Prehistoric bedrock features: recent advances in 3D characterization and geometrical analyses

Bedrock features such as hewn mortars, cupmarks and cupules are known around the world. In the Levant they first appear in Natufian sites (ca. 15,500-11,500 Cal BP), in large numbers and a wide variety. Traditional archaeological documentation was commonly limited to hand drawing and general photography. In order to better document these features and provide a high-resolution analysis platform, we hereby introduce a protocol based on photogrammetry, 3D modeling and geometrical characterization even of the deepest features. As case studies, we analyze a deep narrow mortar and a bowl-like mortar from the Natufian site of Raqefet Cave, Mt. Carmel, Israel. Using 20 images per feature was sufficient to create a 3D model for each, with a millimeter level of accuracy. We then characterized each by measurements of volume, shape, vertical and horizontal reflective symmetries. The method offers quick and affordable in-field archaeological recording apparatus, facilitating the derivation of high-resolution 3D models. Using the method provides new avenues for bedrock features documentation and analyses, both on intra- and inter-site levels.