Geochemical and mineralogical analysis of pre-Columbian stone tools from La Piedra Pintada, Baja California Sur, Mexico

Piedra Pintada is located in San Pablo Canyon, one of a series of major canyons that bisect the mountainous interior of the southern Baja California Peninsula, Mexico. Among the resources used by the canyon's prehistoric inhabitants were lithic materials suitable for the production of flaked stone tools. To help better define the spatial scale of resource procurement by the canyon's prehistoric population elemental analysis of samples collected from the dikes and selected stone tools was done by ICPMS (Inductively Coupled Plasma Mass Spectrometry). ICPMS was used because it can provide elemental "fingerprints" that can be used to distinguish source materials and correlate specific stone tools with individual source material sites. Relative abundances of minor elements, including transition metals and rare earth elements, can differ sufficiently between source rocks that elemental ratios can be used to link a stone tool with its source material in many cases. Comparison of elemental spectra from four stone tools with local dike rocks suggests that two of the four tools examined were manufactured from stone obtained from San Pablo Canyon.