Geomorphic controls on lacustrine isotopic compositions: Evidence from the Laney Member, Green River Formation, Wyoming

Abstract

Research Article| January 01, 2010 Geomorphic controls on lacustrine isotopic compositions: Evidence from the Laney Member, Green River Formation, Wyoming Amalia C. Doebbert; Amalia C. Doebbert † 1Department of Geology and Geophysics, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA †E-mail: doebbera@geology.wisc.edu Search for other works by this author on: GSW Google Scholar Alan R. Carroll; Alan R. Carroll 1Department of Geology and Geophysics, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA Search for other works by this author on: GSW Google Scholar Andreas Mulch; Andreas Mulch 2Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305-2115, USA3Institut für Geologie, Universität Hannover, 30167 Hannover, Germany Search for other works by this author on: GSW Google Scholar Lauren M. Chetel; Lauren M. Chetel 1Department of Geology and Geophysics, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA Search for other works by this author on: GSW Google Scholar C. Page Chamberlain C. Page Chamberlain 2Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305-2115, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Amalia C. Doebbert † 1Department of Geology and Geophysics, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA Alan R. Carroll 1Department of Geology and Geophysics, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA Andreas Mulch 2Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305-2115, USA3Institut für Geologie, Universität Hannover, 30167 Hannover, Germany Lauren M. Chetel 1Department of Geology and Geophysics, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA C. Page Chamberlain 2Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305-2115, USA †E-mail: doebbera@geology.wisc.edu Publisher: Geological Society of America Received: 20 Aug 2008 Revision Received: 02 Mar 2009 Accepted: 30 Mar 2009 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2010 Geological Society of America GSA Bulletin (2010) 122 (1-2): 236–252. https://doi.org/10.1130/B26522.1 Article history Received: 20 Aug 2008 Revision Received: 02 Mar 2009 Accepted: 30 Mar 2009 First Online: 08 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 Amalia C. Doebbert, Alan R. Carroll, Andreas Mulch, Lauren M. Chetel, C. Page Chamberlain; Geomorphic controls on lacustrine isotopic compositions: Evidence from the Laney Member, Green River Formation, Wyoming. GSA Bulletin 2010;; 122 (1-2): 236–252. doi: https://doi.org/10.1130/B26522.1 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 SocietyGSA Bulletin Search Advanced Search Abstract Oxygen isotope values from lacustrine carbonate in the Laney Member of the Green River Formation (Wyoming) exhibit a sudden, basinwide, ∼6‰ upsection decrease in δ18O at ca. 49 Ma. 40Ar/39Ar geochronology constrains the duration of the isotopic shift to ≤∼200,000 years. This change coincides with a sudden change in lake type, from balanced-filled in the lower LaClede Bed to overfilled in the upper LaClede Bed, as well as an increase in the proportion of calcitic (>80% calcite out of total carbonate by X-ray diffraction [XRD]) samples from 32% to 73%. The δ18O shift is correlatable through several locations across the Greater Green River Basin, and also coincides with a previously observed shift to less radiogenic 87Sr/86Sr. Minimum δ18O values observed are the same as values previously reported in aragonitic bivalves from the same unit, indicating that low δ18O in this record is not diagenetic. A simultaneous shift to evaporative conditions in the Uinta Basin to the south indicates that the δ18O shift and lake-type change are not driven by regional climatic cooling and/or humidity increase. We propose that all of these observations resulted from the capture by Lake Gosiute of a river that drained higher elevations in central or north-central Idaho. Mass-balance modeling of Eocene Lake Gosiute indicates that capture of a river with an annual average discharge of ∼20 billion m3/a (slightly larger than the modern Snake River) and δ18O of –24‰ standard mean ocean water (SMOW) or lower would be capable of producing the observed change. A more likely alternative is a river with less negative δ18O and greater discharge. For example, if river waters had a δ18O composition of ∼−16‰, an estimated river discharge of ≥50 billion m3/a would produce the same effect. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.