Doctoral Dissertation Research: Timing and the Paleoenvironmental Significance of Wind-Blown Sand Activity During the Last Glacial Period in the Upper Mississippi River Basin.

这一博士论文项目将调查北美中部最后一次冰期风沙活动的分布和时间。风沙沉积的景观背景、形态和年龄表明，过去风沙供应的变化、风况、植被覆盖以及影响植被的因素，如温度和降水。这一信息对于重建劳伦蒂德冰盖南部最后一次冰川时期的过去气候变化以及改进气候模型的边界条件输入是重要的。过去21,000年来对北美中部大陆环境状况的大部分了解依赖于生物指标(例如花粉和动植物化石)，但风成沉积物提供了补充这些数据的重要附加参数。确定风沙活动的准确年龄是重建过去气候变化的一项重要任务。该项目将使用光学模拟发光(OSL或光学)测年来确定风沙的年龄。光学年龄提供了运输过程中暴露在光线下的沙子埋藏时间的估计。该项目将解决几个研究问题：1)随着冰盖和永久冻土(永久冻土)在大约21,000年前的最后一次冰盛期后向北退缩，风沙活动的时间是否从南到北(即，南方年龄较大，北方年龄较小)？2)风沙的年代学和景观背景是否表明，在最后一次冰川消融期间，风沙活动是对突然的气候变化的反应？这些问题将通过收集和分析从威斯康星州西部和明尼苏达州东南部到爱荷华州东部约500公里南北交线上的光学测年样本来解决。风沙活动的时间序列将为了解北美中大陆最后一次冰期的景观对气候变化的响应提供关键的洞察。了解过去的景观对环境变化的响应是预测未来响应及其对社会影响的重要一步。这与北美中部的干旱地区尤其相关，这些地区很容易受到未来变暖和日益变化的降水量的影响。这些条件可能会影响风沙活动，这对保护生产性农田以及与空气扬尘有关的人类健康问题具有重大影响。该项目调查了最近一次相对快速变暖(约21-1万年前)的气候参数，并为预测北美中部未来风沙活动的变化提供了背景。该项目的成果将通过出版物和会议报告，以及与私营机构(自然保护协会)和公共机构(几个州的自然资源部)的合作，向学术界和更广泛的受众介绍，重点是在当地沙地草原遗址进行宣传。作为博士论文研究改进奖，该项目将为有前途的学生建立独立的研究生涯提供支持。

This doctoral dissertation project will investigate the distribution and timing of eolian (wind-blown) sand activity during the last glacial period in central North America. The landscape setting, form, and age of eolian sand deposits indicate past changes in the supply of sand for movement by the wind, wind regime, vegetation cover, and factors that influence vegetation such as temperature and precipitation. This information is important for reconstructing past climate change south of the Laurentide Ice Sheet during the last glacial period as well as for improving boundary condition inputs to climate models. Much of the understanding of environmental conditions in the North American midcontinent over the last 21,000 years relies on biological proxies (e.g., pollen and plant or animal fossils) but eolian sediments provide important additional parameters to complement these data. Determination of an accurate age for eolian activity is an important task in reconstructing past climate change. This project will use optically simulated luminescence (OSL or optical) dating to determine the age of eolian sand. Optical ages provide an estimate of the timing of burial of sand after exposure to light during transportation. The project will address several research questions: 1) Was the timing of eolian sand activity time-transgressive from south to north (i.e., older in the south and younger in the north) as the ice sheet and permafrost (permanently frozen ground) retreated northward after the last glacial maximum ca. 21,000 years ago? 2) Does the chronology and landscape setting of eolian sand indicate a response to abrupt climate change during the last deglaciation? These questions will be addressed by collecting and analyzing samples for optical dating along a ca. 500 km north-south transect from western Wisconsin and southeastern Minnesota to eastern Iowa. The time sequences of eolian activity will provide key insight into the landscape response to climate change during the last glacial period in the North American midcontinent.Understanding past landscape response to environmental change is an important step in predicting future response and its impact on society. This is especially relevant for dry areas in central North America, which are vulnerable to future warming and increasingly variable precipitation. These conditions may influence eolian sand activity, which has major implications for preserving productive agricultural land as well as human health concerns related to airborne dust. This project investigates the climatic parameters during the most recent past episode of relatively rapid warming (ca. 21-10 thousand years ago) and provides background for predicting future changes in eolian activity in central North America. Results from this project will be presented to academic as well as broader audiences through publication and conference presentations, and also collaboration with private (The Nature Conservancy) and public (Department of Natural Resources of several states) agencies, with an emphasis on outreach at native sand prairie sites. As a Doctoral Dissertation Research Improvement award, this project will provide support to enable a promising student to establish an independent research career.