Chemical characterization of obsidian in west-central Argentina and Central Chile: archaeological problems and perspectives

Abstract

Trace element analysis has been performed on 911 samples from 106 archaeological sites and more than 100 samples from six sources. The samples come from archaeological sites located in all environments within a large area located between 32º and 37º south and 67º and 72º west, and in a chronological range of 9000 to 300 years BP. Analyses were performed to determine the spatial distribution of sources and to investigate the potential of these data to test models of mobility and exchange proposed for different regions in that area. Three different X-ray fluorescence (XRF) spectrometers were used: two energy dispersive and one wavelength dispersive. This paper discusses some problems of interpretation of archaeological and geological records related to the application of different methods and equipment. This experience shows the need to improve the geochemical sampling of sources and to confront different methods of analysis and calibration. The results provide an adequate resolution for discriminating the use of different sources throughout the Holocene, indicating variable spatial and temporal distributions. The general trend shows a preferential use of the sources located in the mountainous regions. Las Cargas source, used since the early Holocene (ca. 9000-8000 BP), together with Laguna del Maule source, were the most important sources in the entire area (including eastern and western slopes of the Andes).