[N] 2004 Impact occured 300.000 years before C/T extinction
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Researchers led by Gerta Keller of Princeton University contends that the impact that caused the crater occurred 300,000 years before the C/T extinction. In a paper appearing in 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.