Brown, E. T., R. F. Stallard, M. C. Larsen, D. L. Bourlès, G. M. Raisbeck, and F. Yiou. 1998. Determination of predevelopment denudation rates of an agricultural watershed (cayaguas river, puerto rico) using in-situ-produced 10Be in river-borne quartz. Earth and Planetary Science Letters 160 (3-4): 723-8.
Accurate estimates of watershed denudation absent anthropogenic effects are required to develop strategies for
mitigating accelerated physical erosion resulting from human activities, to model global geochemical cycles, and to
examine interactions among climate, weathering, and uplift. We present a simple approach to estimate predevelopment
denudation rates using in-situ-produced cosmogenic 10Be in fluvial sediments. Denudation processes in an agricultural
watershed (Cayagua´s River Basin, Puerto Rico) and a matched undisturbed watershed (Icacos River Basin) were compared
using 10Be concentrations in quartz for various size fractions of bed material. The coarse fractions in both watersheds
bear the imprint of long subsurface residence times. Fine material from old shallow soils contributes little, however, to the
present-day sediment output of the Cayagua´s. This confirms the recent and presumably anthropogenic origin of the modern
high denudation rate in the Cayagua´s Basin and suggests that pre-agricultural erosional conditions were comparable to
those of the present-day Icacos.