黄土10Be示踪第四纪地磁极性事件及重建古降水变化研究

在申请者团队利用黄土10Be示踪B/M界线及重建古降水历史研究取得突破的基础上，开展黄土10Be示踪第四纪地磁场极性事件及定量重建季风降水变化历史的综合研究。通过10Be浓度与磁化率、粒度等代用指标的综合分析，首次在国际上建立2.6Ma以来黄土10Be记录的大气10Be相对产率及地磁场相对强度变化时间序列，确定M/G、Olduvai、Jaramillo等极性事件以及其它重要极性漂移事件在黄土中的确切记录层位，为中国黄土可靠年代框架的建立及与全球气候记录的准确对比提供精确时间参考序列。通过10Be示踪结果与古地磁测试记录的对比，揭示海、陆沉积物相同地磁极性事件存在差异的原因。同时探索利用黄土10Be定量恢复2.6 Ma以来季风降水变化历史，与10Be重建的地磁场相对强度变化曲线及全球记录进行对比研究，深化对第四纪大陆水循环过程及动力学机制的理解，提升基于黄土序列的过去全球变化研究的国际地位。

Based on the breakthroughs in B/M geomagnetic boundary tracing and paleoprecipitation reconstructions using loess 10Be record made by the application group, the comprehensive studies on the precise locations of the whole Quaternary geomagnetic polarity events in Chinese loess sequence and the quantitative reconstructions of Monsoon precipitation variation history using the loess 10Be are presented this time. Through the analysis of 10Be concentration records versus climatic proxies such as the magnetic susceptibility and grain size, the time series of the atmospheric relative 10Be production rate and the corresponded relative geomagnetic field intensity recorded by loess 10Be since 2.6Ma are established for the first time, which will provide the new evidences to determine the precise locations of the geomagnetic polarity boundaries like M/G, Olduvai, Jaramillo and other important geomagnetic excursion events in the loess. These new records serve as the accurate time reference sequence for the establishment of a robust chronology framework for Chinese loess and the good comparison with global climatic records. By comparing the geomagnetic polarity events results traced by 10Be and traditional paleomagnetic measurements, the possible reasons for discrepancy in the record of the same geomagnetic polarity events between marine sediments and Chinese loess are further discussed and clarified. As the important complement, the loess 10Be records are further explored to quantitatively reconstruct the Monsoon precipitation changes since 2.6Ma, and in turn to compared with the 10Be resulting geomagnetic field intensity curve and other global climatic forcing records, to improve our understandings on the Quaternary continental hydrological cycle process and dynamics, and enhance the international status of past global change research based on Chinese loess sequences.