New surface exposure ages for petroglyphs from the Olary Province, South Australia

Abstract Exposed surfaces of rock engravings in the Olary Province of South Australia develop coatings of rock varnish, amorphous silica, and oxalate‐rich crusts. Instead of relying on any single approach, we use three experimental approaches to assign minimum ages to the petroglyphs. Three methods involve dating manganiferous rock varnish formed over the petroglyphs: 14 C measurements of organic matter at the varnish/weathering rind interface provides numerical ages; calibrated ages are obtained by cation‐ratio dating; and sequences of layers within varnish are used to discriminate relative ages. A different approach is radiocarbon dating of organic remains within the weathering rind entombed by either rock varnish or amorphous silica. In addition to updating our 1988 results, we report two dozen new radiocarbon ages, eight new cation‐ratio ages, and studies of varnish stratigraphy. Although the techniques we use are experimental, our data suggest that petroglyphs have been made in the Olary Province for the last 40,000 radiocarbon years, making its rock art the oldest known in the world. Broader implications of our findings for the cultural history of the Olary Province and for different approaches to dating rock art are explored.