PRESERVATION OF MIOCENE GLACIER ICE IN EAST ANTARCTICA

ANTARCTIC climate during the Pliocene has been the subject of consider able debate. One view holds that, during part of the Pliocene, East An tarctica was largely free of glacier ice and that vegetation survived on the coastal mountains(1-4). An alternative viewpoint argues for the development of a stable polar ice sheet by the middle Miocene, which has persisted since then(5-10). Here we report the discovery of buried glacier ice in Beacon valley, East Antarctica, which appears to have survived for at least 8.1 million years. We have dated the ice by Ar-4 0/Ar-39 analysis of volcanic ash in the thin, overlying glacial till w hich, we argue, has undergone little (if any) reworking. Isotope and c rystal fabric analyses of the ice show that it was derived from an ice sheet. We suggest that stable polar conditions must have persisted in this region for at least 8.1 million years for this ice to have avoid ed sublimation.