The radiocarbon method measures the rate of decay in the C14 of organic matter therefore estimating how long ago death occurred.
Archaeologists can use this method to date bone, teeth, plants, seeds, burned food remains, coprolites, wood, and any artefact that contains organic materials such as an iron axe head (iron cannot be tested using C14) with a wooden handle or a bronze spear with a wooden shaft.
Organic matter, being porous, can easily be contaminated by organic carbon in groundwater.
This increases the C12 content and interferes with the carbon ratio.
For more information on the history of radiocarbon dating, its usage in climate change studies, and a brief description of other fields that rely on radiocarbon dating, visit The American Institute of Physics link: a list and description of applications of radiocarbon dating–such as dating Stonehenge and determining that mammoths were still alive 4,000 years ago–please visit the site: come from?