In 1979, the huge Chicxulub crater, measuring about 180 km (112 miles) in diameter, was discovered on the northern Yucatan Peninsula, Mexico. Scientists made the obvious conclusion that something rather large had hit the Earth in this location, probably causing all kinds of global devastation 65 million years ago. At around the same time, 65% of all life on the face of the planet was snuffed out of existence. The dinosaurs that roamed the planet up to that point were no more.
The timing of asteroid impact and the time of the mass extinction was too much of a coincidence to be ignored. When particles from the asteroid impact were discovered just below the Cretaceous-Tertiary (K-T) boundary, there was a strong causal link: the effects of the asteroid impact had driven the dinosaurs to extinction.
However, a problem with this theory has come to light. It turns out the Chicxulub impact may pre-date the K-T boundary by 300,000 years…
A number of scientists have disagreed with the theory that the Chicxulub impact caused the death of the dinosaurs 65 million years ago, and this newest research appears to show the two events may not be linked after all.
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Gerta Keller of Princeton University in New Jersey, and Thierry Adatte of the University of Lausanne, Switzerland, are set to publish this new work in the Journal of the Geological Society today, using data from the analysis of sediment from Mexico to prove the asteroid impact pre-dated the K-T boundary by as much as 300,000 years.
“We know that between four and nine meters of sediments were deposited at about two to three centimeters per thousand years after the impact,” said Keller. “The mass extinction level can be seen in the sediments above this interval.”
This means that the mass extinctions appeared to take place a long time after the impact. However, impact-extinction advocates point out that this inconsistency in sediment data is probably down to sediment disruption by tsunamis and geological upheaval immediately after the impact.
According to Keller, there is no indication that this could be the case. Deposition of impact sediment occurred over a huge time period, not the hours or days deposition would have taken if a tsunami affected sedimentary records.
Another problem with the impact extinction theory is that the Chicxulub impact may not have had the radical extinction effect on plants and animals as we previously thought. The researchers found a total of 52 fossilized species that appeared to be happily living before the layer of impact sediment… and the same 52 species appeared to by happily living after the layer of impact sediment.
“We found that not a single species went extinct as a result of the Chicxulub impact.” — Gerta Keller
Although this is some very interesting research, sure to turn dinosaur extinction theory on its head, if an asteroid didn’t kill the dinosaurs, what did?
Keller points the finger at volcanic activity. Massive amounts of dust and gas was released from eruptions at the Deccan Traps in India 65 million years ago, possibly plunging the planet into a prolonged period without Sun.
Update: With any scientific debate, there are details behind new research that may not be immediately apparent. As Ethan Siegel highlights in a recent ScienceBlogs article (What Wiped Out The Dinosaurs?, April 27th), the evidence for an asteroid impact wiping out the dinosaurs is overwhelming. Just because there appears to be a discrepancy in the location of impact sediment and K-T boundary does not mean the impact-extinction theory is wrong in any way. Keller’s research is an interesting investigation, worthy of further study, but this doesn’t change the fact that huge global damage would have been caused by the Chicxulub impact. This remains the prime candidate as to why the dinosaurs were suddenly made extinct 65 million years ago.