Holocene History of Bison Lake, White River Plateau, Colorado Based on Seismic Reflection Profiles and XRF Elemental Data

The future of water availability in the southwestern United States is of serious concern, especially given recent droughts and uncertainty over the effect of climate change on regional precipitation. Much of the southwestern U.S. receives its water supply from the headwaters of the Colorado River. Lake sediments in this region have the potential to extend our understanding of the spatial patterns and severity of Holocene droughts. Bison Lake (39.764˚N, 107.347˚W, 3255 m a.s.l.) is located on the White River Plateau at the headwaters of Deep Creek, a tributary of the Upper Colorado River. In 2006, two sediment cores were collected from the deepest basin (~9 m water depth) and a shallow bench (3.8 m water depth) in the lake. The cores span the Holocene and are undergoing multi-proxy sediment analysis, including oxygen and carbon isotope ratios of endogenic carbonate. Sediment elemental data were obtained using a high-resolution x-ray fluorescence (XRF) core scanner. This broad range of data indicates Bison Lake levels have varied during the Holocene.

To further explore variations in lake conditions identified by the sediment core data, an acoustic sonar geophysical survey was carried out in July 2008. Geophysical data provide high-resolution images of lake sediments that identify complexities in erosional and sedimentary processes within the lake basin. The seismic data are anticipated to identify facies changes that correlate with the sediment cores to reconstruct the effective moisture history of Bison Lake and the White River Plateau region.