A 12 000 year radiocarbon date of deglaciation from the Continental Divide of northwestern Montana

Canadian Journal of Earth Sciences
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Abstract

During the Pinedale (Late Wisconsinan) glaciation, an outlet glacier from a mountain ice field flowed eastward across the Continental Divide through Marias Pass in northwestern Montana. This outlet glacier was the major source of the Two Medicine glacier, a large piedmont glacier that extended from the mountain front east about 55 km onto the plains. An accelerator mass spectrometry radiocarbon age of 12 194 ± 145 BP (AA-9530) was obtained from a wood fragment, underlying a Glacier Peak tephra and a Mount Saint Helens set J tephra in a section of lake sediments, near Marias Pass. This radiocarbon age provides a minimum date of deglaciation for the Marias Pass area that is about 800 years older than a previous estimate. Furthermore, the radiocarbon age indicates that the Two Medicine glacier was no longer being supplied by its major source and if it still existed was only as a dying, stagnant ice mass.

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Publication type Article
Publication Subtype Journal Article
Title A 12 000 year radiocarbon date of deglaciation from the Continental Divide of northwestern Montana
Series title Canadian Journal of Earth Sciences
DOI 10.1139/e95-106
Volume 32
Issue 9
Year Published 1995
Language English
Publisher Canadian Science Publishing
Contributing office(s) Geosciences and Environmental Change Science Center
Description 5 p.
First page 1303
Last page 1307
Country United States
State Idaho, Montana
Other Geospatial Northwestern Montana
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