14Cdatering

14Cdatering, also called radiocarbon dating, is a method for estimating the age of carbon-based materials by measuring the amount of the radioactive isotope carbon-14 (14C) relative to stable carbon isotopes. 14C is produced in the upper atmosphere and is incorporated into living organisms through the carbon cycle. While an organism is alive, its 14C/12C ratio matches the atmosphere; after death, 14C decays with a half-life of about 5,730 years, enabling age determination from the remaining 14C.

Two main measurement approaches are used. Traditional radiometric dating counts the beta decays of 14C, known as decay counting. More commonly today, accelerator mass spectrometry (AMS) directly counts 14C atoms, requiring much smaller samples and offering greater sensitivity. AMS is now the standard method for many applications, including dating tiny samples such as seeds, small pieces of charcoal, or archaeological artifacts.

Calibration is required to convert radiocarbon ages into calendar ages because atmospheric 14C levels have varied over time. Calibrated age estimates rely on curves such as IntCal, which are built from independent dating data. For marine or lake materials, reservoir effects can make samples appear anomalously old; corrections using a reservoir age (Delta R) are applied to obtain accurate calendar dates.

Limitations include a practical dating range up to about 50,000 years; beyond that, 14C levels become too low for reliable measurement. Contamination and post-depositional processes can bias results, and the method only dates carbon-containing materials. Dates are commonly reported as uncalibrated radiocarbon years BP (present defined as 1950) or as calibrated calendar dates (cal BP or cal AD) with associated uncertainties.