Ancient Oklahoma Crater Is 100 Million Years Younger Than Scientists Thought

A Buried Secret Beneath the Oklahoma Plains

Beneath the quiet town of Ames, Oklahoma, nearly two miles underground, lies a scar left by one of the most violent events in North American geological history. The crater spans about 10 miles in diameter and is buried under 9,000 feet of sedimentary rock. For decades, scientists thought they understood when it formed. They were off — by about 100 million years.

According to a recently published study in *Meteoritics & Planetary Science*, researchers dated zircon crystals from the site and found that the Ames crater likely formed about 370 million years ago, during the Late Devonian. That represents a whopping 100-million-year gap with the Ordovician meteor event, when Earth saw a large increase in meteor events roughly 467 million years ago. The implication is staggering: this crater doesn't belong to the chapter of Earth history scientists assigned it to — and its true chapter may be far more consequential.

How Scientists Got It Wrong the First Time

The Ames meteor impact site had previously only been dated biochronologically; researchers found the teeth of an ancient eel-like creature called a conodont in the rock, which were around during the older Ordovician age. It seemed like solid evidence. But there was a flaw in that reasoning.

The teeth were likely already millions of years old when the asteroid struck Ames, and likely just got jumbled around in the mix of the impact, remaining preserved. The fossils that originally dated the crater likely belonged to organisms that were already millions of years old when the meteorite struck. A powerful impact churns up older material, mixing older biological remnants into newly formed deposits without destroying them. In other words, ancient fossils got swept into the chaos of a younger collision — and fooled scientists for decades.

Zircon Crystals and a More Reliable Clock

For the latest study, the researchers studied zircon samples from the site using a number of different techniques, including uranium-lead dating, which revealed both the age of the crater and the shock pressure left behind by the meteor. The team then collaborated with NASA to confirm that the zircon crystals were indeed affected by the meteor impact. The result was consistent no matter how they approached it.

"No matter what technique we used, it was coming back to this younger signal," said lead author Elizabeth Catlos, associate professor at UT's Department of Earth and Planetary Sciences. Most of the extracted crystals preserved much older crystallization ages reaching back roughly 1.4 billion years to the region's original basement granite. However, a younger population of zircons produced a weighted mean age of 369.7 million years, with an uncertainty of about 5.9 million years, pointing to a major Late Devonian heating and recrystallization event.

A New Link to One of Earth's Deadliest Chapters

This new radiometric date from the zircons shows that the Ames impact squarely fits into the timing of the Frasnian-Famennian mass extinction event, which occurred about 372 million years ago, and led to the extinction of a huge percentage of marine life on Earth. The new age ties it in with the Late Devonian mass extinction that wiped out an estimated 40% of all marine life on Earth. That's a catastrophe of almost incomprehensible scale.

The new study notes that its crater age overlaps the best current constraints on this extinction interval, suggesting the Ames impact might be part of a still-emerging pattern of environmental stress, volcanism, and possible impact events that together reshaped life on the planet. While the paper stops short of claiming Ames caused the extinction, tying a buried Midwestern impact structure to a global biological crisis gives researchers a fresh data point in longstanding debates about what actually killed off so many Devonian species.

The impact that formed the Ames crater has also allowed for the extraction of significant amounts of oil and natural gas since its discovery in 1991, as the fractures caused by the impact created underground reservoirs for hydrocarbons. Now, beyond its industrial value, the crater may hold clues to one of the most devastating die-offs in the history of life on Earth. As Catlos put it, "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." The story of what ended the Devonian world may still be buried — waiting to be found.