Meteoric Be-10 from Sirius Group suggests high elevation McMurdo Dry Valleys permanently frozen since 6 Ma

A long-standing debate concerning Neogene Antarctic climate in the McMurdo Dry Valleys relies largely on evidence from landscape evolution, glacial modeling and stratigraphy. We provide new evidence from meteoric 10Be for the onset of frozen, hyper-arid conditions on a high elevation (1840 m) interfluve at Table Mountain. A simple decay model for the co-occurrence of meteoric 10Be and illuviated clay in cores of ice-cemented glacial sediments indicates that the clays were actively migrating down from the surface in a warm climate until the system froze between 6 and 9 Ma. Although this age range may be sensitive to possible interference by in situ produced 10Be, the implied minimum age of 6 Ma for the Sirius Group indicates that the Dry Valleys were permanently frozen down to this elevation at this time. The model also suggests denudation rates of 1–6 cm Myr−1 since freezing. These data provide an independent test of glacial-stratigraphic evidence used to determine Antarctic paleoclimate.