Petroglyphs Age Estimates Using Portable X-Ray Fluorescence Measurements

Summary

This is an abstract from the "New approaches to the intractable problem of dating rock art" session, at the 90th annual meeting of the Society for American Archaeology.

Petroglyphs are often created by removing the dark rock varnish that covers rock surfaces in arid and semiarid regions. Subsequently, the varnish redevelops over time. We have developed a non-destructive in-situ technique, using portable X-ray fluorescence (pXRF), for the measurement of the areal density of Mn and Fe on rock surfaces, which acts as a proxy for the amount of redeveloped varnish. When applied to surfaces of known age, such as dated lava flows, inscriptions, or petroglyphs, the accumulation rate of Mn can be obtained. We will present results from Arabia North America and discuss the observed variability at all scales from microscopic to global.

Once accumulation rates have been obtained, they can be used to determine the exposure ages of surfaces of unknown age. Age estimates are obtained by measuring the Mn areal densities on these surfaces and dividing them by the Mn accumulation rate. This approach was successfully applied to obtain age estimates for petroglyphs in North America and Arabia. While these estimates are still subject to significant uncertainty due to the inherent variability of the accumulation rates, they are extremely valuable in an archaeological context, where little or no alternatives exist for dating these important prehistoric artifacts.

This Resource is Part of the Following Collections

• Society for American Archaeology 90th Annual Meeting, Denver, CO (2025)   •
• New approaches to the intractable problem of dating rock art

Keywords

Record Identifiers

Abstract Id(s): 51394