Le rôle du ruissellement dans la formation des sites préhistoriques : approche expérimentale

This study focuses on run-off as a natural process in prehistoric site formation. A set of experiments and observations in natural contexts has been generated in order to describe this sedimentary agent. Two axes of research have been investigated: (1) sedimentary facies genesis and (2) prehistoric assemblage modification. Regarding this second point, an emphasis is put on criteria that can be used to determine the level of modification in various sedimentary contexts produced by run-off processes. This represents a necessary first step in an integrated approach to the study of prehistoric sites. In this study, runoff is first characterized sedimentologically. The effects of runoff on the archaeological assemblages are then evaluated based on a set of experimentally-derived criteria. This approach is applied to the analysis of four assemblages: three rockshelters, Toutifaut (Dordogne), Caminade (Dordogne) and Diepkloof (South-Africa) and one cave, Isturitz (Pyrenees atlantiques). For each of these locations, it is shown that runoff has played a major role in site formation. After describing the way the archaeological assemblages have been modified by natural agents, two major types of disturbances are discussed with respect to stratified deposits. The first type of disturbance results in pseudo-level formation and is observed when runoff occurs after the site abandonment. The second type of disturbance concerns sites in which sedimentation and the succession of occupations are penecontemporaneous. In this case, artefacts from distinct occupations become associated in a single level in areas dominated by sedimentary transfer. Conversely, in areas of net deposition, the addition of translocated artefacts to the archaeological assemblages contributes to level dilatation and produces a loss of resolution in the "stratigraphic signal. "