Expanding radiogenic strontium isotope baseline data for central Mexican paleomobility studies

by Sofía I. Pacheco-Forés, Gwyneth W. Gordon, Kelly J. Knudson

Radiogenic strontium isotopes (⁸⁷Sr/⁸⁶Sr) have long been used in analyses of paleomobility within Mesoamerica. While considerable effort has been expended developing ⁸⁷Sr/⁸⁶Sr baseline values across the Maya region, work in central Mexico is primarily focused on the Classic period urban center of Teotihuacan. This study adds to this important dataset by presenting bioavailable ⁸⁷Sr/⁸⁶Sr values across central Mexico focusing on the Basin of Mexico. This study therefore serves to expand the utility of strontium isotopes across a wider geographic region. A total of 63 plant and water samples were collected from 13 central Mexican sites and analyzed for ⁸⁷Sr/⁸⁶Sr on a Thermo-Finnigan Neptune multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). These data were analyzed alongside 16 published ⁸⁷Sr/⁸⁶Sr values from two additional sites within the region of interest. A five-cluster k-means model was then generated to determine which regions of the Basin of Mexico and greater central Mexico can and cannot be distinguished isotopically using ⁸⁷Sr/⁸⁶Sr values. Although the two clusters falling within the Basin of Mexico overlap in their local ⁸⁷Sr/⁸⁶Sr ranges, many locations within the Basin are distinguishable using ⁸⁷Sr/⁸⁶Sr values at the site-level. This study contributes to paleomobility studies within central Mexico by expanding knowledge of strontium isotope variability within the region, ultimately allowing researchers to detect intra-regional residential mobility and gain a greater understanding of the sociopolitical interactions between the Basin of Mexico and supporting outlying regions of central Mexico.