西藏林芝黄土记录的末次冰期粉尘活动与西风-季风变化  

Dust activity and westerlies-monsoon variations during the last glacial period recorded in loess sediments in Linzhi area,southern Tibetan Plateau

作　　者：韩一筱 宋友桂[2] 程良清 张明玉 兰敏文 HAN Yixiao;SONG Yougui;CHENG Liangqing;ZHANG Mingyu;LAN Minwen(Xi'an Institute for Innovative Earth Environment Research,Xi'an 710061,Shaanxi;State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences,Xi'an 710061,Shaanxi;State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,Jiangsu;Department of Geology,Northwest University,Xi'an 710069,Shaanxi)

机构地区：[1]西安地球环境创新研究院,陕西西安710061 [2]中国科学院地球环境研究所,黄土与第四纪地质国家重点实验室,陕西西安710061 [3]中国科学院南京地理与湖泊研究所,湖泊与环境国家重点实验室,江苏南京210008 [4]西北大学地质系,陕西西安710069

出　　处：《第四纪研究》2024年第6期1688-1699,共12页Quaternary Sciences

基　　金：科技部第二次青藏高原综合科学考察研究项目(批准号:2019QZKK0101);陕西省自然科学基础研究计划资助项目(2023-JC-QN-0353)共同资助。

摘　　要：雅鲁藏布江流域的风成黄土是研究区域粉尘堆积过程及西风与季风协同演化的重要载体。本研究对雅江中游林芝地区900 cm的末次冰期黄土剖面进行了粒度分析,采用参数化粒度端元分析分离出对气候变化和粉尘活动响应敏感的粒级组分,重建了末次冰期的粉尘活动及其与西风和季风变化的历史。粒度端元分析分离出了4个端元组分,解释为3种不同的沉积动力特征:EM1(众数粒径7.76μm)代表高空西风搬运的远源粉尘,反映西风强度变化;EM2(众数21.48μm)和EM3(众数38.20μm)为近地面风搬运的近源粉尘,其组合(EM2+EM3)的含量能够反映印度冬季风(IWM)强度的变化;EM4(众数粒径78.35μm)则为强沙尘暴组分。对比研究发现在末次冰期期间IWM和西风环流对北半球中纬度夏季太阳辐射变化敏感响应。当太阳辐射降低时,IWM增强,西风减弱,导致粉尘活动加强,远源组分减少;而当太阳辐射增加时,IWM减弱,西风增强,粉尘活动减弱,远源组分则相应增加。The Yarlung Zangbo River basin,located in the southern Tibetan Plateau,is an important area for loess distribution.The aeolian loess deposit serves as an excellent archive for studying the dust accumulation process and the coevolution of Westerlies and Indian monsoon systems.This study presents grain size analysis results of a 900 cm loess-paleosol section(KSM:29°33'28.01″N,94°29'48.59″E;3150 m a.s.l.)developed during the last glacial period at Linzhi area in the middle reaches of the Yarlung Zangbo River.The luminescent dating results(pIRIR)of potassium feldspar from this loess profile indicate ages of 28.2±1.6 ka for the top 75 cm and 83.5±4.5 ka for the bottom 875 cm.This suggests that the loess primarily formed during the last glacial period,with no Holocene deposits present.The deposition rates across the entire section range from 12.1 cm;ka to 20.8 cm;ka,averaging 18.0 cm;ka.We employed a Bayesian age-depth model to establish the geochronological timescale.Using Gen.Weibull parametric end-member modeling,we isolated grain size components sensitive to climate change and dust activity.Then we reconstructed the history of dust activity and westerlies-monsoon variations during the last glacial period.The grain size end-member analysis identified four end-member components(EMs),which were interpreted as reflecting three distinct sedimentary dynamics.EM1(mode particle size of 7.76μm)represents far-traveled dust transported by the upper-level westerlies and reflects westerly intensity;EM2(mode:21.48μm)and EM3(mode:38.20μm)are associated with near-surface winds,indicating short distance suspension of local dust.We contribute the combined content of(EM2+EM3)to reflect the intensity of the Indian winter monsoon(IWM).EM4(mode:78.35μm)represents the component of strong sandstorms.Overall,dust in the Linzhi area mainly consist of local coarse particle components transported by IWM,as well as a small amount of distant fine particle components transported by the upper-level westerlies.Comparative studies indic

关 键 词：雅鲁藏布江 黄土 西风 印度冬季风 粉尘活动 

分 类 号：P534.63[天文地球—第四纪地质学] P512.21[天文地球—古生物学与地层学]