Oklahoma Meteor Impact Was 100 Million Years Younger Than Previously Thought

No matter what technique we used, it was coming back to this younger signal, said Elizabeth Catlos, associate professor at the University of Texas at Austin Department of Earth and Planetary Sciences, regarding a revision to the geologic timeline of Oklahoma.

Researchers at The University of Texas at Austin have revised the geologic history of the Ames impact structure in Oklahoma, shifting its formation date from the Middle Ordovician period to the Late Devonian period roughly 370 million years ago. As reported, this finding decouples the buried Oklahoma crater from a widely cited cluster of North American meteor impacts that occurred approximately 467.5 million years ago.

Ames Impact Structure Shifting 100 Million Years Down the Timeline

Beneath the surface of Ames, Oklahoma, lies a meteor impact structure spanning miles underground that remains a significant producer of oil and gas. For years, scientists linked this crater to the Ordovician Meteor Event, a cluster of impacts that led some researchers to propose that Earth was once surrounded by a Saturn-like ring of asteroid debris. However, new work published in July in Meteoritics & Planetary Science demonstrates that the Ames impact is nearly 100 million years younger than previously estimated, placing it at roughly 370 million years old.

Jackson School of Geosciences dean Danny Stockli noted that uranium-lead dating of zircon provides one of the most accurate methods for determining ancient timelines. To confirm the crystals experienced a high-pressure collision, the team collaborated with NASA to image them using cathodoluminescence and electron backscatter diffraction.

Zircon Data Corrects Previous Fossil Timeline

The previous timeline relied strictly on biochronological evidence recovered from the rock layers. Researchers had previously identified teeth from an ancient eel-like creature known as a conodont, which lived during the Ordovician period. Catlos explained that those fossils were likely already millions of years old when the asteroid struck and were simply churned up and mixed into the younger impact strata while remaining preserved.

By contrast, the zircon U-Pb data yielded a consistently younger signal that precluded an Ordovician origin. Instead, the new radiometric date aligns closely with the Frasnian-Famennian mass extinction event. That extinction pulse occurred about 372 million years ago and eliminated a vast proportion of marine life on Earth.

Reevaluating Ancient Mass Extinction Triggers

Establishing precise dates for major geological events helps scientists determine whether mass extinctions were driven primarily by extraterrestrial impacts or internal planetary processes such as massive volcanic activity. Catlos described the shift of the Ames structure by stating that researchers are taking a major pawn out of the Ordovician event and placing it squarely into the Frasnian-Famennian timeline.

The research project was initiated by the late Andrew Parisi, a former Jackson School graduate student who obtained the rock core from the Oklahoma Geological Survey, extracted the zircon crystals, and helped calculate their ages.

Zircon Analysis Methods for Future Impact Studies

Stockli emphasized that microscopic structures within zircon crystals preserve the extreme shock pressures generated during asteroid impacts.

The Ames crater was previously thought to belong to a North American impact cluster dated around 467.5 million years ago.