By IANS,
Toronto : A fossilised dinosaur bone unearthed in New Mexico shows that dinosaurs survived mass extinction by 700,000 years, according to a new dating method.
Many paleontologists believe the catastrophic event, between 65.5 and 66 million years ago, wiped all non-avian dinosaurs off the face of earth.
A University of Alberta team, led by atmospheric scientist Larry Heaman, determined the femur bone of a hadrosaur as surviving the catastrophe by 700,000 years, the journal Geology reports.
Heaman and colleagues used a new direct-dating method called U-Pb (uranium-lead) dating. A laser beam unseats minute particles of the fossil, which then undergo isotopic analysis, according to a University of Alberta statement.
This new technique not only allows the age of fossil bone to be determined but potentially can distinguish the type of food a dinosaur eats.
Living bone contains very low levels of uranium but during fossilization (typically less than 1,000 years after death) bone is enriched in elements like uranium.
The uranium atoms in bone decay spontaneously to lead over time and once fossilization is complete the uranium-lead clock starts ticking.
The isotopic composition of lead determined in the hadrosaur’s femur bone is therefore a measure of its absolute age.
Currently, paleontologists date dinosaur fossils using a technique called relative chronology.