Spatial and temporal variability in denudation across the Bolivian Andes from multiple geochronometers

Abstract

We quantify spatial and temporal variations in denudation rates across the central Andean fold-thrust belt in Bolivia with particular focus on the Holocene. Measured and predicted 10Be cosmogenic radionuclide (CRN) concentrations in river sediments are used to (1) calculate catchment-averaged denudation rates from 17 basins across two transects at different latitudes, and (2) evaluate the sensitivity of Holocene climate change on the denudation history recorded by the CRN data. Estimated denudation rates vary by two orders of magnitude from 0.04 to 1.93 mm yr − 1 with mean values of 0.40 ± 0.29 mm yr − 1 in northern Bolivia and 0.51 ± 0.50 mm yr − 1 in the south. Results demonstrate no statistically significant correlation between denudation rates and morphological parameters such as relief, slope or drainage basin size. In addition, the CRN-derived denudation rates do not reflect present-day latitudinal variations in precipitation. Comparison to ∼ 130 previously published denudation rates calculated over long (thermochronology-derived; > 10 6 yrs), medium (CRN-derived; 10 2–10 4 yrs), and short timescales (sediment flux-derived; 10 1 yrs) indicate temporal variations in denudation rates that increase between 0 and 200% over the last ∼ 5 ka. CRN modeling results suggest that the CRN-derived denudation rates may not be fully adjusted to wetter climate conditions recorded in the central Andes since the mid-Holocene. We conclude that large spatial variability in CRN denudation may be due to local variations in tectonics (e.g. faulting), while large temporal variability in denudation may be due to temporal variations in climate.