Weathering Stages of Proboscidean Bones: Relevance for Zooarchaeological Analysis

This paper describes weathering modifications to elephant bones in Zimbabwe, southern Africa, and discusses possible implications about conditions of deposition and the time elapsed since death or skeletonization. The observed patterns of proboscidean bone weathering, the times elapsed since death, and burial times may not be same as for bones of smaller terrestrial mammals typically found in fossil assemblages. A system of weathering stages is proposed for proboscidean long bones, flat bones, mandibles, and ribs. Special attention is given to drying cracks that affect breakage patterns when weathered bones are trampled or impacted. Weathering effects on elephant bones vary for several reasons, such as differences between juvenile and adult cortical bone and frequency of wet/dry cycling. Also briefly discussed are the observed or possible effects of burning, dissolution, organic erosion such as root etching, and inorganic carbonate (calcite) encrustation. Comparable weathering effects are also reported on bones of Mammuthus spp., supporting the probability that (1) bone weathering in fossil proboscidean assemblages can be described in corresponding terms, and (2) implications about assemblage origins may be similar, although this inference must be cautiously drawn. The data reported here will allow analysts to describe assemblage materials in consistent terms.