Interaction and isolation as concepts play a critical role in models of how the Sepik coast developed such amazing linguistic and cultural diversity over time.  While it is impossible to directly observe past human interaction, it is possible to trace the exchange of material culture between people living in different locales in the past by measuring the chemical properties of the objects they left behind. 

Regenstein Postdoctoral Fellow Mark Golitko has been collaborating with Dr. John Terrell to document prehistoric and modern exchange relations along the Sepik coast using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry.  This is housed in the Field Museum Elemental Analysis Laboratory, which was set up with funding from NSF Archaeometry grant BCS-0320903, and is under the direction of Dr. Patrick Ryan Williams and Dr. Laure Dussubieux. 

LA-ICP-MS uses a powerful laser to remove small amounts of material from archaeological artifacts, the chemical composition of which is then measured.  This allows large numbers of objects to be rapidly chemically characterized in an essentially non-destructive way, thus permitting not only the analysis of excavated finds, but also Museum objects housed in the Field Museum’s Pacific collections that cannot be destructively analyzed. 

After measurement of the composition of artifacts, chemical “fingerprints” were established for specific locations along the coast, and the movement of objects can now be established by identifying samples found at one locations that are chemically similar to those produced elsewhere.  For instance, some of the chemical differences between ceramics produced in the Serra Hills and those produced in the Aitape area (Aitape-Barida Groups 1-3) are evident in a bivariate plot of strontium and calcium concentrations. This chemical patterning is matched by that measured in clays from the respective locations, further indicating that these chemical differences are telling us about where different objects were produced.  Additionally, several chemical signatures have been identified at archaeological sites further east on Tarawai and Walis islands, as well as ceramics produced in the Aitape area and prehistorically transported there.

To date, over 300 ceramic objects and over 400 pieces of obsidian (volcanic glass) from past and present village sites along the Sepik coast have been analyzed by LA-ICP-MS.  This research is beginning to demonstrate that for at least the last 2,000 years, people living along this coast have been in frequent contact with one another and have received objects that originated as far away as New Britain, some 1,200 kilometers east of the Sepik coast.  Ceramics, however, appear to have been primarily exchanged from important production centers in the Aitape area within the last 1000 years of prehistory.

For further discussion please see:

 Golitko, M. (2011)  Provenience Investigations of Ceramic and Obsidian Samples Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Portable X-Ray Fluorescence.  In Exploring Prehistory on the Sepik coast of Papua New Guinea, edited by J.E. Terrell and E.M. Schechter, pp. 251-287, Fieldiana Anthropology New Series No. 42.  Field Museum of Natural History, Chicago.

Golitko, M, J.V. Dudgeon, H. Neff, and J.E. Terrell (2011) Identification of Post-Depositional Chemical Alteration of Ceramics from the North Coast of New Guinea (Sandaun Province) by Time of Flight-Laser-Ablation-Inductively Coupled Plasma-Mass Spectrometry (TOF-LA-ICP-MS).  Archaeometry online early view: doi: 10.1111/j.1475.2011.00612.x.

Mark Golitko

Mark Golitko in the LA-ICP-MS Facility at The Field Museum (© The Field Museum)

A plot of concentrations of Strontium and Calcium in pot sherds analyzed by LA-ICP-MS showing the chemical distinction between Aitape area pottery and clay (Aitape-Barida Groups 1-3) and pottery and clays from sites on the adjacent mainland (© 2011, Mark Golitko)