Magazine article Science News

Iridium Spike Not a Comet Strike?

Magazine article Science News

Iridium Spike Not a Comet Strike?

Article excerpt

Iridium spike not a comet strike?

When researchers discovered a high iridium level in sediments that had been deposited during the Cretaceous-Tertiary (K/T) mass extinctions, it stood out like a sore thumb. Iridium is rare on the earth's surface, and since it's found in greater concentrations on comets or asteroids, some scientists proposed that an impact of an extraterrestrial body caused the iridium spike, as well as the extinctions. And so began a fervent debate over what killed the dinosaurs and other life 65 million years ago (SN: 2/1/86, p.75).

Recently, however, scientists at Exxon Production Research Co. in Houston concluded that the K/T iridium spikes may have nothing to do with the extinctions. Art Donovan and his co-workers have studied what they say is one of the most complete K/T sections known. They have found three iridium spikes created in a time span of about 1 million years at a site in the Clayton formation in central Alabama. …

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