塔克拉玛干沙漠河湖相沉积平原风蚀地貌发育的外营力作用机制

 河湖相沉积是一种非固结沉积物，是风蚀地貌发育的一种重要地质基础。在塔克拉玛干沙漠中发育在这种沉积物上的风蚀地貌分布非常普遍，但相关研究较少，尚缺乏风蚀地貌发育过程方面的研究。基于野外调查信息和理论分析，结合相关文献，分析了塔克拉玛干沙漠河湖相平原风蚀地貌发育的外营力作用机制。研究结果表明：（1）风蚀地貌发育的外营力作用主要有：风化作用、流水作用、风蚀作用以及重力作用；（2）风蚀作用是风蚀地貌发育的主要外营力，但是风化作用、流水作用和重力作用也发挥着重要的作用，它们的关键作用是形成风蚀突破口，而重力作用和风化作用是促进风蚀地貌后期快速发展的重要作用；（3）各种外营力协同作用和互为条件，它们在风蚀地貌发育的各阶段的重要性不同；（4）沉积层特殊沉积构造和外营力作用共同造成了风蚀地貌形态特征。

Exogenic forces action mechanism in the development process of erosion landform on alluvial plains composed of fluvial-lacustrine deposits in the Taklimakan Desert

Fluvial-lacustrine deposit is a kind of consolidation sediments that is one important geological basis for erosion landform. The erosion landform developed on alluvial plains composed of fluvial-lacustrine deposits is widely distributed. But its relevant studies, especially about the development process of erosion landform are very less. Based on the field survey information, theoretical analysis and some relevant articles, this paper comprehensively analyzed the exogenic forces action mechanism in the development process of erosion landform on alluvial plains composed of fluvial-lacustrine deposits in the Taklimakan Desert. The results show as the following:(1) These main exogenic forces including weathering, running water, aeolian erosion and gravity drive the erosion landform development on alluvial plains composed of fluvial-lacustrine deposits in the Taklimakan Desert. (2) Because aeolian activities in the Taklimkan Desert occur very frequent, so aeolian erosion plays a leading role in erosion landform development. (3)At the same time, weathering, running water and gravity also play important roles. Some records of summer strong rainfall events in the Taklimakan Desert indicate that the function of running water in erosion landform development can't be neglected. Rain infiltration and soil cracks, main weathering forms, loosen the surface soil structure, smash sediments to pieces, and make soil be eroded easily. Moreover, all these exogenic forces have different importance in different stages of erosion landform development. But they work co-operatively and mutually reinforce. Wind erosion breakthroughs can develop under aeolian erosion together with weathering and running water in the initial stage. A series of erosion landforms, including deflation furrow, wind erosion groove, blowout pit, wind erosion depression, erosion platform, wind erosion residual pier, and wind erosion plain, can rapidly develop under aeolian erosion together with gravity and weathering in the rest of stages. Sand wedges, composed of sand particles deposited in the wedge-shaped space of soil cracks, are of great importance in erosion landform development. Rainwater flows into sand wedges and is adsorbed by sand. Due to good penetrability of sand deposits, water can infiltrate quickly without evaporation loss and reach the bottoms of cracks. The deep soil can be destroyed by soil expansion of wetting and unfreezing; soil cracks widen and extend into deep soil further. Lateral erosion and undercutting are the main forms of wind erosion as well as sheet erosion, they make the sediments hang up. Lateral erosion, undercutting and sand wedges provide good conditions for gravity collapse and accelerate the negative erosion landform development on the sediments with nonhomogeneous texture. Collapse diluvium also can slow down the speed of wind erosion landform development.(4) The morphological characteristics of erosion landform depend on the special exogenic forces combination and the interbedded sedimentary structure of alluvial plains, namely, compact sediment and soft sediments are distributed in turn in vertical profile.