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- Title
Early Holocene ice retreat from Isle Royale in the Laurentian Great Lakes constrained with 10Be exposure-age dating.
- Authors
Portenga, Eric W.; Ullman, David J.; Corbett, Lee B.; Bierman, Paul R.; Caffee, Marc W.
- Abstract
The timing of the Laurentide Ice Sheet's final retreat from North America's Laurentian Great Lakes is relevant to understanding regional meltwater routing, changing proglacial lake levels, and lake-bottom stratigraphy following the Last Glacial Maximum. Recessional moraines on Isle Royale, the largest island in Lake Superior, have been mapped but not directly dated. Here, we use the mean of 10 new 10 Be exposure ages of glacial erratics from two recessional moraines (10.1 ± 1.1 ka, one standard deviation; excluding one anomalously young sample) to constrain the timing of Isle Royale's final deglaciation. This 10 Be age is consistent with existing minimum-limiting 14 C ages of basal organic sediment from two inland lakes on Isle Royale, a sediment core in Lake Superior southwest of the island, and an estimated deglaciation age of the younger of two subaqueous moraines between Isle Royale and Michigan's Keweenaw Peninsula. Relationships between Isle Royale's landform ages and Lake Superior bottom stratigraphy allow us to delineate the retreat of the Laurentide ice margin across and through Lake Superior in the early Holocene. We suggest that Laurentide ice was in contact with the southern shorelines of Lake Superior later than previously thought.
- Subjects
GLACIAL landforms; LAST Glacial Maximum; ISLANDS; BOULDERS; HOLOCENE Epoch; LAKES
- Publication
Geochronology, 2023, Vol 5, Issue 2, p413
- ISSN
2628-3697
- Publication type
Article
- DOI
10.5194/gchron-5-413-2023