10Be and 26Al Evidence for Exceptionally Low Rates of Australian Bedrock Erosion and the Likely Existence of Pre-Pleistocene Landscapes

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Abstract
Analysis of in situ-produced 10Be and 26Al demonstrate that some Australian inselbergs (granitic domes) are among the most stable geomorphic surfaces in the world, eroding at rates as low as 0.6 m/myr. Twenty isotopic analyses of ten samples suggest that the bare bedrock tops of these isolated granitic domes have been exposed to cosmic radiation for at least 0.5 myr and are eroding at a mean model rate less than 0.7 ± 0.1 m/myr (n = 6). Isotopic analyses of samples collected from the top of Mt. Wudinna, Little Wudinna, and Yarwondutta Rock are most consistent with continuous exposure during erosion. On the other hand, samples collected from the flanks of some domes and the tops of other domes have isotopic abundances suggestive of complex exposure histories including burial and reexposure. These unique isotopic data provide the first quantitative information for evaluating longstanding, but previously untested, hypotheses regarding the antiquity and development of these enigmatic landforms and indicate that some Eyre Peninsula inselbergs are probably relict features of pre-Pleistocene landscapes.

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