Abstract

Obsidian was a key toolstone for the development of maritime lifeways in the western archipelago of southernmost South America. This area is a fragmented landscape where the major north–south movement of people along the Pacific was only possible by navigation because it is constrained by major biogeographic barriers. Two obsidian sources have been recorded, each one located on the extremes of the archipelago, and each has played a key role in the canoe-adapted societies that used them. As indicated by repeated inductively coupled plasma mass spectrometry analyses, obsidian from Chaitén Volcano to the north was distributed between 38°26? S and 45°20? S, and obsidian from Seno Otway to the south was distributed between 50° and 55° S, although it mainly occurred in sites close to the Strait of Magellan and within constrained time periods. This study explores the distribution of these two types of obsidians, their chronology, their frequencies in the archaeological record, the main artifact classes that are represented, and the technological processes in which they were involved. This examination indicates common aspects in the selection of high-quality toolstones for highly mobile maritime groups and discusses the different historical trajectories of two obsidians that appear decoupled across the Holocene. © 2025 by the authors.