第四紀研究
Online ISSN : 1881-8129
Print ISSN : 0418-2642
ISSN-L : 0418-2642
13 巻 , 4 号
選択された号の論文の5件中1~5を表示しています
  • 加藤 好武, 山田 裕
    1974 年 13 巻 4 号 p. 177-186
    発行日: 1974/12/30
    公開日: 2009/08/21
    ジャーナル フリー
    Andosol (volcanic ash soil) has the widest distribution in the western part of Tama River fan. There are four major terraces in this region. The relationships between the characteristic of Andosol and four different terraces have been researched, based on the result of soil survey and mineralogical and chemical analysis of the soils. There is a close correlation between soil distribution and landform evolution.
    Conclusions are shown listed as follows:
    1) The highest terrace (Sayama hill) has undergone severe erosion continuously during the Holocene period. In the ridge of the hill, the Tachikawa and Musashino tephras have been eroded, resulting in the exposure of Shimosueyoshi or Tama tephra. The clay of the soil consists mostly of metahalloysite and halloysite.
    2) The soils on the higher and middle terrace (Shimosueyoshi and Musashino terrace) are typical and mature Andosol. The parent materials of the soils are presumably from the upper part of the Tachikawa tephra. These soils are characterized by the prevalence of amorphous inorganic matter; highly humified organic matter, and other properties associated with them.
    3) The soils on the northern part of the lower terrace (Tachikawa terrace) are presumably fluvial re-deposits in the earlier Jomon period, because a few small amount of gravel occur in the profiles. On the southern part of this terrace, about half of the soils are derived from typical aeolian deposits, and the other half are fluvial re-deposited Andosol.
    4) The soils on the lowest terrace (Aoyagi terrace) mostly contain gravel bed in the lower part of their profiles.
  • 中村 純
    1974 年 13 巻 4 号 p. 187-198
    発行日: 1974/12/30
    公開日: 2009/08/21
    ジャーナル フリー
    In order to examine the possibility of distinguishing rice pollen from other grasses, the sculptural details of 68 species including wild and cultivate type were studied based on the transmission electron (TEM) and phase contrast microphotographs (PCM).
    It was found that TEM of surface replicas might help the interpretation of phase contrast observations and might clarify the appreciation of differences in cases where a discrimination of the various types was difficult.
    Three types of grass pollen could be distinguished based on PCM.
    1. Punctate type: Grains have single spinules occurring one by one on the surface based on TEM. In this type each spinule appears as a distinct dark dot with phase contrast. Zea, Coix, Secale and sometimes Hordeum.
    2. Areolate (negative reticulate) type: More than three spinules appear grouped on small islands or clumps which are isolated by incised grooves based on TEM. Each spinule clump is seen as an irregularly delimited dark dot and their sculpture is areolate. Most wild grasses were studied.
    3. Maculate type: Mixed type of single spinules and clumps of two or three spinules. According to PCM, grains of this type are seen as indistinct punctate in lower focus but more or less indistinct areolate in upper focus. Oryza, Hordeum, Triticum and some Agropyron. Some of Bambusoidae such as Arundinaria, Chinobambusa and Sasa have grains of spinule clump type, but each clump is so small that it is seen as a indistinct dot and their sculpture is maculate.
    From this fact Oryza pollen can be distinguished from those of punctate and areolate types, but it is difficult to distinguish Oryza from other maculate pollen except for Hordeum and Triticum which have larger pollen than that of Oryza.
  • 当間 唯弘
    1974 年 13 巻 4 号 p. 199-215
    発行日: 1974/12/30
    公開日: 2009/08/21
    ジャーナル フリー
    The Shimosueyoshi terrace in and around Yokohama is a marine terrace in which a former shoreline is located at its western boundary. The terrace is composed of the marine Shimosueyoshi formation. Its original surface named “Shimosueyoshi surface” in this paper, is the depositional surface of the Shimosueyoshi formation in the middle and eastern zones of the area, and the wave-cut platform in the western zone near the former shoreline. The surface is conformably covered with the Shimosueyoshi Loam which is weathered materials of the air-fall ash. The pumice beds in the lower part of the Shimosueyoshi Loam have been dated as 120, 000-130, 000F.T.y.B.P. In this paper, the emergence of the Shimosueyoshi surface is discussed in detail through the author's investigation of the Shimosueyoshi Loam based on the tephrochronological method and the observations of the Shimosueyoshi formation.
    The lower members of the Shimosueyoshi Loam (SP0, SP1, SL2, SP2 in ascending order) are useful in indicating the positions of the shorelines at the time of ash fall. As shown in Fig. 3 and 8, SP0 rests immediately on the Shimosueyoshi surface at the former shoreline. The western zone of the Shimosueyoshi surface is capped with SP1 and the succeeding zones in the east are mantled with SL2 and SP2. Therefore, it is understood that the emergence proceeded eastward successively.
    The paleogeography at the time of the emergence (Fig. 9) is inferred by the observations of facies in the upper member of the Shimosueyoshi formation. At the transgression peak just before the fall of SP0, the wave-cut platform and sea cliff were formed at the former shoreline. Then, as the emergence proceeded the flat sea-floor of the wave-cut platform became the marshy plain in the western zone of the Shimosueyoshi surface. In the middle and eastern zones, the slightly undulating sea-floor had been formed by the accumulation of sand and silty sand. The seafloor emerged and changed into the marshy plain in the middle zone. But, there remained a bay at the hollow of the Shimosueyoshi surface. The bay was embayed by the two narrow ridges. The eastern one of them is a beach ridge running from NNE to SSW in the eastern zone.
    In this area, generally speaking, the shallow sea-floor emerged unless being covered with beach deposits or deltaic materials except the eastern zone of the Shimosueyoshi surface. Such process of the emergence resulted from the lack of the rivers which supplied sufficient materials for the development of beach ridges and vast deltas.
  • 海津 正倫
    1974 年 13 巻 4 号 p. 216-219
    発行日: 1974/12/30
    公開日: 2009/08/21
    ジャーナル フリー
    The alluvial plain of the Iwaki in the central part of the Tsugaru Plain is divided into terraces of two levels. The upper surface which was inferred to have been formed at the culmination of Postglacial rise of sea level in the early Jomon period, had been dissected, forming flat valley floors, which then were overlaid with sediments of the lower surface. Relics of forest, which grew on the former valley floors and were buried by the sediments of the lower surface, were discovered, being stripped its cover, on the river bed of the Iwaki. The species of the sampled tree was “Ulmus davidiana var. japonica”, being dated 2240±9014C years B.P. (GaK-4776). The forest was estimated to have grown during the period from the later half of the latest Jomon to the early Yayoi period of the Japanese neolithic age.
    From the above-mentioned, the following three stages can be recognized in the development of the alluvial plain; that is, an erosional stage of valley cutting before the latest Jomon period, a stable stage of forest-growing during the period from the later half of the latest Jomon to the early Yayoi period, and a sedimentary period of burying forest after the early Yayoi period.
    The stable stage in this area corresponds in age fairly well to the so-called low sea level stage in Hokuriku District and the cooler and moister period in northeastern Japan.
  • 阪上 正信, 吉岡 満夫
    1974 年 13 巻 4 号 p. 220-224
    発行日: 1974/12/30
    公開日: 2009/08/21
    ジャーナル フリー
    東京大学西アジア洪積人類遺跡調査団がネアンデルタール人骨を発見したイスラエルのアムッド洞窟から採取された化石骨試料 (主としてカモシカ類) の年代測定を, その中にとりこまれた238Uおよび235Uからそれぞれ成長した230Thおよび231Pa量を放射化学的方法で正確に定量することによって行った. さきに求められていた14C年代では同様の試料について石器等からも推定される考古年代にくらべ, かなり若い年代となっていたが, 本法によって得られた絶対年代 (34,000~62,000年) は考古年代とも矛盾しない. 238U, 234U, 230Th (232Thは検出されず), 231Paの放射化学的分離とαスペクトロメトリーを組合せた方法による定量のほか, フィッショントラック法によるウランの分布と定量も行い, 試料中のウラン分布は均一であることも確めた.
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