Chemical characterization of sources of obsidian from the Sepik coast (PNG)

We report here on the chemical analysis by portable x‐ray fluorescence (PXRF) and laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) of 438 obsidian flakes recovered from Sepik coastal sites spanning the last two millennia of prehistory. Our results demonstrate the continuous involvement of local people in exchange networks moving obsidian from both the Admiralty Islands and West New Britain to this coast, possibly as far back as the mid‐Holocene. Suspected early assemblages contain significantly higher frequencies of obsidian from the more distant sources on New Britain. Assemblages dated to after ∼2000 calBP contain obsidian predominately from the nearer Admiralty sources. Site by site differences in the relative frequencies of obsidian from different Admiralty sub‐sources suggest that prehistoric patterns of interaction on the coast were complex, and cannot be accounted for by simple patterns of ‘down the line’ connections.