These rocks are not as old as was assumed, new research suggests.
Joel Kontinen
Radiometric dating methods have problems that cannot be characterised as minor. Last week Science published two reports that have a bearing on the age of rock layers.
The problems have to do with the half-lives or the time in which certain atoms decay or turn into other atoms.
According to the first study, the half-life of Samarium-146 is approximately 30 per cent shorter than previously assumed. The previous figure of 103 ± 5 million years has to be discarded. The new figure is about 68.7 million years.
The second paper indicates that the ratio of Uranium-238 to Uranium-235 was not the same in all rocks (137.88:1) but that it varies from 137.743:1 to 138.490:1.
Commenting on the importance of the study for Nature news, Daniel Condon of the British Geological Survey, whose team conducted the research, says that many rocks are roughly 800,000 years younger than previously assumed.
This means that in practice, everything else, including meteorites and moonstones, are younger than assumed. Thus even fossils found in rock layers should be somewhat younger than what textbooks state.
For two centuries, the idea of millions of years has been respected as a dogma that cannot be criticised.
Science publications have occasionally reported on discrepancies in dating methods. Read more here and here.
Sources:
Cressey, Daniel. 2012. Ratio rethink will adjust rock clocks Nature news (29 March).
Kinoshita, N. & al. 2012. A Shorter 146Sm Half-Life Measured and Implications for 146Sm-142Nd Chronology in the Solar System. Science 335:(6076), 1614-1617. (30 March).
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