Archaeological Research Facility

The analysis here of 300 artifacts (12 not obsidian and a few not analyzed) from three sites (SON:F:2:4, 61, and 82) in the Valle de Altar in the northern State of Sonora, Mexico indicates a very diverse provenance assemblage with known sources on both sides of the border, including Arizona, New Mexico, Chihuahua and Sonora, and a large proportion of, as yet, unlocated sources (73.9%) dominated by one unusual trachyte obsidian source (72.9%). The main unknown source is likely located somewhere along the Río Altar or somewhere above that stream basin, and called provisionally here SON Valle de Altar Unknown. The diversity of obsidian source provenance decreases from west to east as the unknown source dominates the assemblage (see cover image). This study is one of the largest archaeological obsidian provenance studies in Sonora, and despite the number of "unknown" sources provides a good basis for further archaeological and geoarchaeological research in Sonora (see also Shackley 2019a).