Interpreting Intrasource Variation in the Composition of Obsidian: The Geoarchaeology of San Martin Jilotepeque, Guatemala

Compositional analyses have long been used to assign obsidian artifacts to particular source areas. In most cases, the chemical “fingerprint” of a particular source area has been determined through the assay of only a few geological specimens from one or two outcrops. As a result, the full range of intrasource compositional variation has rarely been noted, and its spatial patterning frequently has not been studied. This report describes the results of geoarchaeological survey at the important Guatemalan source area of San Martín Jilotepeque. Neutron activation analysis demonstrates the presence of seven distinct chemical “fingerprints” corresponding to spatially discrete subsources within the region. Ancient procurement and production are associated with only three of these subsources. Statistical procedures that can be used to assign artifacts to particular quarries or quarry systems are presented. Several minor Guatemalan source areas also are examined, and one (Media Cuesta) also can be characterized as consisting of two distinct subsources.