Researchers at The University of Texas at Austin have re-dated the subsurface Ames impact structure in Oklahoma, finding the meteor crater formed approximately 370 million years ago during the Late Devonian rather than 467 million years ago, decoupling the site from the Ordovician Meteor Event and aligning it with a major mass extinction.
Re-dating a Buried Oklahoma Crater via Zircon Crystals
Deep beneath the surface, an impact crater spanning roughly 9 miles across has sat hidden under sedimentary strata since oil companies first discovered it in 1991. Known as a major oil and gas producer, the Ames structure had long been categorized as part of the Ordovician Meteor Event. That grouping placed its origin around 467.5 million years ago, alongside a series of significant meteor impacts that peppered North America.
A research team led by Elizabeth Catlos, an associate professor at the University of Texas at Austin, approached the site with a high-precision dating technique. The researchers analyzed microscopic zircon crystals found in impacted granites. Because zircon traps uranium that steadily decays into lead at a known rate, it functions as a geological stopwatch that records the timing of extreme heat and shock pressures.
The investigators found that zircon crystals clustered near 369.7 million years.
Why Fossil Evidence Provided the Wrong Age for Decades
The assumption that Ames belonged to the Ordovician period rested on biochronology. Previous investigators recovered fossilized teeth from conodonts—tiny, eel-like ancient creatures—within the rock. Because those creature remains originated in the Ordovician, researchers assumed the crater formed at the same time.
According to Catlos and her team, the teeth likely possessed an age of millions of years prior to the asteroid impact at Ames, merely becoming mixed up within the impact debris while staying intact. Under that scenario, the conodonts recorded the age of the strata that were struck rather than the exact moment of the collision.
Danny Stockli, dean of the Jackson School of Geosciences and co-author of the study, noted that microstructures in shocked zircon provide a reliable tool for establishing planetary timelines. “These small crystals allow us to go back in time and learn about the major changes to Earth’s ancient landscapes,” Stockli explained.
Connecting the Ames Impact to the Frasnian-Famennian Extinction
Moving the Ames crater forward by nearly 100 million years places its formation squarely within the Late Devonian epoch, right around 370 million years ago. This updated chronology temporalizes the structure in tandem with the Frasnian-Famennian mass extinction event, taking place roughly 372 million years ago and wiping out a massive share of marine organisms globally.
While the study notes the meteor was too small to drive global extinction on its own, the chronological overlap injects a fresh data point into debates regarding whether extraterrestrial strikes or massive internal volcanism drove the era’s biological crisis. Catlos described the adjustment by noting that the team is taking a major pawn out of the Ordovician Meteor Event and placing it into the Frasnian-Famennian timeline.
Researchers suggest that applying similar high-precision radiometric dating to other meteor impact sites across the continent could resolve discrepancies in how scientists interpret ancient environmental stress and geological history.