Scientists using a new and highly precise dating technique have concluded that the late Cretaceous asteroid strike in Mexico's Yucatan Peninsula coincided almost exactly with the extinction of the dinosaurs — give-or-take a few tens of thousands of years. While it's clear that other factors were contributing to the rapidly deteriorating environmental conditions, it's now obvious that the asteroid was the final coup-de-grace for the dinosaurs.
Indeed, all was not well on Earth when the asteroid struck. Volcanoes in India were wreaking havoc to the planet's ecosystems, and earlier asteroid strikes may have contributed to an already fragile environment. Other research shows that Earth experienced six abrupt temperature shifts of two degrees or more in mean temperatures in the one million years before the impact. In one instance, the temperature swung 6-8 degrees.
These factors left doubt in the minds of some researchers, who wondered what it was, exactly, that truly caused the dinosaurs to go extinct. Moreover, previous studies showed considerable inconsistencies with the timing of certain events, leading researchers from Berkeley's Geochronology Center (BGC), the University of California, Berkeley, and universities in the Netherlands and the United Kingdom to investigate further — but this time with a new tool.
Their re-analysis utilized a recalibrated argon-argon dating technique that allowed for more accurate measurements of both the impact date and the dinosaurs' extinction.
Researchers Paul Renne, Jan Smit and colleagues determined that the Yucatan impact event happened 66,038,000 years ago — give or take 11,000 years. It's an extraordinarily precise measurement, as it was only a few decades ago that the margins for error were measured in the millions of years.
The scientists also updated the date of dinosaur extinction. It happened about 33,000 years after the asteroid impact, which is a revision from the previous estimate of 300,000 years (which, when considering the cataclysmic effects of the impact, didn't really make a lot of sense). Given the narrow margins of error for the dating technique, it's very likely, therefore, that the asteroid impact coincided almost exactly with the demise of the dinosaurs. Consequently, the researchers are describing the event as the final blow. It was not the only factor, they admit, but it was certainly a major contributor.
The scientists reached this conclusion after analyzing the tektites (glassy spheres) and ash left over from the impact. The team looked at evidence from both the dinosaur extinction date (including ash collected from the Hell Creek Formation in Montana, the source of many dinosaur fossils) and the crater formation event (namely tektites from Haiti).
"The impact was clearly the final straw that pushed Earth past the tipping point," said Renne through a statement. "We have shown that these events are synchronous to within a gnat's eyebrow, and therefore the impact clearly played a major role in extinctions, but it probably wasn't just the impact."
You can read the entire study at Science.
Images: Photobank.kiev.ua via Shutterstock andKerem Beyit.