Brad and his co-author Professor L. Keith Fifield came to that conclusion by measuring levels of Berylllium 10. This is a radioactive isotope that accumulates in the surfaces of rocks because of radiation from space and indicates how long they have been exposed to the elements.
These findings support the idea that some of the rock art predates the last ice age, which occurred around 22,000 years ago, says Dr Ken Mulvaney, an archaeologist with Rio Tinto who produced the most recent age estimates based on the style of the art and weathering patterns.
The erosion “is such a slow process that the petroglyphs could remain visible for 60,000 years,” says Ken, who adds that neither he nor Brad think the rock art actually is that old. Based on current evidence people only arrived in this part of Australia sometime between 35,000 and 42,000 years ago, he says.
Story: Jude Dineley, Australian Geographic | Photo: Ken Mulvaney, Australian Geographic