Characterising the stone artefact raw materials at Liang Bua, Indonesia

Abstract

Abstract At Liang Bua, the type site of Homo floresiensis on the Indonesian island of Flores, the stone artefact assemblages are dominated by two raw materials, qualitatively classified as chert and silicified tuff in previous studies. Field observations describe both stone types as locally abundant and of good flaking quality, but no systematic analysis has yet been carried out to characterise their nature. In this study, we conducted the first geological, mechanical, and quantitative assessment of these two raw materials using a suite of analytical approaches. Our results show that the two stone types are mineralogically alike in composition and derive from fossiliferous limestone that had undergone diagenetic silica replacement, but they clearly differ from one another geochemically. Therefore, the ‘chert’ and ‘silicified tuff’ categories used in previous studies are more aptly described as silica-dominated (i.e., SiO2-dominated) nodular chert and iron-rich (i.e., Fe2O3-rich) nodular chert, respectively. We discuss the implications of our results on the shift in raw material utilisation patterns at Liang Bua that occurred after ~ 46 ka and coincided with the arrival of Homo sapiens at the site.