Cation-ratio dating of rock-engravings from the Olary Province of arid South Australia

Desert varnish, the distinctive coating on exposed rock surfaces in arid regions, can be dated by cation ratios, providing a rare means directly to date petroglyphs. A first application of the method, much used in north America, is here reported from Australia, where it indicates minimum ages up to 30,000 years old. And it also shows that the style of figures, so often taken as a measure of chronology, is in this instance largely independent of age.