|White mineral coating descending down the rock face. Samples for radiocarbon highlighted. Photo: Tristen Jones. Image enhancement: Daryl Wesley|
A new technique, developed at ANSTO’s Centre for Accelerator Science, has made it possible to produce some of the first reliable radiocarbon dates for Australian rock art in a study just published online in The Journal of Archaeological Science Reports.
The approach involved extracting calcium oxalate from a mineral crust growing on the surface of rock art from sites in western Arnhem Land, according to paper co-author research scientist Dr Vladimir Levchenko, an authority on radiocarbon dating using accelerator mass spectrometry.
Levchenko, who supervised the radiocarbon dating, collaborated with lead author of the paper, Ms Tristen Jones, a PhD candidate at the Australian National University (ANU) and co-authors from ANU.
Generally speaking, radiocarbon dating cannot readily be used to date Australian indigenous rock art directly, because it is characterised by the use of ochre, an inorganic mineral pigment that contains no carbon.
The paper authors explain that carbon found in the mineral crusts on the rock surface was most probably was formed by microorganisms.
“These microorganisms are photosynthetic bacteria, like cyanobacteria or algae, which can utilise carbon from the air normally, and are active through wet periods,” said Levchenko.
One of the peer review authors who reviewed the paper prior to publication predicted it could become a benchmark for studies of this type as it addressed a complete lack of chromometric data for rock art in Australia and elsewhere.
Another reviewer called it the most significant rock art and dating paper to have been produced in Australia for over 25 years. [...] ANSTO / Link 2