Researchers at The University of Texas at Austin have revised a key piece of Oklahoma's geologic history, with possible implications for how scientists interpret major events in the history of life on Earth. Beneath the town of Ames, Oklahoma, lies a meteor impact structure that stretches for miles underground. Layers of sediment now cover the crater, but it remains significant both scientifically and economically.
The Ames impact structure is also a major producer of oil and gas. A Crater Long Linked to an Ancient Meteor Event For years, the Ames crater was thought to belong to a cluster of major meteor impacts across North America dating to roughly 467.5 million years ago. That period is known as the Ordovician Meteor Event.
Because so many impact structures appear to date from around the same time, some researchers have proposed that Earth may once have been surrounded by a Saturn-like ring of asteroid debris during the Middle Ordovician. New work from UT researchers now shows that the Ames impact does not belong to that episode. By dating zircon crystals taken from granite altered by the impact, the team determined that the meteorite struck about 370 million years ago during the Late Devonian.
That makes the crater nearly 100 million years younger than previously believed. "No matter what technique we used, it was coming back to this younger signal," said lead author Elizabeth Catlos, associate professor at UT's Department of Earth and Planetary Sciences. The research was published in July in Meteoritics & Planetary Science.
Before this study, the Ames impact had only been dated using biological evidence. Researchers had found teeth from an ancient eel-like animal called a conodont preserved in the rock. Those fossils came from organisms that lived during the older Ordovician period.
But Catlos said the teeth were probably already millions of years old by the time the asteroid struck. The impact likely churned up older material and mixed the fossils into the rocks while still preserving them. The zircon dating provides a very different timeline.
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