“It looked like a gold mine”
New evidence comes from old samples. Dozens of radiocarbon dates obtained from wooden artifacts unearthed at L’Anse aux Meadows in the 1960s show that the archaeological site was around a thousand years old. However, at the time, radiocarbon dating was in its infancy and the margin of error was typically measured in decades, if not centuries.
Fortunately, avant-garde archaeologists have predicted that better dating methods may be developed in the future. When Margot Kuitems, an archaeologist from the University of Groningen and co-author of the study, visited the warehouse a few years ago, was surprised. The thousand-year-old wood “looked incredibly fresh, like it had been stored yesterday,” she notes. “It looked like a gold mine.”
But Kuitems was not looking for the best preserved woods. She is Michael dee, an expert in radiocarbon dating, also from the University of Groningen, was looking for places to test a new dating method based on tree rings. To see if they could delineate L’Anse aux Meadows’ age more precisely, Kuitems collected four pine and juniper trunks still in their bark, all of which had been cut down and left near one of the Scandinavian houses. “These are not real artifacts, nor beautiful pieces made by the Vikings,” Kuitems explains of the main samples. “These are discarded pieces of wood.”
All four samples had something in common that made them perfect for Dee and Kuitems’ purposes: They had been found in layers of soil alongside other Viking artifacts, which connected them to the activities of this people. In addition, they had been cut or carved with metal tools (then unknown to other peoples of North America), as well as other evidence of Viking manual labor. And all of them still had bark: a clear indication of when the tree’s growth stopped.
There was another aspect that stood out: Three of the wood samples were from trees that had been alive during the solar event of 993, when the cosmic storm emitted a pulse of radiation so powerful it was recorded in tree rings around the world. Called a “radiocarbon cosmogenic event” by researchers, the phenomenon has only happened twice in the past two thousand years.
The cosmic storm, along with a similar event in AD 775, left “spikes” that distort the radiocarbon dating of wood by about a century, a fact first noticed by researchers in 2012. Identifiable only by comparing individual trees derived from the radiocarbon. -ring dates, the resulting anomaly creates a sort of tree ring timestamp. “When there are spikes, it’s pretty obvious,” says Dee, who led the new study.
The team carefully sampled and radiocarbon dated more than 100 tree rings, some less than a millimeter thick, in an effort to find the peak of the year 993 in radiocarbon age. In three of the pieces of wood, the exact indication sought was found. Simple counts allowed us to calculate when the Vikings cut down the tree. “If the tree has a lot of rings to the bark, it’s just a matter of math,” Dee explains. In this case, there were 28 rings separating the bark and the tree ring on which the solar pulse of 993 was recorded.
“The previous radiocarbon dating spanned a period from the beginning to the end of the Viking Age,” Dee explains. “Now we can prove that the arrival of the Vikings took place in 1021 at the latest.”
In addition, this date confirms two Icelandic sagas: the “Saga of the Greenlanders” and the “Saga of Erik the Red”, which relate the attempts to establish a permanent colony in “Vinland”, in the far west of the Viking world. Although written in the 13th century, both sagas refer to people and historical events, allowing researchers to piece together an approximate chronology of expeditions made in the 11th century.
Zori agrees that the new dating will not revolutionize what we know about Vikings in the Americas. But using the peak cosmic radiation of 993 to date, other places can offer new information, especially in places where historical records cannot be easily linked to archaeological finds. “To relate specific events to monuments or buildings, having an exact date can change our understanding,” Zori notes.
For Dee, the setting of dates creates a palpable connection to a time when humanity completed its expansion across the planet and reached a dense forest on the shores of the North Atlantic. “The moment of crossing the Atlantic was sort of the last step,” he continues. “The date obtained proves this real event.”
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