Serpentine bends site #1: Radiocarbon dating prehistoric soot and associated pictographs

Abstract

At Serpentine Bends Site #1, we employed plasma oxidation followed by accelerator mass spectrometry to radiocarbon date two prehistoric rock paintings as well as soot on the shelter ceiling. Pictograph results are 2325 ± 30 14C years BP for a black line and 1315 ± 40 14C years BP for a red outline of a circle motif. We also utilized X-ray diffraction to chemically identify pyrolyzed carbon in the black stain on the shelter ceiling, confirming that it is from fire smoke. Four radiocarbon ages for the soot represent a weighted average of multiple fires, instead of a single event. The oldest result of 2740 ± 70 14C years BP is from the underlying black soot closest to the rock substrate and, as a weighted average of multiple layers, represents a minimum age for human activity at the site. Dating both pictographs and prehistoric soot provide novel methods for dating human activity within rockshelters around the world, especially when there is a lack of excavated materials for study.