Quantifying denudation rates on inselbergs in the central Namib Desert using in situ-produced cosmogenic Be-10 and Al-26

In situ-produced cosmogenic isotope concentrations in bedrock surfaces prov ide valuable estimates of site-specific, long-term rates of denudation and provide constraints for numerical landscape evolution models. Measurements of cosmogenic Be-10 and Al-26 from granite inselbergs in the arid to hypera rid central Namib Desert, Namibia, indicate a mean rate of summit lowering of 5.07 +/- 1.1 m/m.y. over the past greater than or equal to 10(5) yr. The persistence of an arid climate in the region suggests that a similar rate may have prevailed for the past similar to 10 m.y. and possibly throughout much of the Cenozoic. Some samples have complex exposure histories that can be explained by the mode of inselberg weathering and mass wasting. The den udation rates estimated here are an order of magnitude higher than those re ported for inselbergs in a significantly more humid environment in South Au stralia. This difference may largely be due to active salt weathering in th e central Namib as a result of high levels of coastal fog precipitation.