摘要
选取巴丹吉林沙漠东南部全球高差最大(约420 m)的诺尔图湖东大沙山和较高的苏木巴润吉林湖西大沙山(高差约400 m),对其迎风坡沉积物进行系统采样分析,讨论了高大沙山迎风坡沉积物粒度成分特点、变化规律、原因及其活动性。结果表明,全球高差最大的诺尔图东沙山和苏木巴润吉林湖西沙山迎风坡沉积物具有双层结构,表层沉积物的粒度组成较下层粗,表层沉积物的中砂含量高于细砂,而下层沉积物的细砂含量明显高于中砂;两层沉积物中的极粗砂、粗砂、极细砂和粗粉砂含量均很少,且不含粘粒。表层沉积物粒度成分比下层粗是表层沉积物受到了风蚀作用造成的。从沙山下部到上部,迎风坡沉积物粒度成分逐渐变细,分选变好,偏度趋于负偏。两个大沙山粒度组成与变化特点一致表明,大沙山表层粒度成分在发生粗化,物质组成还在发生移动,大沙山仍然处在活动阶段。大沙山地貌与风力作用可分为3个带,下部是以较平坦洼地为代表的侵蚀、搬运带,中部是新月形沙丘密集分布的物质堆积和运移并存带或风沙物质转运带,上部是风沙物质堆积的陡峭沙山主峰带。大沙山物质运移的基本模式是下部以侵蚀搬运为主,中、上部物质则是堆积与运移并存,风沙物质经过多次的运移传递而到达沙山顶部和背风坡。
Sediments were sampled on the windward slope of a typical barchan compound mega-dune with a height of about 420 m in the southeastern Badain Jaran Desert for grain-size distribution analysis.The study discussed the grain composition,the reasons for variation and the law of variation of the mega-dune,activity and changes in power of the mega-dune.The results indicate that there is double-decker on the windward slope of the mega-dunes,and the surface layer sediment size is higher than that of sub-surface layer.The content of medium sand is higher than that of fine sand in the surface layer sediment;it is contrary in the sub-surface.The fraction of coarse silt sand,very fine sand,very coarse sand,and coarse sand in both surface and sub-surface sediments is insignificant,and clay is absent.Wind erosion is responsible for the difference in grain size between the two layers.In general,grain on the crestal zone of the mega-dune is finer and better sorting than that at toe of wind-ward slope.The frequency distribution curve becomes more negatively skewed.The fact that the size of the sediments in the upper part is larger than that in the lower part results from wind erosion.The particle size composition and change features of two mega-dunes jointly indicate that the particle size of the surface layer of the mega-dunes is coarsening and components continue to migrate,indicating that the mega-dunes are still very active.The mage-dune landform and wind action can be divided into three belts： the lower part represents flat erosive transport belt;the middle part is accumulation and migration of materials from intensive barchan-shaped distribution;and the upper part is the peak of mage-dune accumulated by sand material.The fundamental mode of material migration is dominated with erosion transport in the lower part,along with material accumulation and migration co-existing in the middle and upper parts.The sand material was transported to the peak or leeward slope of mage-dune through several migration.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2011年第8期1389-1398,共10页
Acta Geologica Sinica
基金
教育部"长江学者"特聘教授项目
国家自然科学基金项目(编号40672108)资助成果
关键词
高大沙山
粒度组成
沙山活动
沙山物质运移模式
巴丹吉林沙漠
mega-dunes
grain size composition
mega-dune move
Move model of mega-dune substance
Badain Jaran desert.
