SOIL RESIDENCE TIMES OF UNCULTIVATED HILLSLOPES IN NAVARRES, SP, AND ARIZONA, US, USING METEORIC 10-BERYLLIUM

Soil erosion and soil production rates dictate long-term hillslope coverage and downslope sedimentation of landscapes. Anthropogenic forcings have evolved, but the most extensive human actions remain subsistence-level agriculture and animal grazing. What is the long-term cumulative effect of grazing, agriculture, and other human land use on the landscape? Semi-arid environments and carbonate landscapes collectively cover a large part of the inhabited earth, where erosion responds to land use. Quantification of soil production and erosion on a millennial timescale can characterize land use history. This preliminary study estimates the soil residence times of two currently uncultivated hillslopes in regions with diverse land use histories; we chose the Sonoran Desert (Mescal Mountains, AZ) and the Navarres Valley, Spain, for the thousands of years’ gulf in initiation of domesticated grazing and the disparity in farming duration and extent. Soil residence times and rates and depths of physical mixing are interpreted through meteoric ¹⁰Be concentrations of the two hillslope crests and a soil profile. The significant uncertainty of dust concentration and quantity is examined in the context of these soils. Other authors have explored the mixing meteoric 10Be concentrations in fluvial systems. We extend that interest to an alluvial profile with a radiocarbon age constraint and compare the concentrations and variability at depth to modern soils.