Tracking an exotic raw material: Aboriginal movement through the Blue Mountains, Sydney, NSW during the Terminal Pleistocene

Abstract

A compliance-based excavation on Parramatta River (western Sydney) found evidence of a brief visitation by Aboriginal people during the terminal Pleistocene (c.14 ka), from which an exotic raw material–medium-grained porphyroblastic andalusite-cordierite hornfels–was recovered. This raw material is rare in the region, only found in the Megalong Valley situated some 75 km west of the site in Parramatta, and separated from the site by the Blue Mountains–a 40 km wide, 1 km high dissected sandstone upland. Historical observations and geological evidence suggest that the Coxs River, which runs through the upland, formed the probable connection between the two locales. The formation of the site at c.14 ka, along with our broader understanding of the region, suggests that the upland was only explored after the Last Glacial Maximum (LGM) and that the Great Dividing Range may have formed a significant barrier to early peopling of Sahul. Further, a delay between the end of the LGM and the exploration of the region implies populations were severely affected by the event and required considerable time to recover. The coincident timing of rapid sea-level rise from Meltwater Phase Pulse 1A and an increased supply of moisture associated with the Antarctic Climate Reversal at the time of many site initiations may have been factors in the upland and south west slopes visitation. Finally, the movement of the unusual hornfels artefact provides a coarse indication of the ranging territory for hunter-gatherers living in a temperate region (c. 8,000 km2) at this time. This is probably a lower estimate but begins to provide a quantitative value with which to begin to ratify the increasing divergence between archaeological and genomic studies in their definitions of mobility, sedentism and regional nomadism.