K. Nishiizumi, C.P. Kohl, J.R. Arnold, University of California, San Diego

J. Klein, D. Fink, R. Middleton, University of Pennsylvania

Earth and Planetary Science Letters, 104 (1991) 440-454

We have measured cosmic ray produced (t1/2 ~1.5 million years) 10Be and (t1/2 = 0.705 million years) 26Al in purified quartz fractions of selected rock samples from Antarctic mountains. From these data we calculate (1) mean erosion rates, for the limiting case of steady-state surface exposure to cosmic rays. and (2) minimum exposure ages, for the limiting case of no erosion. Calculated mean erosion rates are very low, on the order of a few times 10-5 cm/yr; we believe the sampling to be sufficient to generalize this result to exposed bedrock in Antarctica. In favorable cases it is possible to distinguish between the limiting cases: steady-state erosion seems a better description in such cases. Most samples, including some taken a few meters above the present ice level, seem to have been exposed for millions of years. without major episodes of burial or abrasion by ice.