Open Access Honors Program Thesis
James C. Walters
Ice-wedge casts and polygonal patterned ground are common features of the Iowan Surface of Northeast Iowa. Paleoenvironmental studies in Iowa and adjacent states indicate that tundra conditions existed in Northeast Iowa between 21,000 and 16,500 years BP, the coldest part of late \\'.'isconsinan time. Degradation of permafrost and formation of ice-wedge casts must have occurred near the end of this cold climate episode, which also promoted extreme erosion of the landscape in Northeast Iowa. The sediment-filled wedges in Northeast Iowa occur in pre-Illinoian till with the infilling material consisting mostly of sand. The details of the infilling history of the wedges are largely unknown.
Since quartz grain surface textures can be successfully used as fingerprints to identify sediment transport processes and depositional environments, we examined surface textures of quartz grains from ice-wedge casts using binocular and scanning electron microscopy in an effort to clarify this infilling history. Features indicative of glacial, fluvial, and eolian transport are evident. Preliminary results indicate that surface texture signatures and rounding of sand grains do not vary significantly throughout the wedges implying that the infilling of the wedges was fairly uniform and the infilling material homogeneous. Observation of the wedges does suggest that there were smaller periods of localized infilling such as slumping or brief washing in of material
Year of Submission
Department of Earth and Environmental Sciences
University Honors Designation
A thesis submitted in partial fulfillment of the requirements for the designation University Honors
1 PDF file (29 pages)
©2007 Michael Loux
Loux, Michael, "Quartz Grain Surface Textures as Indicators of Infilling Processes and Depositional Environments Associated With Ice-Wedge Casts in Northeast Iowa" (2007). Honors Program Theses. 670.