Beryllium isotopes are often used to estimate rates of landscape change, but results from different beryllium isotope systems have rarely been compared. Here, we combine measurements of in situ and meteoric 10Be (10Bei and 10Bem, respectively) with the reactive and mineral phases of 9Be (9Bereac and 9Bemin, respectively) to elucidate short- and long-term rates of erosion and sediment transport in the Potomac River basin on the North American passive margin. Sixty-two measurements of 10Bei in alluvium show that the Potomac watershed is eroding on average at 11 m m.y.−1 (∼30 Mg km−2 yr−1), which is consistent with regional erosion rate estimates. The 10Bei erosion rates correlate with basin latitude, suggesting that periglacial weathering increased proximal to the Laurentide ice sheet. The average of 55 10Bem/9Bereac-derived sediment generation rates (26.2 ± 18.3 Mg km−2 yr−1) is indistinguishable from the average of 62 10Bei rates; however, 10Bem/9Bereac- and 10Bei-based sediment generation rates are uncorrelated for individual basins. The lack of correlation on a basin-by-basin basis suggests biogeochemical assumptions inherent to the 10Bem/9Bereac technique are not valid everywhere. Contemporary sediment yields (n = 10) are up to 10 times greater than 10Bei- or 10Bem-derived sediment generation rates. However, we find that benchmark levels set to manage sediment export into Chesapeake Bay are within the uncertainty of long-term sediment generation rates. Erosion indices derived from 10Bem measurements range from 0.07 to 1.24, signifying that sediment retention occurs throughout the basin, except in the Appalachian Plateau. Paleo−erosion indices, calculated from the 150 k.y. Hybla Valley sediment core, suggest sediment excavation and storage under colder and warmer climate conditions, respectively.
- Received 6 April 2016.
- Revision received 2 September 2016.
- Accepted 18 November 2016.
- © Geological Society of America