Archaeological Site Formation in Rain Forests: Insights From the Ituri Rock Shelters, Congo

Abstract

This contribution complements the existing literature on rock shelter geoarchaeology and site formation processes by presenting data from 10 granite rock shelters in a tropical rain forest environment. Geological, taphonomic, pedological, and archaeological data are used to assess the geomorphological evolution of rock shelters in the Ituri rain forest, Northeast Democratic Republic of Congo. Mechanisms of sediment production and deposition, soil formation, and related site formation processes were investigated. The implications for the preservation of archaeological materials and stratigraphic resolution are discussed. Rock shelters in the tropical environment of the Congo basin are formed by mechanical and chemical denudation of large granite boulders. The current geomorphological cycle of rock shelter formation and collapse dates to the late Pleistocene and may have been accelerated by anthropogenic forces. The sedimentary record includes in situ breakdown products from the rock shelter walls, while off-site sources are represented by a minor influx of colluvium. Soil-forming forces have acted on these matrices. Humans introduced charcoal, phytoliths, endocarps, shell, animal and human bone, as well as inorganic materials such as stone, ceramics, and metal. Lags of archaeological materials are common under driplines where fine sediments have been washed away and include artefacts of different ages. There is no evidence of extensive bioturbation, but limited disturbance by roots, burrowing animals, and termites has been documented. Although there is some horizontal and vertical movement of prehistoric artefacts, the post-depositional translocation of materials is not significant. We conclude that the stratigraphic integrity of these granite rock shelter sites, with multiple archaeological horizons, and the potential for the long-term preservation of organic materials in a tropical environment are better than previously thought.