10Be analysis of a Quaternary weathering profile in the Virginia Piedmont
Samples from a residual weathering profile in the Virginia Piedmont have been analyzed for cosmogenic 10 Be. Concentrations are highest in clay-rich soil and decrease exponentially to a depth of about 15 m. Despite uncertainties about the processes by which 10 Be may be intercepted before entering the solum and eroded after incorporation, a minimum age may be calculated for the regolith. This calculation is based on the delivery rate of 10 Be and its decay rate and suggests that this residual profile developed during a period no shorter than 8 × 10 5 yr. The calculated minimum age may be within a factor of 2 of maximum-age estimates based on surface lowering by erosion and on the rate of rock weathering to saprolite. The vertical distribution of 10 Be in the profile could result from a steady-state balance of deposition, weathering, radioactive decay, and erosion.