fossilized dinosaur bone discovered in New Mexico contradicts previous
scientific data that suggests that dinosaur extinction occurred between 65.5
and 66 million years ago, says a team of researchers from the University of Alberta.
Heaman, study leader from the Department of Earth and Atmospheric Sciences at
the University of Alberta, along with a team of researchers from the
university, have found a fossilized femur bone of
a hadrosaur in New Mexico that is only 64.8 million years old, showing that
dinosaurs lived 700,000 years beyond mass extinction in the late Cretaceous
believe that dinosaurs became extinct between 65.5 and 66 million years ago
when debris from a large meteorite impact blocked the sun, changing the climate
drastically and killing vegetation. Paleontologists determined this time period
as the age of extinction by using a traditional technique called relative
chronology, which has been used in this field of science to estimate the age of fossils.
Relative chronology is when a fossil's age is determined by the depositional
age of a layer of sediment where the fossil was found, or by the depositional
age of layers of sediment above and below the fossil. But the problem with this
method is that environmental and geologic forces can cause fossils to shift or
migrate from their original layers of sediment, leading to a potentially
inaccurate estimate of age.
particular study, Heaman and the University of Alberta team checked the age of
the recently discovered dinosaur bone using a technique called U-Pb
(uranium-lead) dating. This method uses a laser beam to "unseat" tiny
particles of the fossil. These particles are then subjected to isotopic
analysis, which both determines age and the type of food the dinosaur
dating method is accurate because living bone carries low levels of uranium,
but fossilized bone is rich with uranium. These uranium atoms decay into lead
over time, and determining the isotopic composition of the lead in fossilized
bones leads to its absolute age.
using this technique on the femur bone of the hadrosaur, Heaman and his team
concluded that the bone is 64.8 million years old, which means that this
hadrosaur came from a line of dinosaurs that
survived the great mass extinction in the late Cretaceous
period, and lived 700,000 years beyond it. Researchers believe these particular
plant-eaters were able to survive mass extinction because some of the
vegetation may have survived the climate change allowing them to eat.
researchers are looking to figure out if dinosaur eggs could have potentially
survived during the period of mass extinction, which would further explain the
survival of these dinosaurs. They also plan to use the U-Pb dating method to
continue measuring the absolute age of other dinosaur fossils. Heaman believes
that this technique will replace relative chronology, and will be used to
rewrite the history of the extinction of the dinosaurs.
This study, titled
"Direct U-Pb dating of Cretaceous and Paleocene dinosaur bones, San Juan
Basin, New Mexico," was published in Geology.