Terrestrial ages and exposure ages of Antarctic H-chondrites from Frontier Mountain, North Victoria Land

• Main Authors: Welten,Kees C., Nishiizumi,Kunihiko, Caffee,Marc W., Schafer,Joerg, Wieler,Rainer
• Format: Report
• Language: English
• Published: Space Sciences Laboratory, University of California/Space Sciences Laboratory, University of California/Geosciences and Environmental Technologies and Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory/ETH Zurich, Isotope Geochemistry/ETH Zurich, Isotope Geochemistry 1999
• Subjects: Antarctic; East Antarctica; Victoria Land; Frontier Mountain; Antarc*; Antarctica
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=5947; http://id.nii.ac.jp/1291/00005947/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=5947&item_no=1&attribute_id=18&file_no=1

We measured the isotopic compositions and concentrations of He, Ne and Ar as well as the concentrations of cosmogenic ^<10>Be, ^<26>Al and ^<36>Cl in 26 H-chondrites and 1 L-chondrite from a meteorite stranding area near the Frontier Mountain Range, East Antarctica. Based on the radionuclide concentrations and the noble gas signatures we conclude the 26 H-chondrite samples represent at least 13 different falls. The exposure ages of most H-chondrites are in the range of 4-10 million years (My). This age range encompasses the well-established exposure age peak at ∿7 My and an additional feature at ∿4 My. We determined the terrestrial ages on the basis of the ^<36>Cl concentration as well as using the relation between the ^<36>Cl/^<10>Be ratio and the ^<10>Be concentration. This relation also corrects for shielding effects and reduces the uncertainty in the age by ∿25% compared to simple ^<36>Cl terrestrial ages. About 40% of the meteorites are older than 100 thousand years (ky), but none are older than 200ky. The relatively short terrestrial ages suggest that Frontier Mountain is a young meteorite stranding area. This seems to be supported by the bedrock exposure history, which shows a recent surface exposure≤70ky.