High-frequency polarity swings during the Gauss-Matuyama reversal from Baoji loess sediment

查看全文 作　　者：YANG [1,2]TianShui;Masayuki [3]HYODO;YANG [4]ZhenYu;ZHANG [1,2]ShiHong;Toshiaki [3]MISHIMA;WU [1]HuaiChun;LI [1]HaiYan;LI [5]Yi;SHI [2]XingAn;WANG [2]Kan;MA [2]YiMing

机构地区：[1]State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences;[2]School of the Earth Sciences and Resources, China University of Geosciences;[3]Research Center for Inland Seas, Kobe University,Kobe 657-8501, Japan;[4]Institute of Geomechanics, Chinese Academy of Geological Sciences;[5]Henan Institute of Nonferrous Metal Exploration

出　　处：《Science China Earth Sciences》索引2014年第57卷第8期,共15页

基　　金：supported by the National Natural Science Foundation of China (Grant No. 41172038);the Program for New Century Excellent Talents in University (Grant No. NCET-11-0720);the Fundamental Research Fund for the Central Universities (Grant Nos. 26520100, 2652011110);the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT) (Grant No. 19340151);Part of this study was performed under the cooperative research program of CMCR, Kochi University (Grant Nos. 07A017, A07B027) 摘　　要：Paleomagnetic records of the Gauss-Matuyama reversal were obtained from two loess sections at Baoji on the Chinese Loes Plateau. Stepwise thermal demagnetization shows two obvious magnetization components. A low-temperature component iso lated between 100 and 200–250℃ is close to the present geomagnetic field direction, and a high-temperature component iso lated above 200–250℃ reveals clearly normal, reversed, and transitional polarities. Magnetostratigraphic results of both sec tions indicated that the Gauss-Matuyama reversal consists of a high-frequency polarity fluctuation zone, but the characteristic remanent magnetization directions during the reversal are clearly inconsistent. Rock magnetic experiments demonstrated tha for all the specimens with normal, reversed, and transitional polarities magnetite and hematite are the main magnetic carriers Anisotropy of magnetic susceptibility indicates that the studied loess sediments have a primary sedimentary fabric. Based on virtual geomagnetic pole latitudes, the Gauss-Matuyama reversal records in the two sections are accompanied by 14 short-lived geomagnetic episodes(15 rapid polarity swings) and 12 short-lived geomagnetic episodes(13 rapid polarity swings), respec tively. Our new records, together with previous ones from lacustrine, marine, and aeolian deposits, suggest that high-frequency polarity swings coexist with the Gauss-Matuyama reversal, and that the Gauss-Matuyama reversal may have taken more than11 kyr to complete. However, we need more detailed analyses of sections across polarity swings during reversals as well a more high-resolution reversal records to understand geomagnetic behavior and inconsistent characteristic remanent magnetiza tion directions during polarity reversals. 关键词：极性反转黄土沉积物高斯松山波动高频逆转宝鸡

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High-frequency polarity swings during the Gauss-Matuyama reversal from Baoji loess sediment

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