Here we present 127 14C measurements, of which 115 were performed at the Centre for Isotope Research (CIO Groningen), and 12 at the Curt-Engelhorn-Center Archaeometry (CEZA Mannheim). On the basis of the state of development of the earlywood and latewood cells in the waney edge, one can even determine the precise felling season. Moreover, it is not necessary to have 14C dates for the outermost growth rings, because once the ring that contains the ad 993 anomaly has been detected, it simply becomes a matter of counting the number of rings to the waney edge. In so doing, if the bark edge (or more specifically, the waney edge) is also present, it becomes possible to determine the exact felling year of the tree 20. By uncovering these features in tree-ring samples of unknown age, it is possible to effect precise pattern matching between such samples and reference series. These sudden increases were caused by cosmic radiation events, and appear synchronously in dendrochronological records all around the world 25, 26, 27, 28, 29. However, such time series have also revealed that production of the isotope rapidly increased in the years ad 775 and ad 993 by about 12‰ (which manifests as a decrease of about 100 14C yr) 24 and about 9‰ (about 70 14C yr) 6, respectively. Measurements on known-age (dendrochronological) tree rings show that 14C production usually fluctuates by less than 2‰ per year 23. Exact-year 14C results can be achieved by high-precision accelerator mass spectrometry (AMS) in combination with distinct features in the atmospheric 14C record 20, 21, 22. In our study, we use an advanced chronometric approach to anchor Norse activity in the Americas to a precise point in time. This offset was also sometimes inappropriately incorporated into summary estimates 3. The term inbuilt age refers to the difference in time between the contextual age of the sample and the time at which the organism died (returned by 14C analysis), which can potentially reach hundreds of years. Furthermore, many of these samples were subject to an unknown amount of inbuilt age. ![]() Such impediments included far greater measurement uncertainty and restrictive sample size requirements. The unfavourable spread in the 14C dates is down to the limitations of this chronometric technique in the 1960s and 1970s when most of these dates were obtained. The latter offer differing scenarios for the frequency and duration of Norse activity in the Americas, but both the archaeological and written records are consistent with a very brief occupation (Supplementary Note 3 and Extended Data Fig. This is in contrast with the archaeological evidence and interpretations of the sagas. However, the calibrated age ranges provided by these samples extend across and beyond the entire Viking Age ( ad 793–1066) (Fig. More than 150 14C dates have been obtained, of which 55 relate to the Norse occupation 19. Most previous estimates have been based on stylistic analysis of the architectural remains and a handful of artefacts, as well as interpretations of the Icelandic sagas, oral histories that were only written down centuries later 2, 16 (Supplementary Note 2). Radiocarbon ( 14C) analysis has been attempted at the site, but has not proved especially informative 3, 17, 18. The received paradigm is that the Norse settlement dates to the close of the first millennium 9 however, the precise age of the site has never been scientifically established. ![]() Evidence has also revealed that L’Anse aux Meadows was a base camp from which other locations, including regions further south, were explored 15. Extensive field campaigns have been conducted at this UNESCO (United Nations Educational, Scientific, and Cultural Organization) World Heritage Site, and much knowledge has been gained about the settlement and its contemporary environment 2, 13, 14, 15 (Supplementary Note 1). However, the only confirmed Norse site in the Americas is L’Anse aux Meadows, Newfoundland 9, 10, 11, 12 (Extended Data Figs. ![]() The Vikings (or Norse) were the first Europeans to cross the Atlantic 9.
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