Knowledge Resource Center for Ecological Environment in Arid Area
| 库姆塔格沙漠北部三垄沙地区风沙运动规律研究 | |
| 其他题名 | Field observation of Aeolian sediment transport in the Sanlongsha Dune-field of the Northern Kumtagh Desert |
| 杨转玲 | |
| 出版年 | 2016 |
| 学位类型 | 硕士 |
| 导师 | 钱广强 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 库姆塔格沙漠是我国第四大流动性沙漠，也是最晚开展全面科学考察的沙漠。自19世纪60年代、尤其是本世纪以来，研究者们相继对该沙漠进行了详细的风沙地貌学研究，工作区域涵盖了沙漠主体。位于库姆塔格沙漠北部边缘的三垄沙地区，狭长的沙带穿越阿奇克谷地与沙漠主体相连，二者之间存在复杂的沉积物输送与风沙地貌继承关系；探明该地区的风沙运动规律，对于揭示区域风沙地貌演化过程、追溯沙漠物质来源具有重要意义。本研究通过野外地貌调查和风沙运动定位观测，在认识三垄沙地区主要风沙地貌类型和地表沉积物空间差异的基础上分析了一个完整年度内不同时段、不同方向、不同高度的输沙特征和运动沙粒粒度特征，探讨了该地区风沙运动规律与沙丘移动和形态演化之间的关系，得到以下主要结论：（1）三垄沙地区的风沙地貌类型主要为新月形沙丘、新月形沙丘链和线形沙丘。地表沉积物的平均粒径介于0.95～1.89Φ（0.27～0.52mm）之间，属于中沙到粗沙粒级；分选系数介于0.55~1.55之间；新月形沙丘表面粒度分布模式为独特的“粗顶型”，即由沙丘底部到丘顶，粒径变粗，分选变好。沉积物粒度特征在空间上表现为沿主导风向（NE-SW）由物源区向沉积区沙粒变细、分选变好。（2）八方向四层梯度集沙仪的观测结果表明，0-1m高度内捕获的沉积物总重量为405.2kg，其中约75.3%集中在近地表0-20cm范围内。来自于N方向的沉积物最多，占18.1%，SW方向最少，占7.5%。在2014年5月至2015年5月的观测周期中，不同时段、不同方向的输沙率变化介于0.1~23.0之间，其中最大输沙率发生在4~5月份，沉积物主要来自于N、NE和NW三个方向。年度平均输沙通量廓线（风沙流结构）呈指数函数递减趋势，部分通量廓线出现了戈壁风沙流的“象鼻效应”。该地区的合成输沙方向存在显著的季节性变化，年度合成输沙方向为193.2度，反映了潜在的沙丘移动方向和沉积物来源方向。（3）风沙流中沙粒的平均粒径介于1.21~1.90Φ之间，属于中沙范围，分选呈好、中等至较差，偏态为近对称和正偏分布，频率曲线扁平度中等或较宽；四个高度的平均粒径和分选性差异显著。沙粒粒度的空间分布特征表现为：随高度增加中沙和粗沙含量增加，细沙含量减少，平均粒径呈现为先变细后变粗，分选呈先变好后变差的变化特征。各方向的变化，最粗在8~10月份的S方向，最细在12~次年2月份的W方向；从粒级百分含量来看，均以中沙为主，占43.0%，粗沙和细沙次之，三者之和占90%以上，砾石含量介于0.01%~0.1%之间。（4）三垄沙地区的输沙特征、风况和沙丘移动基本一致。从风向、输沙方向和沙丘移动方向看，主风向为北风和东北风，合成输沙方向呈SSW方向，沙丘自北东北向南西南方向移动，与合成输沙方向(192.3°)一致。从季节变化看，春、夏两季风速最大，沙丘移动距离最大，风沙活动也最为强烈，与输沙率观测结果一致。沙丘移动方式为前进式，移动速度为快速型，沙丘体积不断增大，沙丘不断发育。本研究结果表明，区域沉积物粒度特征和沙源丰富程度，显著影响风沙运动过程。风沙运动规律的季节性和方向性变化，直接反映了风力、沉积物丰富度的时空组合。长周期的风沙运动观测，是联系微观风沙运动规律与宏观沙丘演化过程的纽带，对风沙地貌研究具有重要参考意义。 |
| 英文摘要 | The Kumtagh Desert is the fourth largest shifting desert in China and it is also the latest one for comprehensive scientific investigation. Since the 1960s, especially in this century, the researchers have studied aeolian geomorphology of the desert in detail and the working area covers the main desert body. The Sanlongsha Dune-field, located in the northern edge of the Kumtagh Desert, is a narrow sand belt connected to the main desert through the Aqik Valley. The dune-field is closely related to the main body of the desert because of the complex processes of aeolian sediment transport and landform inheritance between them. For the purpose of revealing the regional geomorphological process and of tracing the source region of the desert, it is significant to conduct field observations on aeolian sediment transport in this region. Based on field investigations and in-situ observations, the aeolian landforms and the regional variations of surface sediments, the seasonal, directional and vertical characteristics of aeolian sediment transport rate and grain size distribution during the period from May 2014 to May 2015, have been analyzed and discussed in the present study. Meanwhile, the relationship between aeolian sediment transport patterns and geomorphological evolution in this region has also been discussed. Finally we have got the following main conclusions:(1) The main aeolian landforms include the crescent dunes, barchanoid chains and linear dunes. The mean grain size of surface sediments ranges between 0.95 ~ 1.89Φ (0.27~0.52mm) with the sorting coefficient between 0.55~1.55Φ, which indicates that the surficial sediments are medium to coarse sands. The surface particle size distribution model of barchan dune is the unique "the coarsest crest", namely the mean grain size becomes coarser and the sorting becomes finer from the bottom to the crest of the sand dune. The spatial variations of mean grain size and sorting parameters indicate that there is a finer and better sorting tendency from the source region to the sink area along the dominant wind direction (NE-SW).(2) During the one-year field observations by means of the segmented, eight-directional sand trap (SEDST), the total weight of the captured sediments is 405.2kg within 1m above the ground and about 75.3% of them are transported within 0cm to 20cm. The sediment from the N direction is the most which occupy 18.1%, and the SW direction is the least which only occupy 7.5%. Sediment transport rate changes in the range of 0.1 to 23.0 at different stages and directions during the period from May 2014 to May 2015, and the maximum transport rate occurred during the April to May with sediments mainly from the N, NE and NW directions. The annual average sediment flux profile (blowing sand structure) shows exponential decline trend, part of the flux profile has presented the "trunk effect" over the gobi surface. The resultant sediment transport direction in the region has significant seasonal variation, the annual mean resultant sediment transport direction is 193.2 degree, which implies the potential direction of dune movement and sediment source area.(3) The mean grain size of the sand particles in aeolian saltation ranges between 1.21Φ and 1.90Φ, which belongs to medium sands. The moving particles can be well, moderate to poorly sorted, nearly symmetrical to positively and mesokurtic to platykurtic distribution. The mean grain size and sorting characteristics at four sampling heights are significantly different. The spatial distribution characteristics of sand particle size is shown as: the medium and coarse sands increase with height whereas the fine sand reverse, the mean grain size becomes finer first and becomes coarser then, sorting characteristic is becoming well first and poorly later. The coarsest sand occurred in S direction during the August to October and the finest occurred in W direction during the period of December to February next year from the aspect of each direction. From the curves of grain size distribution, the medium sands, coarse sands and fine sands account for 43.4%, 22.0% and 28.0%, respectively. The gravel content is between 0.01%~0.24%.(4) The characteristics of sediment transport, wind condition and sand dune movement are basically identical. From the point of wind direction, sediment transport direction and dune moving direction, the main wind direction is from north and north east, the resultant sediment transport direction is to SSW, sand dunes moves from the north northeast to south southwest direction which is consistent with the resultant sediment transport direction (192.3 °). From the point of seasonal variation, both the maximum wind speed and moving distance of dune occur in spring and summer, the wind speed of spring and summer is the strongest, so the sand dune movement distance and aeolian activities, all consistent with the results of sediment transport rate observation. In addition, the mode of dune moving is advancing type, moving speed is fast, and the volume of sand dune is increasing, sand dune developing continuously.This study shows that regional sediment granularity characteristics and sediment supply had significant effect on the sand movement process. The seasonal and directional variations of sand movement pattern directly reflect the spatial-temporal combination of wind and sediment supply. Long-term observation of aeolian sand movement is the connection link of the micro aeolian sand movement and macro dune evolution process which has important significance on the aeolian geomorphology research. |
| 中文关键词 | 三垄沙 ; 风沙运动 ; 输沙率 ; 粒度特征 ; 沙丘移动 |
| 英文关键词 | Sanlongsha Aeolian sand movement Sediment transport rate Grain size characteristics Dune movement |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287703 |
| 推荐引用方式 GB/T 7714 | 杨转玲. 库姆塔格沙漠北部三垄沙地区风沙运动规律研究[D]. 中国科学院大学,2016. |
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