10-Mile-Wide Ames Impact Crater Linked to 372-Million-Year-Old Violent Extinction Event

Researchers at the University of Texas at Austin have determined that the 10-mile-wide Ames impact crater was formed 100 million years later than previously believed, linking its formation to a violent extinction event that wiped out much of Earth’s marine life 372 million years ago. The study used zircon crystal radiometric dating to show the crater was formed 370 million years ago, not 467.5 million years ago as previously thought. This date aligns with the Frasnian-Famennian mass extinction event, which occurred about 372 million years ago. The findings challenge the previous assumption that the Ordovician Meteor Event was the cause of the extinction.

The study used a technique that examines the structure of zircon crystals found in rocks at the site to determine when they formed. Zircon microstructures can record the shock pressures of violent events, making radiometric dating the most accurate method for dating such impacts. The research team found that the zircon crystals were formed around 370 million years ago, proving that the impact event that caused the now underground crater could not have been part of the Ordovician Meteor Event. The new date lines up with the Frasnian-Famennian mass extinction event, which wiped out much of Earth’s marine life.

The study’s lead author, Elizabeth Catlos, said the result takes “a major pawn out of the Ordovician Meteor Event” and places it into the Frasnian-Famennian event. The research team also noted that more accurate dating of meteor impact sites could help clarify the timeline of Earth’s violent ancient past. The findings could help scientists better understand the timing and causes of mass extinction events.

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