| This research examines the distribution, thickness and textural characteristics of thin, patchy, loess deposits in the western Upper Peninsula of Michigan. Although local soil surveys have documented loess in Baraga, Marquette and Iron Counties, at the northeastern margins of the North American, midcontinent loess region, this thesis is the first detailed study of these loess deposits. Within the study area, loess is∼30-60 cm thick and is usually underlain by sandy glacial deposits. Where the loess deposits are thin, it appears that pedoturbation processes have likely mixed some of the lower, sandy materials into the loess. For this reason, most of the loess has a bimodal continuous textural curve, with a primary modal particle-size within the 25-75 microm fraction (the loess) and a secondary mode in the 250-500 microm fraction (the in-mixed sand). These loess deposits were likely sourced from both distant and local areas, including ground moraines, outwash plains, and the floodplains of small meltwater streams. Within the Peshekee Loess region, I have identified four loess sections, each of which has unique characteristics that set it apart from the whole: the Amasa, Covington, Republic, and Champion sections. This research (1) recognizes multiple source areas for loess, (2) develops and interprets textural data on the thin Peshekee Loess, and (3) documents the effects of mixing within these loess deposits. This research is the first to document both the extent and textural characteristics of loess deposits situated at the extreme margins of much larger and thicker, regional-scale, loess region. |
