocks in the Oriai Formation of the Imaidani Group in the Shirokawa area, Ehime Prefecture, Southwest Japan
    Shin-ichi Sano, Peter W. Skelton, Masahiko Takei, Atsushi Matsuoka
    2007 Volume 113 Issue 9 Pages 500-503
    Published: 2007
    Released on J-STAGE: October 10, 2008
    DOIhttps://doi.org/10.5575/geosoc.113.500
    JOURNAL FREE ACCESS
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    Two rudist taxa, Epidiceras speciosum (Münster) and Monopleura sp. were discovered from the allochthonous Torinosu-type limestone blocks in the Oriai Formation of the Imaidani Group in the Shirokawa area, Southwest Japan. The occurrence of Epidiceras speciosum, indicating a late Kimmeridgian to early Valanginian age, is consistent to the previous age assignment based on the occurrences of middle Kimmeridgian to early Tithonian ammonites (Hybonoticeras) from the overlying Nakatsugawa Formation and the Tithonian radiolarian assemblage of the Imaidani Group. These limestone blocks were thus originally deposited in a shallow marine shelf in the late Kimmeridgian-early Tithonian, and were transported into a deeper environment of shelf slope in the early Tithonian. Monopleura sp. from the Shirokawa area possibly represents the earliest record of this genus and family. The occurrence of Late Jurassic rudists in Torinosu-type limestone suggests that rudists had already expanded globally and that a tropical-subtropical condition prevailed in the shallow marine shelf of East Asia, where the Torinosu-type limestone was deposited at that time.
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