Ames Impact Crater Dated to 370 Million Years Ago, Study Finds

The Ames impact structure, a buried crater in Oklahoma measuring 14 to 16 kilometers in diameter, formed approximately 370 million years ago near the late Devonian biological crisis, according to new radioisotopic dating of zircon and plagioclase crystals published in Meteoritics & Planetary Science, tech.icrewplay.com reported.

Zircon Crystals Reveal a Younger Timeline

For years, geologists linked the subsurface Ames structure to a much older impact event dating back to the Ordovician period. Previous reconstructions relied heavily on fossils recovered from sedimentary layers that filled the basin. Researchers analyzed zircon and plagioclase minerals extracted directly from the impact rocks to re-evaluate that timeline. Uranium-lead isotopic ratios preserved within the youngest zircon crystals yielded a weighted average of 369.7 ± 5.9 million years. Study authors interpret this reading as the best available estimate for the high-temperature event that created the crater, though subsequent thermal activity in the region introduces some degree of geological uncertainty.

Geological Context of the Late Devonian Period

The newly calculated timeframe places the Ames impact near the Frasnian-Famennian boundary, a major biological crisis during the late Devonian. Marine organisms suffered heavy losses during this era, and ocean ecosystems underwent profound transformations. The chronological coincidence brings fresh attention to the Oklahoma site, though researchers caution against labeling the impact as a definitive cause of the extinction. Because the crater is much smaller than structures tied to global catastrophes, study authors suggest evaluating Ames as a potential contributing factor alongside parallel environmental shifts and other impact events.

Evaluating Potential Extinction Triggers

Whether a single impact causes a mass extinction depends on the energy released, the impact location, the composition of the target rocks, and subsequent atmospheric and oceanic effects. An asteroid strike can loft massive volumes of dust and aerosols into the air, temporarily altering solar radiation and disrupting global climate patterns. Scientists analyzing the late Devonian period also study ocean deoxygenation, widespread volcanic activity, and climate fluctuations as drivers of the extinction event. The revised date for the Ames structure does not replace this complex framework, but it supplies a new piece of chronological data for geologists mapping North American impact history.

Establishing a precise formation date allows researchers to cross-reference crater data with environmental signals recorded in ancient rocks and fossils. When dates align, scientists search for independent indicators such as ejecta layers, geochemical anomalies, or coeval impact sites. The primary study, titled The Ames impact structure, Oklahoma: New radioisotopic constraints and implications for North American impact chronology, establishes a firmer temporal window, leaving the exact role of the Ames impact in the Devonian crisis open to ongoing verification.