旱麻岗沙漠风沙地貌发育与演化

Formation and Development of the Hanmagang Desert

旱麻岗沙漠位于腾格里沙漠南部,是腾格里沙漠的重要组成部分。目前对该沙漠几乎没有研究。旱麻岗沙漠最主要的地貌是风沙地貌和流水地貌,且近似南北方向平行相间排列。该沙漠主要的沙丘类型有新月形沙丘链、反向沙丘和灌丛沙丘,其中新月形沙丘链和反向沙丘分布在海拔相对高的区域,且呈条带状分布,而灌丛沙丘主要分布在冲沟内。旱麻岗沙漠的起沙风主要为西北风,其次为东南风。风能环境属于低等风能环境,合成输沙方向为282°~331°,方向变率为中等变率。流动沙丘表面平均粒径最大,其次为结皮下层和结皮表层;分选性与平均粒径有相似的规律。石羊河流域、祁连山东端的冲积-洪积物和湖相沉积为旱麻岗沙漠的形成与演化提供了重要的沙源。根据野外考察,结合以往研究成果,该沙漠的形成与演化可以概括为以下几个阶段:大湖期;湖水干涸期,在退水过程形成近似平行排列的小冲沟;沙漠形成与扩张期,流动沙丘覆盖整个区域;沙漠萎缩期,降雨量增加,沙漠萎缩,平行排列的冲沟宽度和深度增加,冲沟内的流沙随流水冲向下游,而冲沟间的沙丘仍然保留在原来的位置,形成现代的地貌格局。

Hanmagang Desert is an important section of the Tengger Desert and lies in the southern region of the Tengger Desert.The most important landforms in the Hanmagang Desert are the aeolian geomorphology and fluvial landform coexisted and paralleled each other for south-north direction.The aeolian landforms are sand dunes and lie in the higher latitude,but the fluvial landforms are gully and lie in the lower latitude.The main dune types are barchan chains,reversing dunes and shrubbery dunes.Barchan chains and reversing dunes are distributed like partial mulching,shrubbery dunes are distributed in the gully.Threshold wind direction are mainly northwest and then southeast.Wind energy environment belongs to lower,the resultant sand drift potential direction is 282-331,the directional index is intermediate.Sediment particle are coarser over dune surface,and then lower layer of crust and crust and there are similar rule of the sorting.The material for the Hanmagang Desert formation was from the Shiyanghe River and the Qilian Mountain.According to the field observation and previous studies,we could build a model for the formation and development of the Hanmagang Desert:the great lakes period,the lakes dry up period,the desert formation and development period and the atrophy period.