Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica

Buizert, C.; Baggenstos, D.; Jiang, W.; Purtschert, R.; Petrenko, V. V.; Lu, Z.-T.; Muller, P.; Kuhl, T.; Lee, J.; Severinghaus, J. P.; Brook, E. J. (2014). Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica. Proceedings of the National Academy of Sciences of the United States of America - PNAS, 111(19), pp. 6876-6881. National Academy of Sciences NAS 10.1073/pnas.1320329111

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We present successful 81 Kr-Kr radiometric dating of ancient polarice. Krypton was extracted from the air bubbles in four∼350-kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The 81 Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean abso-lute age offset of 6±2.5 ka. Our experimental methods and sampling strategy are validated by (i) 85 Kr and 39 Ar analyses that show the samples to be free of modern air contamination and (ii)air content measurements that show the ice did not experience gas loss. We estimate the error in the 81 Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130–115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA 81Kr analysis requires a 40–80-kg ice sample; as sample requirements continue to decrease, 81 Kr dating of ice cores is a future possibility.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics

UniBE Contributor:

Purtschert, Roland

Subjects:

500 Science > 530 Physics

ISSN:

0027-8424

Publisher:

National Academy of Sciences NAS

Language:

English

Submitter:

Doris Rätz

Date Deposited:

18 Dec 2015 15:50

Last Modified:

18 Dec 2015 15:50

Publisher DOI:

10.1073/pnas.1320329111

BORIS DOI:

10.7892/boris.74092

URI:

https://boris.unibe.ch/id/eprint/74092

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