Uranium series dating
The differing chemistries and half-lives of these nuclides (with timescales ranging from seconds to billions of years) make them exceptionally useful chronometers for variety of natural processes and materials Perhaps the most important and commonly used isotopes are Ra, the first three of which are commonly used to date the formation of carbonate minerals and skeletal materials (e.g., corals and cave deposits) and the full suite of which are used to date volcanic materials, such as lavas and the crystals they contain.
The largest radioactive disequilibria are always found in the youngest materials.The sample age is based on the difference between the initial ratio of U with the environment (i.e., that it is a closed system.) The method is used for samples that can retain Uranium and Thorium, such as carbonate sediments, bones and teeth. Ages between 1000 and 300,000 years have been reported. U-Th ages obtained by mass spectrometry in corals from Barbados: sea level during the past 130,000 years. Calibration of the 14C timescale over the past 30,000 years using mass spectrometric U-Th ages from Barbados corals.