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Science 23 July 2004:
Vol. 305. no. 5683, pp. 499 - 502
DOI: 10.1126/science.1097780
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Reports

Rapid Late Pleistocene Incision of Atlantic Passive-Margin River Gorges

Luke J. Reusser,1* Paul R. Bierman,1 Milan J. Pavich,2 E-an Zen,3 Jennifer Larsen,1 Robert Finkel4

The direct and secondary effects of rapidly changing climate caused large rivers draining the Atlantic passive margin to incise quickly into bedrock beginning about 35,000 years ago. Measured in samples from bedrock fluvial terraces, 10-beryllium shows that both the Susquehanna and Potomac Rivers incised 10- to 20-meter-deep gorges along steep, convex lower reaches during the last glacial cycle. This short-lived pulse of unusually rapid down-cutting ended by 13,000 to 14,000 years ago. The timing and rate of downcutting are similar on the glaciated Susquehanna and unglaciated Potomac Rivers, indicating that regional changes, not simply glacial meltwater, initiated incision.

1 Department of Geology and School of Natural Resources, University of Vermont, Burlington, VT 05401, USA.
2 U.S. Geological Survey (USGS), National Center, Reston, VA 20192, USA.
3 Department of Geology, University of Maryland, College Park, MD 20742, USA.
4 Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.

* To whom correspondence should be addressed. E-mail: lreusser{at}uvm.edu

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