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Geochronology Advances in geochronological science
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Preprints
https://doi.org/10.5194/gchron-2020-14
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gchron-2020-14
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  30 Apr 2020

30 Apr 2020

Review status
A revised version of this preprint is currently under review for the journal GChron.

Calibrating a long-term meteoric 10Be delivery rate into Western US glacial deposits through a comparison of complimentary meteoric and in situ-produced 10Be depth profiles

Travis Clow1, Jane K. Willenbring1,2, Mirjam Schaller3, Joel D. Blum4, Marcus Christl5, Peter W. Kubik5, and Friedhelm von Blanckenburg2 Travis Clow et al.
  • 1Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92037, USA
  • 2GFZ German Research Centre for Geosciences, Earth Surface Geochemistry, Telegrafenberg, 14473 Potsdam, Germany
  • 3Geodynamics, University of Tübingen, Wilhelmstraße 56, 72076 Tübingen, Germany
  • 4Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
  • 5ETH Zurich, Laboratory of Ion Beam Physics, HPK G23, Schafmattstrasse 20, ETH-Zurich, 8093 Zurich, Switzerland

Abstract. Meteoric 10Be (10Bemet) concentrations in soil profiles great potential as a geochronometer and a tracer of Earth surface processes, particularly in fine-grained soils lacking quartz that would preclude the use of in situ-produced 10Be (10Bein situ). One prerequisite for using this technique for accurately calculating rates and dates is constraining the delivery, or flux, of 10Bemet to a site. However, few studies to date have quantified long-term (i.e. millennial) delivery rates. In this study, we compared existing concentrations of 10Bein situ with new measurements of 10Bemet in soils sampled from the same depth profiles to calibrate a long-term 10Bemet delivery rate. We did so on the Pinedale and Bull Lake glacial moraines at Fremont Lake, Wyoming (USA) where age, grain sizes, weathering indices, and soil properties are known, as are erosion/denudation rates calculated from 10Bein situ. After ensuring sufficient beryllium retention in each profile, solving for the delivery rate of 10Bemet via Monte Carlo simulations, and normalizing to Holocene-average paleomagnetic intensity, we calculate best-fit fluxes of 0.92 (+/− 0.08) × 106 and 0.71 (+0.09/−0.08) × 106 atoms cm−2 y−1 to the Pinedale and Bull Lake moraines, respectively, and compare these values to two widely-used 10Bemet delivery rate estimation methods. Accurately estimating 10Bemet flux using these methods requires careful consideration of spatial scale as well as temporally varying parameters (e.g. paleomagnetic field intensity) to ensure the most realistic estimates of 10Bemet-derived erosion rates in future studies.

Travis Clow et al.

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Latest update: 26 Sep 2020
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Short summary
Meteoric Beryllium-10 concentrations in soil profiles have great capacity to quantify earth surface processes, such as erosion rates and landform ages. However, determining these requires an accurate estimate of the delivery rate of this isotope to local sites. We present a new method to constrain the long-term delivery rate to a western US site and then compare it against existing delivery rate estimates, revealing considerable disagreement between methods, and suggest best practices.
Meteoric Beryllium-10 concentrations in soil profiles have great capacity to quantify earth...
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