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

1.末次冰期风沙通量的增加大于全新世。末次冰期第2和第4阶段沙尘通量的增加反映了盛行风和季风的加强。阶段2的沙尘通量比阶段4大，反映了西风带和冬季风较强，大陆架的出现范围较广，成为重要的沙尘源.本文测量了小于20 μ m的石英细颗粒的电子自旋共振（ESR）谱，以确定风尘源区。对来自中国、朝鲜和日本的59个黄土、土壤、古土壤和钻孔岩芯样品进行了测定。风成尘石英的ESR信号强度是石英物源的有效示踪剂.中国和朝鲜第2阶段风尘细石英的测量值（以任意单位计）如下：塔克拉玛干和奎丹：6.2至8.2，马兰黄土上部：5.8至8.3，朝鲜土壤：6.0至7.7。中国黄土和朝鲜土的石英与ESR强信号的范围非常相似。这种相似性归因于它们在同位素阶段2.4来自干旱和半干旱亚洲大陆地区的共同风成成因。从细石英ESR谱的角度将日本列岛分为三个区域。(1)与那国岛土壤石英含量为9.8，起源于南亚大陆前寒武纪岩石区。(2)从冲绳到福井的土壤石英含量为5.8 ~ 8.5，与中国黄土的石英含量基本一致。结果表明，沙尘是由青藏高原等亚洲干旱、半干旱地区带入的。（3）从青森到北海道的土壤石英有10余种，来源于亚洲大陆北部的前寒武纪岩石区，3个地区的细石英是在第2阶段由多个方向的盛行风从亚洲大陆带来的。

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.