Green River Lowlands Sand Dunes Project Completed

Xiaodong Miao completed the project "Sand Dunes in the Green River Lowland, Northwestern Illinois." The recent increase in dune studies in North America has been heavily focused in the Great Plains, and less attention has historically been given to the dune fields east of the Mississippi River. This project gives new absolute ages and suggests a potential sediment source for sand dunes in the Green River Lowland, Illinois. The new information provides scientists with a better understanding of the dynamic interactions between the eolian, glacial, lacustrine, and fluvial processes that shaped the landscapes of the upper Midwest.

Seven coherent optically stimulated luminescence ages (OSL, or optical ages) obtained from four sites suggest that major dune construction in the Green River Lowland occurred within a narrow time window around 17,500 ± 570 years ago. Contrary to previous assertions that dune sand was sourced from the deflation of underlying outwash sand deposited when the Lake Michigan Lobe retreated from the area, Green River Lowland dunes were formed as a result of drainage from the Green Bay Lobe through the Rock River.

The optical and radiocarbon ages from multiple sites indicate that dunes were reactivated during early, middle, and late Holocene times. If the dunes were the relics of Pleistocene glaciation, the future activation of dunes will be very limited. However, the multiple periods of eolian activity during the Holocene suggest high potential for future sand activation in the region, and these results are informative for environmental prediction and potential future mitigation. The findings were presented at the 2009 North-Central Geological Society of America meeting. A paper also has been submitted for journal publication. Additionally, two maps have been produced to differentiate the surficial eolian and outwash sand in Bureau and Lee Counties.