Long-term sediment-generation rates derived from 10 Be in river sediment of the Susquehanna River basin Joanna M Reuter 1 , Paul R. Bierman 1 , Milan J. Pavich 2 , Allen C. Gellis 2 , Jennifer Larsen 1 , and Robert C. Finkel 3 1 University of Vermont, 2 USGS, 3 Lawrence Livermore National Laboratory Overview We are using cosmogenic 10 Be measurements of quartz extracted from sediments of the Susquehanna River basin to address geomorphic questions of where and how quickly Earth’s surface erodes. We seek to determine if long-term (10 4 -10 5 year) rates of sediment generation, as inferred from cosmogenic 10 Be, correlate with GIS-measurable components of the present-day landscape, such as topography, relief, and precipitation. Such correlations, or a lack thereof, will provide insight into the tempo and pattern of landscape erosion and change. Though we currently have results for only a small subset of the collected samples, the 10 Be-based sediment-generation rates (10-20 meters per million years) agree broadly with other erosion rate estimates for the Susquehanna basin. Basin-scale sediment-generation rates from in-situ-produced 10 Be The continual bombardment of Earth’s surface by cosmic rays results in the production and accumulation of cosmogenic nuclides in near-surface materials. One such nuclide, 10 Be, is often measured in purified quartz (Lal and Peters, 1967). In an eroding landscape, quartz grains accumulate 10 Be as they approach the surface (Lal, 1991). When such grains enter a river system, they carry isotopic concentrations that record their near-surface exposure histories (Bierman et al., 2001; Brown et al., 1995). Rivers collect, transport, and mix grains from various parts of the basin. The abundance of cosmogenic nuclides in stream sediments reflects the integrated cosmic ray dosing and thus, by inference, the erosional history of the basin. For example, slowly eroding basins have relatively high nuclide activities because quartz grains, on average, have spent a long time near the surface. Measurement of 10 Be in sediment provides sediment generation rates on a 10 3 -10 6 year time scale, depending on the erosion rate and the associated sediment residence time in the basin. Susquehanna River and sampled basins The Susquehanna River drains >70,000 km 2 of the North American passive margin (Figure 1). The basin spans three major physiographic provinces: the Appalachian Plateaus, Valley and Ridge, and Piedmont. We sampled two groups of drainage basins. The first 26 samples were collected from USGS gage sites representing basins that range in size from 15 km 2 to 62,400 km 2 (Figure 1