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Science 25 April 2008:
Vol. 320. no. 5875, pp. 500 - 504
DOI: 10.1126/science.1154339
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Research Articles

Synchronizing Rock Clocks of Earth History

K. F. Kuiper,1,2 A. Deino,3 F. J. Hilgen,1 W. Krijgsman,1 P. R. Renne,3,4 J. R. Wijbrans2

Calibration of the geological time scale is achieved by independent radioisotopic and astronomical dating, but these techniques yield discrepancies of ~1.0% or more, limiting our ability to reconstruct Earth history. To overcome this fundamental setback, we compared astronomical and 40Ar/39Ar ages of tephras in marine deposits in Morocco to calibrate the age of Fish Canyon sanidine, the most widely used standard in 40Ar/39Ar geochronology. This calibration results in a more precise older age of 28.201 ± 0.046 million years ago (Ma) and reduces the 40Ar/39Ar method's absolute uncertainty from ~2.5 to 0.25%. In addition, this calibration provides tight constraints for the astronomical tuning of pre-Neogene successions, resulting in a mutually consistent age of ~65.95 Ma for the Cretaceous/Tertiary boundary.

1 Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands.
2 Faculty of Earth and Life Sciences, Institute of Earth Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands.
3 Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA.
4 Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)