Researchers at the University of Texas at Austin have revised the age of a buried meteor crater beneath Ames, Oklahoma. Using zircon crystals from granite altered by the impact, they determined the meteorite struck about 370 million years ago, during the Late Devonian. That makes the crater nearly 100 million years younger than the roughly 467.5-million-year-old age previously assigned to it.
The earlier date came from conodont fossils found in the rock. Those fossils belonged to organisms from the Ordovician period, but the researchers say the teeth were likely already millions of years old when the asteroid hit. The impact probably churned up older material and mixed the fossils into the rocks while preserving them. Zircon dating, verified with NASA imaging techniques, showed a distinct recrystallization pattern consistent with an impact.
The revised age places the Ames impact close to the Frasnian-Famennian mass extinction event, which occurred about 372 million years ago and devastated marine life. The study's lead author, Elizabeth Catlos, said the finding moves the crater out of the Ordovician Meteor Event and into the later extinction episode. The research was published in July in Meteoritics & Planetary Science.
The source is a single study from UT Austin, so there are no conflicting findings to compare. The researchers note that the Ames structure remains economically significant as a producer of oil and gas, and they suggest that similar zircon dating could refine the timeline of other impact sites across North America.