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.
Independent confirmation of these dates can be provided by varve counting and/or the recognition of historical events.
Assuming a constant rate of production, the number of atoms of Be-10 and Al-26 that accumulate in a rock surface will be proportional to the length of time the rocks were exposed to cosmic ray bombardment and the respective rates of radioactive decay for each isotope.
An age determined by measurement of the amount of each nuclide would be an estimate of the age of the surface exposure, that is, the surface could have been exposed for much longer than the minimum calculated age.
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.
However, radionuclide profiles can be “corrected” by subtracting the influence of instantaneous deposits that have been identified from detailed sedimentological studies.
Thus, radionuclides can be used to provide approximate dates for sediment.
For Lake Icalma, there is a good agreement between radionuclide dates and the dates of the three tephra layers formed during large eruptions of the Llaima volcano in 1946, 19.
For both lakes, artificial radionuclide fallout, which culminated in 1965, provides more robust chronological information than Present address: Geological Institute, ETH Zürich, CH-8092 Zürich, Switzerland.
These particles interact with atoms in atmospheric gases (and thereby producing northern lights) and the surface of Earth.
When one of these particles strikes an atom it can dislodge protons and/or neutrons from that atom, producing a different element or a different isotope of the original element.
In rock and other materials of similar density, most of the cosmic ray flux is absorbed within the first meter of exposed material in reactions that produce new isotopes called cosmogenic nuclides.