Local or interregional exchange systems? A study of Estonian iron provenancing

The aim of this study is to address questions about the differences in chemical composition of iron smelting slag finds in Estonia. The chemical analyses of smelting slag will allow to establish a production regions reference dataset for further research. Currency blooms have been also included, of which some have been dated to the Estonian Viking Age (800–1050 AD) and the Late Iron Age (1050–1227 AD). The blooms are examined about their relationships with possible production regions. Using a multi-method analytical approach (SEM-EDS, LA-ICP-MS) and a multivariate data analysis (PCA, AHC and a set of supervised methods) it is argued that Estonia most likely had a highly interconnected local exchange of iron between different regions. An existence of exchange centres which specialised in the production of such blooms is also possible. A key methodological finding is that contrary to results reported in the literature covered, there exists a considerable overlap between the discussed production regions. This indicates that even with multiple samples, chemical elements and sophisticated statistical methods, a perfect separation of production areas may not always be achievable, especially when solely bog ores served as raw material for ironmaking. However, this study demonstrates that despite such a strong overlap of data in the chemical composition of the slags, a successful provenance study of artefacts is still possible. • Provenance study with up-to-date slag and slag inclusions analytical methods. • Testing the potential of provenancing iron from different geological settings in Estonia. • 26 samples, 11 currency blooms, 1 bar and 14 iron smelting slags or other byproducts like unprocessed iron analysed with SEM-EDS and LA-ICP-MS. • Different statistical methods (PCA, AHC, Kruskal-Wallis, ANOVA) used. • Interregional trade of iron in Estonia where currency blooms might have been the main tradeable item.