中文摘要：

干旱区绿洲演变与其水系变迁有密切关系，以黑河下游水系变迁的年代学研究为出发点，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；利用光释光测年获取古河道上灌丛沙丘的发育年代，讨论了近1450年以来古居延绿洲水系演变过程与机制。发现距今1450年以来古居延绿洲水系演变过程中，古水系曾在约1450a B.P.、850a B.P.和600a B.P.发生3次大规模萎缩；DEM和实测高程数据显示现代黑河纵比降（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的整体地形特征为东南高、西北低，地形因素控制着水系向现代额济纳绿洲方向转移。额济纳盆地水系的演变可能主要受控于区域古气候演化和地形条件。

英文摘要：

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.The evolution of the lower reaches of Heihe River water course is the key to explain the degradation of AJO.In the ancient water courses on AJO, there developed a large number of shrub dunes.The bottom ages of these high shrub dunes（5~10m）can represent the age of these ancient water courses shrinking; only if the water course drought up totally, these shrub dunes could be developed.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.5 samples for optical stimulated luminescence（OSL）dating are collected from the bottom of 5 shrub dunes（GCSQ-2, GCSQ-3, GCSQ-4, GCSQ-5, and GCSQ-6）which developed on the ancient water course on AJO.One modern shrub dune（GCSQ-7）is also collected near the terminal lake——Swan Lake.One OSL lake sample（TEH）is colleceted from the top of a lacustrine section which is in the ancient Juyan Lake.The age of the top of lacustrine sediments TEH is 1.45±0.06ka, suggested the ancient Juyanze drought out after that time.The OSL ages of the shrub dunes on the ancient water course（GCSQ-2, GCSQ-3, GCSQ-4, GCSQ-5, GCSQ-6, and GCSQ-7） are 0.85±0.07ka, 0.65±0.08ka, 0.88±0.12ka, 0.16±0.06ka, 0.85±0.06ka, and 0.08±0.05ka respectively.They indicated that the water course of Heihe River on AJO shranked gradually.Using the DEM data and the elevation data obtained in the field trip, we analysed 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 cha