A centennial-resolution terrestrial climatostratigraphy and Matuyama–Brunhes transition record from a loess sequence in China
| Autor: | Jun-ichi Fukuda, Meinan Shi, Tianshui Yang, Shigehiro Katoh, Masako Miki, Balázs Bradák, Yuki Yasuda, Kenta Banjo, Masayuki Hyodo |
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| Rok vydání: | 2020 |
| Předmět: |
Polarity reversal
Marine isotope stage Paleomagnetism 010504 meteorology & atmospheric sciences Polarity (physics) lcsh:QE1-996.5 Early–Middle Pleistocene transition lcsh:Geography. Anthropology. Recreation Loess–paleosol Geomagnetic pole Loess magnetism 010502 geochemistry & geophysics 01 natural sciences Geomagnetic reversal lcsh:Geology Paleontology lcsh:G Loess General Earth and Planetary Sciences East Asian monsoon Chronostratigraphy Geology 0105 earth and related environmental sciences |
| Zdroj: | Progress in Earth and Planetary Science, Vol 7, Iss 1, Pp 1-18 (2020) |
| ISSN: | 2197-4284 |
| Popis: | Terrestrial records of the last geomagnetic reversal often have few age constraints. Chronostratigraphy using suborbital-scale paleoceanic events during marine isotope stage 19 may contribute to solving this problem. We applied the method to an 8 m long, high-resolution paleomagnetic record from a loess sequence in China and revealed millennial-to-sub-centennial scale features of the Matuyama–Brunhes (MB) transition. All samples were subjected to progressive thermal demagnetization with 14–15 steps up to 650–680 °C. As a result, 96% of the samples yielded a high-quality remanent magnetization. The MB transition terminated with a 75 cm thick zone with nine polarity flips. The polarity flip zone, dated at about 779–777 ka, began between the warm events “I” and “J” and terminated at the end of the cooling event coincident with the lowest axial-dipole strength interval. Most polarity flips occurred within 70 years. The virtual geomagnetic poles (VGPs) in the upper polarity flip zone clustered in the SW Pacific region, where the MB transitional VGPs from lavas of the Hawaiian and Canary Islands and lacustrine deposits of Java also clustered. These sites were probably dominated by dipolar fields. The absence of transitional fields across polarity flips implies a short time span for averaging fields due to a thin loess-magnetization lock-in zone. The reverse-to-normal polarity reversal dated at about 778 ka in Lingtai occurred at the end of the SW Pacific VGP zone, an important key bed for MB transition stratigraphy. The reversal is a good candidate for the main MB boundary. We found an excursion at about 766 ka spanning about 1 ka. |
| Databáze: | OpenAIRE |
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