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A new study dates zircon from Oklahoma’s buried Ames impact structure to a minimum age of 369.7 ± 5.9 million years, potentially placing the impact near the Late Devonian Frasnian–Famennian extinction, about 372 million years ago. That is a possible timing connection, not evidence that Ames caused the extinction. The study concerns the Late Devonian event—not the end-Permian extinction.
What the new Ames crater study says
In a paper published July 7, 2026, in Meteoritics & Planetary Science, Elizabeth Catlos and coauthors reported new radioisotopic age constraints for the Ames impact structure. They analyzed zircon in impact-melt material using uranium–lead (U–Pb) dating. The youngest grains produced a weighted mean of 369.7 ± 5.9 million years. The authors interpret this as a minimum-age constraint, not a definitive date for when the crater formed. Read the study.
The result could place Ames near the Frasnian–Famennian boundary, calibrated in the paper to 371.8–372.4 million years ago. The authors describe this as a possible interpretation and condition it on the U–Pb dates being correct. They also note that the textures of the youngest zircon grains do not uniformly establish impact deformation. The study therefore raises a potential temporal association with a cluster of Devonian impacts; it does not settle the crater’s age or establish a role in the extinction.
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Which mass extinction is meant?
The proposed connection is to the Late Devonian Frasnian–Famennian event, around 372 million years ago. It is not a claim about the end-Permian extinction, which occurred around 252 million years ago. USGS research identifies Siberian Traps magmatism, particularly sill emplacement, as the likely trigger of the end-Permian event; the Ames study does not connect the crater to it. USGS: Initial pulse of Siberian Traps sills as the trigger of the end-Permian mass extinction.
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Why the crater’s age is being reconsidered
Ames was traditionally assigned a late Ordovician age largely from conodont fossils found in crater-fill material. The 2026 study tests that chronology with radioisotopic dating of impact-melt material and reports a younger minimum-age constraint. The authors say the fossil evidence came from limited material and caution against relying on only a few conodont fragments. But their own dating is also limited by the available sample, so the new result does not by itself resolve the conflict.
| Evidence | Material and result | What it indicates—and its limitation |
|---|---|---|
| Conodont biostratigraphy | Fossils in crater-fill strata; supports the established late Ordovician assignment. | Dates fossil-bearing fill rather than directly dating impact-melt crystallization; the study notes the constraint relied on limited material. |
| U–Pb zircon dating | Zircon from impact-melt material; youngest-grain weighted mean of 369.7 ± 5.9 Ma. | Interpreted as a minimum-age constraint that may place Ames near the Late Devonian boundary. Limited material and uncertainty about whether the analyzed grains record impact crystallization leave the impact date unsettled. |
| Plagioclase 40Ar/39Ar dating | Approximate total-fusion dates of 310.5 Ma and 250.5 Ma. | The authors interpret these younger dates as later thermal overprinting during burial and basin evolution, not as the impact age. |
These methods do not provide interchangeable readings of one event. Fossils constrain the age of the strata in which they occur; zircon dates offer a different signal from impact-melt material; and argon dates can reflect later heating. Further representative samples and dates are needed to clarify which evidence best constrains the impact.
What Ames looks like—and why you cannot see it
Ames is a buried structure beneath the town of Ames in northwestern Oklahoma, not an exposed crater at the surface. Seismic exploration identified its unusual form in 1991. The Oklahoma Geological Survey describes it as roughly circular, about 10 miles (16 km) across, and buried under approximately 9,000 feet (2.7 km) of sediment. Oklahoma Geological Survey: Meteorites and Impact Structures.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteThe 2026 paper describes a complex crater with a central uplift and gives an outer-rim diameter of 14–16 km. These dimensions refer to structural boundaries that need not be identical, so the figures should not be treated as competing measurements of precisely the same feature.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Does the timing mean Ames caused the extinction?
No. Even if the proposed Late Devonian age is confirmed, overlap in time would not show that Ames triggered or materially worsened the extinction. The study offers a possible chronological association, not evidence demonstrating causality. Catlos was quoted in Space.com’s October 5, 2026, report describing Ames as being moved from the Ordovician impact grouping into the Frasnian–Famennian event. That is the news report’s characterization of her remarks; the journal paper itself uses more cautious language and calls for additional material and dating. Space.com’s report.
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