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

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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.