EVIDENCE FOR EARLY HOLOCENE EOLIAN ACTIVITY, NORTH-CENTRAL MINNESOTA
Dunes are most common near the western shoreline of the basin. They occur as dense clusters adjacent to source areas, but are scattered when more distal. Maximum dune amplitude are ~2.5 meters. Granulometry indicates a 4phi grain size signature characterizes dunes throughout the Glacial Lake basin.
An 8.57 meter sediment core was collected from Hay Lake, located within a dunefield on the bottom of Glacial Lake Upham. Three prominent peaks in the whole-core magnetic susceptibility record are evident between 10.1k and 6.6k 14C years B.P. Granulometry and microscopy confirm these peaks are due to influx of 4phi clastic sediment. No clastic input is evident after 6.6ka, suggesting dune stability.
The dune fields of north-central Minnesota are intimately related to sand source areas and supply, which were at their peak immediately after the drainage of the Glacial Lakes. Thus, a significant component of dune formation in north-central Minnesota likely took place during the early Holocene.