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According to the team, the carbon-14 data has similarities to the geomagnetic record and indicates an abrupt increase in radiocarbon around the Laschamp excursion.
This, they say, suggest that changes in the Earth’s magnetic field could be responsible for much of the historic fluctuations in atmosphere radiocarbon.
“When do different species of animal disappear over the last 50,000 years?
Stalagmites in a Chinese cave have given scientists all they need to reconstruct the historical record of atmospheric radiocarbon (carbon-14) back to the carbon dating limit of around 54,000 years ago.
These do not always provide a direct record of atmospheric carbon levels, however, as the carbon-14 has often passed through other systems that add more carbon to the mix.
The water that helps form a stalagmite, for example, will have passed through soil and rock – collecting additional carbon.
Scientists from China and the US have created a precise record of atmospheric radiocarbon for the last 54,000 years, from isotopes locked inside a pair of stalagmites.
According to Tom Higham, of the School of Archaeology at the University of Oxford, this work is an exciting and important contribution to radiocarbon data as it is “a very detailed and high coverage record”.
He adds that it overlaps well with other records and is in “good agreement with tie points such as the Campanian Ignimbrite volcanic ash event”, indicating its accuracy.
“This new dataset will have significant implications for our ability to calibrate radiocarbon and get the right answers to some of the big questions prehistorians are grappling with,” Higham says.
As levels of carbon-14 in the atmosphere fluctuate over time, to enable accurate dating the atmospheric carbon-14 record needs to be calibrated against a calendar time-scale.
Tree rings provide some of the best information on historic radiocarbon levels, as trees take carbon dioxide directly from the atmospheric and turn it into cellulose with little delay.
Plants incorporate this radiocarbon from carbon dioxide during photosynthesis.