COSMIC-RAY PRODUCED BE-10 AND AL-26 IN ANTARCTIC ROCKS - EXPOSURE AND EROSION HISTORY

We have measured cosmic ray produced (t1/2 = 1.5 million years) Be-10 and (t1/2 = 0.705 million years) Al-26 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.