The OSL chronology of eolian sand deposition in a perched dune field along the northwestern shore of Lower Michigan

Abstract

Extensive coastal dunes occur in the Great Lakes region of North America, including northwestern Michigan where some are perched on high (~100m) bluffs. This study focuses on such a system at Arcadia Dunes and is the first to systematically generate optical ages from stratigraphic sections containing buried soils. Dune growth began ca. 4.5ka during the Nipissing high lake stand and continued episodically thereafter, with periods of increased sand supply at ca. 3.5ka and ca. 1.7ka. The most volumetrically dominant phase of dune growth began ca. 1.0ka and continued intermittently for about 500years. It may have begun due to the combined effects of a high lake phase, potential changes in lake hydrodynamics with final isostatic separation of Lake Superior from Lakes Michigan and Huron, and increased drought and hydrologic variability associated with the Medieval Warm Period. Thus, this latest eolian phase likely reflects multiple processes associated with Great Lakes water level and climate variability that may also explain older eolian depositional events. Comparison of Arcadia ages and calendar corrected 14C ages from previous studies indicate broad chronological agreement between events at all sites, although it appears that dune growth began later at Arcadia.