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Title: Age-erosion constraints on an Early Pleistocene paleosol in Yukon, Canada, with profiles of 10Be and 26Al: Evidence for a significant loess cover effect on cosmogenic nuclide production rates

We report that Wounded Moose type paleosols developed on remnant deposits of Late Pliocene to Early Pleistocene [pre-Reid] Cordilleran Ice Sheet [CIS] glaciations in central Yukon, Canada. It is an important regional soil-geomorphic marker at the boundary between early CIS advances and the non-glaciated regions of Yukon and Alaska. Yet, at present, its age is poorly constrained between the Reid [0.2 Ma] and earliest [2.84 Ma] CIS advances. Here, we apply depth profiles of in situ-produced cosmogenic 26Al and 10Be to obtain both a minimum exposure age [1.12 +0.44/ -0.36 Ma, 2σ] and maximum erosion rate [1.1 +0.9/ -0.5 m Myr -1] for the Wounded Moose paleosol. Here, our results show that this soil formed under exceptionally stable conditions [max erosion rate similar to polar bedrock erosion rates] and that it pre-dates the emergence of the 100 ka [eccentricity] climate cycle. Contrasting our results from single- and joint-nuclide depth profile models reveals a significant discrepancy between calculated and effective 10Be and 26Al production rates [40–65% of expected values]. We interpret this discrepancy as the result of intermittent loess cover—with a time-averaged depth between 60 and 110 cm—which significantly reduced apparent exposure ages obtained from the single–nuclide model. The observation ofmore » such a significant loess-cover effect on cosmogenic nuclide production has implications for exposure dating in glacial and periglacial environments; a multi-nuclide sampling strategy is required to quantify this effect.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Accelerator Mass Spectrometry; Dalhousie University, Halifax, Nova Scotia (Canada)
  2. Dalhousie University, Halifax, Nova Scotia (Canada)
  3. University of Northern British Columbia, Prince George, British Columbia (Canada)
  4. University of Alberta, Edmonton, Alberta (Canada). Department of Earth and Atmospheric Sciences
Publication Date:
Report Number(s):
LLNL-JRNL-735086
Journal ID: ISSN 0341-8162
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Catena
Additional Journal Information:
Journal Volume: 165; Journal Issue: C; Journal ID: ISSN 0341-8162
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Multi-nuclide TCN approach; Loess cover; Soil dating; Periglacial setting; Depth profile dating
OSTI Identifier:
1424118

Hidy, Alan J., Gosse, John C., Sanborn, Paul, and Froese, Duane G.. Age-erosion constraints on an Early Pleistocene paleosol in Yukon, Canada, with profiles of 10Be and 26Al: Evidence for a significant loess cover effect on cosmogenic nuclide production rates. United States: N. p., Web. doi:10.1016/j.catena.2018.02.009.
Hidy, Alan J., Gosse, John C., Sanborn, Paul, & Froese, Duane G.. Age-erosion constraints on an Early Pleistocene paleosol in Yukon, Canada, with profiles of 10Be and 26Al: Evidence for a significant loess cover effect on cosmogenic nuclide production rates. United States. doi:10.1016/j.catena.2018.02.009.
Hidy, Alan J., Gosse, John C., Sanborn, Paul, and Froese, Duane G.. 2018. "Age-erosion constraints on an Early Pleistocene paleosol in Yukon, Canada, with profiles of 10Be and 26Al: Evidence for a significant loess cover effect on cosmogenic nuclide production rates". United States. doi:10.1016/j.catena.2018.02.009.
@article{osti_1424118,
title = {Age-erosion constraints on an Early Pleistocene paleosol in Yukon, Canada, with profiles of 10Be and 26Al: Evidence for a significant loess cover effect on cosmogenic nuclide production rates},
author = {Hidy, Alan J. and Gosse, John C. and Sanborn, Paul and Froese, Duane G.},
abstractNote = {We report that Wounded Moose type paleosols developed on remnant deposits of Late Pliocene to Early Pleistocene [pre-Reid] Cordilleran Ice Sheet [CIS] glaciations in central Yukon, Canada. It is an important regional soil-geomorphic marker at the boundary between early CIS advances and the non-glaciated regions of Yukon and Alaska. Yet, at present, its age is poorly constrained between the Reid [0.2 Ma] and earliest [2.84 Ma] CIS advances. Here, we apply depth profiles of in situ-produced cosmogenic 26Al and 10Be to obtain both a minimum exposure age [1.12+0.44/-0.36 Ma, 2σ] and maximum erosion rate [1.1+0.9/-0.5 m Myr-1] for the Wounded Moose paleosol. Here, our results show that this soil formed under exceptionally stable conditions [max erosion rate similar to polar bedrock erosion rates] and that it pre-dates the emergence of the 100 ka [eccentricity] climate cycle. Contrasting our results from single- and joint-nuclide depth profile models reveals a significant discrepancy between calculated and effective 10Be and 26Al production rates [40–65% of expected values]. We interpret this discrepancy as the result of intermittent loess cover—with a time-averaged depth between 60 and 110 cm—which significantly reduced apparent exposure ages obtained from the single–nuclide model. The observation of such a significant loess-cover effect on cosmogenic nuclide production has implications for exposure dating in glacial and periglacial environments; a multi-nuclide sampling strategy is required to quantify this effect.},
doi = {10.1016/j.catena.2018.02.009},
journal = {Catena},
number = C,
volume = 165,
place = {United States},
year = {2018},
month = {2}
}