UNIVERSITY OF ILLINOIS

This research addresses the lack of chronologic information that exists for Midwestern glacial and postglacial environments. Absolute dates for key geomorphic events are lacking in the geomorphic literature, mainly because of the paucity of wood for radiocarbon dating. We propose to enrich and to make more precise this chronology, facilitating a more complete understanding of the timing of Late Pleistocene landscape evolution for the upper Midwest. This research goal will be accomplished by enumerating geomorphic sites where a significant, but as yet undated, geomorphic event is linked - spatially - to locally sourced loess. Dating the loess with optically stimulated luminescence (OSL) techniques will, by association, establish the age of the related geomorphic event. We will obtain OSL dates on small-medium sized loess sheets at each of several research sites; we propose that the mean date for each site will be a reasonably precise estimate of the age of the geomorphic event that sourced the loess. This method may be the only way that the dates of these geomorphic events can be determined, because the likelihood of finding more wood for radiocarbon dating is extremely low. Most of the loess deposits we will study have only recently been determined to have local (as opposed to distant, meltwater valley) sources, providing the opportunity and impetus for this research. Developing a clearer and more accurate understanding of the deglacial chronology for the upper Midwest is essential for continued advances in paleoenvironmental modeling. Clarifying soil and parent material ages and distributions in the upper Midwest will assist soil mappers, paleoenvironmental modelers and pedologists. Each of our study areas provides an ideal opportunity for undergraduate and graduate students to examine and study soils and paleoenvironments. We expect that at least two undergraduate and graduate theses will result from this study, and that several graduate students will work on the project. All three PIs will also incorporate study sites and findings into their courses and outreach exercises, including field and lab exercises.

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