Ames crater in Oklahoma found to be nearly 100 million years younger — ScienceDaily
The Ames meteorite impact structure, buried beneath the town of Ames in the US state of Oklahoma, formed about 370 million years ago — nearly 100 million years later than previously believed. A group of researchers at the University of Texas at Austin established this age, ScienceDaily reports.
New age of the crater
Previously, the Ames crater was linked to the Ordovician meteor event, which occurred approximately 467.5 million years ago. This period was characterized by a series of significant meteorite impacts in North America. Because of a cluster of craters of the same age, some scientists suggested that Earth may have been surrounded in the Middle Ordovician by a ring of asteroid debris similar to Saturn’s rings.
The new study excludes Ames from this group. The team analyzed zircon crystals extracted from granite altered by the impact. Uranium-lead radioisotope dating showed that the celestial body struck in the Late Devonian, approximately 370 million years ago.
Why the previous dating was inaccurate
Previously, the age of the structure was determined from biological remains: conodont teeth, from ancient eel-like animals that lived during the Ordovician period, were found in the rocks. The study’s lead author, Elizabeth Catlos, suggested that these remains were already ancient at the time of the impact, and that the celestial body’s fall likely mixed older materials with the crater rocks.
More current news is available on the UA.News Telegram channel Telegram.
To make sure that the zircon crystals had indeed preserved traces of the collision, the scientists studied them together with NASA using cathodoluminescence and electron backscatter diffraction. Under the extreme pressure of an impact, zircon recrystallizes, and such changes can be detected using these methods.
Connection to extinction
The crater’s new age brings its formation closer to the Frasnian-Famennian mass extinction, which occurred about 372 million years ago and led to the death of a significant portion of marine organisms. The researchers noted that more precise dating of impact structures is needed to study the possible link between cosmic impacts, volcanic activity, and major changes in the history of life on Earth.
The work was published in July in the journal Meteoritics & Planetary Science. The Ames impact structure is now covered by sedimentary rocks and is also an area of oil and gas extraction.
