库姆塔格沙漠沉积物粒度端元特征及其物源启示

The characteristic of grain size end members in Kumtagh Desert and its implication for sediment source

关于沙漠沉积物粒度的研究已经开展得十分广泛,但是从粒度资料中提取沙漠沉积物的搬运和物源信息的工作仍较薄弱。为此,将端元模型分析技术应用到沙漠沉积物物源判断研究中,对库姆塔格沙漠的沉积物(包括沙丘和丘间地)进行粒度端元提取,并结合各端元的沉积动力特征、空间分布格局及与潜在物源的对比,对沙漠的物质来源进行了判断。结果表明:端元1(66.90~309.52μm)为由三垄沙、雅丹和阿尔金山冲洪积物共同组成的细粒跃移质;端元2(163.48~586.00μm)为全由三垄沙和雅丹贡献的较粗跃移质;端元3(309.52~2 711.36μm和66.90~143.90μm)则为被后期改造了的阿尔金山冲洪积物。通过各端元的空间分布格局和与潜在物源沉积物端元的对比,我们认为三垄沙、雅丹和阿尔金山冲洪积物均为库姆塔格沙漠沙丘和丘间地提供了物源供应,但北部的三垄沙和雅丹对沙丘贡献较多,而南部的阿尔金山冲洪积物则对丘间地贡献较多。另外,通过对端元1的分析,我们更倾向于认为在库姆塔格沙漠沉积物的部分粒级和局部地区存在丘间地为沙丘提供物源这一过程。

Research on the grain size of desert sediment has been extensively and maturely conducted, however, extracting sediment transport and source information from grain size data is still weak. Herein, we applied end member modeling analysis to separate end members from grain size distributions data of sediment(including dune and interdune) in the Kumtagh Desert, and combined dynamic feature, spatial patterns of these end members and their relationship to the potential sources, aiming to identify source areas. The results show that the EM1 represents the relative fine saltation load which is the combination of Sanlongsha sand, yardang sand and alluvial deposits of Altyn Tagh Mountains;EM2 represents the aeolian saltation load which is completely contributed from Sanlongsha and yardang sediments;and EM3 represents the reworked alluvial deposits which is completely derived from Altyn Tagh Mountains. The spatial patterns of these end members and their comparison to potential sources indicate that Sanlongsha, yardang and alluvial deposit of Altyn Tagh mountains provided sediments to both dune sand and interdune in Kumtagh Desert, therein, dune sand was mainly transported from northern Sanlongsha and yardang area, while interdune sands was mainly delivered from southern Altyn Tagh Mountains. In addition, based on the analysis for EM1, we are inclined to that interdune can provide source materials for dunes in some grain size and in some local areas of Kumtagh Desert.