TRENDS IN EOLIAN FEATURES ON THE IOWAN EROSION SURFACE

The formation of the Iowan Erosion Surface (IES) of central northeastern Iowa has long been a source of debate. First thought to be a pre-Wisconsinan till plain, it was later shown to be formed during a period of landscape downcutting from Middle Wisconsinan to the early Holocene. Recent studies have put forth periglacial models of erosion, and others have coupled that with the effects of saltating eolian sand. The landscape shows evidence for both, however, there are clear trends on the distribution of eolian features on the IES.

This study looks at prevalence of eolian features on the IES. Using LiDAR, surficial geologic maps, collected cores, and NRCS soils maps, an inventory of wind generated or eroded features was created and analyzed. While sand catchment and mobilization are subject to local features, there appear to be regional trends of eolian features on the IES. The southern margin includes areas of prevalent sand bodies, zones of anomalously thick (> 10m) loess accumulation, and pahas. The northern area of the IES lacks these strongly wind-dominated features, even while having large volumes of outwash to act as sources for eolian sand. Mechanisms that enable more eolian features to be expressed near the southern margin of the IES include spatially variable rates of periglacial erosion due to climate, wind direction and strength, proximity to the ice margin, vegetation, and river valley orientation. With the IES being a geomorphic palimpsest, the addition of chronology would help this data set become useful for paleoclimate reconstruction.