Gary sent in the link https://www.sciencenews.org/article/viking-age-ancient-solar-flare-trade-archaeology … trade from Ribe in Denmark has been dated as starting around 700AD. Glass beads, including beads manufactured in the Middle East, were discovered during an archaeological dig – but could not be dated precisely by C14. Evidence of prolific metal working was also found with numerous workshops over a couple of hundred years. Hide was prepared, weaving took place, and bones were carved. The Viking trading community did not display any evidence of violence of the sort they visited on the Irish and British, and the Russians and various others they raided. Ribe was apparently a safe town – for the Vikings. However, Viking raids took place mainly in the 9th and 10th centuries – coinciding with environmental downturns, so this is not a surprise.
Some 100,000 artifacts have been unearthed, we are told, and these include an amber battle axe pendant, and other rare items made from local products. Tools, accessories, and tribute. Int Cal20’s tree ring data are sparse during the 8th and 9th centuries, so the archaeologists decided to try out a novel approach, using a massive solar flare as a dating aid. This is the famous Miyake event, named after Japanese physicist Fuso Miyake, dated at AD775/6. The solar flare, or injection of C14 into the atmosphere, was first discovered in Japanese cedar trees. The Ribe workshops come in a layer cake format, with constant rebuildings and repairs delineating a succession of dating possibilities. The first began around AD700 with evidence of trading expeditions with the Franks. By the 740s the Vikings were shipping in large blocks of stone, and shipping out sharpening tools made from the stone as well as small objects. In the 750s they came upon antlers with an origin in Norway and in the 790s ample evidence of trade with the Middle East. Another solar flare, but not so prominent, was also used as a dating aid, from AD993. This was used to date object at L’Anse aux Meadows in Newfoundland.