降尘^(10)Be浓度对黄土^(10)Be示踪地磁场变化研究的影响  

Influence of variation in dust ^(10)Be concentration amplitude on the reliability of geomagnetic tracing study from Chinese loess

作　　者：鲜锋[1,2] 孔祥辉[1,2] 姜峻[3] 赵国庆[1,2] 武振坤[1,2] 

机构地区：[1]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,西安710061 [2]陕西省加速器质谱技术及应用重点实验室,西安710061 [3]中国科学院水利部水土保持研究所,杨凌712100

出　　处：《地球环境学报》2017年第2期103-112,共10页Journal of Earth Environment

基　　金：国家自然科学基金项目(41203019);中国科学院重点部署项目(KZZD-EW-04-06)~~

摘　　要：运用我国黄土地层中的^(10)Be记录来示踪地磁场漂移事件和重建相对强度变化历史在最近几年取得了显著进展。开展上述研究的关键点之一在于如何对黄土^(10)Be记录中包含的源区降尘^(10)Be浓度等信号的相对贡献进行合理估算。本文参考最新的现代粉尘^(10)Be浓度观测数据,设计了3种改变降尘^(10)Be浓度的情景分别建立了130 ka以来黄土^(10)Be记录的地磁场漂移事件时间序列。综合对比表明,3种情景下的重建结果并无差异,说明源区降尘^(10)Be浓度幅值变化不会对^(10)Be示踪地磁场变化的结果产生显著影响。同时分离的130 ka以来受地磁场变化影响的^(10)Be记录可与PISO-1500等全球典型地磁场强度曲线良好对比,并完整地记录了蒙诺湖(Mono Lake)、拉尚(Laschamp)、挪威海-格陵兰(Norweigian-Greenland sea event)和布莱克(Blake)等主要地磁场漂移事件,揭示了黄土^(10)Be重建的地磁场变化曲线的全球尺度意义并印证了中国黄土在千年尺度的连续性问题。Background, aim, and scope Studies on geomagnetic excursion tracing and relative paleo-intensity reconstruction using Chinese loess ^10Be proxy have greatly progressed in recent years. In these studies, one of the key points lies in how to reliably estimate the relative contribution from the dust source ^10Be concentration as well as other ^10Be concentration fractions contained in loess. To evaluate the possible influence of variation in dust ^10Be concentration amplitude on the reliability of related geomagnetic tracing study, 3 kinds of separation models are designed by gradually changing the dust ^10Be concentration amplitude as well the dust source magnetic susceptibility amount, to respectively reconstruct the geomagnetic excursion events series using the Chinese loess ^10Be record since the 130 ka. Materials and methods The ^10Be concentration and other climatic proxies such as the magnetic susceptibility are measured from a 1490 cm core of the Luochuan section （35°45′N, 109°25′E） in central Chinese Loess Plateau, which was described in Zhou et al （2010）. To present the 3 different separation models, the observation studies on the modern falling dust ^10Be in Northern China by Xian et al （2012） is also cited to gradually change the dust ^10Be concentration for calculations. The basic step for the test calculation is to firstly separate the dust effects on the ^10Be and magnetic susceptibility in loess, by subtracting a constant value from the total measured ^10Be and magnetic susceptibility respectively. Then a linear regression between the dust free ^10Be concentration and pedogenic susceptibility is developed to separate the Monsoon rainfall effects on loess ^10Be records, and to derive the residual ^10Be signals which is dominantly modulated by geomagnetic field intensity. As for the separation model 1 and model 2, the same amount of dust source magnetic susceptibility （SUS（D）） is assumed, and the dust ^10Be concentration （Be（D）） is the variable to be allowed to change

关 键 词：降尘^10Be浓度 地磁场漂移事件 全球尺度 连续性 

分 类 号：S151.9[农业科学—土壤学] P318[农业科学—农业基础科学]