Scientists at the University of Texas at Austin have significantly revised the geological timeline of Oklahoma, offering new insights into how researchers interpret pivotal moments in Earth’s evolutionary history.
Deep beneath the town of Ames, Oklahoma, lies a massive meteor impact structure extending for miles underground. Though buried under layers of sediment, the crater remains highly significant both scientifically and economically, serving as a major producer of oil and gas.
A Crater Long Linked to an Ancient Meteor Event
For decades, scientists believed the Ames crater was part of a cluster of major meteor impacts across North America dating back to approximately 467.5 million years ago, a period known as the Ordovician Meteor Event.
The coincidence of numerous impact structures from this era led some researchers to hypothesize that Earth might have been encircled by a Saturn-like ring of asteroid debris during the Middle Ordovician period.
New research from the University of Texas at Austin reveals that the Ames impact does not belong to that ancient cosmic bombardment.
By dating zircon crystals extracted from granite altered by the impact, the research team determined that the meteorite struck approximately 370 million years ago during the Late Devonian epoch. This finding indicates that the crater is nearly 100 million years younger than previously estimated.
“Regardless of the analytical techniques we applied, the results consistently pointed to this younger timeframe,” said lead author Elizabeth Catlos, associate professor in the Department of Earth and Planetary Sciences at UT Austin.
The findings were published in July in the journal Meteoritics & Planetary Science.
Why the Earlier Date Was Misleading
Prior to this study, the Ames impact was dated using biological evidence alone. Researchers had discovered teeth from an ancient, eel-like organism known as a conodont preserved within the rock, which dated back to the older Ordovician period.
However, Catlos explains that these teeth were likely millions of years old when the asteroid struck. The violent impact probably excavated and mixed older material, incorporating the fossils into the rock while preserving them.
The zircon dating presents a completely different timeline, demonstrating that the Ames crater could not have formed during the Ordovician Meteor Event.
Instead, the revised age places the impact close to the Frasnian-Famennian mass extinction event, which occurred around 372 million years ago and decimated a significant portion of Earth’s marine life.
Tiny Zircon Crystals Preserve the Impact
Danny Stockli, dean of the Jackson School of Geosciences and a co-author of the study, notes that zircon uranium-lead (U-Pb) dating provides one of the most accurate methods for pinpointing events deep in Earth’s history.
Furthermore, zircon crystals can preserve microscopic structures created by the extreme pressures generated during an impact event.
“These small crystals allow us to travel back in time to understand the major changes to Earth’s ancient landscapes,” Stockli remarked. “Applying this method to more meteor impact sites across the continent would provide a much more accurate timeline for these major geological events.”
To verify that the zircons were indeed affected by the meteor strike, the team collaborated with NASA to image the crystals using cathodoluminescence and electron backscatter diffraction.
When zircon undergoes the extreme conditions of an impact, it recrystallizes in a distinctive manner. These changes can be detected using these advanced imaging techniques, enabling researchers to confirm that the crystals recorded the actual collision.
A New Piece of a Mass Extinction Puzzle
According to Catlos, establishing more precise dates for mass extinctions and other major geological events is crucial for understanding how Earth has changed over time.
A key scientific question is whether extinction events were primarily triggered by extraterrestrial forces, such as meteor impacts, or by internal Earth processes, including episodes of massive volcanic activity.
“With this research, we are essentially removing a major piece from the Ordovician Meteor Event and placing it into the Frasnian-Famennian event, establishing exactly where this impact belongs,” she explained.
The project was initiated by former Jackson School of Geosciences graduate student Andrew Parisi, who graduated in 2018 and has since passed away. Parisi traveled to Oklahoma to obtain the Ames rock core from the Oklahoma Geological Survey, extracted zircon crystals from the material, and contributed to determining their ages.
Co-author Michael Brookfield, an affiliated researcher at the school, also passed away prior to the paper’s publication.
Research Professor Sean Gulick and Professor Emeritus Mark Cloos at the Jackson School also contributed to the research.
