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

本博士论文项目将研究北美中部末次冰期风成沙活动的分布和时间。风沙沉积的景观背景、形式和年龄表明了过去风对沙的供应、风况、植被覆盖以及影响植被的因素（如温度和降水）的变化。这些信息对于重建末次冰期Laurentide冰盖以南过去的气候变化以及改善气候模式的边界条件输入具有重要意义。在过去21000年里，对北美大陆中部环境条件的了解大部分依赖于生物代用物（如花粉和植物或动物化石），但风成沉积物提供了重要的附加参数来补充这些数据。确定风成活动的准确年代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）定年来确定风成沙的年龄。光学年龄提供了沙子在运输过程中暴露于光后被掩埋的时间的估计。该项目将解决几个研究问题：1)风沙活动的时间是否从南向北海侵（即，南方较早，北方较年轻），因为冰盖和永久冻土（永久冻土）在大约21,000年前的最后一次冰川高峰后向北退缩？2)风成沙的年代学和景观背景是否反映了末次冰消期气候突变的响应？这些问题将通过收集和分析样本来解决，这些样本将沿着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公里的南北样带进行光学测年。风成活动的时间序列将为了解北美中部大陆末次冰期气候变化对景观的响应提供关键的见解。了解过去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。这对北美中部的干旱地区尤其重要，这些地区很容易受到未来变暖和降水变化越来越大的影响。这些条件可能影响风沙活动，这对保护生产性农业用地以及与空气中灰尘有关的人类健康问题具有重大影响。该项目研究了最近一段相对快速变暖时期（约21-1万年前）的气候参数，并为预测北美中部风成活动的未来变化提供了背景。这个项目的成果将通过出版物和会议报告向学术界和更广泛的受众展示，并与私人（大自然保护协会）和公共（几个州的自然资源部）机构合作，重点是在当地的沙质草原地区进行推广。作为博士论文研究进步奖，该项目将提供支持，使有前途的学生建立一个独立的研究生涯。

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.