Geophysical evidence for Holocene lake-level change in southern California (Dry Lake) |
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| Authors: | BROXTON W BIRD MATTHEW E KIRBY IAN M HOWAT SLAWEK TULACZYK |
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| Institution: | University of Pittsburgh, Department of Geology and Planetary Science, Pittsburgh, PA 15260, USA;;California State University, Fullerton, Department of Geological Sciences, Fullerton, CA 92834, USA;;The Ohio State University, School of Earth Sciences &Byrd Polar Research Center, Columbus, OH 43210, USA;;University of California, Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA 95064, USA |
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| Abstract: | Bird, B. W., Kirby, M. E., Howat, I. M. & Tulaczyk, S. 2009: Geophysical evidence for Holocene lake-level change in southern California (Dry Lake). Boreas , 10.1111/j.1502-3885.2009.00114.x. ISSN 0300-9483.
Ground penetrating radar (GPR) data are used in combination with previously published sediment cores to develop a Holocene history of basin sedimentation in a small, alpine lake in southern California (Dry Lake). The GPR data identify three depositional sequences spanning the past 9000 calendar years before present (cal. yr BP). Sequence I represents the first phase of an early Holocene highstand. A regression between <8320 and >8120 cal. yr BP separates Sequence I from Sequence II, perhaps associated with the 8200 cal. yr BP cold event. Sequence II represents the second phase of the early-to-mid Holocene highstand. Sequence IIIa represents a permanent shift to predominantly low lake stands beginning ～5550 cal. yr BP. This mid-Holocene shift was accompanied by a dramatic decrease in sedimentation rate as well as a contraction of the basin's area of sedimentation. By ～1860 cal. yr BP (Sequence IIIb), the lake was restricted to the modern, central basin. Taken together, the GPR and core data indicate a wet early Holocene followed by a long-term Holocene drying trend. The similarity in ages of the early Holocene highstand across the greater southern California region suggests a common external forcing – perhaps modulation of early Holocene storm activity by insolation. However, regional lake level records are less congruous following the initial early Holocene highstand, which may indicate a change in the spatial domain of climate forcing(s) throughout the Holocene in western North America. |
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