Magnetic parameter variations in the Chaona loess/paleosol sequences in the central Chinese Loess Plateau,and their significance for the middle Pleistocene climate transition |
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| Affiliation: | 1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth and Environment, Chinese Academy of Sciences, Xi''an 710075, China;2. Key Laboratory of Western China''s Environmental Systems, Ministry of Education of China, Lanzhou 730000, China;3. Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China;4. Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA;5. Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan;1. Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, China;2. Laboratoire Géosciences Rennes, CNRS-UMR6118, Université Rennes 1-Observatoire des Sciences de L''Univers de Rennes, Rennes, France;3. Qinghai Oilfield Company, PetroChina, Dunhuang, Gansu 736202, China;4. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China;1. MOE Key Laboratory of Western China''s Environmental Systems, Collaborative Innovation Centre for Arid Environments and Climate Change, Lanzhou University, Gansu, Lanzhou 730000, China;2. State Key Laboratory of Cryospheric Science, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China;1. MOE Key Laboratory of Western China’s Environmental Systems, Collaborative Innovation Centre for Arid Environments and Climate Change, Lanzhou University, Lanzhou 73000, China;2. State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China;1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi''an 710075, China;2. Resources & Chemical Laboratory, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Lanzhou 730000, China |
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| Abstract: | A high-resolution rock magnetic investigation was performed on the Chaona Quaternary loess/paleosol sequences in the Central Chinese Loess Plateau. Based on a newly developed independent unturned time scale and magnetic records, we reconstructed the history of the East Asia monsoons during the last 3 Ma and explored the middle Pleistocene climate transition (MPT). Rock magnetic results show that the loess layers are characterized by relatively high coercivity and remanent coercivity, lower magnetic susceptibility (MS), and that the paleosol layers are characterized by relatively high MS, saturation magnetization and remanent saturation magnetization. Spectrum analyses indicate that there are various periods in addition to orbital periodicities. According to the onset and stable appearance of 100 kyr period, we consider that the MPT recorded in this section began at ~ 1.26 Ma and was completed by ~ 0.53 Ma, which differs from previous investigations based on orbitally tuned time scales. The forcing mechanism for the MPT was more complicated than just the orbital forcing. We conclude that the rapid uplift of the Tibetan Plateau may have played an important role in the shift of periodicities during the middle Pleistocene. |
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