中国黄土高原の黄土-古土壌層序と大阪層群中の相当層準に含まれる石英について〔英文〕

概要

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Quartz has been isolated from the Sandy Loess of loess-paleosol sequence on the Loess Plateau and non-marine clay in the Osaka Group. Grain-size distribution and oxygen isotope composition of quartz suggest that loess-derived dust was transported, by the Westerly Winds, to the Japanese Islands even around one million years ago. Quartz of loess-derived dust is primarily concentrated in a narrow grain-size fraction finer than 10μm in diameter. Oxygen isotope composition of quartz from non-marine clay in the Osaka Group remarkably varies with the grain-size fractions, which implies that quartz grains of different size fractions were derived from geochemically distinct sources. Grain-size distribution of quartz illustrates that non-marine clay in the Osaka Group was subjected to various sedimentary environments during different geological periods, i. e., prevailing transportation alternated between the transport by the wind (including in situ) and by local surface waters as the paleoevironment changed. Grain-size distribution and oxygen isotope composition of quartz isolated from Chinese Sandy Loess and non-marine clay in the Osaka Group suggest that the content of fine-grained quartz contained in clay sediments in Japan recorded, to a certain extent, the intensity of Asian winter monsoon, and would be supposed to play an important part in the reconstruction of the history of Asian monsoon variation during the Quaternary.
日本第四紀学会の論文