Collaborative Research: Linking loess landforms and eolian processes

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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.