Radioactive dating uranium lead
It is widely assumed that the extinction was caused by debris from a giant meteorite which struck Earth, blocking out the sun, causing extreme climate conditions and killing vegetation around the world.
Heaman suggests it is possible that vegetation, and hence dinosaurs, survived in some areas.
Such processes can cause the daughter product to be enriched relative to the parent, which would make the rock look older, or cause the parent to be enriched relative to the daughter, which would make the rock look younger.
This calls the whole radiometric dating scheme into serious question.
The results from Heaman's team show that the sauropod in question was alive 64.8 million years ago, 700,000 years after the mass extinction, bringing into question the fate of the dinosaurs after the KT extinction.
Currently, palaeontologists date dinosaur fossils by a method called relative chronology, estimating the age of a fossil relative to the known depositional age of the sedimentary rock in which it was found.These long time periods are computed by measuring the ratio of daughter to parent substance in a rock and inferring an age based on this ratio.This age is computed under the assumption that the parent substance (say, uranium) gradually decays to the daughter substance (say, lead), so the higher the ratio of lead to uranium, the older the rock must be.The possibility that dinosaur eggs might survive extreme climatic conditions is also a possible avenue to be explored.If the new U-Pb dating technique is borne out by more fossil samples, then the KT extinction paradigm and the end of the dinosaurs will have to be revised, Heaman and his colleagues believe.