New Visual Analytics Tool and Spatial Statistics to Explore Archeological Data: the Case of the Paleolithic Sequence of La Roche-à-Pierrot, Saint-Césaire, France

The archeological record of La Roche-à-Pierrot (France) is central to debates on the Middle to Upper Paleolithic transition. To this day, it is the only site to have provided a relatively complete Neandertal skeleton associated with an industry identified as transitional, the Châtelperronian, which had been attributed until then to 'Homo sapiens'. The site was the subject of several excavation campaigns led by F. Lévêque in the 1970s, 1980s, and 1990s, and ongoing fieldwork resumed in 2013. Spatial representations and statistical analyses of the original excavation data are of invaluable help in assessing the coherence of the first archeological stratigraphy established in the 1970s. A 3D reconstruction of Lévêque’s spit record was developed for exploratory purposes, based on reassessment of the faunal collection and completed by information recorded in the excavation notebooks filled out by Lévêque’s team. It was then used in order to evaluate the feasibility of modeling the data recorded during the first excavations. Geovisualization tools, associated with appropriate 3D spatial statistics using the Queen contiguity applied to the archeological sequence, such as the similarity and coherence indices, provided an understanding of the spatial inconsistencies in the first archeological sequence, as well as revealed the spatial organization (geometry) of the archeostratigraphic units. The resulting interactive visualization application provides researchers with a new tool to explore the stratigraphic units spatially, as well as according to their indices. Where inconsistencies are observed, use of similarity and coherence indices allows discussion of any biases potentially related to topography, spatial heterogeneity of the deposits (facies), excavation history, or primary data acquisition/recording. Such spatial analyses contribute to a better understanding of site formation processes and provide novel means to explore archival information interactively, as well as to produce models including data from old and new excavations on the same site.