A not so isolated fringe: Dutch later prehistoric (c. 2200 BCE-AD 0) bronze alloy networks from compositional analyses on metals and corrosion layers

Using a corpus of over 370 compositional analyses of Dutch Bronze Age and Iron Age (c. 2000 BCE AD 0) copper alloy artefacts, long-term patterns in the types of alloys used for specific bronze objects are identified. As the Low Countries are devoid of copper ores and alloying elements, a combination of typo(chrono)logical and compositional analysis is used to identify through which European contact networks (such as Atlantic, Central European or Nordic exchange networks) these alloys were obtained. We employ a methodology that (following Bray et al., 2015) defines alloy groups by presence of As, Sb, Ag and Ni over 0.1 %wt, but expanded this classification to include Pb and to track high-impurity (>1%wt) alloys. Due to interfering soil-derived iron hydroxides, and preferent dissolution of copper from the objects’ surface, the determination of tin is in most cases overestimated when using p-XRF, so Sn was not systematically reviewed. Objects were assigned a calendar age in years BCE to facilitate chronological sorting. Using this classification, we could show how different alloys (using different base ores) were used in different periods, and in different combinations. Moreover, particular alloys were used for different groups of functional types of objects. Also, we show diachronic differences in the influx of new (or less frequently mixed) alloys and chronological trends in the substitution of As by Sn as main alloying element in the Early Bronze Age as well as the rise of leaded alloys at the close of the Bronze Age. Combining information on the composition of the objects with their typological traits, allowed us to reconstruct the scales and geographic scopes of the European contact networks in which the copper alloys used throughout later prehistory were obtained.