Lead uranium dating
The zircon has been cut and polished, then treated with high-temperature annealing and chemical abrasion with hydrofluoric acid.
The term 'U-Pb dating' normally implies the coupled use of both decay schemes."Zircons have produced complicated data that are hard to interpret, though people have pulled dates out," said Mundil, a former UC Berkeley postdoctoral fellow now at the BGC, a non-profit scientific research institute dedicated to perfecting dating techniques for establishing the history of Earth and life on Earth."Many of these studies will now have to be redone." The U/Pb isotopic dating technique has been critical in dating geologic events more than 100 million years old, including volcanic eruptions, continental movements and mass extinctions."The beauty of this new technique is that we now can analyze samples we previously could not get an accurate date for," Mundil said.When Mundil used this treatment, the zircon dates were much more consistent, requiring no selective interpretation of the data.The calculated uncertainty is about a quarter of a million years, which means the extinction took place over a very short time, the researchers concluded.