Obsidian in the Caribbean islands? Mysterious Ceramic Age glass artefacts in the Lesser Antilles

The Caribbean islands witnessed a population expansion of ceramic-using horticulturalists during the Early Ceramic Age (ca. 500 BC to 750 AD) from the Orinoco Valley to Puerto Rico. We examined 18 lithic artefacts from Guadeloupe and Dominica initially thought to be obsidian, a material believed to be absent from those islands. We investigated the volcanic or meteoritic origin of this unique and yet unknown material through observation (binocular, SEM, microtomography) and geochemical analyses (PIXE, SEM-EDS, ED-XRF, EPMA, LA-ICP-MS). Elemental analyses rule out the hypothesis of an origin from a meteoritic impact (i.e. identification as tektites). Most of the artefacts have an andesitic composition (<63% SiO₂), which appears to be unique among ‘massive’ glasses. The only artefact with a rhyolitic composition has been traced back to the Guadeloupe's Volcan du Tuf, where glassy fragments have been collected and analysed. The geological source of the other vitreous artefacts that exhibit an andesitic composition could be from a sublocal subduction-arc volcanism (maybe from Martinique), although no volcanic vitreous material of this kind has ever been reported worldwide. These results once again highlight the regional mobility of Early Ceramic populations and the production of standard lithic products using a highly original, albeit low-quality, local lithic resource, and provide valuable references for future identification of similar materials.