The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Volume 56, Issue 652
Displaying 1-9 of 9 articles from this issue
  • George Kojima, Den-ichi Sasaki
    1950 Volume 56 Issue 652 Pages 1-5
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The district lies on the northeastern end of the region of crystalline schists north of Tokyuama., The schists belong to the Sangun-Motoyama Group, which is a metamorphic, facies of the Palaeozoic Chichibu rocks in the Inner Zone of Southwestern Japan., The crystalline schists of the district are due to the regional type of metamorphism., They are composed of graphite-sericite-schists of argillaceous rock origin, sericite-chlorite-schists of arenaceous rock origin, quartz-schists of chert origin and green-schists or green-rocks., Two large masses of green-rocks at Deai (D in Fig., 1) and Miyanokushi (M in Fig., 1) are represented by coarse-grained albite-epidote-gabbros in the centre, and the marginal parts exibit some schistosity., Compared with the metamorphic grade of schists of the district, these two masses of green-rocks may be synkinematic intrusives of spilitic nature., Near Meotobuchi (Mb in Fig., 1) is a green-schist carrying relic minerals, only sample in the district showing basic igneous rock., Stilpnomelane group of minerals is universally found in green-rocks of the district, but the metamorphic differentiation is not distinct., The district is cut from SW to NE by an overthrust, which is named Kitayama overthrust in the adjoining Sugane district to the west., The overthrust can be traced to the WSW about 70 m, and may safely be regarded as the western continuation of the oga overthrust in the Nariwa district, Okayama prefecture., Kawayama ore body lies in the crushed zone of the hanging wall of the overthrust., The shape of ore body is almost parellel to the thrust plane., Synclinal axes of the northern and the southern parts intersect near the Kawayama ore body on the overthrust.,
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  • [in Japanese]
    1950 Volume 56 Issue 652 Pages 6
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
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  • [in Japanese]
    1950 Volume 56 Issue 652 Pages 7-12
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
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  • Toshio Sudo
    1950 Volume 56 Issue 652 Pages 13-16
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The mineralogical composition of a tuff which has strong adsorptive power is described., This tuff is composed mainly of glass fragments altered to the Clay mineral, montmorillonite, and the interspaces of the altered glass fragments are filled by opal, zeolite crystal aggregate and very transparent glass fragments., The mineralogical composition was determined by optical properties, chemical analyses, X-ray powder pattern and thermal properties., The zeolite crystal aggregate and very transparent glass fragments and opal may have been produced by secondary alteration by hydrothermal action., The adsorptive power and the base exchabnge capacity shown by the rock may be due to the existence of zeolite crystal and montmorillonite.,
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  • Koichiro Ichikawa
    1950 Volume 56 Issue 652 Pages 17-22
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The direct use of the terms, Norian, Carnian, etc., in the extra-Alpine region is not adequate, since the fossil content is fairly different from that in the Alpine province., Another system of nomenclature is herein proposed., In the Triassic of Japan eight ages (chronological unit) distibuted in three epochs are distinguished., Epochs are called Eo-, Meso-, and Neo-Triassic and new names for the ages are proposed., Their names, as well as the fossil contents, are presented in the list on-p., 22., Saragian and Sakawan ages in the Neo-Triassic epoch are tentatively subdiveded into two and three Sub-ages, repectively., Species marked with (+) range into the later ages, while those with (-) range from the earlier age, and the occurrence of species marked with is very rare., The time range of the remaining species in confined to one age.,
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  • Mitsuo NODA
    1950 Volume 56 Issue 652 Pages 23-34
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
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  • Katura OYAMA
    1950 Volume 56 Issue 652 Pages 35-37
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
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  • [in Japanese]
    1950 Volume 56 Issue 652 Pages 38
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
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  • MOORE Raymond C.
    1950 Volume 56 Issue 652 Pages 39-47
    Published: May 25, 1950
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    Two distinct categories of stratigraphic units are to be recognized, among which a unit of either category has no direct bearing on definition of units belonging to the other., This is because they are defined entirely by different criteria., Stratigraphic units defined solely by physical characters, including contained organic remains, include : (1) formation as the fundamental unit ; (2) subdivisions of formation, such as member, lentil, tongue, and bed ; and (3) aggregations of formations, called groups., These units are designated by a geographic name (treated as a noun) combined with a lithologic or classificatory term belonging to this category., Stratigraphic units defined solely on the basis of geologic time concepts include any and all sorts of rocks formed during a specified part of geologic time., Such units are (1) stage ; which may be considered as the fundamental unit of this category ; (2) series ; (3) system ; and (4) erathem., These units are designated by an adjectival name, generally of geographic origin, combined with a classification term belonging to this category., Geochronologic units, which comprise divisions of time, are not stratigraphical units, althouth they are defined by stratigraphical observations., Such units are (1)age, (2)epoch, (3)period, and (4)era., These units are designed by adjectival name identical to that of the stage, series, system, or erathem, which represents the geochronologic unit.,
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