Obsidian Sources of Prehispanic Artefacts from Cultures near Ceboruco Volcano, Nayarit, Mexico

Nayarit, Mexico, with the last historic eruption in 1870–1875. The fertile valleys around this volcano
have been occupied for several thousands of years. The recognised pre-Hispanic human settlements
include the Shaft tomb and Aztatlán cultures, which were present in the vicinity of the volcano before
and after the well-studied Plinian Jala eruption in 890 AD, respectively. Both cultures left abundant
archaeological materials in housing units and cemeteries, including obsidian tools. In this study, we
compare archaeological samples (poorly preserved tools or parts of them) with obsidian samples from
local outcrops, as well as other known regional obsidian mine sites. We use hand sample and chemical
analyses of main and trace elements. The results are statistically evaluated by using the Mahalanobis
distance-method in order to assign probable sources. We show that obsidian has been locally extracted
from long-known obsidian mines near Ixtlán del Río, but also from obsidian layers at the nearby Sierra
Madre Occidental Mountain Range and the Pochotero obsidian dome. Nevertheless, clear evidence
for obsidian trade since the earliest occupations has also been found, as we identified sources from the
neighbouring states such as Jalisco.