Early Pleistocene incision of the San Juan River, Utah, dated with 26Al and 10Be
- 1Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana 47907, USA
Abstract
Cosmogenic 26Al and 10Be in alluvial gravel on a strath 150 m above the San Juan River, Utah, reveal a depositional age of 
Ma. This gravel is correlative with a series of terraces that grade to Glen Canyon on the Colorado River, indicating a similar
age for incision there. The calculated incision rate, 110 ± 14 m/m.y., is somewhat slower than that of the Colorado River
in the eastern Grand Canyon and suggests active steepening of the Colorado River. The cosmogenic nuclides also indicate rapid
erosion in the sediment source area and are consistent with alluviation due to enhanced Pleistocene erosion in the San Juan
Mountains.
Footnotes
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↵GSA Data Repository item 2004130, Appendix DR1, sample preparation and data analysis, 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, CO 80301-9140, USA.
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- Accepted May 4, 2004.
- Received February 6, 2004.
- Revision received April 30, 2004.
- Geological Society of America
