Correlation between modern plant δ 15N values and activity areas of Medieval Norse farms

Abstract

This further nitrogen isotopic study of Greenlandic Norse archaeological sites provides new evidence of the affect of past human activity on modern plant δ 15N values. Grass samples were taken from a number of spatially defined features at four Norse farms and one site interpreted to be a seasonally occupied herding station (sæter). At the farms, un-naturally high δ 15N values were found for plants from each sampled feature, including those from the likely infields and a churchyard. At the sæter no strong isotopic effect was expected and none was found. Comparing the data from the farms we found that the average plant δ 15N values were similar for features that were functionally alike. We conclude from these observations, that the unusually high plant δ 15N values reflect the strong conservation of the isotopic composition of the nitrogenous materials deposited in the past, and the magnitude of the values reflects the amount of this material admixed in the soil. The results confirm previous exploratory studies of this isotopic effect and further demonstrate its potential value as an archaeological tool.