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28-Jun-2020 13:50

But the way Kerr worded his subtitle, he sounds at best tentative about its benefits: “A new, apparently improved, way to date the greatest mass extinction points to a volcanic cause but fails to resolve geochronologists’ long-running differences.” (Emphasis added in all quotes.) Mundil’s team, from the Berkeley Geochronology Center, admits right off that “The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts.” In order to date samples from China, they “adopted a technique recently developed by James Mattinson of the University of California, Santa Barbara, Kerr says.

“ They baked the southern China zircons at 850�C for 36 hours and then leached them with hydrofluoric acid under pressure at 220�C for 16 hours, with the intention of removing the parts most weakened by radiation damage.” This harsh treatment of the samples was intended to eliminate some of the “picking and choosing” that commonly goes on by researchers, who discard samples that don’t give them the results they expect.

Sometimes the most interesting science is in the data the conventional wisdom tosses out.

The stone that the builders rejected sometimes becomes the cornerstone of a new paradigm.

Even if Mundil threw out only 3 of his 79 samples, we want to know if those three had a story to tell: on what basis did he assume they were “obviously too old”?

How can we know the 79 he used were not also obviously too old, at least to someone without Darwin glasses on?

That’s what we learned in high school and on the Discovery Channel.

Now they tell us they have been picking and choosing the samples they want and tossing out over half the rest?

The challenge is that “P-T daters must draw their conclusions from vanishingly small isotopic remains of radioactive decay.” Though the antagonists try to keep a positive spin on the controversy, Kerr indicates that geochronology may not be the exact science we have been led to believe: The new preprocessing technique “is very promising,” says Drew Coleman of the University of North Carolina, Chapel Hill. But Bowring points to the later date that his group estimated for the P-T extinction in China and Kamo’s group independently got for zircon and other minerals from the lavas of the Siberian Traps. Speaking of the geochronologists, Randall Parrish of the British Geological Survey paints them like a secret society: “They’ve been competitive and secretive for decades,” he said.– surprising, because as a believer in the method and an evolutionist, he admitted there is a fair amount of unscientific methodology and controversy involved.“For years, different laboratories using uranium-lead radiometric dating—the gold standard of geochronology—have been getting entirely different ages for the P-T extinction,” he says.By taking into account how volcanic ash beds are stacked around the rock layer that shows the extinction, Bowring believes he can confidently select the reliable zircon ages and discard the rest.

Mundil set out to take this “picking and choosing” out of uranium-lead dating. With this method, Mundil claims he only had to throw out three out of 79 of his zircon samples which were “obviously too old.” He arrived at a date for the extinction a million years older.Samuel Bowring (MIT), for instance, got a date for the P-T extinction that, while it seemed to match some dates for massive Siberian lava flows, disagreed with the age Mundil prefers: Mundil, however, doesn’t believe that either the eruption or the extinction happened that recently.