Ames crater in Oklahoma formed 370 million years ago, not 467.5 million

October 4, 2026 at 06:02 PM2 min

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University of Texas at Austin researchers found the Ames impact structure in Oklahoma formed about 370 million years ago, nearly 100 million years later than previously thought. The team dated zircon crystals from granite altered by the impact, overturning the crater's link to the Ordovician Meteor Event. The revised age places the impact near the Frasnian-Famennian mass extinction about 372 million years ago.

Key Facts

The Ames impact structure beneath Ames, Oklahoma, formed about 370 million years ago in the Late Devonian, according to zircon U-Pb dating by University of Texas at Austin researchers.
The crater was previously dated to roughly 467.5 million years ago during the Ordovician Meteor Event based on conodont teeth fossils.
The revised age places the Ames impact close to the Frasnian-Famennian mass extinction event, which occurred about 372 million years ago and wiped out a large proportion of marine life.
The study was published in July in the journal Meteoritics & Planetary Science.
Lead author Elizabeth Catlos said the conodont teeth were likely already millions of years old when the asteroid struck, and the impact churned up older material and mixed the fossils into the rocks.

Revised Impact Age

Researchers at the University of Texas at Austin dated zircon crystals taken from granite altered by the impact. The team determined that the meteorite struck about 370 million years ago during the Late Devonian. That makes the crater nearly 100 million years younger than previously believed. Lead author Elizabeth Catlos, associate professor at UT's Department of Earth and Planetary Sciences, said no matter what technique the team used, the result came back to this younger signal. The research was published in July in Meteoritics & Planetary Science.

Why Earlier Dating Was Misleading

Before this study, the Ames impact had only been dated using biological evidence. Researchers had found teeth from an ancient eel-like animal called a conodont preserved in the rock. Those fossils came from organisms that lived during the older Ordovician period. Catlos said the teeth were probably already millions of years old by the time the asteroid struck. The impact likely churned up older material and mixed the fossils into the rocks while still preserving them.

Zircon Dating Method

Danny Stockli, dean of the Jackson School of Geosciences and a co-author of the study, said zircon U-Pb dating offers one of the most accurate ways to determine when events occurred deep in Earth's past. Zircon crystals can also preserve microscopic structures created by the intense pressures generated during an impact. Stockli said these small crystals allow scientists to go back in time and learn about the major changes to Earth's ancient landscapes.