uraniumseries

The uranium series refers to the natural radioactive decay chains that begin with uranium isotopes and progress toward stable lead isotopes. In nature, three primary series exist: the 238U series (the radium series), the 235U series (the actinium series), and the 232Th series (the thorium series). Each chain involves a sequence of alpha and beta decays through various intermediate nuclides, ultimately yielding a stable lead isotope: 206Pb from the 238U series, 207Pb from the 235U series, and 208Pb from the 232Th series.

The 238U series is the most widely encountered in geology and archaeology and is commonly used for dating carbonate materials. Uranium-series dating relies on the known production and decay of 238U and its descendants, notably 234U, 230Th, and 226Ra. By measuring the activities of parent and daughter nuclides in a sample, scientists can estimate ages for calcium carbonate deposits such as speleothems (stalactites and stalagmites), corals, and marine carbonates, typically from about a few thousand to several hundred thousand years. In addition, 210Pb dating is used to resolve more recent processes on timescales of up to about a century.

Key concepts include secular equilibrium, when parent and daughter activities are constant in a closed system, and disequilibrium, which arises from geologic or environmental processes that remove or add nuclides. Such disequilibria must be modeled to produce accurate ages. Uranium-series methods complement other radiometric techniques and are widely applied to natural waters, soils, archaeological materials with carbonate components, and paleoclimate records.