New Evidence Found for Global Fire Contributing to Extinctions Eons Ago
NEW YORK (AP) _ Scientists say they have found new evidence that a worldwide fire, triggered by a meteorite impact, contributed to widespread extinctions of dinosaurs and other life forms 65 million years ago.
The evidence comes from close examination of ancient clay samples from five sites in Europe and New Zealand, the researchers said Thursday in the British journal Nature.
The hypothesis had been proposed in 1985 on the basis of similar studies. It built on a suggestion that a huge object crashed into Earth some 65 million years ago.
The impact is hypothesized to have kicked up enough dust to block sunlight for a long time, triggering extinctions by lowering temperatures and killing vegetation.
A worldwide fire could have added other dangers, University of Chicago chemist Edward Anders, a co-author of the new study, said Wednesday in a telephone interview.
Apart from burning or choking in the flames, organisms could have perished from newly formed toxic compounds, or from an eventual warming of temperatures triggered by carbon monoxide the fire poured into the atmosphere, he said.
The new studies found that carbon, thought to be from the soot, settled on the ground at about the same time as did particles of iridium, which are taken to have come from the meteorite. That suggests the fire was ignited by the impact, rather than occurring significantly later, Anders said.
Researchers found uniformity in the types of carbon found at the five sites, suggesting the carbon came from a single global fire, Anders said. Two sites show a particular type of hydrocarbon that may have come from the burning of coniferous trees, he said.
The Nature paper was co-written by Wendy Wolbach and Iain Gilmour at the University of Chicago, Charles Orth at Los Alamos National Laboratory in New Mexico, and a New Zealand researcher.