Geological Society of America

T47 The Last Glacial–Interglacial Transition in Western North America: Paleoclimate Proxies, Environmental Responses, and Data-Model Comparisons

Sunday, 9 October 2022
1:30 PM - 5:30 PM
503

THE COLLAPSE OF THE LAURENTIDE-CORDILLERAN ICE SADDLE AND EARLY OPENING OF THE MACKENZIE VALLEY, NORTHWEST TERRITORIES, CONSTRAINED BY 10BE EXPOSURE DATING

Paper number: T47-2
Program: Technical Sessions
Time: 1:35 PM – 1:50 PM

Authors

Benjamin Stoker Presenting Author
Charles University, Praha 2
Duane Froese
University of Alberta, Edmonton, AB
Martin Margold
Durham University, Durham, N/A
John Gosse
Dalhousie University, Halifax, NS
Alan J. Hidy
Lawrence Livermore National Laboratory, Livermore, CA
Alistair Monteath
University of Southampton, Southampton, AB
Joseph Young
Dept. of Earth and Atmospheric Science1-26 Earth Sciences Building, Edmonton, AB
Niall Gandy
Sheffield Hallam University, Sheffield
Lauren J. Gregoire
University of Leeds, Leeds
Sophie Norris
Department of Earth and Environmental Sciences, Halifax, AB

Abstract

The deglaciation of the northwestern Laurentide Ice Sheet in the central Mackenzie Valley opened the northern portion of the deglacial Ice-Free Corridor between the Laurentide and Cordilleran ice sheets and a drainage route to the Arctic Ocean. In addition, ice-sheet saddle collapse in this sector of the Laurentide Ice Sheet has been implicated as a mechanism for delivering substantial freshwater influx into the Arctic Ocean during the Bølling–Allerød interval. However, there is little empirical data to constrain the chronology of deglaciation in the central Mackenzie Valley where the northern slopes of the ice saddle were located. Here, we present 30 new ¹⁰Be cosmogenic nuclide exposure dates across six sites, including two elevation transects, which constrain the timing and rate of thinning of the Laurentide Ice Sheet in the area. Our new ¹⁰Be dates indicate that the initial deglaciation of the eastern summits of the central Mackenzie Mountains began at ~15.8 ka (17.1 – 14.6 ka), ~1,000 years earlier than in previous reconstructions. The main phase of ice-saddle collapse occurred between ~14.9 and 13.2 ka, consistent with numerical modelling simulations, placing this event within the Bølling–Allerød interval (14.6 – 12.9 ka). Our new dates require a revision of ice margin retreat dynamics, with ice retreating more easterly rather than southward along the Mackenzie Valley. In addition, we quantify a total sea level rise contribution from the Cordilleran-Laurentide ice saddle region of ~11.2 m between 16 ka and 13 ka.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-377266

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