The survival of artefacts from different historical phases in shallow open sites and the need for spit excavations: An overview from the Cumberland Plain, Western Sydney, Australia

Abstract

Abstract It has often been thought that shallow open sites (<50 cm of artefact-bearing deposit) in the undulating landscape of the Cumberland Plain would not retain any chronologically meaningful vertical distributions. The prevailing geomorphic model has proposed that artefacts discarded by people at different times would have been buried and mixed together by bioturbation. To address this model, this paper analyses the vertical distributions of artefacts at 21 open sites and finds that 13 of those sites show vertical variation in the proportions of indurated mudstone/silicified tuff (IMST), silcrete and/or quartz artefacts. The trends shown by the distributions are broadly consistent with a known regional change in raw material use and indicate the survival of some chronologically meaningful artefact variation with depth of the deposit. In addition, sites with increased proportions of older IMST artefacts in deeper deposits tend to be associated with larger streams and tend to occur at low elevations. This suggests that the survival of older artefacts could be related in part to long-term geomorphic processes visible at the landscape scale. The results indicate that sites may have differing histories of visitation, artefact discard, geomorphic processes and survival of evidence, and that careful, stratigraphic excavation is warranted.