The great splat of an asteroid that might have wiped out the dinosaurs apparently didn't get all of them. New fossil evidence suggests some dinosaurs survived for up to half a million years after the impact in remote parts of New Mexico and Colorado.
The whole idea that a space rock destroyed the dinosaurs has become controversial in recent years. Many scientists now suspect other factors were involved, from increased volcanic activity to a changing climate. Either way, some 70 percent of life on Earth perished, and an asteroid impact almost surely played a role.
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"The great difficulty with this hypothesis — that these are the remains of dinosaurs that survived — is ruling out the possibility that the bones date from before the extinction," he said. "After being killed and deposited in sands and muds, it is possible for bones to be exhumed by rivers and then incorporated into younger rocks."
To try to eliminate that scenario, Fassett investigated the rocks surrounding the bones and studied date indicators, such as their magnetic polarity. He said the evidence "independently indicate[s] that they do indeed post-date the extinction."
He also found that the dinosaur bones from the Ojo Alamo Sandstone have distinctly different concentrations of rare earth metal elements than the deeper, older rocks that date from the time of the impact. This suggests that it's unlikely the bones originated in that older rock and were somehow relocated to the more recent, higher level of sediment.
mercredi 29 avril 2009
Yes, and they went on to become Republicans
This is interesting: It seems that not all the dinosaurs were wiped out by that asteroid after all:
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