Asteroid hit didn’t cause dinosaurs’ extinction: Study

April 27th, 2009 - 4:58 pm ICT by IANS  

Washington, April 27 (IANS) An asteroid hit which caused the vast Chicxulub crater 65 million years ago, might not have actually wiped out the dinosaurs, along with 65 percent of all species, according to a new study.
The crater, discovered in 1978 in northern Yucatan in Mexico, measuring about 180 kilometres in diameter, recorded a massive extra-terrestrial impact.

When spherules from the impact were found just below the Cretaceous-Tertiary (K-T) boundary (a thin band of sedimentation found in various parts of the world), it was quickly identified as the “smoking gun” responsible for the mass extinction 65 million years ago.

It was this event that is believed to have caused the extinction of dinosaurs, along with countless other plant and animal species. However, a number of scientists contest this interpretation.

The newest research, led by Gerta Keller of Princeton University in New Jersey and Thierry Adatte of the University of Lausanne, Switzerland, uses evidence from Mexico to suggest that the Chicxulub impact predates the K-T boundary by as much as 300,000 years.

Keller suggested that the massive volcanic eruptions at the Deccan Traps in India may be responsible for the extinction of dinosaurs, releasing huge amounts of dust and gases that could have blocked out sunlight and brought about a significant greenhouse effect.

Advocates of the Chicxulub impact theory suggest that the impact crater and the mass extinction event only appear far apart in the sedimentary record because of earthquake or tsunami disturbance that resulted from the impact of the asteroid.

However, Keller said the problem with the tsunami interpretation is that this sandstone complex was not deposited over hours or days by a tsunami and deposition occurred over a very long time period.

The scientists also found evidence that the Chicxulub impact didn’t have the dramatic impact on species diversity that has been suggested.

At one site at El Penon, the researchers found 52 species present in sediments below the impact spherule layer, and counted all 52 still present in layers above the spherules.

“We found that not a single species went extinct as a result of the Chicxulub impact,” said Keller, according to a Princeton release.

These findings were published in the Journal of the Geological Society Monday.

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