Uranium-series dating of tephra-banded Allan Hills ice

• Main Author: Edward L. Fireman
• Format: Report
• Language: English
• Published: Smithsonian Astrophysical Observatory 1989
• Subjects: Allan Hills; Antarc*; Antarctica
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=4495; http://id.nii.ac.jp/1291/00004495/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=4495&item_no=1&attribute_id=18&file_no=1

Tephra-banded ice samples from the main Allan Hills icefield, Antarctica, are dated by a uranium-series method, which is based on the ^<226>Ra/^<230>Th and ^<226>Ra/^<234>U ratios dissolved in ice from tephra. The consistence between the age determined from the ^<226>Ra/^<230>Th ratio with the age determined from the ^<226>Ra/^<234>U ratio serves as a check on the method. For ice from a location at the western border of the 50-km^2 area that is richly laden with meteorites, the ^<226>Ra/^<230>Th and ^<226>Ra/^<234>U ages are (95±10)×10^3 and (100±10)×10^3 years, respectively. For ice from a location within this meteorite-rich area near its eastern border (approximately 5km closer to the Allan Hills land barrier), these ages are (185±25)×10^3 and (210±30)×10^3 years, respectively. The ice flow is from west to east, the dates indicate that most of the ice in the meteorite-rich area is between 1×10^5 and 2×10^5 years old with the age of the ice increasing in the flow direction as theoretically predicted for ice approaching a land barrier. The comparison of this ice chronology with the terrestrial ages of the meteorites leads to a number of conclusions about the meteorite fall rate and history of the ice movement.