Knowledge Resource Center for Ecological Environment in Arid Area
| 历史时期黑河下游绿洲水系演变及其机制研究 | |
| 其他题名 | Drainage network evolution processes and mechanisms of oasis in the lower reaches of Heihe basin during historical period |
| 耿建伟 | |
| 出版年 | 2017 |
| 学位类型 | 硕士 |
| 导师 | 赵晖 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 绿洲是干旱区生境中的异质生态景观，其发育与演变影响着干旱区生态系统的恢复与稳定。水系演变过程和机制是内陆河绿洲发育与演化研究的核心内容。黑河是我国第二大内陆河，其下游发育了两个重要绿洲—已经沙化消亡的古居延绿洲和现代额济纳绿洲，两大绿洲的演变过程及其机制是当前干旱区研究的热点。黑河下游水系演化过程及其机制是理解居延泽古绿洲和额济纳现代绿洲在历史时期演化过程的关键科学问题。水是干旱区环境的限制性因子，是绿洲演变、内陆湖泊存续的关键。水系的变迁过程与机制对解释绿洲演变具有重要意义。本文以黑河下游水系变迁过程研究为出发点，使用DEM（Digital Elevation Model）数据和高分辨率遥感影像提取额济纳绿洲的现代水系及历史时期发育于古居延绿洲的主要古河道；利用OSL（Optically Stimulated Luminescence）测年获取古河道上灌丛沙丘的发育年代和古河床剖面的年代序列；基于古河床沉积物石英颗粒的扫描电镜对其搬运动力与沉积环境进行恢复。同时，结合黑河下游古气候背景、历史文献记录、古河道地形等因素提取古水系演变的关键因子，探讨其变迁过程与机制，获得了以下认识：（1）1.45 ka以来古居延绿洲水系演变大体经历了3次主要的萎缩过程：约1450 a B.P.下游古居延泽开始萎缩，人类在古绿洲的活动开始向绿洲中部转移，西夏、元初黑城、绿城一带被大规模开垦；850 a B.P.左右古水系再次出现大规模萎缩，灌丛沙丘大量发育于古河道；在约600 a B.P.古居延水系完全萎缩，古居延绿洲完全荒漠化，现代额济纳绿洲成为额济纳盆地的主要绿洲。（2）基于遥感影像、DEM和实测高程数据的地形分析表明，古水系河道在历史时期不断抬高，纵比降逐渐减小，现代黑河纵比降（0.81‰）高于古河道纵比降（0.56‰），东南至西北方向的3条高程纵剖面线性拟合斜率约为-0.40，表明额济纳盆地主要过水河道东南高、西北低。（3）GHDPM1剖面6个扫描电镜样品中，除剖面上部样品GHDPM1-17-D和GHDPM1-52-D具有明显风成成因特征，其余样品水流成因特征明显。剖面GHDPM1样品的扫描电镜和年代序列，可推断古河道从水流环境演变为风沙环境的过程。（4）历史时期额济纳盆地水系的演变是古气候条件与地形因素共同影响下，古居延泽绿洲水系不断萎缩，同时向额济纳绿洲转移的结果。古水系的三次萎缩分别与中国北方3次冷干事件有较好的耦合。在水动力条件减弱的背景下，上、中游河水携带的泥沙含量增加，古水系河道不断抬高，纵比降逐渐减小，致使水系在萎缩的过程中，选择比降更大、地势更低的现代黑河。 |
| 英文摘要 | Heihe is the second largest inland river in China. There are two major oases in the lower reaches of Heihe River in Inner Mongolia of China, the modern Ejina oasis and the desertified ancient Juyanze oasis(AJO). The development and evolution process and their mechanisms of the two oases are important for the study of the ecological system in Ejina Basin，yet are still unclear.Water resource is the limiting factor in arid area, which is the key to the evolution of oases and the existence of inland lakes. Based on the drainage network evolution processes and mechanisms of the lower reaches of Heihe River. The ancient water courses on AJO are simulated using DEM（Digital Elevation Model）data and high resolution remote sensing images, and then confirmed in the field investigation. Using OSL (Optically Stimulated Luminescence), we get the ages of shrub dunes which developed on the ancient water courses on AJO and the ages of the ancient river bed sediments. The scanning electron microscopy of quartz grains of the ancient river bed sediments restore its depositional feature. Combined with the ancient climate background and historical documents，we get some new knowledge about the drainage network evolution processes and mechanisms of the lower reaches of Heihe River：(1) Three large-scale shrinking periods of ancient water system occurred in 1450 a B.P., 850 a B.P. and 600 a B.P. in accordance with three cold and dry envents in North China.(2) Using the DEM data and the elevation data obtained in the field trip, we analyse the longitudinal gradient of the the ancient water course and the modern Heihe River. Three terrain profiles from the southeast to northwest cross the ancient water course and modern river are also analysed to check out the topographic change of Ejina Basin by using the DEM and water courses data.The results are suggested that the modern Heihe River has the higher longitudinal gradient (0.81‰) than the the ancient water course(0.56‰). Longitudinal ratio fittings value of terrain profiles (c-c'、d-d' and e-e') on the upper, middle and lower part of the ancient Juyanze oasis from the southeast to the northwest is or so -0.40. It suggest that the overall terrain of Ejina Basin in southeast is higher than northwest. (3)Scanning Electron Microscopy on sediments of ancient river bed suggest that the sediments of the ancient river bed were transported by water. The GHDPM1-17-D and GHDPM1-52-D in the upper section of the profile were characterized by obvious aeolian features, while the other samples showed obvious characteristics of water flow. Based the scanning electron microscope and the chronological sequence of the profile ，we can infer the process of the evolution of the paleo channel from the water environment to the aeolian environment. (4)The drainage network evolution in Ejina Basin was mainly controled by the change of the ancient local climate and its terrain. The three atrophies of the ancient water system has a good coupling with the three cold-dry events in North china. In the background of the weakening of hydrodynamic condition, the sediment from the upper and middle reaches of the river increased and the ancient river gradually raised. The current pattern of the water network was eventually formed. |
| 中文关键词 | 黑河绿洲 ; 水系变迁 ; 光释光测年 ; 电镜扫描 |
| 英文关键词 | Heihe oases Oasis evolution Drainage network evolution OSL dating Scanning Electron Microscopy |
| 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/2XILL650/287934 |
| 推荐引用方式 GB/T 7714 | 耿建伟. 历史时期黑河下游绿洲水系演变及其机制研究[D]. 中国科学院大学,2017. |
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