Understanding Past Environments and Glacial Processes Through an Analysis of a Newly Discovered Glacial Lake

该项目将研究一个新发现的古冰川湖的古环境和地质历史。初步数据显示，冰川湖罗斯康姆湖(GLR)大约在24-23,000年前就存在了，并持续了7000多年，在这个以前被认为是冰盖的地区，直到近16,000年前。对该湖的研究将加深对中西部冰川动力学的理解，从而改进对北美冰盖厚度的模拟。更好地了解这一地区的冰川消退以及过去的冰川过程，将提高确定集合体、沙子和粘土等冰川地貌产生的重要自然资源的能力，并将有助于模拟含水层的连续性，从而改进当今的地下水管理战略。研究区内仍有GLR残存的几个湖泊，并可能在冰川消融后继续存在。来自这些湖泊的沉积物岩心将对化石花粉、植物大型化石和蜗牛壳进行年代测定和分析，从而对该地区直接的冰后气候产生重要的见解，并为最近冰川消融的寒冷景观中植物殖民的最早形式提供新的见解。该项目为研究生和本科生提供了许多实地和实验室培训和指导的机会。这项研究的结果将在学术和非学术渠道广泛传播，这项工作将成为一次地区性实地会议的重点。最近关于罗斯康姆湖(GLR)的科学文献提供了一个难得的机会来产生新的知识，并为改写中西部上部的冰川史做出贡献。这个湖是独一无二的，它是在其他中西部冰川接近最大范围时在五大湖上游地区发展起来的。这一地区被认为在大约16,000年前之前一直被冰覆盖，这意味着来自该湖的沉积物及其残留物可能包含了中西部上段最长的花粉和其他化石记录。如此长的记录是极其罕见的。这一记录的潜力将通过以下方式进行检验：取几个残留湖泊的岩心，使用放射性碳技术测定每个岩心中最低的植物物质的年龄，并检查这些数据以确定最古老的岩心。然后，将对这些岩芯中的花粉、大型化石和介形虫的数据进行检查，以提供一个前所未有的环境视角，当时冰层主导着地形，冰川后植物殖民才刚刚开始。研究的第二个重点是确定GLR的地质记录和其中的退缩冰缘。该项目的这一部分涉及使用发光技术对海滩和相关沉积物进行测年。这些数据将有助于限制湖泊及其边界冰缘的演化，从而为冰盖模型增加关键数据。由于该湖至少有三个不同的出口，限制这些出口的开放和废弃将有助于确定边界景观的冰消退情景。早期数据表明，附近地貌上的冰也已经退缩，或者已经开始退缩，比目前认为的要早得多。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project will examine the paleoenvironmental and geological history of a newly discovered, ancient glacial lake. Preliminary data suggest that Glacial Lake Roscommon (GLR) came into existence circa 24-23,000 years ago and persisted for over 7000 years, in an area previously thought to be ice-covered until nearly 16,000 years ago. Research on this lake will refine the understanding of Midwestern glacial dynamics, thereby improving modeling of ice-sheet thickness for North America. A better understanding of glacial retreat in this area, and of past glacial processes in general, will enhance the ability to locate important natural resources derived from glacial landforms such as aggregate, as well as sand and clay, and will help model aquifer continuity and hence, improve present-day groundwater management strategies. Several remnant lakes from GLR still exist in the study area and may have existed continuously since deglaciation. Sediment cores from these lakes will be dated and analyzed for fossil pollen, plant macrofossils, and snail shells, yielding important insights into the immediate postglacial climate of the region, and providing new insights into the earliest forms of plant colonization of cold, recently deglaciated landscapes. The project provides many opportunities for graduate and undergraduate student training and mentoring, both in the field and in the laboratory. Results from the research will be broadly disseminated in academic and non-academic outlets and the work will be the focus of a regional field conference.The recent scientific documentation of Glacial Lake Roscommon (GLR), offers a rare opportunity to generate new knowledge and contribute to the rewriting the glacial history of the upper Midwest. The lake is unique, having developed in the upper Great Lakes region at a time when other Midwestern glaciers were near their maximum extent. This area was thought to have been ice-covered until about 16,000 years ago, implying that the sediments from the lake and its remnants may contain the longest record of pollen and other fossils in the upper Midwest. Such a long record is exceedingly rare. The potential of this record will be examined by coring several remnant lakes, dating the lowermost plant matter in each core using radiocarbon technology, and examining those data to determine the oldest core. Data on pollen, macrofossils, and ostracodes from these cores will then be examined to provide an unprecedented view into the environment at a time when ice dominated the landscape, and postglacial plant colonization was just beginning. A second focus of the research is the determination of the geological record of GLR and the retreating ice margin within it is. This part of the project involves dating of beach and related sediments, using luminescence technologies. Such data will help constrain the evolution of the lake and its bounding ice margins, and thus, add key data for ice-sheet models. Because the lake had at least three different outlets, constraining the opening and abandonment of these outlets will help determine the ice retreat scenarios for bounding landscapes. Early data suggest that ice on nearby landscapes had also retreated, or had begun retreating, far earlier than is currently thought.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.