Rock Magnetic and Pedogenic Studies of the Paleoclimate Record of Loess Deposits

世界各地的古土壤和黄土单元序列被解释为陆地气候变化的地质记录。特别重要的是发现了中国黄土层序磁化率变化与深海氧同位素记录之间的相关性。通过将岩石磁性测量与土壤化学提取过程相结合的方法，我们获得了新的数据，挑战了之前对磁化率信号的来源和性质的解释。在此提案中，我们请求支持对中国和其他地区的古土壤/黄土序列的岩石磁性和土壤化学进行全面的跨学科研究。我们的研究目标是：1)利用岩石磁性和土壤化学技术的结合完成磁化率信号的一般特征的确定；2)将我们对中国黄土/古土壤序列的岩石磁性分析与阿拉斯加和新西兰的黄土/古土壤序列的类似分析进行比较。3)从选定的黄土和古土壤单元中获得完整的土壤描述以及土壤化学和岩石磁性质的详细剖面。最后这一目标的工作将与中国同事密切合作。

Sequences of paleosols and loess units throughout the world have been interpreted as geologic records of terrestrial climate change. Of particular significance has been the discovery of a correlation between variations in the magnetic susceptibility in the Chinese loess sequence and the oxygen isotope record of the deep sea. Using an approach that combines rock magnetic measurements with a soil chemistry extraction procedure, we have obtained new data that challenges previous interpretations about the origin and nature of the magnetic susceptibility signal. In this proposal we request support for a comprehensive, interdisciplinary study of the rock magnetism and soil chemistry of paleosol/loess sequences in China and elsewhere. The goals of our study are 1) to complete our determination of the general characteristics of the magnetic susceptibility signal using a combination of rock magnetic and soil chemistry techniques, 2) to compare our rock magnetic analyses of the Chinese loess/paleosol sequence with similar analyses of loess/paleosols sequences in Alaska and New Zealand, and 3) to obtain complete soil descriptions and detailed profiles of soil chemistry and rock magnetic properties from selected loess and paleosols units. The work for this last objective will be done in close collaboration with Chinese colleagues.