粒度和磁化率记录的毛乌素沙地东缘全新世气候变化  

Holocene Climate Change Revealed by Grain Size and Magnetic Susceptibility in the Eastern Mu Us Sandy Land

作　　者：韩瑞 苏志珠[2] 李想 柳苗苗 马义娟 Han Rui;Su Zhizhu;Li Xiang;Liu Miaomiao;Ma Yijuan(College of Environment and Resources,Shanxi University,Taiyuan 030006,China;Historical Culture School,Shanxi University,Taiyuan 030006,China;College of Geography Science,Taiyuan Normal University,Jinzhong 030619,Shanxi,China)

机构地区：[1]山西大学环境与资源学院,山西太原030006 [2]山西大学历史文化学院,山西太原030006 [3]太原师范学院地理科学学院,山西晋中030619

出　　处：《中国沙漠》2019年第2期105-114,共10页Journal of Desert Research

基　　金：国家自然科学基金重点项目(41330748);国家重点研发计划项目子课题(2016YFC0500805)

摘　　要：通过对毛乌素沙地东缘大柳塔剖面地层沉积物粒度及磁化率特征的分析,结合光释光测年结果,探讨了毛乌素沙地全新世气候变化。结果表明:(1)剖面沉积物粒度组成以中砂、粗砂为主,古土壤中黏粒组分含量高(3.32%),风成砂中几乎不含黏粒组分(0.01%),粒度参数的平均粒径M_z和分选系数σ也表现为古土壤高值、风成砂低值;(2)磁化率在全剖面呈有规律的变化,低频、高频磁化率在古土壤中呈高值,湖沼相、弱成壤次之,风成砂最小;低频磁化率χ_(lf)与黏粒(<2μm)含量、平均粒径M_z呈显著正相关,垂向剖面上变化规律一致,指示了相似的气候环境意义;(3)毛乌素沙地在10.39 ka BP附近存在明显的3次冷干-暖湿气候波动; 10.39～9.34 ka BP,气候冷干,风沙活动盛行; 9.34～8.68 ka BP,冬季风衰退,夏季风增强,成壤作用强烈; 8.68～8.29 ka BP,气候寒冷干燥; 8.29～2.72 ka BP,气候整体温暖湿润,在6.55～3.80 ka BP达到鼎盛后转向冷干; 2.72～1.34 ka BP,冬季风占主导,沙丘活化,沙漠扩张; 1.34 ka BP至今,逐渐接近现代气候。毛乌素沙地的全新世气候变化是东亚冬、夏季风此消彼长作用下全球气候变化的区域响应。Located in the northwestern edge of the East Asian summer monsoon,Mu Us Sandy Land is sensitive to climate changes,which is an ideal area for studying paleoclimate changes and desert vicissitudes. Through the characteristics of the sediments grain size and magnetic susceptibility analysis of the Daliuta( DLT) section,based on data of OSL dating,we discussed the climate change process in Holocene of Mu Us Sandy Land. The results showed that:( 1) The grain size composition of DLT section was mainly composed of medium( 3. 39%-73. 84%) and coarse sand( 1.46%-75. 79%). In different sedimentary facies,the grain size components of aeolian sand were mainly medium( 42.97%) and coarse sand( 43.37%),the paleosol was dominated by silt( 26.06%) and very fine sand( 23.26%),the weak soil was dominated by medium( 32.84%) and coarse sand( 30.30%),and the lakeswamp sediment was mainly composed of fine( 32.83%) and very fine sand( 27.60%). In terms of grain-size parameters,the mean grain size ranged from fine to coarse in order of paleosol( 2.86 Φ),lake-swamp sediment( 2.50 Φ),weak soil( 1.84 Φ) and aeolian sand( 1.04 Φ),and the sorting coefficient also showed high value in paleosol( 1.78) and low value in aeolian sand( 0.60).( 2) The magnetic susceptibility changed regularly in the whole section. The variation ranges of low,high frequency magnetic susceptibility(χlf,χhf) are similar,with the ranging from 2.50 to 115.66(×10^-8 m^3·kg^-1) and 2.36 to 105.32(×10^-8 m^3·kg^-1) respectively,and they showed the regularity of paleosol>lake-swamp sediment>weak soil>aeolian sand in different sedimentary facies. Meanwhile,the χlf was significantly positively correlated with the content of clay components and the mean grain size,and they showed consistent patterns of variation in vertical profile,which indicated similar climate changes.( 3) The Holocene climate change in Mu Us Sandy Land has experienced at least 6 times distinct cold-warm fluctuations. Before 10.39×10^3 yr BP,the climate of Mu Us Sandy Land fluctuated frequently,

关 键 词：粒度 磁化率 气候变化 全新世 毛乌素沙地 

分 类 号：P531[天文地球—古生物学与地层学]