Cosmic ray produced 10Be and 26Al in Antarctic rocks: exposure and erosion history

Abstract

We have measured cosmic ray produced (tsol1 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. © 1991.