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

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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.