The Quaternary Research (Daiyonki-Kenkyu)
Online ISSN : 1881-8129
Print ISSN : 0418-2642
ISSN-L : 0418-2642
Volume 43, Issue 2
Displaying 1-5 of 5 articles from this issue
  • Kana Nagashima, Ryuji Tada, Hiroyuki Matsui
    2004 Volume 43 Issue 2 Pages 85-97
    Published: April 01, 2004
    Released on J-STAGE: August 21, 2009
    JOURNAL FREE ACCESS
    The hemipelagic sediments of the Japan Sea contain a significant amount of eolian dust (Kosa) derived from inland Asia. The grain size and flux of Kosa are considered to reflect wind speed and aridity in the source area, and these parameters have been used to estimate the intensities of the Asian monsoon and the westerly. In this study, we analyzed the samples from a piston core, KT94-15-PC-5, retrieved 150km off Akita, to reconstruct 140kyr variations in the Asian monsoon and westerly intensities on the basis of grain size analysis.
    After removing the biogenic fraction, we measured the grain size distribution of detrital sediments using a laser diffraction-scattering grain size analyzer (Horiba LA-920). The results showed negatively-skewed unimodal grain size distribution on a logarithmic scale. We resolved the original grain size distribution curve into two log-normal populations. The finer population, whose median diameter is approximately 3μm, corresponds to the detrital material derived from the Japanese Islands, and the coarser one, whose median diameter is roughly 5 to 8μm, corresponds to Kosa derived from inland Asia. Temporal variations in grain size and content of Kosa during the last 140kyr indicate that glacial-interglacial changes and millennial-scale abrupt oscillations are strikingly similar to those of the δ18O records of a GRIP ice core from Greenland. Smaller grain size and lower content of Kosa during glacial interstadials may suggest a stronger summer monsoon and/or a weaker westerly, while larger grain size and abundance of Kosa during glacial stadials may suggest a weaker summer monsoon and/or a stronger westerly. It is worth noting that the similarity between the variations in Kosa grain size and δ18O records of the GRIP ice core can be traced back to the marine isotope stage (MIS) 5e. Our results suggest millennial-scale large climatic changes in East Asia during MIS 5e.
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  • Jong-Hwa Chun, Ken Ikehara, Han Sang-Joon
    2004 Volume 43 Issue 2 Pages 99-112
    Published: April 01, 2004
    Released on J-STAGE: August 21, 2009
    JOURNAL FREE ACCESS
    A distinctive lithofacies sequence in marine sediment cores related to eustatic sea-level changes made it possible to determine the eruption age of the Aso-3 tephra, which was identified in marine cores taken from the Ulleung Basin, East Sea/Japan Sea, by its characteristic major element and mineral compositions and grain-size distribution. Ten tephra layers belonging to four tephra groups (Ulleung, SKP, Aira, and Aso groups), based on the source volcanoes, were identified. The Aso-3 tephra occurred only a few (e. g., 95PC-6, 95PC-9, and 95PC-10) among 48 marine cores. These three cores, which were obtained from sites adjacent to the Ulleung deep-sea channel in the northeastern Ulleung Basin, were characterized by relatively low, constant sedimentation rates. The Aso-3 tephra was distinguished from Aira group tephras and the Aso-4 tephra by its grain morphology (prevailing pumiceous glass fragments), grain size (median diameter 3.5∅), and relatively low silica (67.2-68.6wt%) and alkali (8.0-8.3wt%) contents. The lithofacies containing the Aso-3 tephra is a thick-bedded gray (5Y4/1) bioturbated mud (BM-b lithofacies) with extensive pyrite filaments characteristic of deglaciation sediments. This lithofacies overlies thick-bedded fine-grained turbidites deposited by turbidity flows during sea-level low-stands in the Ulleung Basin and underlies thick-bedded grayish olive bioturbated mud with sediment-filled burrows (BM-a lithofacies), which reflects ventilation changes associated with sea-level highstands. This distinctive lithofacies sequence was deposited during the Termination II penultimate deglaciation to interglacial transition in the Ulleung Basin sediments and is repeated during the Termination I period. Therefore, the eruption age of the Aso-3 tephra is inferred to have been about 133ka with lithofacies sequence, assuming constant sedimentation rates in the three cores of the Ulleung Basin.
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  • Masako Okoshi, Shinichi Miyamura
    2004 Volume 43 Issue 2 Pages 113-128
    Published: April 01, 2004
    Released on J-STAGE: August 21, 2009
    JOURNAL FREE ACCESS
    Silica-bodies of Gramineae plants that are found in soil and in remains originate from and have species-specific forms. They give important information for the identification of fossil grass species. However, it has not been clear where the silica-bodies were formed in the plant cells. In this study, the high-pressure fixing method was applied to the transmission electron microscopy (TEM) of silica cells and long cells of rice, Oryza sativa L. Study of the silica cells in the epidermis of 2nd leaves revealed that electron-dense particles accumulate in the basal region of the cuticles, in the secondary cell walls, and in the cytoplasms, but not in the primary cell walls. In long cells with no secondary cell walls, electron-dense particles precipitated not only in the basal region of cuticles and the outer layers of the primary cell walls (outer and middle layers) but also in vacuoles. The EF-TEM studies revealed that the particles are composed of oxidized Si (SiO2). Therefore, it can be concluded that in leaf tissue of rice the SiO2-particles are fundamental components of the silica-bodies. The different distribution of the SiO2-particles in silica cells and long cells may suggest that the mechanism of particle accumulation is different in these cells.
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  • Yoshihiko Kariya, Shinji Sugiyama, Akihiko Sasaki
    2004 Volume 43 Issue 2 Pages 129-137
    Published: April 01, 2004
    Released on J-STAGE: August 21, 2009
    JOURNAL FREE ACCESS
    Like many other nival mountains in Japan, Mount Tairappyo in the Mikuni Mountains (36°48′N, 138°49′E, 1, 984m a. s. l.) lacks the subalpine conifer forest zone. Instead of conifers, grasses cover large areas of slopes above the upper limit of montane broadleaf forest (1, 600-1, 700m a. s. l.). An examination of phytoliths from peat soils focused on understanding the Holocene landscape evolution, particularly for changes in Bambusoideae (mostly Sasa) grasses occupying the present-day subalpine zone. Bambusoideae grasses, which densely covered slopes in the early Holocene, would have begun to decline between 5, 600 and 4, 940 cal yrs BP. This situation seemed to have persisted until 1, 300 to 680 cal yrs BP, when Bambusoideae grasses began to recover. This change in grassland vegetation from the middle to late Holocene epoch was probably induced by variance of snowmelt timimg related to climatic variabilities.
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  • [in Japanese]
    2004 Volume 43 Issue 2 Pages 139-163
    Published: April 01, 2004
    Released on J-STAGE: August 21, 2009
    JOURNAL FREE ACCESS
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