Controlling Levallois: the effect of hammer angle of blow on Levallois flake morphology and fracture trajectory

Abstract Discussions of the Levallois method typically focus on the preparation of the core surface geometry as the primary factor in determining the characteristics of Levallois products. While some studies have acknowledged the role of knapping gestures, there is still limited empirical investigation into how different force application parameters influence the formation of these flakes. This study presents the results from a set of controlled experiments designed to assess the effect of hammer striking angle on the morphology and fracture trajectory of preferential Levallois flakes. By using standardised glass cores with surface morphologies that replicate those of a flintknapped Levallois core, the findings show that variations in the hammer angle of blow significantly alter the direction of fracture propagation through the core. These changes affect how fractures intersect with the core surface convexities, ultimately impacting the size and shape of the detached flakes. The results challenge existing models of conchoidal fracture and highlight the key role that force application variables play in controlling Levallois flaking outcomes. This study has important implications for interpreting the Levallois method in the archaeological record, emphasising the need for further research on the variability of hammer angle of blow in Levallois flake assemblages.