| 中国黄土的物质来源及其粉尘的产生机制与搬运过程 |
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| 引用本文： | 孙继敏.中国黄土的物质来源及其粉尘的产生机制与搬运过程[J].第四纪研究,2004,24(2):175-183. |
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| 作者姓名： | 孙继敏 |
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| 作者单位： | 中国科学院地质与地球物理研究所,北京,100029 |
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| 基金项目： | 国家杰出青年科学基金项目 (批准号 :40 12 5 0 0 9)资助 |
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| 摘 要： | 长期以来,黄土高原的物质来源被笼统认为来自包括西北三大内陆盆地(准噶尔、塔里木、柴达木)在内的广阔的沙漠、戈壁地区,而且中国黄土被看作“沙漠”黄土的典型代表。但我们最新的研究揭示出,源自准噶尔和柴达木盆地的粉尘主要由低空气流搬运,受下风方向的山脉阻挡,就近堆积成山麓黄土。源自塔里木盆地的粉尘如果被近地面风搬运,则不可能移出盆地,而是堆积在昆仑山北麓,但如果被飙升到高空,则被西风急流携带,移出盆地而降落在北太平洋地区,无论哪种情况,该盆地的粉尘都不可能对黄土高原有重要贡献。因此,西北三大内陆盆地并非黄土高原的重要物源,而蒙古国南部及与之相邻的包括巴旦吉林、腾格里、乌兰布和、库布其、毛乌素等在内的戈壁、沙漠地区才是黄土高原的主要物质来源区,且主要由近地面风(基本在3000m以下)从上述戈壁、沙漠地区搬运而来。中国黄土并不能简单看作“沙漠”黄土,包括冰川研磨作用、山体剥蚀作用、山前冲洪积作用等在内的“高山过程”,才是产生大量粉土级物质的原因,戈壁、沙漠、黄土的带状分布,只不过是近地面风对山前冲、洪积物质的风力分异而已。
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| 关 键 词： | 黄土 物质来源 产生机制 搬运过程 |
| 文章编号： | 1001-7410(2004)02-175-09 |
| 收稿时间： | 2003-09-30 |
| 修稿时间： | 2003年9月30日 |
PROVENANCE,FORMING MECHANISM AND TRANSPORT OF LOESS IN CHINA |
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| Sun Jimin.PROVENANCE,FORMING MECHANISM AND TRANSPORT OF LOESS IN CHINA[J].Quaternary Sciences,2004,24(2):175-183. |
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| Authors: | Sun Jimin |
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| Institution: | Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029 |
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| Abstract: | Although Chinese loess studies have been in the scientific literature for a long period, the origin and provenance of loess materials in different geomorphological units still remains controversial. For the most extensive and the thickest loess deposits on the well known Loess Plateau, a desert origin and a vast provenance (including the gobi and sand deserts in the nearby region and those in the three northwestern inland basins (the Junggar Basin, the Tarim Basin, and the Qaidam Basin) had been proposed. However, the isotopic, chemical and mineralogical characteristics of loess derived from the three basins are quite different from that of the Loess Plateau samples, suggesting that these basins are not the source areas of loess deposits on the plateau. It is argued that the gobi in the southern Mongolia and the adjoining gobi and sand deserts (including the Badain Jaran Desert, Tengger Desert, Ulan Buh Desert, Hobq Desert and Mu Us Desert) in China are the source areas for the Loess Plateau. However, although these gobi and sand deserts are regarded as the main source regions, they serve as dust and silt holding areas rather than dominant producers. Mountain processes (including glacial grinding, frost weathering, salt weathering, tectonic processes, and some fluvial comminution) in the Gobi Altay Mts., Hangayn Mts. and the Qilian Mts. have played an important role in producing the vast amounts of loess sized material for forming the Loess Plateau. In contrast, the alluvial sediments of the Yellow River and eolian abrasion processes in the sand deserts can be only minor sources for the plateau. The zonation of gobi, sand desert and loess from northwest to southeast, is largely the results of wind sorting of the huge alluvial deposits from the above high mountain regions. Dust entrained from different geomorphological units of China has different contributions to the proximal and distal regions. Dust derived from the Junggar and Qaidam basins is transported by near surface winds, and thus mainly accumulates on the windward slopes of the local mountains (local dust). For the Tarim Basin, dust can be transported not only by the near surface winds (accumulated in the windward slopes of the Kunlun Mts., known as local dust), but also by the westerlies whenever the dust is entrained to an elevation of > 5 000m a. s. l. In the latter case, dust from the Tarim Basin (the Taklimakan Desert) can be transported out of the basin and ultimately to the remote Pacific (long distance dust). In most cases, dust entrained from the gobi in Mongolia and adjoining gobi and sand deserts in China is transported by near surface winds to the plateau region, southeastern China and the near Pacific, serving as medium distance dust. Occasionally (about 10%), the entrained dust from the above gobi and sand deserts can be transported by the westerlies to the remote Pacific Ocean and even to the United States (long distance dust). |
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| Keywords: | Chinese loess provenance forming mechanism transportation |
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