Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsiTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
The buried Ames impact structure in northwestern Oklahoma may have formed about 370 million years ago—not roughly 467–470 million years ago, as scientists long believed. A 2026 study dates zircon crystals from impact-melt material and favors a Late Devonian age, but the authors say more samples and dates are needed to tie that age more directly to the impact.
Which crater is being redated?
The finding concerns the Ames impact structure beneath the town of Ames in Major County, northwestern Oklahoma. The research paper describes a complex crater with a central uplift and an outer rim 14–16 kilometers across. The Oklahoma Geological Survey’s 2016 overview says the structure lies about 9,000 feet beneath sediment and was recognized in 1991, after seismic exploration revealed a roughly circular feature about 10 miles wide. The 2026 study provides the new age analysis; the Oklahoma Geological Survey overview supplies historical and geological context.
What changed in the age estimate?
For decades, Ames was assigned a Late Ordovician age, around 467–470 million years old, based on conodont fossils found in material associated with the crater. The 2026 study instead reports a youngest zircon population with a weighted mean age of 369.7 ± 5.9 million years. The University of Texas at Austin’s Jackson School of Geosciences summarizes the older Ordovician Meteor Event age as about 467.5 million years and describes the new result as nearly 100 million years younger. Its September 2026 report includes comments from the researchers.
Why the fossil-based age may not date the impact
Conodont teeth can be older than the rock or deposit in which they are later found. The study’s authors argue that impact-related disruption, mixing and redeposition could have incorporated older conodonts into material associated with Ames. In that case, the fossils’ age would not establish when the crater formed.
#1 Best Overall
What the zircon dates measure
The researchers analyzed zircon in impact-melt material using secondary ion mass spectrometry and laser-ablation inductively coupled plasma mass spectrometry. The reported youngest population includes 10 of 11 analyses, with one statistical outlier excluded, and yields a weighted mean of 369.7 ± 5.9 million years. The authors interpret this as the best current maximum-age constraint on impact-related zircon recrystallization and say it supports a Late Devonian age for Ames.
The paper also reports a zircon emplacement age of 1401.2 ± 8.1 million years for the impacted granodiorite. That dates the target rock before the impact, not the crater-forming event. Imaging found primary oscillatory zoning and no deformation in most analyzed zircons, including the youngest Devonian-age grains; two crystals showed textures the authors identify as impact-related.
Rank #2
- Used Book in Good Condition
How certain is the new date?
The result changes the best-supported interpretation, but it is not a definitive timestamp for the impact. The study describes 369.7 ± 5.9 million years as a maximum-age constraint on impact-related zircon recrystallization. The authors also note that sample availability is limited and that additional suitable material and zircon dates are needed to connect the dated population more directly to the impact itself. Accordingly, “Late Devonian” is the authors’ favored current estimate, not an uncontested final date.
Does the new age link Ames to a mass extinction?
The youngest zircon dates fall near the Frasnian–Famennian boundary, an extinction interval around 372 million years ago. The paper says Ames may belong with Devonian impacts rather than the North American Ordovician Meteor Event, a cluster centered around 467.5 million years ago. That is a timing association, not evidence that the Ames impact caused the extinction. The broader question of how extraterrestrial impacts and terrestrial processes such as volcanism contributed to extinction events remains distinct from dating this crater.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why the redating matters
If the Late Devonian interpretation is confirmed, Ames would no longer belong in the Ordovician impact cluster on the basis of its former age assignment. That would change the timeline scientists use to compare North American impact structures and assess possible links between impacts and major changes in Earth’s history. Ames is also notable as a major oil- and gas-producing impact structure, but that economic significance is separate from the evidence for its age.
Quick Recap
Best Value
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
