摘要
受气候振荡的影响,沙漠边界多次往复摆动,在地层中留下了黄土、古土壤与古风成沙的迭覆沉积。通过传统粒度参数和端元分析模型方法对陕西横山HS剖面L2以来风成沙—沙质黄土—沙质古土壤所蕴含的粒度成分、相应的沉积信息和沙地进退进行探讨。结果表明:HS剖面粒度组成不同于黄土区,以极细砂(31.07%)、细砂(30.20%)和粗粉砂(23.38%)为主,具有大小混杂的宽粒级范围的明显特征。因此在黄土区具有全球古环境意义的粒度指标未必适合本区,运用参数化端元分析模型对本区粒度指标进行分离,以期得到适宜本区的气候环境指标。其中,端元1(EM1)的众数粒径为8.93μm,反映了西风环流的信息;端元2(EM2)的平均粒径为32.82μm,很大程度上间接指示东亚冬季风强度的变化;端元5(EM5)的平均粒径为235.46μm,是极强冬季风或强风暴的替代性指标,其含量反馈当时冬季风的强烈程度。由此,研究认为陕西横山自L2以来发生了5次沙地扩张和3次沙地后退事件,其中风成沙层为强烈冬季风环境引发毛乌素沙地扩张时堆积的;而冬季风强度大为减弱时,沙丘迁移被沙尘堆积所取代,形成沙质黄土层;古土壤层是在冬季风相对萎缩时发育的。冰期形成的风成沙层对目前区域沙漠化存在不可忽视的潜在威胁,保护全新世形成的土壤层是防治区域沙漠化的重要措施。
Influenced by climate oscillation, the desert boundary swings back and forth many times, consequently leaving overlapping deposits of loess, paleosol, and paleo-eolian sand in the stratum. Based on the traditional grain size parameters and the end member analysis model, this study attempts to discuss the grain size composition, corresponding sedimentary information, and sand advance and retreat of aeolian sand-sandy loess sandy paleosol since L2 of the HS profile in Hengshan County, Shaanxi Province, China. The results show that the grain size composition of the HS profile is different from that of the loess area. It is mainly composed of very fine sand (31.07%), fine sand (30.20%), and coarse silt (23.38%). Therefore, the grain size index with a global paleoenvironmental significance in the loess region may not be suitable for this region. The parameterized end member analysis model was used to separate the grain size to obtain the climate and environmental indicators suitable for this region. The mode particle size of EM1 was 8.93 μm, reflecting the westerly circulation information. Meanwhile, the average particle size of EM2 was 32.82 μm, indirectly indicating the change of the East Asian winter monsoon intensity to a large extent. The average particle size of EM5 was 235.46 μm, which is a substitute index of an extremely strong winter monsoon or a strong storm. Its content feeds back the winter monsoon intensity at that time. Research has shown five times of sand expansion events and three times of sand retreat events since L2 in Hengshan, Shaanxi Province. The aeolian sand layer appeared to reflect the southeastward extensions of the Mu Us Desert in response to the episodic regional aridity controlled by the enhanced winter monsoon. A sandy loess layer was formed when the active dune migration was replaced by dust accumulation when the regional climate was still dominated by the winter monsoon, albeit with a greatly decreased strength. The paleosol developed when the winter monsoon was relatively shrinkin
作者
刘蓉
岳大鹏
赵景波
苏志珠
石浩
王晓宁
LIU Rong;YUE Dapeng;ZHAO Jingbo;SU Zhizhu;SHI Hao;WANG Xiaoning(School of Geography and Tourism,Shaanxi Normal University,Xi’an 710119,Shaanxi,China;Historical Culture School,Shanxi University,Taiyuan 030006,Shanxi,China)
出处
《干旱区地理》
CSCD
北大核心
2021年第5期1328-1338,共11页
Arid Land Geography
基金
国家自然科学基金重点项目(41930641)
黄土与第四纪地质国家重点实验室项目(SKLLQG1874)。
关键词
粒度
端元分析
气候变化
沙地进退
横山
grain size
end member modeling analysis
climate change
sand advance and retreat
Hengshan
