River ice as a taphonomic agent: An alternative hypothesis for bone “artifacts”

Abstract

The annual freezeup and violent breakup of temperate and high-latitude rivers produces unique geomorphic features that can be recognized in ancient sediments. The forces and materials involved in the breakup process could modify entrained bones in ways similar to those attributed to human activity. An intuitive taphonomic model is developed to explain how river ice may affect bones, and to predict the modifications expected. Partial testing of the model by experiments designed to simulate river breakup produced bone modifications such as fractures, flakes, facets, striations, isolated cuts, and polish. The taphonomic effects of river ice must be discounted prior to the interpretation of such features as human in origin.