Isotopic dating

 

ANSTO can provide information used to establish chronological scales (dating) and for environmental monitoring (tracing).

 

Such information is useful for studies ranging from dating an archaeological artefact or forensic evidence to climate studies using ancient air trapped in glaciers and even for establishing the viability of a potential source of groundwater.

 

ANSTO's ability to analyse your samples for long-lived, naturally-occurring radioisotopes opens up a huge range of dating and tracing applications. ANSTO's researchers can accurately measure these radionuclides in natural archives such as ice-core air bubbles, tree rings, corals, speleothems, rocks as well as marine and lacustrine sediments.

 

Radiocarbon dating is possible in diverse materials, such as charcoal, bones, textiles, foramifera, pollen grains and rock art, to name just a few. In some instances, ANSTO is capable of radiocarbon dating samples containing just five micrograms of carbon.

 

The Accelerator Mass Spectrometry Group operates the AMS resources at ANSTO, including the measurement capabilities at the Australian National Tandem for Applied Research (ANTARES), the two million volt tandem accelerator STAR and sample processing and target preparation in the AMS chemistry laboratories.

 

Dating services and capabilities

 

Radiocarbon carbon-14 dating is a well-known method for determining the age of materials up to the age of 50,000 years. ANSTO boasts world-class tandem accelerator facilities that can detect minute quantities of carbon-14 and a range of other long-lived naturally-occurring radioisotopes (e.g. beryllium-10 and aluminium-26) in a variety of materials, gaseous, liquid and solid.

 

Carbon-14 decays at a constant rate, typically over thousands of years.

 

By measuring its concentrations in a sample, it is possible to determine the age of sample. Beryllium-10 and aluminium-26 work the opposite way. The amount of these radioisiotopes build up over time as they are created by cosmic rays hitting rock surfaces. So the greater the concentration of these, the older the rock.

 

ANSTO is also capable of analysing samples to the lowest levels of radiometric detection and are routinely applied to samples of late Quaternary age (the last 350,000 years).

 

Older samples in this range are dated using the uranium/thorium disequilibrium method whilst younger samples are dated using the lead-210 dating method. We also offer caesium-137 analysis in addition to lead-210 for determining recent sediment ages.

 

Recent applications of ANSTO's isotopic dating methods include:

 

Age and origin of ground water

 

Radiocarbon and tritium analyses provide age-related information about the water from sandstone aquifers in the Sydney Basin assisted water authorities to identify groundwater sources that might be exploited sustainably.
 

Regional and global climate variability

 

Measurement of carbon-14 and stable isotopes in southern hemisphere tree rings, cave structures and corals provided researchers information on variations in atmospheric transport, ocean water circulation and rainfall over the last 15 000 years.

 

Ocean water circulation

 

ANSTO researchers used radiocarbon dating of coral samples collected in 1836 from the Cocos (Keeling) Islands to gain valuable insights into the upward movement of deep ocean waters in the north-western Indian Ocean.

 

Continental glacial cycles

 

Researchers have tested for beryllium-10 and aluminium-26 in exposed rocks to date the ebb and flow of alpine glacier systems in the southern hemisphere over the past 100,000 years.

 

Greenhouse gas sources and contributions

 

Radiocarbon levels were measured in atmospheric greenhouse gases (e.g. methane and carbon dioxide) to work out the origin of these gases and their contribution is to global warming.

 

ANSTO's dating services have also been applied to Pacific island lake sediments, Aboriginal rock art and archaeological artefacts, to mention just a few of the many applications of these powerful techniques. To read in more depth print off our fact sheet (pdf).

 

To discuss your dating requirements, contact Dr David Fink.