Washington, April 25 : Scientists have pinpointed the date of the dinosaurs' extinction more precisely than ever, suggesting that the event, which marked the mass extinction, occurred much earlier than previously believed.
Scientists at the University of California, Berkeley, and the Berkeley Geochronology Center did the analysis, using refinements to a common technique for dating rocks and fossils.
The argon-argon dating method has been widely used to determine the age of rocks, whether they're thousands or billions of years old. Nevertheless, the technique had systematic errors that produced dates with uncertainties of about 2.5 percent.
Now, Paul Renne, director of the Berkeley Geochronology Center and his colleagues have lowered this uncertainty to 0.25 percent and brought it into agreement with other isotopic methods of dating rocks, such as uranium/lead dating.
As a result, argon-argon dating today can provide more precise absolute dates for many geologic events, ranging from volcanic eruptions and earthquakes to the extinction of the dinosaurs and many other creatures at the end of the Cretaceous period and the beginning of the Tertiary period.
That boundary had previously been dated at 65.5 million years ago, give or take 300,000 years.
But latest research has now determined that the best date for the Cretaceous-Tertiary, or K/T, boundary is now 65.95 million years, give or take 40,000 years.
"The importance of the argon-argon technique is that it is the only technique that has the dynamic range to cover nearly all of Earth's history," said Renne.