库姆塔格沙漠古水系变迁与沙漠地貌的形成

Evolution of Palaeo-drainage System and Its Relationship with the Formation of Desert Landform in the Kumtag Desert

通过库姆塔格沙漠现场考察,借助卫星遥感影像并结合地形图和相关研究文献,对库姆塔格沙漠古水系变迁及其与沙漠地貌形态的形成和变化关系进行了研究,初步认为:阿尔金山北麓洪积扇发育和古水系变迁奠定了库姆塔格沙漠形成和演化的基础。第四纪初期阿尔金山强烈抬升之后,大量剥蚀物质通过洪水搬运,在阿尔金山北麓堆积,形成巨厚的第四纪洪积扇层。洪积物不断堆积过程抬高了洪积扇前缘海拔高度,导致洪积扇和古水系逐渐向海拔较低的右侧(东)偏转发育和变迁。受卡拉塔什塔格—多坝沟一线的低山阻挡,洪水携带剥蚀物在低山北侧堆积少而导致低山北侧的洪积扇海拔比其西部海拔低是洪积扇和古水系向右侧(东)偏转发育和变迁主要原因。当阿尔金山隆升稳定后,古水系的功能由对剥蚀物搬运转变为对洪积扇的冲蚀,在洪积扇上形成冲蚀浅沟。流水进一步冲蚀洪积扇层和底部基岩,形成了恰什坎萨依、厄格孜萨依、梭梭沟、八龙沟、多坝沟等冲蚀沟谷。同时,流水不断改造洪积扇,形成了沙漠地貌的基本框架。库姆塔格沙漠是在流水地貌的基础上,经过强烈的风蚀风积作用塑造,形成了"帚状"形态和"羽毛状沙丘"独特的沙漠地貌景观;广布于沙漠中的砾石体是洪积扇发育完成及沙漠形成后在较短时间里发生的大规模洪水事件的产物,是古水系对剥蚀物的又一次搬运和堆积所致。

After surveying the Kumtag Desert, the evolution of palaeo-drainage system and its relationship with the formation of desert landform in the Kumtag Desert were studied using survey data, by combining remote sensing images with 1：100,000 scale topographic map and literatures. Some preliminary conclusions were obtained, that is, aKer the intense upliK of the Altun Mountains in the early Quaternary, a mass of deposition were denuded and conveyed by flood and accumulated on the northern piedmont of the Altun Mountains. The process of accumulation increased not only the depth of the pluvial fan but also lined its anterior elevation, resulting in eastward deflexion of the palaeo-drainage system, due to lower elevation in the eastern side. AKer stabilization of the upliK of the Altun Mountains, the flood eroded the pluvial fan, and the gullies, such as Hongliu, Xiaoquan, Suosuo and so on were formed. On the basis of fluviation, the unique desert landscape such as plumed dunes had been formed through intensive wind erosion. The widespread gravel reliefs occurring in desert were constructed by flood events in a relatively short period of time. In addition, the lacustrine sediments appeared at 840 m above sea level reveals that Lop Nur was once connected with Hala lake by Aqik valley. AKer lake shrinkage, the ancient Shule river and floods from the northern hills gullied the lacustrine sediments from east and north respectively, and two groups of almost vertical Yardang landforms were shaped by wind erosion.