Oklahoma Impact Crater Dated 100 Million Years Younger

Researchers at the University of Texas at Austin have dated the buried Ames impact structure in Oklahoma to about 370 million years ago, revising its estimated age by roughly 100 million years and placing the meteor strike near a major Late Devonian marine extinction. The findings do not establish that the impact caused the extinction. The team analyzed zircon crystals from rocks affected by the impact using uranium-lead dating and examined the crystals for changes associated with the shock of a meteor strike. With NASA imaging assistance, researchers looked for impact-related features in the zircons. The results pointed to an age near 370 million years across the methods described in the study, which was published in Meteoritics & Planetary Science. The new date moves Ames out of the Ordovician Meteor Event, a period around 467 million years ago associated with a cluster of impact sites across North America. The Ames structure had been assigned to that earlier period largely because researchers found conodont teeth in rock at the site.