Collaborative Research: Linking loess landforms and eolian processes

该奖项由2009年美国复苏和再投资法案(公法第111-5条)资助。该项目将调查北美、中国北部和中欧厚黄土地区(风吹尘埃沉积形成的沉积物)中巨大、引人注目的地貌的起源。这些地貌可能绵延数十公里，并与盛行的风向一致，在将进行研究的美国内布拉斯加州，它们尤其发达。将检验两种关于黄土地貌发育的假设，每一种假设对粉尘在初始沉积后的稳定性做出明显不同的假设。一种假说认为，尘埃不会被再动员，除非它受到风沙的扰动，这些沙子通过跳跃(接近地面的短跳跃)移动。另一种假设认为，形成大多数厚黄土沉积物的粗粒沙尘很容易被风再活化，许多黄土地貌是在初始堆积后由侵蚀形成的。将使用最近开发的便携式现场风蚀实验室(PI-SWERL)来研究由风引起的黄土沉积的可能性，无论有没有沙子跳跃。此外，这两个假设导致了对黄土粒度和沉积速率的空间模式的不同预测，以及这些特性将如何随着时间的变化而变化。这些预测将通过风尘输送的定量模拟得到修正，然后将使用黄土切片的粒度分析和光学受激发光(OSL)测年进行验证，这直接确定了黄土最初沉积的时间。该项目将为黄土沉积在哪里以及如何成为粉尘来源提供新的见解，以响应气候或土地利用的变化。例如，如果第二个假设成立，那么过去的黄土风蚀足以形成巨大的地貌，潜在地产生大量的尘埃。沙尘是当今一些厚黄土地区常见的环境危害，如中国北部，在20世纪30年代和50年代曾是大平原的危险，但历史观察可能并不能代表潜在的风蚀和沙尘产生的全部范围。厚厚的黄土沉积物也是过去数千年至数百万年来气候变化信息的重要来源。通过记录影响黄土沉积和长期稳定性的复杂过程，该项目的结果应该能够更好地评估气候因素。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project will investigate the origin of large, striking landforms that occur in areas of thick loess (sediment formed by deposition of wind-blown dust), in North America, northern China, and central Europe. These landforms may extend for tens of kilometers and are aligned with prevailing winds, and they are especially well-developed in Nebraska, USA, where the research will be conducted. Two hypotheses on loess landform development will be tested, each of which makes distinctly different assumptions about the stability of dust after its initial deposition. One hypothesis assumes that settled dust will not be remobilized unless it is disturbed by wind-blown sand moving by saltation (short hops near the ground surface). The other hypothesis assumes that the coarse-grained dust forming most thick loess deposits is readily remobilized by the wind, and many loess landforms are formed by erosion after initial accumulation. The potential for loess deposits to be set in motion by the wind, with or without saltating sand, will be investigated using the recently developed Portable In Situ Wind Erosion Laboratory (PI-SWERL). In addition, the two hypotheses lead to different predictions about the spatial patterns of loess grain size and deposition rate, and how these properties would have changed over time. These predictions will be refined through quantitative modeling of dust transportation by wind, and will then be tested using grain size analysis and optically stimulated luminescence (OSL) dating of loess sections, which directly determines the time since the loess was originally deposited. This project will provide new insight on where and how loess deposits can become sources of dust in response to climatic or land-use change. If the second hypothesis is valid, for example, past wind erosion of loess was sufficient to carve out large landforms, potentially producing enormous quantities of dust. Dust is a common environmental hazard today in some areas of thick loess such as northern China, and was a hazard in the Great Plains in the 1930s and 1950s, but historical observations probably do not represent the full range of potential wind erosion and dust production. Thick loess deposits are also an important source of information on past climate change, over thousands to millions of years. The results of this project should allow a better assessment of climate factors, by documenting the complex processes that influence the deposition and long-term stability of loess.