ANT100Y1 Lecture Notes - Lecture 3: Accelerator Mass Spectrometry, Radiocarbon Dating, Radiometric Dating
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A radiometric dating method is based on radioactive decay or isotopes. Isotopes = different forms of an element with different atomic weights. Some isotopes are stable, others are unstable and gradually decay, changing into stable elements. Can be used to date objects if you know . Rate of decay is measured by a half-life (the time it takes for half of the isotope to decay) Most common form of carbon = carbon 12 (stable) Plants absorb c14 in carbon dioxide during photosynthesis; eaten by herbivores, eaten by carnivores. As c14 decays (converting to n14), it releases radioactive beta particles. Allows estimate of amount of c14 left in sample. Accelerator mass spectrometry (ams) - improved radiocarbon dating. Ams measures the amount of c14 directly (requires only tiny samples) If organics are rare, single seeds, twigs, etc. can be dated. Contamination before sampling: carbon in groundwater, modern plant roots, etc. Contamination during sampling: cardboard labels, glue, mold, etc.
