A Re-Evaluation of the Reliability of AMS Dates on Pottery Food Residues from the Late Prehistoric Central Plains of North America: Comment on Roper (2013)

Abstract

Ancient carbon reservoirs in freshwater bodies have the potential to introduce ancient carbon into charred cooking residues adhering to pottery wall interiors when aquatic organisms are parts of cooked resource mixes. This ancient carbon results in old apparent ages when these cooking residues are subjected to accelerator mass spectrometry dating, the so-called freshwater reservoir effect (FRE). Roper's (2013) assessment of the FRE on14C ages from cooking residue in the Central Plains is only the second such peer-reviewed regional assessment in eastern North America. Roper suggests that 13 of 2314C ages on residue are too old as a result of ancient carbon from fish or leached from shell temper or old carbon introduced via maize nixtamalization. Herein, we re-assess Roper's data set of14C ages on cooking residues and annual plants and argue that she is mistaken in her assessment of the accuracies of14C ages from residues. This outcome is placed in the context of the larger FRE literature.