Preprints
https://doi.org/10.5194/gchron-2021-43
https://doi.org/10.5194/gchron-2021-43

  13 Dec 2021

13 Dec 2021

Review status: this preprint is currently under review for the journal GChron.

Reconciling the Apparent Absence of a Last Glacial Maximum Alpine Glacial Advance, Yukon Territory, Canada, through Cosmogenic Beryllium-10 and Carbon-14 Measurements

Brent Goehring1, Brian Menounos2, Gerald Osbron3, Adam Hawkins2, and Brent Ward4 Brent Goehring et al.
  • 1Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118 USA
  • 2Geography Program and National Resources and Environmental Studies Institute, University of Northern British Columbia, Prince George, BC Canada
  • 3University of Calgary, Calgary, AB Canada
  • 4Simon Fraser University, Burnaby, BC Canada

Abstract. We present a new in situ produced cosmogenic beryllium-10 and carbon-14 nuclide chronology from two sets (outer and inner) of alpine glacier moraines from the Grey Hunter massif of southern Yukon Territory, Canada. The chronology potential of moraines deposited by alpine glaciers outside the limits of the Last Glacial Maximum (LGM) ice sheets potentially provide a less-ambiguous archive of mass balance, and hence climate than can be inferred from the extents of ice sheets themselves. Results for both nuclides are inconclusive for the outer moraines, with evidence for pre-LGM deposition (beryllium-10) and Holocene deposition (carbon-14). Beryllium-10 results from the inner moraine are suggestive of canonical LGM deposition, but with relatively high scatter. Conversely, in situ carbon-14 results from the inner moraines are tightly clustered and suggestive of terminal Younger Dryas deposition. We explore plausible scenarios leading to the observed differences between nuclides and find that the most parsimonious explanation for the outer moraines is that of pre-LGM deposition, but many of the sampled boulder surfaces were not exhumed from within the moraine until the Holocene. Our results thus imply that the inner and outer moraines sampled pre- and post-date the canonical LGM and that moraines dating to the LGM are lacking likely due to overriding by the subsequent Late Glacial/earliest Holocene advance.

Brent Goehring et al.

Status: open (until 24 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2021-43', Jennifer Lamp, 15 Jan 2022 reply

Brent Goehring et al.

Brent Goehring et al.

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Short summary
We explored surface exposure dating with two nuclides, to date two sets of moraines from the Yukon Territory and explain the reasoning for the observed ages. Results suggest multiple processes, including preservation of nuclides from a prior exposure period, and later erosion of the moraines is required to explain the data. Our results only allow for the older moraines to date to marine isotope stages three or four, and the younger moraines to date to the very earliest Holocene.