Abstract:

Up to date, meteorite scientists have searched about 2500km 2 of blue ice and recovered more than 30000 meteorite specimens from different locations on the Antarctic ice sheet. In the past two decades ,terrestrial ages of a few hundred meteorites were determined, mainly on the basis of the 36 Cl or 14 C concentrations. Each stranding area shows a different terrestrial age distribution and provides the information of the local accumulation mechanisms. The Antarctic meteorite density on the blue ice surface are determined by many factors, such as the meteorite fall rate, the ice ablation rate and the snow accumulation rate. Meteorites from Yamato Mountains Icefields have ages up to 200ka,whereas Lewis Cliff and Allan Hills specimens have ages up to 500ka and 1Ma, respectively. Recently, two meteorites have been discovered with exceptional ages of about 2Ma from Allan Hills and 2.35Ma from Lewis Cliff, which indicate that they are deeply inside the ice, near the base of glacier and ice flow rates are much lower than at surface. Their terrestrial ages also indicate the process of meteorite accumulation into present day stranding areas started at least 2 million years ago and the long terrestrial ages are consistent with an assumption concerning the stability and persistence of the East Antarctic ice sheet. The residence time on the surface is an important parameter in determining the history of the meteorite. In addition, terrestrial ages can be used to estimate the average transport time of meteorites from accumulation to ablation area and the mean weathering lifetime.