Geographic Differentiation of the Last Interglacial Paleosol Layer in the Chinese Loess Plateau: Its Climatic and Chronological Implications

中国黄土高原拥有地球上最完整和最广泛的第四纪沉积陆地记录，土壤形成及其地理分异的分析将为气候历史和全球环流模拟提供有用的信息。该项目将研究中国黄土高原东南-西北样带沿线的最后一次间冰期古土壤(称为“S1”，年代为12.8万至7.3万年前)。这项研究的目标是重建最后一次间冰期亚洲季风的详细历史。为了实现这一目标，将进行四组分析。首先，通过样品测年和其他实验室分析，建立古土壤S1的土壤地层和年代学。其次，研究土壤特性，包括中尺度和微观尺度的形态。第三，将通过分析土壤剖面的淋溶历史和一般风化来标定夏季风代理。第四，将通过分析体积尺寸分布和较大的石英粒度来标定冬季季风代理，以确定沉积后风化的程度。为了在考虑严重人类影响的情况下理解未来气候变化的范围，最后一个间冰期值得特别关注，因为它最有利于我们理解间冰期的自然过程。然而，这一时期的全球气候变化记录并不一致，需要来自不同地区的更多数据来验证各种突发性气候事件的空间尺度。一些基本问题需要更好地了解大陆内陆的气候历史。例如，大气和海洋环流在将热量和水蒸气从低纬度输送到高纬度以及从海洋输送到内陆方面发挥了什么相对作用。只有确定和量化区域环境系统对全球变化的具体反应，才能了解全球变化机制的主要不确定性。中国黄土高原是高纬度大陆冬季风和低纬海洋夏季风相互作用的产物，是验证全球变化机制的各种假说的绝佳地点。这种季风史的研究将有助于未来更准确的全球变化模拟。

The Loess Plateau of China has the most complete and extensive terrestrial records of Quaternary sedimentation on Earth, and analysis of the soil formation and its geographic differentiation should provide useful information on climate history and global circulation modeling. This project will study the last interglacial paleosol (called "S1" and dates from 128,000 to 73,000 years ago) with soil samples selected along a SE-NW transect in the Chinese Loess Plateau. The goal of the research is to reconstruct the detailed history of the last interglacial Asian monsoons. To achieve the goal, four sets of analyses will be conducted. First, the paleosol S1 pedostratigraphy and chronology will be established through sample dating and other laboratory analyses. Second, the soil characteristics will be examined, including the meso-scale and mirco-scale morphology. Third, the summer monsoon proxy will be calibrated through analyses of the histories of leaching and general weathering of the soil profiles. Fourth, the winter monsoon proxy will be calibrated through analyses of the bulk size distribution and larger quartz size to determine the degree of post-depositional weathering.To comprehend the scope of future climate changes with considerations of severe human impacts, the last interglacial period deserves special attentions because it serves us best in understanding the natural processes of interglacial times. However, the global records of climate change for this period are inconsistent, and more data are needed from different regions to validate the spatial scale of various abrupt climatic events. A number of basic questions require an improved knowledge of climate histories of continental interiors. For instance, what are the relative roles played by atmospheric and oceanic circulation in transporting heat and water vapor from low to high latitudes and from oceans to interiors. Only by defining and quantifying the specific responses of regional environmental systems to global changes will major uncertainties about the mechanisms of global changes be understood. The Chinese Loess Plateau, a product of interactions between a high-latitude continental winter monsoon and a low-latitude oceanic summer monsoon, is perfectly located to validate the various hypotheses of the mechanisms of global changes. This study of monsoon history will be useful to future more accurate global change modeling.