PALAEOTOPOGRAPHY AND GLACIER EROSION: TERMINAL REGION, OHIO USA

Understanding the interaction between palaeotopography and glacier erosion is an important aspect of glacial geology because glaciers do not lie with simple, planar landscapes. An increased knowledge of the spatial variability of glacial erosion provides a better understanding of glacial processes and, by inference, climate change by the fine-tuning of calibration data sets. One approach to understand the spatial variability of glacier erosion is by study in the terminal area of Pleistocene ice sheets. Two interlobate areas in northeastern (NE) and southwestern (SW) Ohio were analyzed using three techniques: 1) bedrock-topography patterns in both the SW and NE study areas; 2) optically stimulated luminescence (OSL) and till stratigraphy data from the NE study area; and 3) glacial geomorphology of the SW study area. The bedrock-topography studies reveal spatial variations in glacial erosion at the mesoscale (1,000's km2) as a result of ~2.0 my of glacial erosion. In both study areas, patterns of preserved bedrock channels, parallel and perpendicular to flow, reveal adjacent “deep” and “shallow” erosion zones associated with the palaeotopography. The OSL dating and till stratigraphy data of NE Ohio show an early Wisconsin kame terrain that survived a later glacial advance and was possibly a nunatak during the Last Glacial Maximum. The glacial geomorphic study in SW Ohio shows that a bedrock high influenced spatial differences in erosion and deposition of glacial drift. Results show that topographic uplands are impediments to glacial advance and are bypassed by the majority of ice flow; consequently, they receive meager amounts of weak, thin, cold-based ice resulting in little to no erosion. Directed around these uplands is the focused flow of thicker, warm-based ice, which is an effective erosive agent in the lowland. The erosion patterns reported here are consistent with emerging work, but are the first to illustrate the relatively minor, long-term erosive nature at the Laurentide ice-sheet margin.