Working at multiple sites across the continent, researchers found nanodiamonds - microscopic particles thought to be found on comets - in a 13,000-year-old layer of rich sedimentary soil called a "black mat." Beneath the layer with the nanodiamonds, fossils of the animals are abundant. After that layer, they disappear, West said.
"It's extraordinary that tens of millions of animals disappeared synchronously at exactly the time when the diamonds and carbon layer are laid down across the continent," said West, whose co-authors include DePaul University chemist Wendy Wolbach.
Arrowheads and other artifacts from the Clovis culture of humans - an early hunter-gatherer society - also vanish after the black mat was laid down 13,000 years ago.
In 2007, West and a team of scientists published an analysis of black mats from several regions that found heavy metals, soot and charcoal suggestive of meteorite impacts and subsequent fires. The new report says the discovery of nanodiamonds in the same material is more evidence of a cosmic strike.
http://www.physorg.com/news150097682.html
http://www.cnn.com/2009/TECH/science/01/02/comet.diamonds/index.html
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