青海省贵南县土地沙漠化驱动机制

doi:10.7522/j.issn.1000-694X.2015.00194

摘要/Abstract

摘要： 贵南县木格滩流沙区是共和盆地最大的连续沙带，当地现代沙漠化是由古沙丘活化形成的，但古沙丘活化过程尚不明确。通过实地考察、遥感卫星影像解译、DEM高程数据分析、沉积地层分析及粒度测试，对贵南县土地沙漠化驱动机制从微观层面进行了研究。结果表明：古沙丘表面发育良好的草皮层及粉沙土层是古沙丘的保护层，保护层完整性的破坏，使下伏松散古风成沙暴露，遭受风蚀，形成侧向凹槽，引起草皮层或粉沙土层崩塌，使更多的古风成沙暴露。风力侵蚀与重力侵蚀交替进行，导致风蚀坑不断扩大，相互连接成片，形成流动沙丘。

关键词: 木格滩, 土地沙漠化, 驱动机制, 古沙丘活化, 风蚀坑

Abstract: The Mugetan dune field in Guinan is the largest continuous dune system in the Gonghe Basin, Qinghai-Tibet Plateau. The modern sandy desertification is derived from reactivation of fossil dunes. However, it is not yet clear how this reactivation has occurred in Guinan. By means of field investigations, interpretation of remote-sensing images, analysis of sedimentary stratigraphy, and grain-size tests, we analyze the current situation of sandy desertification in Guinan and its spatial distribution, the stratigraphic sequence and the grain size of the fossil dune sediments, and proposes a microcosmic explanation for the driving mechanism of sandy desertification. The research results show that the mobile dunes are mainly distributed on the Mugetan. The small scale geomorphology of Mugetan can be divided into two types:the plateau and sandy hills, and about 96.1% of mobile dunes is distributed on the sandy hills, and only 3.9% is distributed in the edge of the plateau. The grain size characteristics of modern mobile dunes and fossil dunes are very similar, showing obvious relationship of inheritance and transformation. Modern mobile dunes is derived from reactivation of fossil dunes. The turf and silty sand are protective layers of fossil dunes. Mechanical destruction of protective layers, leading to exposure of underlying loose sands is the key step that leads to sandy desertification in Guinan. The exposed loose sands are blown out by the wind, and created lateral recession at the bottom of the surface protective layer. When the lateral recession reached a certain depth, turf or silty sand collapsed and accumulated at the foot the scarp. The collapsed materials partly or wholly covered the exposed loose sands. Afterwards, the collapsed materials are eroded and carried away by wind, rain and gravity, and the loose sands exposed again. Alternating of wind erosion and gravity erosion, lead to blowouts expansion and connection, finally, formed mobile dunes.

Key words: Mugetan, sandy desertification, driving mechanism, reactivation of fossil dunes, blowouts

中图分类号:

P931.3

李晓英, 姚正毅, 王宏伟, 肖建华. 青海省贵南县土地沙漠化驱动机制[J]. 中国沙漠, 2016, 36(6): 1539-1546.

Li Xiaoying, Yao Zhengyi, Wang Hongwei, Xiao Jianhua. Driving Mechanism of Sandy Desertification in Guinan, Qinghai, China[J]. JOURNAL OF DESERT RESEARCH, 2016, 36(6): 1539-1546.

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