Beneath the quiet surface of the town of Ames, Oklahoma, lies a massive meteor impact structure that stretches for miles underground. Although thick layers of sediment and topsoil have long since covered the crater, it remains a site of immense scientific curiosity as well as economic vitality. Beyond its geological significance, the Ames impact structure functions as a major producer of oil and gas, tying the energy industry directly to the history of ancient cosmic collisions.
A Crater Long Linked to an Ancient Meteor Event
For many years, the geological consensus held that the Ames crater belonged to a vast cluster of major meteor impacts across North America, all dating back roughly 467.5 million years. That extended epoch is widely known among geologists as the Ordovician Meteor Event.
Because so many distinct impact structures across the continent appeared to share roughly the same chronological window, some researchers had previously proposed a dramatic hypothesis: that Earth may once have been surrounded by a Saturn-like ring of asteroid debris during the Middle Ordovician period. Such a ring, scientists theorized, could have showered the planet with a continuous series of high-energy impacts over an extended period.
However, new work from researchers at The University of Texas at Austin now conclusively demonstrates that the Ames impact does not belong to that ancient episode after all.
By carefully dating microscopic zircon crystals extracted from granite that had been altered by the extreme heat and pressure of the impact, the research team determined that the meteorite actually struck about 370 million years ago, during the Late Devonian period. That revised timeline makes the crater nearly 100 million years younger than previously believed.
"No matter what technique we used, it was coming back to this younger signal," said lead author Elizabeth Catlos, an associate professor in UT’s Department of Earth and Planetary Sciences.
The comprehensive research detailing these findings was published in July in the academic journal Meteoritics & Planetary Science.
Why the Earlier Date Was Misleading
Before this comprehensive study was conducted, the Ames impact structure had primarily been dated using biological evidence rather than direct radiometric measurements of the rock itself. Previous researchers had discovered the fossilized teeth of an ancient, eel-like animal known as a conodont preserved within the impact-altered rock layers. Because those specific fossils originated from organisms that lived during the older Ordovician period, scientists naturally assumed the impact occurred during that same timeframe.
However, Catlos explained that those fossilized teeth were likely already millions of years old by the time the asteroid actually collided with the region. The catastrophic force of the impact likely churned up pre-existing, older geological material and seamlessly mixed the ancient fossils into the younger impact breccia while miraculously preserving their structural integrity.
The advanced zircon dating techniques utilized in the new study provide a drastically different and far more reliable timeline. The data clearly shows that the Ames crater could not possibly have formed during the Ordovician Meteor Event.
Instead, its newly established age places its formation dangerously close to the Frasnian-Famennian mass extinction event. That devastating ecological collapse occurred approximately 372 million years ago and wiped out a staggeringly large proportion of marine life inhabiting Earth’s ancient oceans.
Tiny Zircon Crystals Preserve the Impact
Danny Stockli, dean of the Jackson School of Geosciences and a co-author of the study, emphasized that zircon uranium-lead (U-Pb) dating offers one of the absolute most accurate ways for geologists to determine when momentous events occurred deep in Earth’s past.
Beyond simply providing a precise numerical age, resilient zircon crystals possess the unique ability to preserve microscopic physical structures created by the hyper-intense pressures generated during a high-speed meteor impact.
"These small crystals allow us to go back in time and learn about the major changes to Earth’s ancient landscapes," Stockli said. "It would be great to do this for more of the meteor impact sites across the continent so we could get a more accurate timeline for these major events."
To confirm with absolute certainty that the zircons had indeed been shocked and altered by the meteor strike rather than some other geological process, the team collaborated closely with NASA. Researchers imaged the microscopic crystals using advanced cathodoluminescence and electron backscatter diffraction techniques.
When zircon is subjected to the extreme physical conditions of a hypervelocity impact, it recrystallizes in a highly distinctive and recognizable manner. Those microscopic structural changes can be readily detected with specialized imaging equipment, allowing researchers to definitively verify that the crystals recorded the intense shock of the collision itself.
A New Piece of a Mass Extinction Puzzle
According to Catlos, establishing much more precise dates for catastrophic mass extinctions and other planetary-scale events is an absolute necessity for understanding how Earth’s environment has shifted and evolved over hundreds of millions of years.
One of the most persistent questions in paleontology and geosciences is whether major extinction events throughout Earth’s history were triggered primarily by extraterrestrial forces—such as sudden meteor impacts—or by internal geological processes originating deep within the planet, including massive, prolonged episodes of volcanic activity that spewed greenhouse gases into the atmosphere.
"With this research, we’re basically taking a major pawn out of the Ordovician Meteor Event and dumping it into the Frasnian-Famennian event, and saying, ‘This is where this impact belongs,’" Catlos noted.
This significant scientific project was originally initiated by Andrew Parisi, a former Jackson School of Geosciences graduate student who earned his degree in 2018 and has since passed away. Parisi traveled directly to Oklahoma to obtain the crucial Ames rock core samples from the collections of the Oklahoma Geological Survey. He then meticulously extracted the tiny zircon crystals from the heavy material and helped lay the groundwork for determining their true geological ages.
Michael Brookfield, an affiliated researcher at the school and co-author of the study, also passed away before the manuscript was ultimately published. Additional vital contributions to the research were made by Research Professor Sean Gulick and Professor Emeritus Mark Cloos, both from the Jackson School of Geosciences.