Journal of Geography (Chigaku Zasshi)
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
Volume 93 , Issue 2
Showing 1-6 articles out of 6 articles from the selected issue
  • Sumio SAKAGAMI, Fujio MASUDA, Tetsuya KAWABE, Yasuo NISHIZAWA
    1984 Volume 93 Issue 2 Pages 61-76
    Published: April 25, 1984
    Released: December 22, 2010
    JOURNALS FREE ACCESS
    After the brief introduction on the morphology, taxonomy, phylogeny and ecology of the cheilostome bryozoans, the chemical compositions such as minerals, elemental and isotopic compositions of some bryozoan skeletons were discussed. Bryozoan skeletons are composed of three types of mineral phases, namely, high-Mg calcite, high-Sr aragonite and/or their mixtures.
    Based on the partition coefficient-ionic radius diagrams for bryozoan skeleton system, three groups of elements can be clarified as follows:(1) Group of Mg, Ca and Sr, only controlled by the crystal structure, they are carbonates, (2) Group of Mn, Fe, Zn, Co, Cu and Ni, controlled by the crystal structure and physiological activities, they are “bio-minerals”, and (3) Group of Li, Na, K, Al, V and Cr, not controlled by the crystal structure, they may be treated as inclusions and foreign detrital grains. The diagrams indicate that the bryozoan skeleton is to be the primitive calcification group formed under the nonequili-brium condition. The elemental composition of mineralizing solution, from which the skeleton of the bryozoan Microporina precipitate, was estimated using the two-step model for elemental partition among skeleton, mineralizing solution and environmental water based on the diagram. The elemental composition of the early Pleistocene bryozoan skeletons was also compared with the Recent one on the standpoint of early diagenetic process.
    Both carbon and oxygen isotope compositions of bryozoan skeletons are systematically changed by the water temperature and oxygen isotope composition of seawater.
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  • Hirokazu KATO
    1984 Volume 93 Issue 2 Pages 77-93
    Published: April 25, 1984
    Released: December 22, 2010
    JOURNALS FREE ACCESS
    The North Anatolian Fault is one of the largest strike slip faults (right lateral) in the world and is believed to be a transform fault between Eurasian Plate and Anatolian Plate (Turkey Plate). Many large earthquakes (M>6.5) and related earthquake faults happened to occur along this active fault. It is well known that the migration of those epicenters to westward along the fault since Erzincan Earthquake in 1939. Most of earthquake faults related to those earthquakes have multi-echelon structures. In Erzincan area, main five segments of Erzincan earthquake fault are distinguished, that is, Mihar, Bahik, Hilir, Altintepe and Tanyeri segment from the west to the east. Their length are less than 20km. Though their displacement of each segment shows right lateral one with a slight vertical component, their alingment is not always right lateral echelon pattern. It is rahter resulted from the geological and geomorphological aeolotropic of the surface.
    The result of the measurement of relative Rn concentration by a track etch method at Mihar, Bahik, Hilir and Ismetpasa shows that the peak of track numbers appears mostly on the fault lines. So the a track etch method is effective for the detection of radon ema-nation relating to the earthquake faults. It is expected empirically that the track numbers observed on thin Quaternary cover sediment is generally larger than that on thick Quater-nary cover sediment crossing the active faults. In this case, the numbers of α tracks are less than the expected one though there is very thin or no Quaternary strata. This may be because that the basement rocks, for example, serpentin has little Rn and/or that the weathered clay originated from the fractured serpentine interrupted the carring out of the gas including Rn.
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  • Hisako KURIHARA
    1984 Volume 93 Issue 2 Pages 94-110
    Published: April 25, 1984
    Released: October 13, 2010
    JOURNALS FREE ACCESS
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  • Nobukazu KAMBE
    1984 Volume 93 Issue 2 Pages 111-115
    Published: April 25, 1984
    Released: October 13, 2010
    JOURNALS FREE ACCESS
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  • [in Japanese]
    1984 Volume 93 Issue 2 Pages 116-117
    Published: April 25, 1984
    Released: October 13, 2010
    JOURNALS FREE ACCESS
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  • S. SAKAGAMI, Y. NISHIZAWA, N. NAGANO
    1984 Volume 93 Issue 2 Pages plate1-plate2
    Published: April 25, 1984
    Released: October 13, 2010
    JOURNALS FREE ACCESS
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