Fossils tell story of day meteor struck Earth
WASHINGTON: Paleontologists generally grapple with a time frame of millions of years.
But Robert DePalma believes he can explain the minutes and hours that followed one of the most cataclysmic events in the history of the Earth – the day a meteor slammed into the coast off of what is now Mexico.
The impact of the Chicxulub asteroid 66 million years ago left a massive crater and triggered the mass extinction of land and sea creatures.
DePalma has been digging for the past seven years at a site in North Dakota that he and other scientists believe provides a unique fossilized record of what happened on that day.
“You almost never get this opportunity at fine tuning the timing of any event in geologic history,” DePalma said in an interview with AFP.
“It’s very rare to get this.” DePalma, a paleontologist, and 11 co- authors published a preliminary study of their findings in the Proceedings of the National Academy of Sciences.
It has the scientific world buzzing.
DePalma first began digging, while a graduate student at the University of Kansas, at the site known to dinosaur hunters as Tanis in the Hell Creek Formation in North Dakota.
Over the years, he and several of his assistants discovered in a layer of sediment about 1.3 metres thick the fossils of fish, plants, trees and mollusks jumbled together.
“You’ve got this deposit that was almost instantaneously laid down,” DePalma said. “This muddy deposit that locked in place all these plants and animals almost instantaneously, within moments.”
DePalma likened it to Pompeii, the Roman city buried in a volcanic eruption in 79 AD and left remarkably preserved.
“Very similar to Pompeii. You’ve got this instant preservation of so many different thing,” she said.
The asteroid struck 3,050 kilometres away in what is now the Yucatan Peninsula in Mexico.
Scientists have long pointed to the impact of the Chicxulub meteor as responsible for the extinction of the dinosaurs, paving the way for the rise of mammals including humans.
Fire, smoke, ash and debris engulfed the atmosphere, eventually destroying almost all plants and wiping out 75 per cent of species on Earth.
The scientists believe Chicxulub caused a powerful earthquake whose seismic waves reached Tanis just 13 minutes later.
The seismic surges triggered a sudden, massive torrent of water and debris from an arm of an inland sea known as the Western Interior Seaway.
At Tanis, the surge left “a tangled mass of freshwater fish, terrestrial vertebrates, trees, branches, logs, marine ammonites and other marine creatures,” DePalma said.
Some of the fish were found to have inhaled tiny beads of glass, or ‘spherules’ that were ejected by the Chicxulub event and rained down on Tanis probably about 15 minutes after the impact. Many of the fossils found at the Tanis site are preserved in three dimensions instead of just flat shapes.
“Until this deposit, there were only three or four articulated fish ever found in the Hell Creek Formation, ever,” said DePalma, an adjunct professor of geosciences at Florida Atlantic University. — AFP