Mass Extinction That Led to Age of Dinosaurs Was Swift, Study Shows

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It's widely believed that the dinosaurs were wiped out by a cataclysmic event such as the crash of a giant meteor that was hurled to Earth. Ward speculates that the same kind of thing may have happened in the mass extinction 200 million years ago, paving the way for dinosaurs.

"The suspicion is this is an impact event, an asteroid-related extinction," he said.

Data From Carbon Levels

The fossil evidence of the extinction was gathered at two very remote and still largely untouched sites in the Queen Charlotte Islands, off the coast of British Columbia, in Canada. "These provide the best record of how hasty the extinction was at this [time] boundary," Ward said.

The mass extinction 200 million years ago occurred just before the breakup of Pangaea, which contained all the land on Earth in one supercontinent. At the time, the Queen Charlotte Islands, which now lie between 52 and 54 degrees north, were probably on the equator or in the southern hemisphere, Ward noted.

By using different isotopes (unusual atomic configurations of a chemical element), scientists can date the age of rocks and measure the amounts of life on Earth, in the form of carbon levels. Samples from a spot called Kennecott Point, in the northern Queen Charlottes, and from Kunga Island, about 100 miles (160 kilometers) to the southeast, showed a sharp decline in the presence of organic carbon about 200 million years ago.

Carbon is an essential component of all living organisms. The drop in organic carbon measured by the scientists correlated with a dramatic decline in radiolarians, a kind of protist, that serve as a food source for a number of marine species.

The scientists actually measured levels of productivity, the rate at which inorganic carbon is turned into organic carbon through processes such as photosynthesis. One example of productivity, Ward explained, occurs in the spring when fertilizer washes into waterways and triggers large algae blooms. The situation 200 million years ago was like a reversal of that process, marked by a huge waning of productivity.

Ward, who has also done research on other mass extinctions, plans to return with a team to the Queen Charlottes in the hope of finding more clues about the Triassic-Jurassic extinction.

The other researchers in the new study were James Haggart and Howard Tipper of the Geological Survey of Canada in Vancouver, British Columbia; Elizabeth Carter, a researcher at Oregon's Portland State University; David Wilbur, an oceanographer at the University of Washington; and Tom Evans, a student at the University of Washington.

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