晚全新世毛乌素沙地东南缘沉积物粒度特征及其指示的环境变化  

Grain Size Characteristics of Sediments in the Southeastern Margin of Mu Us Desert,China and Their Implication for Environmental Change During the Late Holocene

作　　者：贾飞飞 徐成琳 张建伟 孙茹 JIA Fei-fei;XU Cheng-lin;ZHANG Jian-wei;SUN Ru(School of Geographical Sciences,Liaoning Normal University,Dalian 116029,Liaoning,China)

机构地区：[1]辽宁师范大学地理科学学院,辽宁大连116029

出　　处：《地球科学与环境学报》2023年第6期1285-1298,共14页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(41601190);北京师范大学防沙治沙教育部工程研究中心开放课题(2019-B-1)。

摘　　要：地处我国东亚季风边缘区的毛乌素沙地,因其对气候变化响应敏感而成为研究古气候环境变迁的理想场所。利用毛乌素沙地东南缘厚273 cm的沉积地层,通过分析沉积物粒度端元特征和环境指示意义,并结合光释光(OSL)测年结果和磁化率指标,重建了研究区2.6 ka B.P.以来的环境变化过程。结果表明:①剖面沉积物的粒度组成以粗粉砂、极细砂和细砂为主,其中细砂最多,平均体积分数为57.29%;粉砂层细砂体积分数明显低于砂层,粗粉砂和极细砂显著增多;沉积物粒度频率分布曲线多呈现典型的风成沉积物特点,峰高且窄,分选性较好。②剖面沉积物粒度可分离为3个端元组分,端元EM1是最细的粒度端元组分,指示了短时间的强尘暴活动,端元EM2和EM3是在不同风动力条件下跃移搬运的亚组分,端元EM3指示了当地风沙活动的强弱。③研究区晚全新世环境变化过程可分为3个阶段。2.6 ka B.P.之前,冬季风较强,气候冷干;2.6 ka B.P.之后到近百年,冬季风减弱,气候趋于暖湿;近百年以来,风沙活动增强,人类活动影响较大。The Mu Us Desert,located in the edge of the East Asian monsoon region in China,is an ideal place to study the changes in paleoclimate and environment because of its sensitivity to climate change.The sedimentary strata with a thickness of 273 cm in the southeastern margin of Mu Us Desert were used to reconstruct the environmental change process since 2.6 ka B.P.in the study area by analyzing the grain size end-member characteristics of sediment and environmental indication significance,and combined with optically stimulated luminescence(OSL)dating results and magnetic susceptibility indicators.The results show that①the grain size composition of sediment is mainly composed of coarse silt,very fine sand and fine sand,among which the fine sand volume fraction is the most with an average of 57.29%;the fine sand volume fraction of the silty sand layer is significantly lower than that of the sand layer,and the coarse silt and very fine sand increase significantly;the grain size frequency distribution curves of sediments mostly show typical characteristics of aeolian sediments with high and narrow peaks and good sorting.②The sediment grain size can be divided into three end-member components;EM1 is the finest end-member component,indicating a short-term strong dust storm activity;EM2 and EM3 are saltation subcomponents transported under different wind dynamic conditions;EM3 indicates the intensity of local aeolian activity.③The environmental change process of Late Holocene in study area can be divided into three stages.Before 2.6 ka B.P.,the winter monsoon is strong and the climate is cold and dry;after 2.6 ka B.P.,the winter monsoon weakens and the climate tends to be warm and humid;in the past century,wind-sand activities are enhanced,and human activities have a greater impact.

关 键 词：晚全新世 环境变化 砂质沉积物 风沙活动 粒度特征 端元分析 光释光测年 毛乌素沙地 

分 类 号：K903[历史地理—人文地理学] P532[天文地球—古生物学与地层学]