Invertebrate faunalturbation of archaeological sites: assessing the impact on archaeological stratigraphy

Abstract

The stratigraphy of an archaeological site is fundamental to the understanding of that site's history of occupation, use and abandonment. Archaeological stratigraphy is subject to a variety of post-depositional processes that may damage or destroy this stratigraphy. This work focuses on one such process, faunalturbation, i.e. the process of mixing by animals. The effects of the invertebrate soil mesofauna, in particular earthworms, were studied in this work. Three archaeological sites were investigated using faunal surveys, thin section micromorphology, 137CS profiling, field recording and determinations of pH, loss on ignition, bulk density and particle size distribution. This study views faunalturbation as a system and attempts to delineate and confirm the relationships within that study. The results demonstrate that soil properties such as loss on ignition and pH have some effect on the populations of soil invertebrates and on the intensity and distribution of faunalturbation, but that there are likely to be other factors which also have a significant influence. Two models of the possible impact that invertebrate faunalturbation has on archaeological stratigraphy are advanced and tested, with one being found to be more accurate. This model posits that the most rapid and complete impact on archaeological stratigraphy is found to occur in the uppermost region of an archaeological site, with significant but lesser impact occurring more slowly in the deeper part of an archaeological site. Where a site has accumulated in an episodic fashion, there may be zones at depth within an archaeological site which have had all stratigraphic units completely reworked by invertebrate faunalturbation.