Some methods used in relative dating are stratigraphy, biostratigraphy, and cross dating. Sometimes sedimentary rocks are disturbed by Relative versus absolute dating, such as fault movements, that cut across layers after the rocks were deposited.
Main article: Potassium—argon dating. The GPTS is divided into periods of normal polarity and reversed polarity.
In relative dating techniques like stratigraphy and biostratigraphy are used to know which of the object is older. Because of this, magnetic minerals in rocks are excellent recorders of the orientation, or polarity , of the Earth's magnetic field. Other radiometric dating techniques are available for earlier periods.
However, if the bone is 70, years or older the amount of 14 C left in the bone will be too small to measure accurately. After another 5, years only one-quarter of the original carbon will remain. Faunal deposits include remains and fossils of dead animals.