Trace element analysis of ochre for modern and prehistoric pigment source use patterns

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

Dependence on symbolism to communicate information and mark identities is an essential attribute of modern humans. The use of red and yellow ochre pigments for symbolic purposes is among the most widespread and persistent of human cultural behaviors. However, the study of archaeological ochre has been hindered by ambiguity over how to interpret this iron-based pigment in the absence of obvious symbolic applications such as cave or rock art. This project combines archaeological, geological, and ethnographic methods to investigate prehistoric through modern use of ochre pigments. The investigators have already conducted interviews with the Maasai and Samburu peoples of Kenya, many of whom still use ochre in their daily lives, and identified outcrops of ochre minerals that these groups exploit for symbolic and functional purposes. Geochemical techniques proven to be effective at telling apart ochre from different sources will be used to analyze samples collected from ochre deposits, and to match them to paint samples from rock art sites and ochre artifacts from archaeological sites in the region. This project will refine minimally destructive methods that can be used to analyze the composition of ochre and other iron-containing materials for anthropological, geological, materials science, and forensic applications. Improving techniques for determining the geographic and geologic origin of ochre pigments and related materials has significant implications for identifying looted heritage items and forgeries. The project will also provide opportunities for public science education via museum outreach, international collaborations, and mentoring in the STEM sciences for underrepresented minority students. Recent discoveries of ochre pigments from Stone Age archaeological sites have shed light on the great temporal depth of human symbolic behavior. Our understanding of the evolutionary significance and potentially the meaning of ancient symbolism using pigments has been enhanced by novel geochemical techniques for provenance studies of ochre, particularly minimally destructive trace element fingerprinting by Inductively Coupled Plasma - Mass Spectrometry. The project builds on improvements in this method over the last decade by creating a database of trace element and stable isotope (strontium, lead, and iron) fingerprints for ochre sources currently or recently used by inhabitants of the Kenya Rift Valley. The Maasai and Samburu are among the few remaining peoples in East Africa with active rock art and ochre self-adornment traditions. They present the best opportunity for studying how modern humans interact with their geologic environment for symbolic purposes. Once completed, the source database will be used to determine the geologic provenance of ochre artifacts and rock art paints of Stone Age through recent origin that were sampled during field and museum research. This will allow for investigation of hypotheses about symbolically mediated versus least-cost (nearest source) models of mineral deposit exploitation, transport and trade of ochre pigments, and preferential use of specific pigment colors. In addition, the source fingerprint database will be made freely available online for other scientists to use in their own research upon completion of the project.