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GEOREF RECORD

(super 10) Be dating of late Pleistocene megafloods and Cordilleran ice sheet retreat in the northwestern United States

Andrea M. Balbas, Aaron M. Barth, Peter U. Clark, Jorie Clark, Marc Caffee, Jim O'Connor, Victor R. Baker, Kevin Konrad and Bruce Bjornstad
(super 10) Be dating of late Pleistocene megafloods and Cordilleran ice sheet retreat in the northwestern United States
Geology (Boulder) (May 2017) 45 (7): 583-586

Abstract

During the late Pleistocene, multiple floods from drainage of glacial Lake Missoula further eroded a vast anastomosing network of bedrock channels, coulees, and cataracts, forming the Channeled Scabland of eastern Washington State (United States). However, the timing and exact pathways of these Missoula floods remain poorly constrained, thereby limiting our understanding of the evolution of this spectacular landscape. Here we report cosmogenic (super 10) Be ages that directly date flood and glacial features important to understanding the flood history, the evolution of the Channeled Scabland, and relationships to the Cordilleran Ice Sheet (CIS). One of the largest floods occurred at 18.2 + or - 1.5 ka, flowing down the northwestern Columbia River valley prior to blockage of this route by advance of the Okanogan lobe of the CIS, which dammed glacial Lake Columbia and diverted later Missoula floods to more eastern routes through the Channeled Scabland. The Okanogan and Purcell Trench lobes of the CIS began to retreat from their maximum extent at ca. 15.5 ka, likely in response to onset of surface warming of the northeastern Pacific Ocean. Upper Grand Coulee fully opened as a flood route after 15.6 + or - 1.3 ka, becoming the primary path for later Missoula floods until the last ones from glacial Lake Missoula at 14.7 + or - 1.2 ka. The youngest dated flood(s) (14.0 + or - 1.4 ka to 14.4 + or - 1.3 ka) came down the northwestern Columbia River valley and were likely from glacial Lake Columbia, indicating that the lake persisted for a few centuries after the last Missoula flood.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 45
Serial Issue: 7
Title: (super 10) Be dating of late Pleistocene megafloods and Cordilleran ice sheet retreat in the northwestern United States
Affiliation: Oregon State University, College of Earth, Ocean and Atmospheric Sciences, Corvallis, OR, United States
Pages: 583-586
Published: 20170508
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 29
Accession Number: 2017-046433
Categories: Quaternary geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2017193
Illustration Description: illus. incl. geol. sketch map
N44°30'00" - N49°00'00", W116°01'60" - W104°01'60"
Secondary Affiliation: Purdue University, USA, United StatesU. S. Geological Survey, USA, United StatesUniversity of Arizona, USA, United StatesIce Age Floodscapes, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201725
Program Name: USGSOPNon-USGS publications with USGS authors

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