Glaciation history of Queen Maud Land (Antarctica) reconstructed from in-situ produced cosmogenic 10Be, 26Al and 21Ne

We present for the first time rock exposure ages primarily for the Wohlthat Massiv/Queen Maud Land, Antarctica, determined from 54 quartz rich samples via in-situ produced Be-10 (T-1/2 = 1.51 Ma) and Al-26 (T-1/2 = 0.7 Ma) using accelerator mass spectrometry (AMS). Measured radionuclide concentrations vary from extremely low values up to saturation. For a scenario with extremely low erosion and minimal tectonic uplift Be-10 and Al-26 surface exposure ages are generally in good agreement. Long exposure ages up to >8 Ma were confirmed by measurement of stable Ne-21 using noble gas mass spectrometry. Our data suggest that the regional highest mountain peaks had risen above the ice surface at least 1-4 Ma ago. Notwithstanding a 200-400 m higher ice sheet elevation persisted in the Wohlthat Massiv/Queen Maud Land until about 0.5 Ma ago. In our interpretation, the successive thinning of the ice sheet was probably in response to global cooling and less annual precipitation since the Pliocene. Our results are in line with published ice sheet modelling results predicting only modest changes in ice thickness in Queen Maud Land during the warmer'' Pliocene and during the transition to the cooler'' present. Low-level changes occurred during the last glacial maximum, but only affected the region located close to the present shelf ice. As the extremely low erosion rates (<5 cm Ma(-1)) inferred for several samples can only exist under extremely cold and hyperarid conditions, we exclude a scenario featuring a prolonged period with warm and humid climatic conditions within the last 8 Ma. Our data do not support the notion of a temporary large scale retreat of the East Antarctic ice sheet during a suspected warming episode in the Pliocene. (C) 2010 Elsevier B.V. and NIPR. All rights reserved.