High-frequency polarity swings during the Gauss-Matuyama reversal from Baoji loess sediment
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？C is close to the present geomag...
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| Published in: | Science China. Earth sciences Vol. 57; no. 8; pp. 1929 - 1943 |
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| Main Authors: | , , , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Heidelberg
Science China Press
01-08-2014
Springer Nature B.V |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | 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？C is close to the present geomagnetic field direction, and a high-temperature component iso lated above 200–250？C 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. |
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| Bibliography: | polarity reversals, geomagnetic episodes, Gauss-Matuyama, loess 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？C is close to the present geomagnetic field direction, and a high-temperature component iso lated above 200–250？C 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. 11-5843/P ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 1674-7313 1869-1897 |
| DOI: | 10.1007/s11430-014-4825-4 |