Uranium-series dating

Uranium-series dating estimates ages by measuring radioactive disequilibrium among uranium, thorium, and their decay products. It is especially useful for materials formed over timescales of thousands to hundreds of thousands of years.

Radioactive decay: The spontaneous transformation of unstable atomic nuclei into more stable nuclei, accompanied by radiation. The method turns predictable nuclear decay into an elapsed-time estimate.
Uranium-thorium dating: A uranium-series method that dates materials using the changing ratio of uranium isotopes to thorium-230. It is the best-known implementation for dating carbonate deposits and corals.
Isotope: One of two or more forms of an element whose atoms have the same proton count but different neutron counts. Uranium-series calculations distinguish isotopes of uranium, thorium, and their decay products.
Radiocarbon dating: A dating method that estimates the age of once-living material from the decay of carbon-14. It dates younger organic remains, whereas uranium-series methods commonly target carbonates and older timescales.
Radioactive disequilibrium: A temporary imbalance between radioactive parent isotopes and their daughter products in a material. Uranium-series ages come from measuring this imbalance rather than a stable isotope ratio.
Radiometric dating: A family of methods that estimates age from measured radioactive decay and isotope ratios. Uranium-series dating is one member of this broader family of clocks.
Isotope ratio: The abundance of one isotope divided by the abundance of another isotope in a sample. Measured isotope ratios encode the disequilibrium used to calculate an age.
Potassium-argon dating: A radiometric method that dates rocks by measuring the decay of potassium-40 to argon-40. It is suited to volcanic rocks and generally much older ages than uranium-series dating.
Uranium-238: A naturally occurring uranium isotope that decays through a long chain of radioactive daughter nuclides. Its decay chain supplies the uranium-series isotopes used in many age calculations.
Speleothem: A mineral deposit formed in a cave, such as a stalactite or stalagmite. Uranium-bearing cave carbonates can preserve datable uranium-thorium disequilibrium.

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