LEAVING NO STONES UNTURNED: INTEGRATING MICROMORPHOLOGICAL, P-XRF, AND STONE TOOL ANALYSES TO ACHIEVE ACCURATE RAW MATERIAL INTERPRETATIONS

Raw material selection is an important issue in the study of lithic technology and techno-economy. Therefore, the unambiguous identification of lithic material, especially in areas with large geological and raw materials variation, is essential. We present an analytical protocol to efficiently and accurately identify the lithic raw material categories at archaeological sites. The protocol combines petrological properties (as studied on micromorphological samples), elemental composition of the specimens and lithics exposed in micromorphological samples (measured with p-XRF) and visual characterization by lithic analysts. We use the lithic assemblages at Umhlatuzana rockshelter (South Africa) as a case study in which we apply and further develop our protocol. Our aim is to establish a raw material database and to provide a more accurate insight in raw material selection during the Middle and Later Stone Age occupational sequence of Umhlatuzana (~70 – 10 ka). The results of this study indicate that the raw materials used at Umhlatuzana are not as previously reported (1985 excavation- quartz 61%, hornfels 38%, quartzite 1% (Kaplan 1990)). We demonstrate that the most commonly used raw material is sandstone (40%), followed by hornfels (30%) and quartz (26%). The combination of micromorphological and p-XRF analysis of the Umhlatuzana assemblages demonstrates that if only visual inspection is done, the variability of raw materials used and the relative frequency of different rock types may be misinterpreted. Overall, the protocol is based on established techniques, is easy to apply, it is non-destructive, and it can provide important new insights into past raw material procurement and prehistoric economic behaviors. We claim that by applying this protocol/approach, geoarchaeologists could achieve more in-depth inter-disciplinary collaborations with other experts working at archaeological sites such as lithic specialists.