Following the devastating impact of a miles wide asteroid with the Earth 65 million years ago the race of dinosaurs went extinct, right?
Not so, says a research team at the University of Alberta, Canada.
New dating method raises doubts about current extinction theory
For years quite a number of palaeontologists have accepted the belief that most dinosaurs became extinct after the Yucatan asteroid impact caused a worldwide “nuclear winter” dimming the sun, killing off most plant life and savaging the higher life forms all the way up the food chain. The die-off is called the great mass extinction of the late Cretaceous period.
Much of that belief centered on dating methods that seemed to support the asteroid collision association theory.
But the Alberta team, led by geologist Dr. Larry Heaman from the Department of Earth and Atmospheric Sciences, used a new ‘direct-dating’ analysis called U-Pb (uranium-lead) to determine the age of a plant-eating hadrosaur’s thigh bone more accurately than any previous method. The results were surprising. The dinosaur bone—discovered in New Mexico—was just 64.8 million years old.
Their test revealed that the creature lived nearly 700,000 years after scientists thought its species had gone extinct.
The new process replaces the old, less accurate dating method called “relative chronology”—a technique that established a fossil’s age by determining the geologic age of the rock where the fossil was discovered.
It’s not that accurate a technique as sedimentary layers can shift or erode over eons and paint a false picture of a fossil’s age.
How the U-Pb dating method works
Fossilized bone matter contains higher levels of uranium than living bone. Uranium, present in living bone tissue at extremely low levels, decay into atoms of lead over long periods of time. The process—that takes about 1,000 years—begins after bone has fossilized. As the years progress, more uranium atoms decay into lead. Since the rate of decay is well-known, it’s possible to determine with a very high degree of accuracy when a bone became fossilized.
To measure the rate of decay and the accumulation of lead in the bone matter, the researchers harvested tiny particles of the fossil with a laser. They then subjected the samples to the advanced radioactive dating method. The process is so sensitive and accurate that it reveals many things about the once living creature—including when it died and even its diet.
Revision of time line may be necessary
Heaman thinks that vegetation survived in some regions leading to a number of hadrosaur species surviving. If true, that leads to the possibility that other dinosaur species also managed to survive hundreds of thousands of years past the great mass extinction event. If so, then the entire time line will have to be revisited and, if necessary, changed.