GSA Connects 2022 meeting in Denver, Colorado

Paper No. 28-6
Presentation Time: 9:00 AM-1:00 PM


SCHOPEN, Emma, Iowa Geological Survey, University of Iowa, 340 Trowbridge Hall, Iowa City, IA 52242 and KERR, Phil, Department of Earth and Environmental Sciences, University of Iowa, 123 Capitol St., Iowa City, IA 52242; Iowa Geological Survey, University of Iowa, 340 Trowbridge Hall, Iowa City, IA 52242

Eolian sediment covers most of the Upper Mississippi Basin. Regions west of the Missouri River and in parts of the upper Midwest United States are known to have large areas of eolian sand. Other areas have like thick loess deposits, like the Loess Hills in western Iowa. In eastern Iowa, however, there are large areas of unrecognized eolian sand. To alleviate this omission, we used remote sensing datasets to estimate the area covered by stabilized dunes in Eastern Iowa. Their shape is generally parabolic, but ‘sand stringers’ are common. The sediment source was outwash from the Des Moines Lobe during MIS 2 (Late Wisconsin). During this period, eastern Iowa was in a periglacial setting and was thought to be more arid than during the Holocene. Currently, these dunes are actively farmed in row-crop after having had the native vegetation removed. To find the area covered by dunes, LiDAR and LiDAR-based derivatives were used including DEMs, slope, and aspect rasters. A multi-resolution analysis for elevation variance was also used. These datasets were combined with a NRCS SSURGO coverage coded to parent materials (eolian sand, alluvium, weathered till, loess, etc.). Selected boundaries were field verified by grainsize of the C horizon. A coverage of dune features was generated using weighted overlay. Other eolian sand features such as sand ramps, sand sheets were also noted. The results show ten dune fields with areas >10km2 around eastern Iowa. The largest is ~1,000 km2 and is adjacent to the Cedar River. Most dune fields are also directly downwind (SE) of outwash sources. The consequences of global climate change on eolian features in this area has not been extensively studied. The continued stability of these dunes in the future is not necessarily guaranteed. Future work should look at various climate scenarios in combination with agriculture practices to determine the further behavior of eolian sediment in eastern Iowa.