Optically stimulated luminescence dating of late holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, upper peninsula, Michigan, USA

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 similar to 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 C-14 ages on swale organics. Modern littoral and eolian sediments yield SAR ages < 100 yr indicating near, if not complete, solar resetting of luminescence prior to deposition. Beach ridges that yield SAR ages < 2000 yr show general agreement with corresponding C-14 ages on swale organics. Significant variability in C-14 ages > 2000 cal yr B.P. complicates comparison to SAR ages at all sites. However, a SAR age of 4280 +/- 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 similar to 1500 yr ago, likely reflecting separation of Lake Superior from lakes Huron and Michigan. This study shows that SAR is a credible alternative to C-14 methods for dating littoral and eolian landforms in Great Lakes and other coastal strandplains where C-14 methods prove problentatic. (c) 2004 University of Washington. All rights reserved.