New research by UC Santa Barbara geologist James Kennett and an international group of investigators has narrowed the date to a year range, sometime between 12, and 12, years ago.
The researchers used Bayesian statistical analyses of dates taken from 30 sites on more than four continents. By using Bayesian analysis, the researchers were able to calculate more robust age models through multiple, progressive statistical iterations that consider all related age data.
A cataclysmic event of a certain age
In a paper, Kennett and colleagues conclusively identified a thin layer called the Younger Dryas Boundary YDB that contains a rich assemblage of high-temperature spherules, melt-glass and nanodiamonds, the production of which can be explained only by cosmic impact. However, in order for the major impact theory to be possible, the YDB layer would have to be the same age globally, which is what this latest paper reports. All together, the locations cover a huge range of distribution, reaching from northern Syria to California and from Venezuela to Canada.
They also examined six instances of independently derived age data that used other dating methods, in most cases counting annual layers in ice and lake sediments.
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Two core studies taken from the Greenland ice sheet revealed an anomalous platinum layer, a marker for the YDB. A study of tree rings in Germany also showed evidence of the YDB, as did freshwater and marine varves, the annual laminations that occur in bodies of water. Even stalagmites in China displayed s of abrupt climate change around the time of the Younger Dryas cooling event.
Geologist James Kennett and an international team narrow the date of an anomalous cooling event most likely triggered by a cosmic impact. By Julie Cohen.
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