title: Synchronizing rock clocks of Earth history.
abstract: Calibration of the geological time scale is achieved by independent radioisotopic and astronomical dating, but these techniques yield discrepancies of approximately 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 approximately 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 approximately 65.95 Ma for the Cretaceous/Tertiary boundary.
authors.affiliation: Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands.
authors.forename: K F
authors.initials: KF
authors.lastname: Kuiper
authors.forename: A
authors.initials: A
authors.lastname: Deino
authors.forename: F J
authors.initials: FJ
authors.lastname: Hilgen
authors.forename: W
authors.initials: W
authors.lastname: Krijgsman
authors.forename: P R
authors.initials: PR
authors.lastname: Renne
authors.forename: J R
authors.initials: JR
authors.lastname: Wijbrans