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.