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Cosmogenic ¹⁰Be ages of the Saglek Moraines, Torngat Mountains, Labrador

¹ Department of Geosciences, Oregon State University, Corvallis, Oregon 97331, USA
² Department of Geology and Program in Environmental Science, Washington State University, Vancouver, Washington 98686, USA
³ Centre de Spectrométrie Nucleaire et de Spectrométrie de Masse, IN2P3-CNRS, Bât 108, 91405 Orsay Cedex, France
⁴ Department of Geosciences, Oregon State University, Corvallis, Oregon 97331, USA

Cosmogenic ¹⁰Be ages on boulders from the Saglek Moraines of the Torngat Mountains, Labrador, suggest that the moraines were deposited in their type area 13.4 ± 1.5 ka. The ¹⁰Be ages on boulders from similar moraines in a valley system 100 km north of the type area yield a mean age of 12.0 ± 2.1 ¹⁰Be ka. These data support the hypothesis that the Saglek Moraines were deposited by a regional system of outlet glaciers that drained the Laurentide Ice Sheet and left extensive areas of the Torngat Mountains ice free as nunataks. Weighted mean ages for erratic boulders and bedrock 5–50 m higher in elevation than the Saglek Moraines at both field areas are indistinguishable at 1 from the weighted mean ages of moraines in each area. These data either indicate that thicker late Wisconsinan ice receded to the level of the Saglek Moraines at 12–13 ¹⁰Be ka, or that the Saglek ice margin represents the maximum late Wisconsinan extent, but the ice margin fluctuated sufficiently to create a vertical zone of 50 m with essentially the same exposure history.

Key Words: Quaternary • cosmogenic dating • chronology • Saglek Moraines

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