Cosmogenic nuclides ¹⁰Be and ²⁶Al imply limited Antarctic Ice Sheet thickening and low erosion in the Shackleton Range for >1 m.y.

Abstract

Concentrations of the cosmogenic nuclides ¹⁰Be and ²⁶Al on bedrock surfaces in the Shackleton Range, Antarctica, indicate minimum exposure ages between 3.0 ± 0.3 and 1.16 ± 0.10 Ma. The isotope data indicate that the maximum long-term erosion rate is 0.10–0.35 m/m.y., and the ratios suggest no prolonged periods of burial by cold-based ice. The findings are important because of the location of the massif close to the junction of the East Antarctic Ice Sheet and the landward extent of the Filchner Ice Shelf. These results point to three conclusions. First, the massif has not been overridden by the East Antarctic Ice Sheet during the late Quaternary. Rather, moraines 200–340 m above outlet glaciers are likely to represent the maximum thickening of the Filchner-Ronne Ice Shelf during the Quaternary. Second, the high radionuclide concentrations on bedrock surfaces, one of which is striated, suggest that some glacial landforms were created in at least Pliocene or more likely Miocene time. Third, the exceptionally low erosion rates imply that the modern cold, arid climate has persisted for millions of years. These findings provide evidence of old, stable landscapes over a wider area of Antarctica than the McMurdo Dry Valleys.