Two independent methods for dating rock art: Age determination of paint and oxalate layers at Eagle Cave, TX

摘要

This study demonstrates a novel approach to overcoming challenges associated with obtaining reliable radio-carbon dates for rock paintings. Using two independent methods, we obtained ages for Pecos River style paintings at Eagle Cave in Langtry, Texas. The first method employed plasma oxidation to isolate organic carbon directly from the paint layer for accelerator mass spectrometry C-14 measurement. The second method treated mineral accretion layers with phosphoric acid to isolate calcium oxalate for plasma oxidation cleaning, com-bustion, and C-14 measurement to obtain minimum and maximum ages for the paintings. Radiocarbon dates for the paintings are statistically indistinguishable, with a weighted average of 3280 ? 70 years BP calibrated to 1740-1420 cal BC (3690-3370 cal BP) at 2 sigma (95.4%) probability. Radiocarbon assays obtained for the overlying accretion layers are younger and underlying accretion layers are older. The chronological stratigraphy of the accretion and paint layers supports the validity of both dating methods. With accurate and reliable dating methods, rock paintings in the region can be studied alongside excavated cultural deposits to provide a more complete understanding of this hunter-gather society. These methods for dating rock paintings can be applied to many rock art provinces around the world.