Quaternary incision rates and drainage evolution of the Uncompahgre and Gunnison Rivers, western Colorado, as calibrated by the Lava Creek B ash
Abstract
Research Article| January 01, 2009 Quaternary incision rates and drainage evolution of the Uncompahgre and Gunnison Rivers, western Colorado, as calibrated by the Lava Creek B ash Andrew L. Darling; Andrew L. Darling * 1Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A. *Correspondence should be addressed to: adarling@unm.edu Search for other works by this author on: GSW Google Scholar Karl E. Karlstrom; Karl E. Karlstrom 1Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A. Search for other works by this author on: GSW Google Scholar Andres Aslan; Andres Aslan 2Department of Physical and Environmental Science, Mesa State College, Grand Junction, Colorado 81501, U.S.A. Search for other works by this author on: GSW Google Scholar Rex Cole; Rex Cole 2Department of Physical and Environmental Science, Mesa State College, Grand Junction, Colorado 81501, U.S.A. Search for other works by this author on: GSW Google Scholar Charles Betton; Charles Betton 3Grand Junction Geological Society, Grand Junction, Colorado 81501, U.S.A. Search for other works by this author on: GSW Google Scholar Elmira Wan Elmira Wan 4U.S. Geological Survey, MS 975, Menlo Park, California 94025, U.S.A. Search for other works by this author on: GSW Google Scholar Author and Article Information Andrew L. Darling * 1Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A. Karl E. Karlstrom 1Department of Earth and Planetary Sciences, Northrop Hall, University of New Mexico, Albuquerque, New Mexico 87131, U.S.A. Andres Aslan 2Department of Physical and Environmental Science, Mesa State College, Grand Junction, Colorado 81501, U.S.A. Rex Cole 2Department of Physical and Environmental Science, Mesa State College, Grand Junction, Colorado 81501, U.S.A. Charles Betton 3Grand Junction Geological Society, Grand Junction, Colorado 81501, U.S.A. Elmira Wan 4U.S. Geological Survey, MS 975, Menlo Park, California 94025, U.S.A. *Correspondence should be addressed to: adarling@unm.edu Publisher: University of Wyoming Received: 20 May 2008 Revision Received: 30 Jan 2009 Accepted: 01 Apr 2009 First Online: 09 Mar 2017 Online Issn: 1555-7340 Print Issn: 1555-7332 UW Department of Geology and Geophysics Rocky Mountain Geology (2009) 44 (1): 71–83. https://doi.org/10.2113/gsrocky.44.1.71 Article history Received: 20 May 2008 Revision Received: 30 Jan 2009 Accepted: 01 Apr 2009 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Andrew L. Darling, Karl E. Karlstrom, Andres Aslan, Rex Cole, Charles Betton, Elmira Wan; Quaternary incision rates and drainage evolution of the Uncompahgre and Gunnison Rivers, western Colorado, as calibrated by the Lava Creek B ash. Rocky Mountain Geology 2009;; 44 (1): 71–83. doi: https://doi.org/10.2113/gsrocky.44.1.71 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyRocky Mountain Geology Search Advanced Search Abstract The Quaternary erosional history of western Colorado is documented in terraces of the Colorado, Gunnison, and Uncompahgre Rivers that contain the Lava Creek B ash (0.64 Ma). This paper reports an important new ash locality that dates ca. 100-m-high river gravels associated with the paleo-confluence of the Gunnison and Uncompahgre Rivers upstream from Grand Junction. Provenance analysis reveals paleo-Gunnison River gravels (containing granite and gneiss clasts) and paleo-Uncompahgre River gravels (containing Uncompahgre Group quartzite and San Juan volcanic field rocks). The paleo-Uncompahgre River gravels are 3 m directly beneath Lava Creek B ash, and the areal distribution of terraces indicates that this area was the paleo-confluence between the Gunnison and Uncompahgre Rivers. This confluence has shifted 11 km to the east since 0.64 Ma due to events related to stream piracy and drainage reorganization. Gunnison terrace straths near the paleo-confluence are estimated to be 106 m above the modern strath, giving an estimated incision rate of 165 m/Ma.Because of excellent age and geologic control, this is one of the best incision-rate data points in the upper Colorado River system. It is similar to previously reported regional rates, but is substantially lower than upstream incision rates in the Black Canyon of the Gunnison River. This dated Gunnison River terrace anchors the projection of Lava Creek B-bearing Grand Mesa pediment surfaces (e.g., Petrie Mesa) to regional base level and helps constrain a regional reconstruction of the 0.64-Ma profile of the paleo-Gunnison River. This reconstruction shows dramatic differences in incision rate in the Gunnison River system since 0.64 Ma, and that a transient knickpoint migrated past Sawmill Mesa prior to 0.64 Ma. This incision data point has important implications for evaluating major Quaternary changes in the configuration of this part of the Rocky Mountain drainage system. It also provides evidence for a young, disequilibrium drainage system that is responding to base-level changes downstream driven by a stream capture event, which in turn may have been driven by tectonic or climatic perturbations. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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