Fluvial dispersal potential of guanaco bones (Lama guanicoe) under controlled experimental conditions: the influence of age classes to the hydrodynamic behavior

Hydrodynamic sorting is a taphonomic process able to transport and scatter bones deposited in archaeological and paleontological sites. This study presents the results of experimentation performed in an artificial flume with guanaco (Lama guanicoe) bones of different ontogenetic development, dry and saturated in water, in hydric flows velocities of 15 and 30 cm/s. The obtained results show that bone global density, the age of the individual, the dry or wet bone state, and the hydric flow velocity influence significantly bone dispersion. In this way, bones from immature individuals with unfused secondary growth centers and relatively low bulk density have better possibility of being transported than fused bones from adult individuals. Taking into account the results obtained in this experimentation and the feasibility of discriminating age categories in fossil assemblages, two bone groups with differential potential transport are presented in this paper. These transport groups constitute a methodological tool to evaluate the role hydric current may had played in the formation of a fossil assemblage.