geochronometer

A geochronometer is a term used in geoscience to denote tools and methods that determine the age of rocks, minerals, or geological events. It is not a single device but a family of dating techniques that provide numerical ages, aiding the construction of Earth's timeline.

The main categories are radiometric dating and non-radiometric methods. Radiometric dating measures parent–daughter isotope ratios (for example uranium–lead in zircon, potassium–argon or argon–argon in volcanic rocks, rubidium–strontium, samarium–neodymium). Non-radiometric methods include luminescence dating (optically stimulated luminescence, thermoluminescence), electron spin resonance, cosmogenic nuclide dating, and fission-track dating.

Principles involve a known decay constant, closed-system behavior, and careful sample handling to avoid contamination. Ages are interpreted with models such as concordia for U–Pb or isochron methods; in luminescence dating, dose–response and environmental dose rates are used. Different methods cover different time ranges, so cross-checks are common.

Applications include dating rock formation, metamorphism, volcanic events, sediment deposition, and archaeological materials. Range examples: carbon-14 for up to about 50,000 years (organic material); uranium–lead for billions of years; potassium–argon and argon–argon for long geological timescales; luminescence dating extends to thousands to hundreds of thousands of years, depending on mineral characteristics.

In summary, geochronometer describes the collective set of dating techniques that quantify geological time, forming core methods in geochronology.