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

中国黄土高原是地球上第四纪沉积记录最完整、最广泛的地区，对黄土高原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。 本项目将在中国黄土高原沿着东南-西北向样带上采集土壤样品，研究末次间冰期古土壤（称为“S1”，距今128，000 - 73，000年）。 研究的目的是重建末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，将通过样品测年和其他实验室分析建立古土壤S1土壤地层学和年代学。 其次，将检查土壤特性，包括中尺度和微尺度形态。 第三，将通过分析土壤剖面的淋溶和一般风化的历史来校准夏季风代理。 第四，通过分析整体粒度分布和较大的石英粒度来确定沉积后风化的程度，从而校准冬季风代用指标。为了在考虑严重的人类影响的情况下理解未来气候变化的范围，末次间冰期值得特别关注，因为它最有助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，需要更多来自不同区域的数据来验证各种突发气候事件的空间尺度。 一些基本问题需要对大陆内部的气候历史有更好的了解。 例如，大气环流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所起的相对作用是什么。 只有通过界定和量化区域环境系统对全球变化的具体反应，才能理解全球变化机制的主要不确定性。 中国黄土高原是高纬大陆性冬季风和低纬海洋性夏季风相互作用的产物，是验证各种全球变化机制假说的理想场所。 季风历史的研究将有助于未来更精确的全球变化模拟。

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.