Precipitation Control on Weathering Intensity and Depositional Flux of Meteoric 10Be Revealed From Soil Profiles Along a Climate Gradient (Chile)

Abstract

Along a climate gradient in the Chilean coastal mountains, we investigated denudation rates using the meteoric cosmogenic nuclide 10Be and its ratio to stable 9Be, and chemical depletion fractions (CDFs) in bulk soil samples. We find that the fraction of 9Be released from bedrock is a sensitive indicator of weathering, similar to CDF. Meteoric 10Be decreases exponentially with depth, reflecting the reactive nature of this tracer. We also measured denudation rates by the well-understood in situ cosmogenic 10Be system on quartz. Assuming that both systems record the same denudation rate we calculated the depositional flux of meteoric 10Be for each study site. The flux agrees to that derived from atmospheric models in the mediterranean and humid areas. In contrast, in the arid and semi-arid areas, the calculated flux agrees with a precipitation-derived flux, indicating delivery of 10Be to be affected by small-scale climatic variations not reflected by current atmospheric models.