Late Pleistocene glaciation in the Mosquito Range, Colorado, USA: chronology and climate

Keith A Brugger, Benjamin Laabs, Alexander Reimers, Noah Bensen

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

New cosmogenic 10Be surface exposure ages from 17 moraine boulders in the Mosquito Range of Colorado suggest that glaciers were at their late Pleistocene (Pinedale) maximum extent at ∼21–20 ka, and that ice recession commenced before ∼17 ka. These age limits suggest that the Pinedale Glaciation was synchronous within the Colorado Rocky Mountain region. Locally, the previous (Bull Lake) glaciation appears to have occurred no later than 117 ka, possibly ∼130 ka allowing for reasonable rock weathering rates. Temperature-index modeling is used to determine the magnitude of temperature depression required to maintain steady-state mass balances of seven reconstructed glaciers at their maximum extent. Assuming no significant differences in precipitation compared to modern values, mean annual temperatures were ∼8.1 and 7.5 °C lower, respectively, on the eastern and western slopes of the range with quantifiable uncertainties of + 0.8/−0.9 °C. If an average temperature depression of 7.8 °C is assumed for the entire range, precipitation differences − that today are 15–30% greater on the eastern slope due to the influence of winter/early spring snowfall − might have been enhanced. The temperature depressions inferred here are consistent with similarly derived values elsewhere in the Colorado Rockies and those inferred from regional-scale climate modeling.

Original languageEnglish (US)
Pages (from-to)187-202
Number of pages16
JournalJournal of Quaternary Science
Volume34
Issue number3
DOIs
StatePublished - Apr 2019

Bibliographical note

Funding Information:
Funding for initial cosmogenic dating and fieldwork was provided to K.A.B. by the UMM's Faculty Research Enhancement Funds. A seed grant to K.A.B. and B.L. from the Purdue University PRIME Lab provided AMS analyses of additional samples. N.B. was supported by the University of Minnesota's Undergraduate Research Opportunity Program. B.L. and A.R. gratefully acknowledge support of the NDSU College of Science and Math. We also thank the reviewers for their thorough and thoughtful comments.

Publisher Copyright:
Copyright © 2019 John Wiley & Sons, Ltd.

Keywords

  • Colorado
  • Pinedale glaciation
  • cosmogenic exposure dating
  • glacial chronology
  • paleoclimate

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