Ajoittuminen

Ajoittuminen is the process of determining the time at which an event occurred or a material formation, such as a layer of sediment or an artifact, came into being. It is a central concept in archaeology, geology, paleontology, and historical studies. The outcome can be an absolute date, a numerical age, or a relative indication of the sequence of events.

Absolute dating methods rely on measurable physical or chemical properties to estimate numerical ages. Examples include radiocarbon dating for organic remains up to about 50,000 years old, dendrochronology for precise calendar-year dating in suitable wood samples, uranium-series dating for carbonate materials, and potassium-argon or argon-argon dating for volcanic rocks. Luminescence dating, including thermoluminescence and optically stimulated luminescence, measures the last exposure of minerals to heat or light to infer age.

Relative dating methods place events in sequence without assigning exact ages. This includes stratigraphy, which uses the order of rock or soil layers; biostratigraphy, which relies on fossil assemblages; magnetostratigraphy, which uses changes in Earth’s magnetic field recorded in rocks; and seriation, which groups artifacts based on styles or frequencies over time. These approaches are often combined with absolute dating to build coherent chronologies in archaeology and geology.

Limitations and history. Dating methods depend on assumptions, calibration, and the preservation of samples; errors can arise from contamination, diagenesis, or environmental factors. The development of radiocarbon dating by Willard Libby in 1949 and subsequent refinements transformed dating practices. In Finnish usage, ajoittuminen generally refers to the practice and result of determining age or timing across disciplines.