GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 81-20
Presentation Time: 9:00 AM-5:30 PM


WALKER, Allison M. and MCLAUCHLAN, Kendra K, Kansas State University, Geography Department, 118 Seaton Hall 920 N. 17th Street, Manhattan, KS 66506-2904,

The general extent of a (0.75 to 0.2 Ma) glacial ice sheet extending into northeastern Kansas has been described; however, many questions remain about the glacial erratic, Sioux Quartzite. The evidence of timing and movement left on the landscape by this glaciation are the Sioux Quartzite erratics (Moh’s scale ~7). Identifying erratic spatial patterns on a widespread scale may illuminate behaviors of older continental ice sheets. Study of Sioux Quartzite deposits on local topographies may reveal deeper understandings of the glacial erratics’ movement. The patterns, connected on a regional scale, may inform the mechanics of how the erratics move in the glacier. These patterns might reveal where the glacier encountered resistance or moved forward rapidly, which may provide an explanation for the patterns found in this study.

 This study maps Sioux Quartzite erratics across 13 sites in Pottawatomie, Wabaunsee, and Shawnee counties, Kansas. Erratics were deposited in two distinct patterns across sites, valley position (n=9) and hilltop position (n=4). At each site, measurements were taken from 20 different erratics (volume, GPS location, density). At valley sites, erratics were concentrated on one slope (mean= 117 erratics), with few rocks on high points or opposite slopes (mean= 16 erratics). Valley sites had rocks distributed along one side, which varied from site to site at similar elevations (mean= 351 m) with opposing erratics seen at a different elevation (mean= 348 m). At hilltop sites, erratics (mean= 84 erratics) were concentrated close to the highest elevation (mean= 373 m). Some erratics could be found along the slopes (mean=36 erratics) with a lower elevation (mean= 367 m). The rock sample size for valley sites (mean= 0.215 m3) was smaller than those for hilltop sites (mean= 1.76 m3). Although these results do not definitively identify patterns of erratic deposition, they may lead to a better understanding of how these erratics were deposited by the glacial ice, meltwater, icebergs, or modern erosion. This project’s future will include analysis of the erratics’ composition and the soil composition around the erratics.

Field Assistants: Wayne Walker, Courtney Ress, Kendra Baird, and Maggie Revell