For more than 3 decades, scholars have debated the authenticity of the Vinland Map--purported to be the first chart of the New World. Now, U.S.-based researchers have confirmed that the parchment dates to the 15th century. But a British team says it was drawn in 20th century ink--putting the parchment and ink camps an ocean apart.

Since the map first surfaced in a private library in 1957, some researchers have argued that its similarities to other documents link it to the Council of Basel, a meeting in Belgium of Catholic clergy held from 1431 to 1449. That timeline is consistent with new radiocarbon dating suggesting that the parchment was made between 1423 and 1445, report physicist Douglas Donahue of the University of Arizona in Tucson, chemist Jacqueline Olin of the Smithsonian Center for Materials Research and Education in Suitland, Maryland, and chemist Garman Harbottle of Brookhaven National Laboratory in Upton, New York. Their results, which appear in the August issue of Radiocarbon, make it harder to explain how the map might have been faked, Olin says. "It would be very fortuitous for a forger to go out and pick a parchment of that exact age."

But only a modern forger could have obtained the ink used to draw the map, argue chemists Katherine Brown and Robin Clark of University College London in the 31 July issue of Analytical Chemistry. Black lines on the map fade to yellow around the edges, as if the ink had soaked into the parchment. However, by studying laser light reflected by the lines, the researchers confirmed that yellow areas contain anatase, a naturally rare compound that has been used as a synthetic ink pigment since the 1920s, which suggests that the yellowing was faked. Ironically, the carbon-based ink in the black lines wouldn't have leached into the parchment naturally, Clark says. "But the forger might not have known that."