The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Volume 61 , Issue 714
Showing 1-4 articles out of 4 articles from the selected issue
  • Syohei K0KAWA
    1955 Volume 61 Issue 714 Pages 93-102
    Published: March 25, 1955
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    To determine the geologic age of the andesite of Mt., Mikasa which is intercalated in fossiliferous strata, the entombed plant and insect fossils were investigated., The Huziwara Formation, a marine deposit referrable to F2-F3, has yielded some plant fossiis, among which Hemitrapa borealis (HEER) MIKI and Leguminocarpa Sakamotoi MIKI n., g., n., sp., are noteworthy., Among the plant fossils from the Zigokudani-Tugeno Formations (?F3-G-H1), subtropical species such as Canarium album RAEUSCH, Fortunearia sinensis REHD., et WILS., Liquidambar formosana HANCE and Stephania Dielsiana WU etc., are worthy of consideration., The abundant occurrence and widespread distribution of the endocarps of Styrax obassioides MIKI in the beds suggest that it may be regarded as an index fossil of the Zigokudani-Tugeno Formations at least on the plateau-land east of the Nara Basin., In the Sirakawaike-Saho Formations, fresh-water deposits referrable to I1-I2? have yielded rich and well-preserved floral remains accompanied with scanty insect fragments., The flora can be divided into lower and upper florulae., The former represents the typical Metasequoia-flora; Metasequoia disticha (HEER) MIKI, Picea Koribai MIKI and Juglans megacinerea CHANEY being characteristic., The upper florule, on the other hand, contains abundant fresh-water and marsh plants of the Pleistocene type such as Trapa macropoda MIKI, Menyanthes trifoliata L., Ceratophyllum demersum L., and Carex rhynchophysa, C., A., MEYER etc., Almost all the insect remains belong to Carabidae and some ecological correlations can be recognized between them and the plant remains.,
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  • Haruhiko KIMURA
    1955 Volume 61 Issue 714 Pages 103-116
    Published: March 25, 1955
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    Vortex is a phenomenon which is often observed in the currents water, but the mode of formation of sediment produced by the vortex has not been well known., In the present paper the writer tried to explain this mode experimentally, and obtained the following results: (1) In the vortex the sedimentary particles are sorted by the rotational flows that are rising and concentrating towards the virtical boundary surface between the parts of free-vortex and forced-vortex., (2) As a result of this sorting action, the bottom particles are eroded by the rotational flows around the vortex and concentrate on the central part of the vortex., (3) The mode of formation of the sediments heaped by vortex varies with the rotational velocity of vortex or the size of the bottom particles, but, in general, it can be said that the greater velocity of rotation forms a kind of graded bedding and the smaller velocity forms a decamposite sediment body has different particle size in the central part of this sediment., These variations are explained by the relationships between the particle size and the critical rotational velocity of vortex required for the concentration or lifting of the particles., (4) In the vortex the shells are very liable to move in spite of their size., Therefore, they often forms a massive heap (so-called "fossil enclosure" as named by IJIRI and FUJITA) being concentrated by vortex on the sedimentary field., Accordingly, if the above mentioned types of sediment are in the stratum, it can be assumed that there existed environment where the vortices are liable to develop (for instance river, river-mouth, bay-mouth, beach or convergent line of sea current etc., ).,
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  • Nobuhide MURAKAMI
    1955 Volume 61 Issue 714 Pages 117-123
    Published: March 25, 1955
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    The granite-porphyry mass in this district consists of tour rock types, namely, hornblende-biotite-granite-porphyry, leucocratic granite-porphyry, coarse-grained granite-porphyry, and aplitic granite-porphyry., The hornblende-biotite-granite-porphyry which distributes most widely with a leucocratic marginal facies, is cataclastic and foliated., The flow planes are parallel to the contact planes and conform to a large anticlinal structure with NE-SW axis., It metamorphoses the Palaeozoic stratum and hornblende-porphyrite dikes with which it is in contact to strongly schistose rocks and forms a peculiar breccia zone in that area., From these evidences it is considered that the body of the hornblende-biotite-granite-porphyry and leucocratic granite-porphyry might have risen into place by upward flow of NW direction, of a partially crystallized magma., The coarse-grained granite-porphyry which is weakly foliated may be perhaps a succesive intrusive body., The aplitic granite-porphyry which is massive may be considered a later sheet-like body.,
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  • Hiroshi KANO
    1955 Volume 61 Issue 714 Pages 124-139
    Published: March 25, 1955
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    There are various types of linear structures in the Palaeozoic and Mesozoic Systems in the central zone of the Kitakami massif., Among them, the most prominent and extensively developed lineation is that shown by the axis of gentle undulation of the bedding-plane., It is noteworthy that the Palaeozoic and Mesozoic formations can be divided into several homo-axial structural groups with respect to the directions and plunges of lineations., These structural divisions almost correspond to the stratigraphical clarssification., (Table 1)., Table 1 Era Homo-axial group of sedimentary formation Plunge of the lineation Main unconformities Paleo-Cretaceous Ofunato series N Jurassic Shishiori series Karakuwa series NNW in the upper part, S in the lower Triassic Inai series Toyoma series Kanokura series S Permian Sakamotozawa series Nagaiwa series Onimaru series Yukisawa basin NNE (absent) N or S (doubly-plunge) Hikoroichi basin NNW Carboniferous Odaira series Arisu series Hikoroichi series S Devonian-Gotlandian Takainari series SW The intrusion-axes of the three granitic masses (Higami granite, Takekoma granodiorite and Hirota quartz-monzonite) already described in the previous paper are in harmony respectively with the Iineations and the fold-axes of such homo-axial structural groups that may have been folded synchronously with or prior to the intrusions of these granitic masses., (Table 2)., Table 2 Granitic mass Principal Lineation Intrusion axis or Fold-axis Sedimentary formation Higami granite NNW-NW The lower Permian (Sakamotozawa series) and the middle Carboniferous (Nagaiwa series) Takekoma granodiorite S The middle and upper Permian (Kanokura and Toyoma series respectively) and the Triassic (Inai series) Hirota quartz-monzonite N The paleo-Cretaceous (Ofunato series)
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