Archaeological Research Facility

The analysis here of 195 obsidian artifacts from the surface and subsurface of Piedras Marcadas Pueblo ruin (LA 290) in the middle Rio Grande River valley indicates a source provenance similar to previous analyses of surface and subsurface contexts dominated by sources from the Jemez Mountains, both pre-and-post caldera, (Shackley 2009, 2013a, 2014a, 2014b). All these sources are present in the Rio Grande alluvium as far south as Albuquerque, although the Valles Rhyolite (Cerro del Medio) nodules are very small, probably too small to produce the one projectile point made from this source (Sample 1911; Shackley 2021). Mount Taylor is not available in Rio Grande Quaternary sediments this far north (Shackley 2021). Refer to Shackley (2021) for a thorough discussion of the sources and secondary distribution.

Most unique and important for the history of the site, and indeed the Coronado presence in the Middle Rio Grande valley is the occurrence of two polyhedral blade fragments produced from the Zinapecuaro obsidian source near the town of the same name in northeastern Michoacan state of west central Mexico (see discussion below). This blade fragments from a source thousands of kilometers south into Mexico was most likely transported to the site during the siege of Piedras Marcadas by Coronado in 1540 by one or more of the West Mexican Indians traveling with Coronado. This source has never been recovered in the U.S. portion of the Southwest to my knowledge, and blade production after the Paleoindian period in North America was not practiced by native artisans (Bradley et al. 2010; Collins 1999). The only other obsidian Mexican artifacts recovered from Arizona and New Mexico are blades and blade fragments produced from one of the Sierra de Pachuca sources from Hidalgo state, Mexico, and no documented obsidian has been recovered in the Southwest from central Mexican or sources south of central Mexico other than these here and the four blades produced from Pachuca sources (Dolan and Shackley 2021).