ESTABLISHING A STRONTIUM ISOSCAPE FOR THE AMERICAN MIDCONTINENT: IDENTIFYING POTENTIAL ‘PLACE/S OF ORIGIN’ FOR CAHOKIA’S IMMIGRANTS

Archaeological research has highlighted the importance of population movement and interaction in promoting cultural and sociopolitical change at the Mississippian (AD 1050-1400) urban center of Cahokia. Cahokia’s extensive sphere of influence and interaction extended across the midcontinent--from the Gulf Coast to the Great Lakes. Strontium isotope analysis provides new insight into the population diversity of this early city. Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) are used increasingly worldwide to study prehistoric human population movement. We recently applied this technique to the question of immigrants at Cahokia. Strontium isotope analysis of tooth enamel from small, and non-migratory mammals recovered from archaeological sites in the American Bottom of Illinois were used to refine the local strontium signature for the Cahokia region. Analyses of human teeth from multiple mound and cemetery contexts at Cahokia were then compared to this range. Approximately one-third of the individuals sampled had strontium isotope ratios falling above or below the local range for Cahokia indicating that they had come to the area from somewhere else (Slater et al., J. Arch. Sci. 2014). The range of ‘non-local’ strontium ratios identified in the Cahokia sample confirms a diverse population with people coming from may different places.

Identifying the homelands of these immigrants has remained problematic due to the lack of regional strontium data. Enamel from ~270 small non-migratory terrestrial and semi-aquatic fauna representing 40 locations important to the question of Cahokia interaction provides baseline regional ⁸⁷Sr/⁸⁶Sr information for the Midcontinent. The results of this study identified considerable overlap in the strontium isotope range across this region, but also identified important isotopic differences. In this paper we present results of this analysis and discuss the implications for identifying the place/s, or potential place/s, of origin for Cahokia’s immigrants.

This research was supported and funded by the Illinois State Archaeological Survey (ISAS) and the Prairie Research Institute (PRI) at the University of Illinois, Urbana-Champaign (FY15-MRAP).