Ames crater, once linked to a 470-million-year-old event, may be nearly 370 million years old

For decades, scientists linked Oklahoma’s Ames impact structure to a meteor event that swept across Earth nearly 470 million years ago. According to research published in Meteoritics & Planetary Science titled ‘The Ames impact structure, Oklahoma: New radioisotopic constraints and implications for North American impact chronology’, new evidence points to a very different timeline. By dating zircon from impact-melted granite, researchers may have found a distinct group of grains with an age of nearly 370 million years, suggesting the crater formed during the Late Devonian. That would place the impact close to the Frasnian-Famennian boundary and the Upper Kellwasser Crisis, a major extinction event.How did new dating place the Ames impact near a major extinctionThe Ames impact structure lies beneath Ames, Oklahoma, with an outer rim measuring 14-16 km in diameter. It was previously considered one of the largest impact structures associated with the Ordovician Meteor Event, which began about 466-468 million years ago. This connection was based on conodonts and moulds identified in material filling the crater.To test the age of the impact, researchers used radioisotopic dating on z...