Doctoral Dissertation Research: Paleoclimatology and Geochronology of a Late Quaternary Eolian System, Columbia Plateau, U.S.A.

哥伦比亚高原的成对风成系统是由广泛的变厚度的帕卢斯黄土和逆风沙丘场组成的，这些沙丘场是由威斯康星州密苏拉冰川湖多次大溃决洪水产生的富含沙子和粉砂的淡水沉积物重新形成的。目前很少有模型能够解释黄土堆积厚度和分布的变化。我们将研究三种描述迁移沙与黄土相互作用的模型，以及地形、生物气候和源沙特征对黄土厚度和分布的影响。野外测绘将包括在区域尺度上收集样本，以确定跃变与悬浮主导的风成单位的时空分布。稳定性（以古土壤为代表）和风成活动（以风成沙和黄土单位为代表）的时间将通过测量沉积物最后暴露在阳光下的发光定年来确定。我们将确定1)在最近的威斯康辛爆发洪水之后，何时何地开始黄土沉积；2)逆风沙丘的风成跃迁是否与顺风的悬浮沉降同时活跃；3)从黄土中富含沙子的间隔推断出的跃迁释放期是否与高度干旱期有关；4)黄土的质量积累率。如今，哥伦比亚高原上的旱地耕作造成的粉尘排放是危险的，因为空气中存在小于10微米的颗粒物质，而且能见度降低。这项区域研究将展示哥伦比亚高原系统如何随着时间的推移对气候变化做出反应，从而预测未来的粉尘排放。虽然配对风成系统在世界其他地方（中国、欧洲、阿拉斯加、北美大平原）确实存在，但哥伦比亚高原提供了在可行的地理尺度上研究多种黄土生成模式的机会，增加了配对风成系统动力学的知识，并加强了哥伦比亚高原晚更新世到全新世气候变化的记录。作为博士论文研究改进奖，该奖项还将为有前途的学生提供支持，使他们能够建立强大的独立研究生涯。

The paired eolian system of the Columbia Plateau is composed of the extensive Palouse loess of variable thickness and upwind dune fields that are derived from reworking of sand- and silt-rich slackwater deposits from multiple episodes of Wisconsin giant outburst flooding from Glacial Lake Missoula. Few models exist that explain changes in the thickness and distribution of loess accumulations. We will investigate three models that describe the interaction of migrating sands with loess and influences of topography, bioclimate, and source sediment character that control the thickness and distribution of loess. Field mapping will include sample collection on a regional scale to determine the temporal and spatial distribution of saltation- versus suspension-dominated eolian units. Timing of stability (represented by paleosols) and eolian activity (represented by eolian sand an loess units) will be determined by luminescence dating that measures the last time sediments were exposed to sunlight. We will determine 1) when and where loess deposition began following latest-Wisconsin outburst floods, 2) if eolian saltation in upwind dunes was active concurrently with suspension fallout downwind, 3) if periods of saltator release inferred from sand-rich intervals in the loess were associated with periods of heightened aridity, and 4) the mass accumulation rates of loess. Dust emissions on the Columbia Plateau today resulting from dryland farming are hazardous through the presence of particulate matter less than 10 microns in size in the air and reduced visibility. This regional study will show how the Columbia Plateau system has responded to climate change through time, allowing future dust emissions to be predicted. While paired eolian systems do exist elsewhere in the world (China, Europe, Alaska, North American Great Plains), the Columbia Plateau offers the opportunity to study multiple models of loess generation on a workable geographic scale, to add to the knowledge of the dynamics of paired eolian systems, and to enhance the record of late-Pleistocene to Holocene climate change for the Columbia Plateau. As a Doctoral Dissertation Research Improvement award, this award will also provide support to enable a promising student to establish a strong independent research career.