A reconstructed reduction sequence for curved bifacial stone tools from the eastern La Plata basin, Argentina.

Abstract

A distinctive regional lithic industry is found in the eastern La Plata basin, known as the Altoparanaense culture in northeastern Argentina, and the Humaitá tradition in southern Brazil. These archaeological cultures are recognised on the basis of large bifacial tools. The earliest deposits are dated to the ninth millennium BP, and elements of these industries continue to be produced into the post-contact period (8640±95 to 310±50 cal BP). One of the most characteristic features of the assemblages in the region is the presence of a particular class of bifacial tool known as “curved cleavers”, whose name stems from their distinctive asymmetrical shape. We describe the reduction sequence of these tools based on a spatially extensive sample from Misiones province, Argentina. This study provides for the first time a full chaîne opératoire for curved cleavers and compares it to the findings of the only published experimental study. We use a logistic regression model to verify the reconstructed five-stage reduction sequence and further support it with a metric analysis of artefact attributes within each identified stage of reduction. Our results support the conclusion that many bifacially reduced artefacts encountered in the larger study region may actually be unrecognised pre-forms of curved cleavers.