泥河湾盆地钱家沙洼剖面中更新世河湖相沉积的环境磁学研究  

Environmental magnetism of the middle Pleistocene fluvio-lacustrine sediment sequence in Nihewan Basin,northern China

作　　者：颜梓幸 沈中山 邓成龙[1,2] YAN ZiXing;SHEN ZhongShan;DENG ChengLong(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家实验室,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049

出　　处：《地球物理学进展》2023年第3期1047-1058,共12页Progress in Geophysics

基　　金：国家自然科学基金项目(41888101)资助。

摘　　要：泥河湾盆地在东亚新生代地层、古气候、古生物、古人类研究领域备受关注.本文选择泥河湾盆地东部钱家沙洼剖面河湖相沉积序列为研究对象,测定和分析沉积物样品的χ-T曲线、磁滞回线、等温剩磁获得曲线和反向场退磁曲线以及矫顽力谱分析.结果显示泥河湾盆地东部河湖相沉积物中磁性矿物含量较低,以磁铁矿和磁赤铁矿为主,含有部分赤铁矿.磁化率、非磁滞剩磁、饱和等温剩磁等磁学参数的测试分析结果表明存在旋回变化.较细的沉积层(主要是粉砂质黏土层)中,磁化率、非磁滞剩磁、饱和等温剩磁为相对低值,且磁铁矿颗粒的粒度较细;而较粗的沉积层(主要是粗粉砂层、砂质粉砂层)中,磁化率、非磁滞剩磁、饱和等温剩磁为相对高值,且磁铁矿颗粒的粒度较粗.磁学参数的变化特征反映了泥河湾古湖流域中更新世期间气候环境变化及相应水文过程的旋回性,可能受冰期-间冰期旋回影响.这些结果有助于理解泥河湾盆地东部河湖相沉积物的磁性信号,对泥河湾盆地古环境和古气候重建等具有研究价值.The Nihewan Basin in northern China is important for the investigations of Cenozoic stratigraphy,paleoclimate,paleontology and paleoanthropology in eastern Asia.In this study,the fluvio-lacustrine sedimentary sequence from the Qianjiashawa section in the eastern part of the Nihewan Basin was selected for environmental magnetic investigations using multiparameters.The magnetic mineral information of the sediment samples was obtained by measuring the temperature-dependent magnetic susceptibility(χ-T)curves,hysteresis loops,Isothermal Remanent Magnetization(IRM)acquisition curves and back field demagnetization curves,and coercivity spectrum analysis.The experimental results show that the magnetic minerals are not much in the fluvio-lacustrine sediments of the Qianjiashawa section,dominated by magnetite and maghemite,which also show the presence of hematite.The variation characteristics of the magnetic parameters were analyzed by magnetic susceptibility(χ),Anhysteretic Remanent Magnetization(ARM)and Isothermal Remanent Magnetization(IRM)of the samples.Parameters changes in cycles.In the fine-grained sediments(mainly silty clays),χ,ARM and IRM are relatively low,and magnetic grain size is small.And coarser sediments(mainly coarse silt and sand silt),χ,ARM and IRM are relatively high,and magnetic grain size is large.The variation characteristics of the magnetic parameters reflect climate change and the corresponding cyclicity of hydrological process on the paleolake during the middle Pleistocene,which may be influenced by glacial and interglacial cycles.These results are helpful to understand the magnetic signals of fluvio-lacustrine sediments in the eastern part of the Nihewan Basin,and are valuable for studies such as palaeoenvironmental and paleoclimatic reconstruction of the Nihewan Basin.

关 键 词：泥河湾盆地 岩石磁学 环境磁学 河湖相沉积 

分 类 号：P318[天文地球—固体地球物理学]