Dominance of an ~150-Year Cycle of Sand-Supply Change in Late

Holocene Dune-Building along the Eastern Shore of Lake Michigan

Walter L. Loope and Alan F. Arbogast

Outcrops of buried soils on lake-plains and glacial headlands along Lake Michigans eastern shore suggest that periodic dune-building has occurred there after relatively long (100 yr) periods of low sand supply. We located, described, and radiocarbon dated 75 such buried soils that crop out in 32 coastal dune fields beside the lake. We assume that peaks in probability distributions of calibrated ¹⁴C ages obtained from wood, charcoal, and other organic matter from buried A horizons approximate the time of soil burial by dunes. Plotted against a late Holocene lake-level curve for Lake Michigan, these peaks are closely associated with many ~150-yr lake highstands previously inferred from beach ridge studies. Intervening periods of lower lake levels and relative sand starvation apparently permitted forestation and soil development at the sites we studied. While late Holocene lake-level change led to development and preservation of prominent foredunes along the southern and southwestern shores of Lake Michigan, the modern dune landscape of the eastern shore is dominated by perched dunes formed during ~150-yr lake highstands over the past 1500 yr.