河北坝上地区中晚全新世粒度端元分析及其环境意义  

MID-LATE HOLOCENE END-MEMBER ANALYSIS AND ITS ENVIRONMENTAL IMPLICATIONS IN BASHANG REGION, HEBEI

作　　者：马罗 鲁瑞洁 陈东雪 刘瑛娜 MA Luo;LU Ruijie;CHEN Dongxue;LIU Yingna(State Key Laboratory of Earth Surface Processes and Resource Ecology,Faculty of Geographical Science,Beijing Normal University,Beijing 100875;MOE Engineering Research Center of Desertification and Blown-Sand Control,Faculty of Geographical Science,Beijing Normal University,Beijing 100875)

机构地区：[1]地表过程与资源生态国家重点实验室,北京师范大学地理科学学部,北京100875 [2]防沙治沙教育部工程研究中心,北京师范大学地理科学学部,北京100875

出　　处：《第四纪研究》2022年第6期1554-1567,共14页Quaternary Sciences

基　　金：国家重点研究发展计划项目(批准号:2017YFC1502401)资助。

摘　　要：河北坝上地区地处东亚夏季风边缘,对气候变化响应敏感,是研究古气候环境演变的理想地区之一。本研究采用粒度端元模型分析方法对坝上地区2 m厚的典型风成砂-古土壤剖面沉积物粒度数据进行分离,同时结合粒度、磁化率和色度指标,探讨剖面沉积物各粒度端元所指示的环境意义以及坝上地区中全新世以来的环境演化过程。结果表明:1)白云湖剖面粒度组分分为3个端元,EM1代表区域暖湿气候背景下的风化成壤作用,间接指示区域的湿度状况;EM2代表区域风沙活动强度;EM3可能反映区域河流对基岩风化产物的搬运作用。2)研究区中晚全新世气候变化大致可以分为5个阶段:7.1 ka B. P.以前,风沙活动和河流搬运作用较强,气候表现为冷干特征;7.1~3.8 ka B. P.风沙活动减弱,气候温暖湿润,区域成壤作用加强;3.8~2.6 ka B. P.期间,气候波动频繁,处于暖湿-冷干过渡阶段;2.6~1.5 ka B. P.风沙活动增强;1.5 ka B. P.以来,气候由冷干向相对暖湿转变,成壤作用稍有加强。Bashang region of Hebei Province is located in the edge of the East Asian summer monsoon and is one of the ideal regions for studying the evolution of paleoclimate environment due to its sensitivity to climate change. In this study, a typical aeolian sand-paleosol profile was obtained in the Bashang Region, named BYH(41° 32′26.44″N, 116° 06′51.73″E, 1563 m a. s. l.;200 cm in thickness), and sampled at 2 cm intervals. Using AMSC and OSL dating techniques combined with linear interpolation and extrapolation, the age range of the profile is determined to be around 0~7.00 ka B. P. At the same time, environmental proxy indicators such as grain size, magnetic susceptibility and chromaticity of sediments were measured.We reveal that the grain size data can be decomposed into 3 end-members. EM1 is the thinnest component in the profile with a peak value of 24.1 μm, consisting of a silt-sized main component, which belongs to the short-term suspended component, and it has the highest content in palaeosol layer(50.9%). Combined with other environmental proxy indicators, we believe that EM1 represents the weathering and pedogenesis under the background of regional warm and humid climate, and indirectly indicates the regional humidity status. The peak value of EM2 is 185.8 μm, showing a weak negative skew state, and it is dominated by ultra-fine sand and fine sand, with high values appearing in aeolian sand layers and fluvial sand-gravel layers(60.06%). Combined with other environmental proxy indicators, we think that EM2 represents the intensity of regional sandstorm activity. The peak value of EM3 is 351.7 μm, mainly medium sand, which is the coarsest component in the section. According to the change of EM3 with lithological depth, the content maximum is located in the fluvial sand-gravel layer(43.51%)before 7.1 ka B. P., and the content is less in other layers. In addition, a large number of poorly rounded gravels with a diameter of less than 1 cm can be seen in this layer. Based on this, it is speculated that

关 键 词：粒度端元 中晚全新世 环境演化 坝上地区 

分 类 号：P534.632[天文地球—第四纪地质学] P512.2[天文地球—古生物学与地层学]