Optically stimulated luminescence dating of late Holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, Upper Peninsula, Michigan, USA Erin P. Argyilan a, * , Steven L. Forman b , John W. Johnston c , Douglas A. Wilcox d a Department of Geosciences, Indiana University Northwest, 3400 Broadway, Marram 243, Gary, IN 46408, USA b Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 W. Taylor St. M/C 186, Chicago, IL 60607, USA c Department of Earth Sciences, University of Waterloo, CEIT Building, 200 University Ave. W., Waterloo, Ontario, Canada N2L 3G1 d Department of the Interior, U.S. Geological Survey, Great Lakes Science Center, 1451 Green Road, Ann Arbor, MI 48105, USA Received 11 February 2004 Available online 27 January 2005 Abstract This study evaluates the accuracy of optically stimulated luminescence to date well-preserved strandline sequences at Manistique/ Thompson bay (Lake Michigan), and Tahquamenon and Grand Traverse Bays (Lake Superior) that span the past ~4500 yr. The single aliquot regeneration (SAR) method is applied to produce absolute ages for littoral and eolian sediments. SAR ages are compared against AMS and conventional 14 C ages on swale organics. Modern littoral and eolian sediments yield SAR ages b100 yr indicating near, if not complete, solar resetting of luminescence prior to deposition. Beach ridges that yield SAR ages b2000 yr show general agreement with corresponding 14 C ages on swale organics. Significant variability in 14 C ages N2000 cal yr B.P. complicates comparison to SAR ages at all sites. However, a SAR age of 4280 F 390 yr (UIC913) on ridge77 at Tahquamenon Bay is consistent with regional regression from the high lake level of the Nipissing II phase ca. 4500 cal yr B.P. SAR ages indicate a decrease in ridge formation rate after ~1500 yr ago, likely reflecting separation of Lake Superior from lakes Huron and Michigan. This study shows that SAR is a credible alternative to 14 C methods for dating littoral and eolian landforms in Great Lakes and other coastal strandplains where 14 C methods prove problematic. D 2004 University of Washington. All rights reserved. Keywords: Optically stimulated luminescence; Littoral sediments; Great Lakes water levels; Radiocarbon; Beach ridges Introduction Strandplains that commonly occur in coastal embay- ments of the Laurentian Great Lakes are comprised of beach ridges, sandy depositional features consisting of waterlain nearshore deposits commonly capped by eolian sediments (Thompson, 1992; Thompson and Baedke, 1997). The combination of regional glacioisostatic uplift, rapid lake-level fluctuations, and abundant sediment supply trapped in coastal embayments results in a prograding shoreline with progressive abandonment of beach ridges, creating chronosequences of beach ridges and associated landforms (Olson, 1958; Thompson, 1992; Thompson and Baedke, 1997). Strandplain deposition in the upper Great Lakes reflects a long-term regression from the Nipissing II phases about 4500 yr ago, when lake level was ~4.1 m higher than the historical average (Baedke and Thompson, 2000). Chronologic control on beach-ridge formation coupled with sedimentological data from cores is critical to quantify rates and magnitudes of water-level fluctuations and to partition the effects of glacioisostasy, variations in sediment supply, and climate on late Holocene lake-level variability. Previously, the lake-level history of Lake Michigan during the past ~4700 yr was reconstructed from the ages and elevations of beach ridges in five strandplain 0033-5894/$ - see front matter D 2004 University of Washington. All rights reserved. doi:10.1016/j.yqres.2004.12.001 * Corresponding author. Fax: +1 219 980 6673. E-mail address: eargyila@iun.edu (E.P. Argyilan). Quaternary Research 63 (2005) 122 – 135 www.elsevier.com/locate/yqres