干旱区生态环境知识资源中心

Meteoric Be-10 concentrations in soil were measured to understand the mechanism, timescale, and climatic dependence of soil formation in the hyper-arid Atacama Desert. The observed systematic decline of soil Be-10 concentrations with depth has been reproduced using a simple model that assumes soil matrix, including Be-10, builds up as layers over time while Be-10 decays in situ. This suggests a mechanism of soil accumulation via atmospheric deposition, which is in agreement with stable isotopic evidence. The model estimates an age of similar to 6.6 +/- 0.4 Ma for the total soil profile. Small discrepancies between the model and observations are likely mainly due to changes in precipitation rates that can impact Be-10 delivery rates and Be-10 movement within the profile. Interpreted in this way, the Be-10 data suggest drying in the Atacama after similar to 4.7 Ma, and returning to an insignificant wet period at similar to 1 Ma, which was possibly connected to El Nino- or La Nina-like climate change. (C) 2015 Published by Elsevier Ltd.