America's Ames Crater Re-dated to 370 Million Years Ago, Coinciding with Major Extinction Event

Introduction

One of the most significant meteor impact sites in the United States, the Ames crater in Oklahoma, has been found to be approximately 100 million years younger than previously estimated. This revised dating, derived from sophisticated analysis of microscopic zircon crystals, places the impact event at 370 million years ago. Crucially, this timing coincides with the Frasnian-Famennian mass extinction event, a period of significant biodiversity loss on Earth, raising questions about the impact's potential role in this ancient catastrophe.

Key Details

• Revised Age: The Ames crater, a submerged impact structure in northwest Oklahoma, is now dated to 370 million years ago, a revision of about 100 million years from previous estimates.
• Impact Event: The crater was formed by an asteroid-sized object striking Earth at high velocity, creating a 10-mile-wide structure that has since been buried by geological processes.
• Dating Method: The new age was determined by analyzing fracture patterns within zircon crystals found within the crater. Zircon's durability allows it to preserve evidence of extreme conditions, making it invaluable for dating ancient geological events.
• Extinction Correlation: The revised date places the Ames impact within the Frasnian-Famennian mass extinction event, also known as the Late Devonian extinction, which saw the loss of a significant portion of marine life.
• Study Publication: The findings were published in the journal Meteoritics and Planetary Science.
• Funding and Authors: The study was led by Elizabeth Catlos and Danny Stockli from the University of Texas at Austin, with contributions from researchers Andrew Parisi and Michael Brookfield, among others.

Background

The Ames crater, measuring about 10 miles (16 kilometers) in diameter, is located in northern Oklahoma and is currently hidden beneath layers of sediment. It was discovered accidentally in 1991 by oil prospectors. Prior to this new research, the prevailing scientific consensus dated the crater to the Ordovician meteor event, around 467 million years ago. This earlier period was characterized by a notable increase in asteroid impacts on Earth, likely due to the breakup of a larger celestial body. Evidence supporting this older dating included marine fossils found in and around the crater that were consistent with the Ordovician era.

Analysis of Zircon Crystals

The breakthrough in re-dating the Ames crater came from the meticulous examination of zircon crystals. Zircons, composed of zirconium silicate, are exceptionally resilient minerals found in many rock formations. Their internal structures act as time capsules, recording the intense heat and pressure associated with geological events like meteorite impacts. By studying the specific fracture patterns and other microstructural evidence within these crystals, geologists can accurately determine the timing of the event that formed them.

“No matter what technique we used, it was coming back to this younger signal,” stated study first author Elizabeth Catlos, a geologist and planetary scientist at the University of Texas at Austin.

This technique has proven instrumental in revising the ages of other impact structures globally, underscoring its reliability in refining our understanding of Earth's impact history. The ability to accurately date these events is crucial for piecing together the planet's geological timeline.

Impact Analysis

The new dating of the Ames crater has significant implications for understanding the Frasnian-Famennian mass extinction event. This extinction, which occurred roughly between 372 and 359 million years ago, led to the demise of approximately half of all marine species due to widespread ocean anoxia (lack of oxygen). While the researchers emphasize that the Ames impact was not the sole cause of this extinction, they suggest it may have been a contributing factor. The immense energy released by the impact would have ejected vast quantities of dust and debris into the atmosphere, potentially triggering or exacerbating global cooling and atmospheric changes that stressed marine ecosystems.

Broader Context

This re-evaluation of the Ames crater’s age fits into a larger trend of scientific discovery where advanced dating techniques are refining our understanding of Earth's history. Similar revisions have occurred for other impact structures, such as the North Pole Dome crater in Australia and the Stac Fada Member structure in Scotland. These ongoing adjustments highlight the dynamic nature of scientific knowledge and the importance of continually re-examining established data with new methodologies. The study also serves as a reminder that geological events, including impacts and extinctions, are often interconnected and can influence each other in complex ways.

Future Outlook

The success in re-dating the Ames crater using zircon analysis opens avenues for further research. Scientists like co-author Danny Stockli express enthusiasm for applying these techniques to more impact sites across the continent to construct a more precise chronological map of Earth's bombardment history. Such a comprehensive timeline would allow for better correlation between impact events and other significant geological and biological phenomena, such as mass extinctions and major climate shifts. Understanding these connections is vital for comprehending Earth's past and potentially predicting future environmental changes.

Conclusion

The revised dating of the Ames crater to 370 million years ago, coinciding with the Frasnian-Famennian mass extinction, represents a significant advancement in our understanding of both impact geology and paleoclimatology. The study, published in Meteoritics and Planetary Science, utilized the robust analytical power of zircon crystals to correct a long-held assumption about the crater's age. While not the cause of the extinction, the impact may have played a role in exacerbating the environmental conditions that led to the widespread loss of life. This research underscores the value of precise dating in unraveling complex historical events and highlights the interconnectedness of Earth's geological and biological past.