库姆塔格沙漠北部三垄沙地区风成沉积物粒度特征

对位于库姆塔格沙漠北部的三垄沙地区,迄今尚未开展详细的风沙地貌研究。对该区域地表沉积物样品进行粒度分析,旨在探讨不同区域、不同沙丘类型以及沙丘不同地貌部位的沉积物特征差异。结果表明:三垄沙地区地表沉积物以中沙和细沙为主,二者平均含量之和为63.20%,平均粒径为0.95~1.89Φ,分选系数为0.55~1.55,粗于库姆塔格沙漠和塔克拉玛干沙漠,与世界其他沙海沙物质相比属于偏粗粒径。三垄沙地区的主要沙丘类型为新月形沙丘或沙丘链,其北部发育有线形沙丘;这两种沙丘表层沉积物平均粒径均属于中沙范围,且从沙丘底部到丘顶平均粒径变大、分选变好,最粗的沙粒出现在沙丘顶部,平均粒径分别为1.64Φ和0.71Φ,不同于其他地区沙丘顶部沉积物最细的分布模式。从概率累积曲线来看,流动沙丘多为二段或三段式,风成沙砾浪和剥蚀残丘多为三段或四段式,表明后者经历的分选过程较短。本区地表沉积物的平均粒径沿主导风向有变小的趋势,其中,新月形沙丘和线形沙丘的这一特征最为明显。

Grain Size Characteristics of the Aeolian Sediments from Sanlongsha Area of the Northern Kumtagh Desert

There are few aeolian geomorphology researches about Sanlongsha area located in the Northern Kumtagh Desert. After analyzing the grain size of surface sediment samples in Sanlongsha area, the paper aims to discuss the characteristics differences of the different dune types and geomorphological positions. Results show that the mean grain size ranges from 0.95 Φ to 1.89 Φ; sorting coefficient varies from 0.55 to 1.55; main components of deposits are fine sand and moderate sand, and both of which content reach 63.20%. It is coarser and worse sorted than sands in the Kumtagh Desert and Taklamakan Desert in China, and has a coarser grain size on global scale. The main types of sand dunes in Sanlongsha area are barchans or dune chains and linear dunes developed in the north. On the surface of these two typical dune types, the average grain size both belongs to moderate, the grains become coarser and better sorted from the bottom of the dune to the crests, and the coarsest sands are found at the crests, with the mean grain size 1.64 Φ and 0.71 Φ, respectively, which is different from the pattern in other areas, the finest sands occurring at the crests. The cumulative probability curve is two-stage or three-stage for drifting dunes while three-stage or four-stage for granule ripples and denudation monadnock, which indicates the latter has experienced shorter sorting process. The paper can provide some useful information for analyzing the material sources and formation processes of aeolian geomorphology in Sanlongsha area and also for revealing the relationship between Sanlongsha and Kumtagh Desert.