Ames Crater in Oklahoma is 97 million years younger — Live Science
In the United States, scientists have revised the age of Ames Crater, hidden beneath sedimentary rocks in northern Oklahoma. An analysis of zircon crystals showed that the impact structure formed about 370 million years ago — 97 million years later than the previous estimate of around 467 million years ago, Live Science reports.
The crater, about 16 kilometers wide, is the fourth-largest impact structure in the United States. It formed after a celestial body the size of the Eiffel Tower struck at a speed of more than 110,000 kilometers per hour. At the time, the area of present-day Oklahoma was covered by a shallow sea, and the depression was later filled with seafloor sediments, making the crater invisible at the surface. It was accidentally discovered in 1991 during drilling for oil.
Dating using zircon crystals
Previously, the crater was linked to the Ordovician meteor event about 467 million years ago. This assumption was based, among other things, on fossil remains of marine animals in the area of the structure. In a new study published on July 7 in the journal Meteoritics and Planetary Science, specialists examined the pattern of cracks in tiny zircon crystals from the crater.
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Zircon is an extremely durable mineral whose internal structure can preserve traces of exposure to high temperatures and pressure. The study's lead author, geologist and planetary scientist Elizabeth Catlos of the University of Texas at Austin, said that all methods used indicated a younger age for the structure.
Connection to a mass extinction
The crater's new age places it within the Frasnian-Famennian mass extinction event, also known as the Late Devonian extinction or the Kellwasser event. It began about 372 million years ago and lasted several million years. During this period, up to half of all marine life may have died out because of declining oxygen levels in the oceans.
The researchers stressed that the impact of the celestial body that created Ames Crater was not the cause of this extinction. At the same time, dust ejected into the atmosphere as a result of the impact may have intensified cooling in the region. Scientists noted that more precise dating of impact structures helps reconstruct the chronology of ancient geological events.
