HR: 0800h
AN: GC41A-0097    [Abstracts]
TI: Late-Quaternary Environmental Change in the Sierra Nevada: A 19,000-Year Sedimentary Organic Matter Record From Swamp Lake, Yosemite National Park, California
AU: * Street, J H
EM: jstreet@stanford.edu
AF: Department of Geological & Environmental Sciences, Stanford University, Stanford, CA 94305, United States
AU: Anderson, R S
EM: scott.anderson@nau.edu
AF: Center for Environmental Sciences and Education, Northern Arizona University, Flagstaff, AZ 86011, United States
AU: Starratt, S W
EM: sstarrat@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, United States
AU: Paytan, A
EM: apaytan@ucsc.edu
AF: Institute of Marine Sciences, University of California, Santa Cruz, Santa Cruz, CA 95064, United States
AB: Paleoclimate and environmental change in California over the last several millennia have received intensive study, in part because future climate warming in this drought-vulnerable region is likely to be expressed most acutely through rearrangements in the hydrological cycle (e.g., changes in the amount and timing of precipitation, snowmelt, and runoff). The 19,000-year sedimentary record from Swamp Lake, a small mid-elevation (1554 m) lake in the central Sierra Nevada, provides a rare opportunity to examine the relationships among climate variability, drought, and ecosystem response over a longer timeframe, spanning deglaciation and the Holocene, including several periods in which the Sierra Nevada is thought to have been warmer and drier than the present. Lake sedimentary organic matter (SOM) preserves paleoenvironmental information in a variety of elemental, isotopic, molecular, and microfossil indicators. In this study we utilize carbon and nitrogen elemental abundances and isotopic compositions (δ¹³C, δ¹⁵N) of bulk organic matter, along with measurements of biogenic silica (BSi), diatom and pollen assemblages, and magnetic susceptibility to reconstruct changes in lake productivity, organic matter sources, and plant and algal community composition in relation to climatic variables. We will also present preliminary measurements of the hydrogen isotope ratios (δD) of specific biomarker compounds extracted from the sediment, providing more direct information about the hydrologic status of the lake and watershed. In addition to tracing the post-glacial recovery and Holocene evolution of Sierra Nevada ecosystems, the Swamp Lake SOM record contains significant millennial- and century-scale variability that may correspond to periods of enhanced/suppressed ENSO activity.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 4914 Continental climate records
DE: 4942 Limnology (0458, 1845, 4239)
DE: 4950 Paleoecology
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting