GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 134-13
Presentation Time: 4:50 PM


SMITH, Alison J., Geology, Kent State University, Kent, OH 44242, ITO, Emi, Earth Sciences and Limnological Research Center, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455; Earth Sciences, University of Minnesota, 116 Church Street, SE, Minneapolis, MN 55455, FRITZ, Sherilyn C., Earth and Atmospheric Science Department, University of Nebraska-Lincoln, 126 Bessey Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0340; Geoscience, University of Nebraska-Lincoln, Lincoln, NE 68588, HATFIELD, Rob, College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, LAYZELL, Anthony L., Kansas Geological Survey, University of Kansas, 1930 Constant Ave, Lawrence, KS 66047, LOWENSTEIN, Tim K., Department of Geological Sciences and Environmental Studies, Binghamton University, Binghamton, NY 13902, MCGEE, David, Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, MOLNAR, Peter, Geological Sciences, University of Colorado, 2200 Colorado Ave, Boulder, CO 80309, STEFANOVA, Ivanka, CSDCO/LacCore, University of Minnesota, 500 Pillsbury Dr SE, Civil Engineering 672, Minneapolis, MN 55455, VALERO-GARCES, Blas Lorenzo, Pyrenean Institute of Ecology, Spanish National Research Council, Avda MontaƱana 1005, apdo 13034, Zaragoza, 50080, Spain, WERNE, Josef P., Department of Geology & Environmental Science, University of Pittsburgh, Pittsburgh, PA 15260 and WILLIAMS, John W., Department of Geography, University of Wisconsin-Madison, 550 N Park St, Madison, WI 53706

Geologic studies of the Pliocene North American West show the evidence of large permanent freshwater lakes and other sedimentological and ecological features of persistent wet conditions, which prevailed until the Quaternary. Basins of Pliocene age with hundreds of meters of paleolacustrine and paleofluvial-lacustrine sediments include among others: Lake Idaho, Idaho; Butte Valley Lake, Tule Lake, Searles Lake, California; Blythe Basin and Verde Valley, Arizona. Paleolimnological studies based on analyses of pollen, ostracodes, diatoms, sediments, vertebrates and stable isotopes have shown the temporal linkage of these sites, but a clear understanding of how these wet conditions could be sustained for 105 to 106 years is lacking. Two proposed mechanisms for a wetter North American West during the Pliocene include permanent El Niño-like conditions, or a lower meridional temperature gradient, leading to expanded Hadley Cell expanding the tropical rain bands, bringing summer rain to the southern Great Basin, and pushing the zone of winter precipitation farther north.

We describe the opportunities presented by these sites for exploring the hydroclimatic conditions of the Pliocene North American West. By considering possible global and hemispheric precipitation processes, we may be able to understand future hydroclimatic changes in the North American West, in a warming world that already shows similarities with the Pliocene Epoch. We hope to generate interest in linking ongoing studies of the western lake basins with those of the Blythe Basin, including the Bouse Formation,and the Pliocene history of the Colorado River, the focus of this session. The considerable and sustained amount of water moving through the Blythe Basin during the early development of the Colorado River in the Pliocene Epoch may be linked to the hydroclimatic processes that supplied and maintained the large lake basins further west during this time. In order to capture a broad understanding of how the North American West responded to wetter and warmer conditions of the Pliocene, future drilling sites should include the Blythe Basin.