FACT SHEETS

Optically Stimulated Luminescence dating

19.09.17 by CABAH

CABAH’s Professor Zenobia Jacobs specialises in Optically Stimulated Luminescence (OSL) dating, a technique that can date objects further back than radio carbon dating, which is limited to around 50,000 years.

Put simply, OSL dating techniques gives us an estimate of the time since mineral grains were last exposed to sunlight. In Professor Jacobs’ PhD, she developed single grain OSL dating, using Professor Bert Roberts’ ground work, with new technologies such as lasers to improve things.

Professor Jacobs used her OSL dating technique to analyse 28,500 individual grains of quartz from Madjebebe, which revealed groundbreaking information about the arrival of the first modern humans in Australia.

 

 

OSL dating expert Professor Zenobia Jacobs

"The radiocarbon dating barrier was a problem across the world"

Professor Jacobs shares her discoveries

Like a rechargeable battery

Little grains moving around in the landscape are like little batteries. When they’re exposed to sunlight, the battery gets drained.

When they’re hidden from sunlight, they start to build up energy as electrons are trapped in the crystal lattice. And when they’re exposed to sunlight again, they get drained.

So, the last time they got exposed to sunlight was the last time they were drained.

Sand gets buried in the archeological site and builds up energy. Scientists go into the site and take the sample in the dark, because of course if the samples are exposed to light, the signal is reset.

Samples are taken back to the lab and carefully handled in darkroom conditions. Scientists can then determine how much energy was stored in that single grain since it was last exposed to sunlight.

OSL dating put samples from Madjebebe at at least 65,000 years old

28,500

Professor Jacobs and her team analysed 28,500 samples from Madjebebe, which dated the archeologically significant site at at least 65,000 years old.

Dating the samples was a very labour-intensive project that relied on a highly skilled team in the lab to work through various stages of preparation and measurement. Professor Jacobs then personally caried out the analysis and interpretation.

The project involved years of work.

28,500

Professor Jacobs and her team analysed 28,500 samples from Madjebebe, which dated the archeologically significant site at at least 65,000 years old.

Dating the samples was a very labour-intensive project that relied on a highly skilled team in the lab to work through various stages of preparation and measurement. Professor Jacobs then personally caried out the analysis and interpretation.

The project involved years of work.

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