We extracted carbon from a sample removed from a small, nondescript, solid monochrome pictograph at the Painted Indian Cave site on the Pedernales River, Blanco County, Texas (41BC1). It contains red iron oxide pigment and is approximately 10-20 cm in size. The sample was taken with a surgical scalpel with a new blade. Plasma chemistry was utilized to extract the organic carbon, without getting contamination by inorganic carbon-bearing minerals, calcite, and calcium oxalate. Because the background of organic carbon in nearby unpainted rock (limestone) was negligible, the age should be reliable. Further, it is supported by archaeological inference. However, as always with only a single radiocarbon date, especially with minimal carbon extracted, caution is advised pending further study. Radiocarbon analysis at the Center for Accelerator Mass Spectrometry of the Lawrence Livermore National Laboratory indicated an age of 770 ± 50 years BP. The age is consistent with the image of a bison within the small cave. The depiction of the bison probably corresponds with the earliest Late Prehistoric sightings of bison as they re-entered the South Plains of Texas in larger numbers.
Three examples of this were the All-American Man, the Pryor Mountain shield figure, and the Texas bison from Painted Indian Cave. The All-American Man rock painting is unique in our studies. We extracted CO2 from a charcoal layer that dated to 750 ± 60 years BP.