Analysis of Mesoamerican Plumbate Pottery Surfaces by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS)

Abstract

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a highly sensitive microprobe technique with many potential applications in chemistry-based archaeological provenance research. Laser sampling makes it possible to characterize individual components of heterogeneous matrices or to characterize surface materials, such as pigments, slips, and glazes on ceramics. Quantifying the analytical data poses a significant challenge, but an approach suggested by Gratuze et al. (2000) seems to perform well if the major oxides are measured. In the present study, LA-ICP-MS is used to characterize the slipped surfaces on specimens of a famous Mesoamerican tradeware known as Plumbate. First, systematic chemical variation with depth in the slipped surface layer is investigated in order to determine how much material to remove by pre-ablation before taking measurements for provenance determination. Slip-compositional subgroups are found to coincide well, but not completely, with paste-compositional subgroups identified in a separate study that employed instrumental neutron activation analysis (INAA). Comparison of LA-ICP-MS data on raw materials from the presumed source region (Pacific coastal southern Mesoamerica near the present border between Mexico and Guatemala) to the slip-compositional groups yields highly specific source attributions that agree with provenances determined for the INAA paste groups. This evidence indicates that the distinctive Plumbate paste preparation and firing technology was shared by two groups of potters who exploited two distinct ceramic resource bases within the Pacific coastal source region. The dominance of Plumbate at sites outside these two source areas indicates the importance of intra-regional commercial interaction during the Late Classic through Early Postclassic periods.