Assessing surface movement at Stone Age open-air sites: first impressions from a pilot experiment in northeastern Botswana

Open-air sites are ubiquitous signatures on most archaeological landscapes. When they are appropriately recorded, well preserved and are single-component occupations, they provide access to high-resolution information that is often not available from rock-shelter sites. These sites are, however, commonly affected by a number of post-depositional factors that are not adequately studied in archaeology. This paper presents the results of an open-air experiment conducted in northeastern Botswana. Two surface scatters modelled on known Bushman open-air camp sites were created to investigate the taphonomic factors affecting such sites. The scattered materials at these sites included stone tools, ostrich eggshell fragments, ceramic sherds, glass beads and faunal remains. Two scatters were laid out consisting of a nested square design; one site was excavated after four months and the other after twelve. The results show little horizontal material movement at these scatters and an initial, rapid, vertical period of mobility, after which the majority of surface artefacts are protected from subsequent movement, preserving the general scatter structures. This experiment suggests that open-air sites can offer detailed spatial information relevant to human settlement structure that is often not accessible at rock-shelter sites.