The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Volume 61, Issue 719
Displaying 1-5 of 5 articles from this issue
  • Kazuhisa NOZAWA
    1955 Volume 61 Issue 719 Pages 367-380
    Published: August 25, 1955
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    Ceramic Clay deposits are widely distributed in Aichi and Gifu Prefectures., All of them belong to the Pliocene Seto group and lie upon granite and Palaeozoic siliceous rocks., Their parent materials have hither to been believed to be decomposition products of granite or granitic rocks., The origin of the various types of clays as called "Kira", "Gaerome", "Shironendo", "Kibushi" etc., has been ascribed to sorting during transportation of the weathered granitic materials by water., The writer studied this problem and as the result, he was led to a different opinion as mentioned below., In some district pumice sands or coarse-grained volcanic glasses, of which the fine part has been already altered to clay minerals of the kaolin group, are distributed in association with clay deposits, and in many clay deposits there are found some quantities of volcanic glass., From these facts, it is clear that the tuffaceous material has played a great role as the parent material of the clays., Near the margin of the depositional basin in granitic areas, there can be seen both kinds of clays produced from granite and from tuff, occurring in complicated relations., Both of these two kinds of clay minerals belong to the kaolin group, though they differ from each other in detailed mineralogical properties such as chemical composition and crystal structure., Namely, the clay minerals delived from granite belong to kaolinite and kaolinite-like haloysite, whereas those derived from volcanic ashes are referred to halloysite and endellite., It seems natural that the granite and the tuffaceus materials have been mixed within various rations during the period of deposition., The coexistence of some different types of clays can be explained, therefore, by the non-uniform mixing of granitic meterial and tuff under the complicated hydraulic conditions as generally seen in marginal areas of a lake.,
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  • Wataru ICHIKAWA, Yoshio KASENO, Kazuo KOJIMA
    1955 Volume 61 Issue 719 Pages 381-386
    Published: August 25, 1955
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    The Yamatoda diatomaceous mudstone member (10∼15 m thick), which is characterized by the dominance of freshwater diatoms, unconformably overlies a two-pyroxene andesite and its agglomerates (Anamizu formation, F2, Middle Miocene), and is disconformably overlain by the marine Hamada mudstone member., The Yamatoda diatomaceous mudstone member also contains several plant fossils such as Comptoniphtyllum sp., Liquidambar sp., etc., and its geological age is refered to later Middle Miocene (F3)., By a detailed research on the diatom remains in the mudstone (Table 2), it is revealed that the marine diatom species (Actinocyclus sp., etc., ) are frequently found at the several localities in the eastern half, while the western half is characterized only by fresh-water species such as Melosira granulata, etc., Therefore, it is suggested that the Yamatoda diatomaceous mudstone member accumulated in a small lake which was connected with the sea (perhaps by a channel) on its eastern end., Latest the sea level rose gradually, and at last, marine water abruptly invaded the whole area, forming the interesting disconformable relation between the Hamada and the Yamatoda mudstone members (Fig 2).,
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  • Keidi OIDE
    1955 Volume 61 Issue 719 Pages 387-395
    Published: August 25, 1955
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
    Three problems on the geology of the south-western area of Sendai City are discussed with the results briefly summarized as follows: (1) The "Kagitori fault" is not really a fault, but represents a part of the werping axis which runs from Iwanuma to Kagitori via Ayashi to Okubushi., This tilting movement occurred after the deposition of the Tsunaki formation, and resulted in the formation of the deposition basin, where the Sendai group was deposited., (2) The horizon of the Mitaki andesite (lowermost formation of the Sendai group) corresponds to the upper part of the Tsunaki formation (uppermost formation of the Natori group)., Consequently, the hiatus between the Natori and Sendai groups is not so large as hitherto believed to be., (3) The facies of the Tsunaki formation changes laterally to that of the Yumoto formation.,
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  • S. EHARA, S. SAWATA
    1955 Volume 61 Issue 719 Pages 396-404
    Published: August 25, 1955
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
  • Katsumi MUNETA
    1955 Volume 61 Issue 719 Pages 405
    Published: August 25, 1955
    Released on J-STAGE: April 11, 2008
    JOURNAL FREE ACCESS
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