An initial survey of the composition of Ethiopian obsidian

Ethiopia is rich in obsidian and prehistoric peoples were utilizing it to make artifacts since at least the Early Stone Age. The unique chemical compositions of obsidian are of considerable interest to archaeologists when obsidian artifacts are recovered at prehistoric sites, both in terms of determining provenance and cultural exchange. Here we present electron microprobe analyses to characterize the major and minor element compositions of a suite of obsidian samples from 45 volcanic source locations along a 700 km extent of the Main Ethiopian Rift and the Afar Triangle. Of the 62 analyzed obsidian, 50 are classified as rhyolite, with subordinate numbers of trachyte and dacite. The Main Ethiopian Rift and its extension into the Afar region to the north have produced obsidian with different chemical affinities which may prove useful in narrowing down possible source regions for artifacts for which sources have not yet been discovered and/or analyzed.