Provenance of iron Age glass types present in Southeast Asia: Strontium and neodymium isotope analysis of glass beads excavated at Angkor Borei, Cambodia

Abstract

We conducted Sr and Nd isotope analysis on 27 glass beads found at Angkor Borei, southern Cambodia (200 BCE-200 CE) belonging to three different glass types: m-Na-Al 1, m-Na-Ca-Al and v-Na-Ca. The m-Na-Al 1 and m-Na-Ca-Al glass types split quite similarly into two sub-groups based on their ε_Nd signatures. High ε_Nd values are associated with a possible Sri Lankan provenance whereas low ε_Nd values point toward a possible eastern South Indian provenance. For both glasses, those sub-groups are correlated to specific trace element signatures and more specifically to distinct Cr and V levels. The high ε_Nd m-Na-Al 1 and m-Na-Ca-Al glasses have low Cr and V concentrations and the low ε_Nd m-Na-Al 1 and m-Na-Ca-Al glasses have higher Cr and V concentrations. Extrapolating these observations to all the Angkor Borei m-Na-Al 1 and m-Na-Ca-Al glass samples analyzed for elemental compositions, we were able to attribute a provenance to most of them. Most of the samples from Angkor Borei seem to come from eastern South India. The v-Na-Ca glass samples were manufactured in the Middle East but from possibly at least two different locations. For this study, we noted that the addition of manganese in glass for coloring purpose could also bring strontium and other elements that interfere with the strontium signature of the glass and also its trace element signature (including V and Cr).