Portable X-ray fluorescence of Lower Pecos painted pebbles: New insights regarding pigment choice and chronology

Abstract

Painted pebbles are the primary mobiliary art found in the Lower Pecos Canyonlands of southwest Texas and northern Mexico. Previous studies of these artifacts have focused on stylistic variation of the imagery and interpretation of the role these artifacts played within Lower Pecos societies. The focus of this study is the use of portable X-ray fluorescence on Lower Pecos painted pebbles to conduct elemental analyses to identify the pigment used by ancient artists in the paint recipe for painted pebble production. Using a sample of recently excavated painted pebbles, as well as a sample from a private collection, a total of 254 pXRF measurements were collected on 70 pebbles. We determined that charcoal was used as a pigment for black paintings and that iron-based mineral pigments were used for red paintings. The newly excavated pebbles range in age from 6500 to 700 RCYBP, and the stratigraphic and chronologic context of these pebbles provides a dataset for analyzing not only pigment selection, but allows us to also address changes in painted pebble production through time. This paper summarizes the results from the pXRF analysis, and discusses the larger archaeological implications for Lower Pecos painted pebbles.