Collaborative Research: Linking loess landforms and eolian processes

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该项目将调查在北美、中国北部和中欧的厚黄土（由风沙沉积形成的沉积物）地区出现的大型、引人注目的地貌的起源。这些地形可能延伸数十公里，并与盛行风对齐，它们在美国内布拉斯加州特别发达，研究将在那里进行。本文将对黄土地貌发展的两种假设进行检验，每种假设对泥沙初始沉积后的稳定性做出了截然不同的假设。一种假说认为，沉降的尘埃不会重新移动，除非它受到风吹沙尘的扰动，沙尘通过跃移（在地面附近的短暂跳跃）移动。另一种假说认为，形成最厚的黄土沉积物的粗粒粉尘很容易被风重新移动，许多黄土地貌是在初始堆积后由侵蚀形成的。利用最近开发的便携式原地风蚀实验室（PI-SWERL），将研究有或没有沙土的情况下，风对黄土沉积物产生运动的可能性。此外，这两种假设对黄土粒度和沉积速率的空间格局以及这些属性如何随时间变化产生了不同的预测。这些预测将通过风沙运输的定量建模来完善，然后将使用粒度分析和黄土剖面的光学激发发光（OSL）测年来验证，这直接决定了黄土最初沉积的时间。该项目将为黄土沉积物在何处以及如何成为应对气候或土地利用变化的沙尘来源提供新的见解。例如，如果第二个假设是正确的，那么过去对黄土的风蚀就足以形成大面积的地貌，可能产生大量的灰尘。沙尘是当今中国北方等一些厚黄土地区常见的环境危害，也是20世纪30年代和50年代大平原的危害，但历史观测可能不能代表潜在的风蚀和沙尘生产的全部范围。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，该项目的结果将有助于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.