HR: 0800h
AN: PP31D-0654    [Abstracts]
TI: Geophysical Evidence for Holocene Lake-Level Change in Southern California (Dry Lake): Additional Evidence for a Regional Early Holocene High Stand
AU: * Kirby, M E
EM: mkirby@fullerton.edu
AF: California State University, Fullerton, Department of Geological Science, Fullerton, CA 92834, United States
AU: Bird, B W
EM: broxton.bird@gmail.com
AF: University of Pittsburgh, Department of Geology and Planetary Science, Pittsburgh, PA 15260, United States
AU: Howat, I M
EM: ihowat@apl.washington.edu
AF: University of Washington, Applied Physics Lab, Seattle, WA 98105, United States
AU: Tulaczyk, S
EM: tulaczyk@pmc.ucsc.edu
AF: University of California, Santa Cruz, Earth and Planetary Sciences, Santa Cruz, CA 95064, United States
AB: Ground penetrating radar data are used to develop a Holocene history of basin sedimentation in a small, alpine lake in Southern California (Dry Lake). We define three depositional sequences spanning the past 9,000 calendar years before present (cy BP). Although, the basin contains sediments clearly older than the Holocene, we focus on the past 9,000 cy BP to match our similarly aged sediment cores. Sequence I represents the first phase of an early Holocene high stand. A major regression, perhaps following the 8,200 year cold event, separates Sequence I from Sequence II. The timing of this regression is approximately coeval with major regressions at Owens Lake (Bacon et al., 2006) in southeastern California and Tulare Lake (Negrini et al., 2006) in the southern Central Valley of California. Sequence II represents the second phase of the early Holocene high stand. This second high stand phase is also observed at Tulare Lake but not at Owens Lake. Sequence III represents a permanent shift to low or dry lake stands. By 4,000 cy BP, the lake earns rightfully its appellation of Dry Lake as indicated by a permanently contracted central basin. The similarity in ages of early Holocene lake level change across the greater region of Southern California suggests a similar external forcing – perhaps modulation of early Holocene storm activity by insolation (Kirby et al., 2007). The lake level records are less congruous for the mid-to-late Holocene across the region. Specifically for Dry Lake, it is not clear what caused the apparently rapid shift from a deep, early Holocene lake to a permanent shallow or dry lake by the mid-Holocene.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1694 Instruments and techniques
DE: 1845 Limnology (0458, 4239, 4942)
DE: 9350 North America
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting