GENESIS AND GEOMORPHOLOGY OF SUPERIMPOSED LANDFORMS IN ICE WALLED LAKE PLAINS IN NORTHERN ILLINOIS

Rationale:

In Illinois, more than 2000 Ice Walled Lake Plains, relicts of the Wisconsin Glaciation, have been identified. Often times these IWLPS have superimposed landforms which appear as elevated circular rims with interior depressions. The origins of these superimposed landforms in Ice Walled Lake Plains (IWLP) have not been researched.

Objectives:

This study was conducted to determine the pedological characteristics and genesis of superimposed landforms commonly found in IWLP in Northern Illinois.

Methods:

The sedimentology and morphometrics (width, height, and circularity) of superimposed landforms on IWLP in Northern Illinois were analyzed and compared to previous studies’ findings on glacial and periglacial landforms. The morphometrics were measured and averaged using applications in ArcGIS 10.3. Additionally, 14 cores from an IWLP and its associated superimposed landform were described and analyzed for particle size.

Results:

The width, height, and circularity of 66 superimposed IWLP landforms were analyzed using ArcGIS. The average width of the samples was 30 meters, average height was determined to be 3 meters, and circularity index averaged 0.8. Width ranged from 3 to 50 meters. Height ranged from 0.9 to 8 meters. Circularity indexes ranged from 0.6 to 0.91. These findings were compared to the lithalsas, pingos, and IWLP analyzed in the studies of Wolfe et al 2014 (lithalsas), Grosse and Jones 2011 (pingos), Jones et al 2012 (pingos), and Allred et al 2014 (IWLP). Our analysis yielded morphometrics closest to modern periglacial features. Core descriptions noted 5 consistent facies, with a facies of lake sediment from an average of 160-540 cm deep. Particle Size Analysis and core descriptions found a lack of additional layers of lacustrine sediment, only the previously acknowledged lacustrine sediment from the known IWLP formed ~20000 years before present were identified.

Conclusions:

These results suggest that the superimposed landforms are likely relict frost mounds (lithalsas), formed in the periglacial environment after IWLP drainage.