RELATIONSHIP AMONG HOLOCENE LAKE-LEVEL CHANGE, DUNE-DAMMING, AND INLAND DUNE ACTIVITY IN EASTERN UPPER MICHIGAN

The relationship between lake-level change and development of perched dunes along the shoreline of the Great Lakes has been the subject of several recent studies. This work, in contrast, will try to explain the development of a small set of inland dunes in response to changes in lake level along the southeastern shore of Lake Superior in Chippewa Co., MI. The formation of perched and coastal dunes can be produced by lake-level change, but inland dune formation is strongly controlled by vegetation and previously not thought to be directly or indirectly related to lake-level change and dune-damming. Recent work has suggested a climatic mechanism for sand mobility and the formation of inland dunes in eastern Upper Michigan. However, this study is focused on one set of inland dunes in northwestern Chippewa Co., MI. We here describe a system wherein the source of inland dune sand appears to be lake-bottom sands from a drained, formerly dune-dammed, lake. Coastal dunes are hypothesized to have formed at the peak of the Nipissing transgression (~5500 ka) in the study area. These dunes were capable of blocking the course of Browns Creek, a short, northward flowing stream into Lake Superior, and creating a dune dam. The reservoir that was created was breached shortly after it was created due to a sharp drop in base level after the peak of the Nipissing transgression. The drained lake provided a source for sand(namely lake-bottom sands) that subsequently accumulated in a dune field downwind of the paleo-lakebed. Optically stimulated luminescence (OSL) is being used to determine an absolute age of the dune field. Soil development within the dune field suggests a mid-Holocene age.