Microfocus X-ray tomography as a method for characterising macro-fractures on quartz backed tools

Abstract: Here we present the first assessment of microfocus X-ray tomography (micro-XCT) as an analytical technique to generate data about macro-fractures on small quartz backed tools similar to those currently held to represent the oldest known evidence for bow hunting. Our experimental results are derived from 21 replicated quartz backed tools randomly selected from a population (n=218) that were broken in a controlled hunting context. We used 3D data obtained from micro-XCT scans to identify macro-fractures and to derive more accurate measurements for these fractures. Our results demonstrate that the micro-XCT technique overcomes reflected-light challenges associated with analysing quartz through conventional macro-fracture approache s. We were able to increase the total observed macrofracture sample by 33% compared with conventional approaches using a hand-lens. Whereas macro-fracture data could be refined, the additionally gained data did not change interpretations obtained from a conventional macro-fracture analysis. It did, however, marginally change the degree of significance in differences between the different applications. During this study, we also detected micro-fracture features, such as possible fracture wings and microscopic linear impact traces (MILTs).With further studies, the morphometric traits of these micro-fracture features could be useful for distinguishing between ancient weapon-delivery systems