OBSERVATIONS ON THE LOESS COVER AND LOESS DEPOSITIONAL SYSTEMS OF THE UPPER GREAT LAKES REGION

Ongoing research into the loess cover of the upper Great Lakes region has led to several preliminary, yet interesting and provocative, findings. In this talk I will present and discuss some of the relevant data and results that have surfaced thus far, and suggest possible avenues for future work. Generally, we have learned that significant amounts of loess on these glaciated landscapes can originate not only from major meltwater valleys such as the Mississippi, but also from active outwash plains, periglacially-influenced bedrock uplands, recently drained lake beds, and even small meltwater streams. Examples of each of these types of systems, and their down-wind loess and cover sand deposits, will be provided and discussed. Research to date has also led to the conclusion that the thickness of loess on a site within the LGM boundary is not only a function of distance to source area, but also of local site/surface stability. Areas that are steeply sloping or that stabilized later - after buried ice and permafrost had melted - have much thinner loess covers. These findings have paved the way for additional research into the ages of these systems, of which we generally know very little, and which can be elucidated using OSL techniques on the temporally related loess deposits. My data also suggest that relatively little of the loess in the upper Midwest is Mississippi River-sourced, and therefore probably should not be referred to as Peoria sensu stricto. Lastly, I draw attention to the fact that many eolian deposits in the region are quite sandy. These cover sands are not usually mapped as loess, but have many of the same genetic characteristics as loess, and may provide fruitful avenues for future research.