Pace of landscape evolution in the Sierra Nevada, California, revealed by cosmogenic dating of cave sediments
- 1 Department of Earth Sciences, University of California Santa Cruz, Santa Cruz, California 95064, USA
- 2Center for Accelerator Mass Spectrometry and Geosciences and Environmental Technology, Lawrence Livermore National Laboratory, Livermore, California 94550, USA
Abstract
We report 26Al/10Be based ages of Sierra Nevada caves that constrain detailed late Pliocene and Quaternary river incision histories for five river canyons. Rapid incision of ∼0.2 mm/yr from 2.7 to ca. 1.5 Ma slowed markedly to ∼0.03 mm/yr thereafter, likely reflecting the combined effects of a transient erosional response to Pliocene rock uplift and periodic mantling of riverbeds with glacially derived sediment in the late Quaternary. While ∼400 m of incision has occurred in the past 2.7 m.y., outpacing interfluve erosion and thereby increasing the local relief, canyons as deep as 1.6 km existed prior to that time. These new erosion rates strengthen the case for tectonically driven late Cenozoic uplift.
Footnotes
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↵*Present address: Anderson—Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309, USA
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↵GSA Data Repository item 2004032, Table DR1, Table DR2, and Appendix 1, methods, is available online at www.geosociety.org/pubs/ft2004.htm, or on request from editinggeosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, Colorado, 80301-9140, USA.
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- Accepted November 18, 2003.
- Received September 12, 2003.
- Revision received November 12, 2003.
- Geological Society of America
