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Report Says Asteroid Did Not Kill Dinosaurs
posted: 10:16 am ET
03 March 2004
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WASHINGTON (AP) _ A Mexican crater often cited as evidence that a single asteroid wiped out the dinosaurs may not have been involved in that extinction at all, according to a new report WASHINGTON (AP) _ A Mexican crater often cited as evidence that a single asteroid wiped out the dinosaurs may not have been involved in that extinction at all, according to a new report. A group of researchers led by Gerta Keller of Princeton University contends that the impact that caused the crater occurred 300,000 years before the extinction. In a paper appearing in this week's online edition of Proceedings of the National Academy of Sciences, the group cites a layer of sediment it found between the impact layer and the co-called K-T boundary that marked the mass extinction 65 million years ago. Because it would have taken hundreds of thousands of years for the limestone layer to form, they argue the impact must have occurred well before the extinction. However, Richard D. Norris of the Scripps Institution of Oceanography, responded that the group has incorrectly located the K-T boundary and noted it suggests the sediments were deposited mainly in deep, quiet water. "The laminations, particularly since they are not of uniform thickness or horizontal, could easily be the product of high-energy bottom currents,'' he said. "The evidence they present, can in most cases be argued either way and so does not really resolve anything,'' Norris commented.
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