Surficial silty and sandy deposits 50 to 100 cm thick commonly occur in the glacial landscape of Michigan's eastern Upper Peninsula. The surficial deposits greatly influence development of upper soil horizons in particular Spodic horizons. We postulate three potential origins for these deposits – eolian, lacustrine, and/or glacial melt-out. Based on geomorphic setting, we selected two study sites to evaluate age and characteristics of the surficial deposits. The selected sites are topographic highs south of the Marquette advance that existed as islands in Glacial Lake Algonquin. We sampled fifteen pedons for characterization in transects across the “islands”. At three pedon locations on each “island”, we collected pipe-encased samples for OSL dating. The measured OSL ages range from 8.7 to 12.6 ka with a mean of 10.3. Glacial Lake Algonquin drained at 11 ka. The surficial mantles are therefore younger than the last Algonquin inundation. This age rules out lacustrine processes as the major origin. Algonquin shorelines cross cut the underlying till, outwash, beach deposits, and bedrock that comprise the “islands” substrata. The substrata predate some, if not all phases of Glacial Lake Algonquin. Pre-Marquette melt-out deposits must also predate 11 ka. This leaves eolian deposition as the only feasible origin for the surficial deposits. Soil mineralogy and particle size further support an eolian origin. Two major events provided open sediments source(s) for eolian reworking. Final drainage of Glacial Lake Algonquin exposed large un-vegetated tracts of sand and silt. Algonquin shorelines are cross cut (buried) by Marquette age (9.9 ka) outwash deposits that served as a second major sand and silt source.
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