Problems in Radiocarbon Dating Human Remains from Arid Coastal Areas: An Example from the Cape Region of Baja California

Abstract

Three AMS radiocarbon dates on bone collagen from Las Palmas culture human skeletons from the cape region of Baja California are analyzed. Carbon derived from both terrestrial and marine sources necessitates correcting the radiocarbon ages for reservoir effects. Complicating this, however, are (a) the uncertain percentage of carbon of marine origin in the samples and (b) the convergence of the Pacific Ocean and the Gulf of California, which differ markedly in reservoir values. Computer program CALIB 3.0.3c is used to correct and calibrate the conventional radiocarbon dates in a simulation using varied values for marine carbon and reservoir effects for each sample. This produces substantial variance in the results and, therefore, difficulties for chronological interpretation. For example, reasonable input values for dR and percent marine carbon yield dates that overlap the first European contact (A.D. 1533), despite the absence of historic documentation of the Las Palmas mortuary complex. Further research on reservoir effects and paleodiet is needed in order to interpret radiocarbon determinations on cape region human remains. Moreover, our findings have serious implications for the proper application of radiocarbon dating to samples from other regions subject to reservoir effects.