第四紀研究
Online ISSN : 1881-8129
Print ISSN : 0418-2642
ISSN-L : 0418-2642
17 巻 , 2 号
選択された号の論文の3件中1~3を表示しています
  • 日高 稔
    1978 年 17 巻 2 号 p. 77-85
    発行日: 1978/08/31
    公開日: 2009/08/21
    ジャーナル フリー
    This paper clarifies that the Late Pliocene to Middle Pleistocene formations distribute in the Hiji area, north of Beppu Bay and these formations are correlated to the Takio Formation of the Oita Group in the Oita area, south of Beppu Bay, where is a standard area for the late Cenozoic stratigraphy in Kyushu.
    The Oita Group in the Hiji area is stratigraphically divided into the Hiji Formation, Oga Formation, Katano Volcanic Rocks and Kanagoe Volcanic Rocks in ascending order. Lower member of the Hiji Formation yields marine molluscan fossils living in coastal water associated with oceanic water and they indicate Late Pliocene to Early Pleistocene. The Hiji Formation consists of hornblende andesitic pyroclastic rock and marine elastic rocks, and the Oga Formation consists of augite hypersthene andesitic pyroclastic rocks and fresh water elastic rocks. The Katano and Kanagoe Volcanic Rocks are hornblende augite hypersthene andesite and augite hypersthene andesite lavas respectively.
    Change of volcanic activity in the Hiji area coincides with that of the formations corresponding to the Takio Formation in surroundings of the Hiji area. Because the basal part of the Hiji Formation suffers epithermal alteration, age of the Usa Group in the marginal area of Beppu Bay which was correlated to Miocene must be reviewed.
  • 会田 信行
    1978 年 17 巻 2 号 p. 86-94
    発行日: 1978/08/31
    公開日: 2009/08/21
    ジャーナル フリー
    The results of both palaeomagnetic and magneto-chemical analyses on the Quaternary volcanic ash layers and also loam deposits around the eastern foot of the Yatsugatake volcanoes in Central Japan will be briefly presented in this note, namely:
    1. The variations of N.R.M.s of these pyroclastic deposits probably suggest the excursion and secular variation of the geomagnetic field.
    2. The greater part of ferromagnetic minerals in the present volcanic ash are titanomagnetites. A small amount of high-temperature oxidated titanomagnetites, ilmenites, hematites is recognized. Maghemites by low-temperature oxidation are rare.
    3. The sequences of these volcanic ash layers and loam deposits may be subdivided into at least three parts, on the basis of the analysis of the Curie temperatures which gradually shift from lower to higher temperature. This may suggest the variation of Ti-content of titanomagnetites occurred during the volcanic activities.
  • 松浦 秀治
    1978 年 17 巻 2 号 p. 95-104
    発行日: 1978/08/31
    公開日: 2009/08/21
    ジャーナル フリー
    Spatial variations in uranium concentration (unit area: 0.25mm in length, 0.5mm in width) from the outside to the inside of Substantia compacta were examined at some points of a given specimen of long bone using fission track techniques. An investigation was also made on the relation between the thickness of compact bone and the uranium content. The results obtained (Table 3, Figs. 3-7) suggest that the maximum uranium concentration of each sample is an adequate indicator for relative dating of fossil bones.
    The uranium content (maximum) of animal bones from the Kannondo cave site reveals a tendency to increase with their horizons (Fig. 8) and shows no strict correlation with the fluorine content (Fig. 9), it confirming the significance of using the two concentrations of buried skeletal remains together as pointers to age.
    There were presented further applications of uranium and fluorine content in bones to estimating such disturbances in archaeological deposits as caused by human activities (see Figs. 10-11), and of the changes in uranium concentration profiles (see Figs. 3-5) to dating bones from postglacial deposits.
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