Electron spin resonance dating
Electron spin resonance dating, or ESR dating, is a method used to date materials where radiocarbon dating isn’t effective. It can be used on minerals (like carbonates, silicates, and sulfates), tooth enamel, some ceramics, and certain foods.
ESR dating began in 1975 when Japanese physicist Motoji Ikeya dated a speleothem from Akiyoshi Cave in Japan. The method measures the amount of unpaired electrons in crystal structures that have been exposed to natural radiation over time.
As radioactive materials in a sample emit radiation, some electrons get excited and become trapped in defects in the mineral’s structure. The number of trapped electrons grows with time, and these trapped charges produce a measurable ESR signal. The stronger the signal, the larger the accumulated radiation dose, and the older the sample.
To use ESR dating, you often work with samples that are either newly formed or have been heated but not too much. Heating or other events can reset the ESR clock. Each mineral has a “closure temperature” above which trapped charges can move freely and the ESR age is reset. For example, quartz in granite typically has a closure temperature around 30–90°C, and barite around 190–340°C.
In simple terms, ESR dating is a trapped-charge dating method. Normal radioactivity makes electrons jump to a higher energy level, and some stay trapped for long times. The ESR signal you measure is proportional to how many trapped electrons are present, which in turn relates to the dose of radiation absorbed and the age of the sample.
The age is found by comparing the paleodose (the total radiation the sample has received since it formed) with the current dose rate (how fast radiation is reaching the sample). If the dose rate has stayed the same, the age is simply the paleodose divided by the dose rate. If the rate has varied, scientists integrate the dose rate over time to estimate the age.
To determine the paleodose, researchers use ESR spectrometry and add known amounts of radiation to the sample until the ESR signal matches the natural signal. To get the dose rate, they calculate internal radioactivity within the sample and external radioactivity from the surrounding environment.
Several factors can affect ESR ages. Trapped electrons don’t last forever; natural changes or heating can erase older signals. In environments with multiple heating events, like hydrothermal vents, only the most recently formed minerals may be reliably dated, and ages may average over the bulk mineral rather than give a precise single date. Consequently, ESR dating often complements other dating methods, and radiometric ages can be biased toward younger mineral phases.
ESR dating has been used to date fossilized teeth, burnt flint and quartz in ancient ceramics, and various geological and archaeological contexts. It also helps study events like earthquakes, volcanic eruptions, coastal tectonics, fluid movement in subsurface structures, and cold seeps.
This page was last edited on 2 February 2026, at 14:32 (CET).