Reconstructing the geomorphic evolution of large coastal dunes along the southeastern shore of Lake Michigan

Coastal dunes are common along the eastern shore of Lake Michigan, with the most common being large (> 30 m high), parabolic dunes that mantle lake terraces south of Manistee, MI. Although these dunes are an important resource in Michigan, and thus intensely managed by various state agencies, their geomorphic history is poorly understood. This study examines four sites near Holland, MI, through stratigraphic and radiocarbon analyses and is the most detailed geomorphic reconstruction conducted of coastal parabolic dunes in the region. Results from this study could benefit the environmental agencies in their management of the coastal dune ecosystem. Deposition of Eolian sand apparently began similar to 5500 cal. years BP (i.e., during the Nipissing high stand). Most (similar to 75%) dune building occurred between similar to 4000 and 2500 cal. years BP but was punctuated by brief periods of stability that resulted in the development of Entisols (A/C horizonation). Entisol burial occurred because the sand supply apparently increased during both the receding and rising lake levels. Subsequently, each dune stabilized for similar to 2000 years, allowing the formation of Inceptisols (i.e., A/E/Bs/C horizonation). This interval of dune stability correlates with sites south of Holland and occurred while Lake Michigan fluctuated slowly and the beach potentially prograded. These combined variables of slow fluctuation and potential beach progradation hypothetically protected the dunes from wave erosion. Dunes near Holland became active again similar to 1000-500 cal. years BP and grew both vertically and laterally. This activity intensified in the past 500 cal. years BP and hypothetically occurred due to recession of the lake shore such that wave erosion at the modem bluff base resumed. Results from this study indicate that coastal dunes along Lake Michigan are similar to many coastal dunes around the world, including those along the intermediate beaches in SE Australia. (C) 2002 Elsevier Science B.V. All rights reserved.