Start Radioactive dating methods are best used to

Radioactive dating methods are best used to

For an element to be useful for geochronology (measuring geological time), the isotope must be reasonably abundant and produce daughter isotopes at a good rate.

This is a common dating method mainly used by archaeologists, as it can only date geologically recent organic materials, usually charcoal, but also bone and antlers.

The Re-Os isotopic system was first developed in the early 1960s, but recently has been improved for accurate age determinations.

The main limitation is that it only works on certain igneous rocks as most rocks have insufficient Re and Os or lack evolution of the isotopes.

This technique has become more widely used since the late 1950s.

Its great advantage is that most rocks contain potassium, usually locked up in feldspars, clays and amphiboles.

The amount of 14C present and the known rate of decay of 14C and the equilibrium value gives the length of time elapsed since the death of the organism.

This method faces problems because the cosmic ray flux has changed over time, but a calibration factor is applied to take this into account.

Some techniques place the sample in a nuclear reactor first to excite the isotopes present, then measure these isotopes using a mass spectrometer (such as in the argon-argon scheme).