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A quarter-million years of paleoenvironmental change at Bear Lake, Utah and Idaho

Darrell S. Kaufman, Jordon Bright, Walter E. Dean, Joseph G. Rosenbaum, Katrina A. Moser, R. Scott Anderson, Steven M. Coleman, Clifford W. Heil, Gonzalo Jimenez-Moreno, Marith C. Reheis and Kathleen R. Simmons
A quarter-million years of paleoenvironmental change at Bear Lake, Utah and Idaho (in Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment, Joseph G. Rosenbaum (editor) and Darrell S. Kaufman (editor))
Special Paper - Geological Society of America (2009) 450: 311-351


A continuous, 120-m-long core (BL00-1) from Bear Lake, Utah and Idaho, contains evidence of hydrologic and environmental change over the last two glacial-interglacial cycles. The core was taken at 41.95 degrees N, 111.31 degrees W, near the depocenter of the 60-m-deep, spring-fed, alkaline lake, where carbonate-bearing sediment has accumulated continuously. Chronological control is poor but indicates an average sedimentation rate of 0.54 mm yr (super -1) . Analyses have been completed at multi-centennial to millennial scales, including (in order of decreasing temporal resolution) sediment magnetic properties, oxygen and carbon isotopes on bulk-sediment carbonate, organic- and inorganic-carbon contents, palynology; mineralogy (X-ray diffraction), strontium isotopes on bulk carbonate, ostracode taxonomy, oxygen and carbon isotopes on ostracodes, and diatom assemblages. Massive silty clay and marl constitute most of the core, with variable carbonate content (average=31+ or -19%) and oxygen-isotopic values (delta (super 18) O ranging from -18 ppm to -5 ppm in bulk carbonate). These variations, as well as fluctuations of biological indicators, reflect changes in the water and sediment discharged from the glaciated headwaters of the dominant tributary, Bear River, and the processes that influenced sediment delivery to the core site, including lake-level changes. Although its influence has varied, Bear River has remained a tributary to Bear Lake during most of the last quarter-million years. The lake disconnected from the river and, except for a few brief excursions, retracted into a topographically closed basin during global interglaciations (during parts of marine isotope stages 7, 5, and 1). These intervals contain up to 80% endogenic aragonite with high delta (super 18) O values (average=-5.8+ or -1.7 ppm), indicative of strongly evaporitic conditions. Interglacial intervals also are dominated by small, benthic/tychoplanktic fragilarioid species indicative of reduced habitat availability associated with low lake levels, and they contain increased high-desert shrub and Juniperus pollen and decreased forest and forest-woodland pollen. The (super 87) Sr/ (super 86) Sr values (>0.7100) also increase, and the ratio of quartz to dolomite decreases, as expected in the absence of Bear River inflow. The changing paleoenvironments inferred from BL00-1 generally are consistent with other regional and global records of glacial-interglacial fluctuations; the diversity of paleoenvironmental conditions inferred from BL00-1 also reflects the influence of catchment-scale processes.

ISSN: 0072-1077
EISSN: 2331-219X
Serial Title: Special Paper - Geological Society of America
Serial Volume: 450
Title: A quarter-million years of paleoenvironmental change at Bear Lake, Utah and Idaho
Title: Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment
Affiliation: Northern Arizona University, Department of Geology, Flagstaff, AZ, United States
Affiliation: U. S. Geological Survey, Denver, CO, United States
Pages: 311-351
Published: 2009
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 58
Accession Number: 2010-045054
Categories: Quaternary geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. sect., sketch maps
N41°57'00" - N41°57'00", W111°19'00" - W111°19'00"
Secondary Affiliation: Northern Arizona University, USA, United StatesU. S. Geological Survey, USA, United StatesUniversity of Western Ontario, CAN, CanadaUniversity of Minnesota, USA, United StatesUniversity of Rhode Island, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201025
Program Name: USGSOPNon-USGS publications with USGS authors
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