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Using 10Be dating to determine when the Cordilleran Ice Sheet stopped flowing over the Canadian Rocky Mountains

Published online by Cambridge University Press:  05 March 2021

Helen E. Dulfer Open the ORCID record for Helen E. Dulfer [Opens in a new window] ,
Martin Margold Open the ORCID record for Martin Margold [Opens in a new window] ,
Zbynĕk Engel Open the ORCID record for Zbynĕk Engel [Opens in a new window] ,
Régis Braucher Open the ORCID record for Régis Braucher [Opens in a new window]  and
Aster Team
Helen E. Dulfer*
Affiliation:
Department of Physical Geography and Geoecology, Faculty of Science, Charles University in Prague, Albertov 6, 12800Praha, Czech Republic.
Martin Margold
Affiliation:
Department of Physical Geography and Geoecology, Faculty of Science, Charles University in Prague, Albertov 6, 12800Praha, Czech Republic.
Zbynĕk Engel
Affiliation:
Department of Physical Geography and Geoecology, Faculty of Science, Charles University in Prague, Albertov 6, 12800Praha, Czech Republic.
Régis Braucher
Affiliation:
CEREGE, Aix-Marseille Univ., CNRS-IRD- Coll. De France-INRAE UM 34, 13545 Aix-en-Provence Cedex 4, France Aster Team: Georges Aumaître, Didier Bourlès, Karim Keddadouche
Aster Team
Affiliation:
CEREGE, Aix-Marseille Univ., CNRS-IRD- Coll. De France-INRAE UM 34, 13545 Aix-en-Provence Cedex 4, France Aster Team: Georges Aumaître, Didier Bourlès, Karim Keddadouche
*
*Corresponding author: Helen E. Dulfer, Email:dulferh@natur.cuni.cz
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Abstract

During the last glacial maximum the Cordilleran and Laurentide ice sheets coalesced east of the Rocky Mountains and geomorphological evidence indicates ice flowed over the main ridge of the Rocky Mountains between ~54–56°N. However, this ice flow has thus far remained unconstrained in time. Here we use in situ produced cosmogenic 10Be dating to determine when Cordilleran ice stopped flowing over the mountain range. We dated eight samples from two sites: one on the western side (Mount Morfee) and one on the eastern side (Mount Spieker) of the Rocky Mountains. At Mount Spieker, one sample is rejected as an outlier and the remaining three give an apparent weighted mean exposure age of 15.6 ± 0.6 ka. The four samples at Mount Morfee are well clustered in time and give an apparent weighted mean exposure age of 12.2 ± 0.4 ka. These ages indicate that Mount Spieker became ice free before the Bølling warming and that the western front of the Rocky Mountains (Mount Morfee) remained in contact with the Cordilleran Ice Sheet until the Younger Dryas.

Keywords

Cordilleran Ice SheetRocky Mountainscosmogenic exposure datingdeglaciation
Type
Research Article
Information
Quaternary Research , Volume 102 , July 2021 , pp. 222 - 233
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Copyright
Copyright © University of Washington. Published by Cambridge University Press, 2021

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