Bayesian mixing models as a tool to explore Bronze Age bitumen trade from Tell Lashkir (Erbil, Iraq)

Bitumen from north-eastern Mesopotamian seeps was exchanged across the Tigris and the Euphrates in antiquity. Nonetheless, recent research proposed a decline in its trade during the Bronze Age alongside the boost of central Mesopotamian (Hit) seeps trade. This paper presents new provenance studies from ancient bitumen recovered at Tell Lashkir, a 4th-2nd millennium BC settlement between the lower and upper Zab Tigris tributaries. The novel application of Bayesian mixing models to biomarker and isotopic data has narrowed down the identification of the bitumen putative sources and improved the apportionment of mixtures. This placed Tell Lashkir within the pathway of bitumen active trade routes in the Bronze Age. Thus, the population inhabiting Tell Lashkir participated in exchange networks which reached southern Mesopotamia, and traded with natural resources most probably originating from central and north-eastern Mesopotamia. From a methodological standpoint, the appraisal of the Bayesian mixing models in our study with modern and archaeological reference samples has provided a better understanding of the strengths and limitations of such an approach to apportion bitumen sources from several Bronze age territories.