In the search for the origin of the barley at Norse farms in Greenland

Strontium (Sr) isotope analyses were performed on a number of individual charred grains of barley recovered from two selected Norse middens (Ø35; Ø49) in southwestern Greenland. The two middens were chosen because remnants of barley had been found in them in a previous project. Here we investigate whether barley was grown locally by the Norse or whether it was imported from Europe. While the Sr isotope signatures in each of the middens are in themselves homogenous through their depth profiles, they are distinctly different in each of their location (site Ø35 with an average ⁸⁷Sr/⁸⁶Sr = 0.70728 +/- 0.00058 (n = 5; 2σ).; site Ø49 with an average ⁸⁷Sr/⁸⁶Sr = 0.70978 +/- 0.00018 (n = 5; 2σ)). These compositions likely represent the homogenized signatures impacted by foodstuffs, mainly bones of domestic animals, fish, whales and seals as major dietary constituents. There is an additional contribution of local bioavailable strontium from the immediate surroundings, as emphasized by the strontium isotope signatures of soil extracts, plants and surface waters that are different from seawater strontium. Strong hydrochloric acid leaching of the barley grains, despite removal of > 90 % of the labile strontium, only led to insignificant isotopic changes in the first residuals attacked by aqua regia. A second aqua regia attack however was successful in recovering systematically more radiogenic ⁸⁷Sr/⁸⁶Sr signatures in both sites (⁸⁷Sr/⁸⁶Sr = 0.711 to 0.718) than those characterizing the respective midden signatures. At Ø49 these are compatible with the environmental soil extracts and plants, while at Ø35 the barley signatures resemble those recovered from site Ø49 and most likely imply local cultivation of barley in the nearby elevated terrains around the sites which are dominated by granitoid basement rocks of the Paleoproterozoic Ketilidian Province. Import of barley from Norway can however not be excluded as bioavailable strontium from some areas along the western coast and inner fjords has the same signature. Our results imply an effective adsorption of strontium from the midden onto the charred grains, making it difficult to fully extract the original strontium isotope biosignature of the barley.

The ¹⁴C dating of the middens show that they had been extensively disturbed and reworked during their period of use, making it impossible to establish a reliable chronological stratigraphy. However, overall, the dates indicate that Ø35 was established in the early 1000 s and operated for at least a couple of centuries. The midden at Ø49 was likely established in the mid-1000 s and operated at least until the mid-1200 s.