Field evidence for climate-driven changes in sediment supply leading to strath terrace formation
- 1National Center for Earth-surface Dynamics, University of Minnesota, Minneapolis, Minnesota 55414, USA
- 2Optical Dating and Dosimetry Lab, Department of Geosciences, North Dakota State University, Fargo, North Dakota 58105, USA
- *Current address: Institut für Mineralogie, Leibniz Universität Hannover, D-30167, Hannover, Germany.
Abstract
Along the South Fork of the Eel River in northern California, paleoerosion rates derived from 10Be concentrations in late Pleistocene strath terrace sediment are a factor of 2 greater than erosion rates derived from modern stream sediment and 3.5 times greater than paleoerosion rates from the Pleistocene-Holocene transition. Using these results as a proxy for sediment supply, we provide quantitative field-based evidence that extensive strath planation is linked to elevated sediment supply conditions. We have used optically stimulated luminescence (OSL) to date strath terrace sediment and find that the highest erosion rates and most extensive period of strath planation occurred during a period of increased precipitation in the late Pleistocene. Based on our OSL data, we estimate that bedrock channel lowering rates have outpaced basin-averaged erosion rates by a factor of three since abandonment of the extensive late Pleistocene strath surface. Thus, our data indicate that hillslope relief has been increasing for the past ~20 ka.
Footnotes
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↵GSA Data Repository item 2009113, scaling factors, production rates, and raw geochemical data for 10Be samples, is available online at www.geosociety.org/pubs/ft2009.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
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- Received 3 September 2008.
- Revision received 2 January 2009.
- Accepted 5 January 2009.
- © 2009 Geological Society of America
