Radiocarbon dating of prehistoric rock paintings

Abstract

Prehistoric rock paintings occur worldwide, but until recently, they could not be dated directly. We have developed a new method utilizing a low-pressure, low-temperature oxygen plasma, that allows direct [^14]C dates to be obtained on these artifacts. The plasma provides the means for separating the organic component in the paint from the inorganic carbon in the substrate, allowing the paint to be dated by accelerator mass spectrometry (AMS). The technique is applicable even to paintings that occur on limestone (CaCO3) walls. The rock paintings from the Lower Pecos region of Texas have been dated (3,865 [plus or minus] 100; 3,355 [plus or minus] 65; and 3,000 [plus or minus] 70 years BP), and are in accord with expectations based on archaeological inference (circa 4,000 to 3,000 years ago). We have further demonstrated the method by dating a known age sample; our method produced an age of 3,665 [plus or minus] 65 years BP, matching the established age of the sample which is 3,655 [plus or minus] 60 years BP. Additional experiments have shown that the technique produces negligible mass fractionation, the maximum deviation in the δ[^13]C produced by our process was found to be 0.16[parts per thousand] from the untreated sample. Each of these results support our conclusion that the technique has the potential of producing accurate and reliable ages for prehistoric rock paintings.