Changes of dust flux and paleo-environments during the Last Glacial Age in Japanese Islands.

1.末次冰期风尘通量增加幅度大于全新世。末次冰期第2阶段和第4阶段沙尘通量的增加表明两个阶段的盛行风和季风的加强。阶段2的沙尘通量大于阶段4，反映了(1)西风和冬季风的增强，以及(2)大陆架的广泛出现，成为重要的沙尘来源。测量了小于20微米的石英微粒的电子自旋共振(ESR)谱，以识别风成尘的源区。对来自中国、韩国和日本的59个黄土、土壤、古土壤和钻孔岩样进行了测量。风尘石英的ESR信号强度是石英来源的有用示踪剂。中国和韩国第二阶段风尘细石英的测定值(单位)分别为：塔克拉玛干和奎达木：6.2~8.2，上马兰黄土：5.8~8.3，朝鲜土壤：6.0~7.7。中国黄土和朝鲜土壤的石英与ESR强信号的范围非常相似。这种相似性归因于它们在2.4同位素阶段共同起源于干旱和半干旱的亚洲大陆地区的风沙。从细石英的ESR波谱来看，日本群岛分为三个区域。(1)与那古岛土壤石英含量为9.8，产于南亚大陆前寒武纪岩区。(2)冲绳至福井地区土壤石英含量为5.8~8.5，与中国黄土的石英含量一致。结果表明，风尘来自亚洲干旱半干旱地区，如青藏高原。塔克拉玛干沙漠、戈壁沙漠等。(3)青森至北海道土壤石英在10个以上，产于北亚大陆前寒武纪岩区，第二阶段有3个地区的细粒石英被多路盛行风从亚洲大陆吹来。

1. Eolian dust flux increased during the last Glacial age more than that of the Holocene. The increases of dust flux in both stages 2 and 4 during the last Glacial age suggests an enforcement of prevailing wind and monsoon during two stages. A bigger dust flux in the stage 2 than stage 4 reflects (1) stronger westerlies and winter monsoon, and (2) a wider emergence of continental shelf which becomes an important dust source.2. Electron spin resonance (ESR) spectra of fine quartz grains less than 20 micro-meter have been measured to identify the source areas of eolian dust. Fifty-nine samples of loess, soils, paleosols and bore cores from China, Korea and Japan were measured. ESR signal intensity of eolian dust quartz is a useful tracer for the provenance of the quartz.3. The measurement values (in arbitrary unit) of eolian dust fine quartz of stage 2 in China and Korea were as follows ; Taklamakan and Quidam : 6.2 to 8.2, Upper Malan loess : 5.8 to 8.3, Korean soils : 6.0 to 7.7. The quartz of Chinese loess and Korean soils are remarkably similar to ranges of ESR intense signal. This similarity is attributed to their common eolian origin from the arid and semi-arid Asian continental areas during the isotope stage 2.4. Japanese Islands are divided into three areas from the view point of ESR spectra of fine quartz. (1) Yonaguni Island soil quartz was 9.8 originated in the Precambrian rock area of southern Asian continent. (2) Soil quartz from Okinawa to Fukui were 5.8 to 8.5 which coinsided with those of Chinese loess. It shows that eolian dust was brought from the Asian arid and semi-arid areas such as Tibetan Plateau. Taklamakan and Gobi deserts etc (3) Soil quartz from Aomori to Hokkaido were more than 10, originated in the Precambrian rock area of north Asian continent.Fine quartz of three areas were brought from the Asian continent by the prevailing winds of several ways in the stage 2.