Our laboratory utilizes plasma oxidation as an alternative to combustion for cave painting samples prior to accelerator mass spectrometry radiocarbon dating. A radio-frequency, capacitive-coupled glow discharge is produced in a custom-built sample chamber at high vacuum, maintained with a turbomolecular and scroll pumping system. Glow discharges oxidize organic material below the decomposition temperature of interfering carbon-containing minerals. To obtain direct dates for paintings, we employed plasma oxidation of organic binders/vehicles in a base-treated paint sample followed by accelerator mass spectrometry. For minimum and maximum ages, we acid treated overlying and underneath accretion layers to isolate calcium oxalate, removed organic contamination with plasma oxidation, and combusted the remaining oxalate for <sup>14</sup>C measurement. At Eagle Cave in Texas, radiocarbon dates for three paint samples are statistically indistinguishable, with a weighted average of 3280±70 years BP calibrated to 1740-1420 cal BC at 2 sigma (95.4% probability). Overlying accretion layers are younger and underlying accretion layers are older. These correctly ordered stratigraphic ages for accretion and paint layers supports the validity of both dating methods. <br/>

Plasma oxidation prior to accelerator mass spectrometry radiocarbon dating

253rd National Meeting (2017)

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