Geologic time rock dating methods
The slope of the line determines the date, and the closeness of fit is a measure of the statistical reliability of the resulting date.Technical details on how these dates are calculated are given in Radiometric dating. As with any experimental procedure in any field of science, these measurements are subject to certain "glitches" and "anomalies," as noted in the literature.It is important not to confuse geochronologic and chronostratigraphic units.
Thermoluminescence and optically stimulated luminescence are used in archaeology to date 'fired' objects such as pottery or cooking stones, and can be used to observe sand migration.
Exposure dating uses the concentration of exotic nuclides (e.g.
Cl) produced by cosmic rays interacting with Earth materials as a proxy for the age at which a surface, such as an alluvial fan, was created.
With the exception of the radiocarbon method, most of these techniques are actually based on measuring an increase in the abundance of a radiogenic isotope, which is the decay-product of the radioactive parent isotope.
A series of related techniques for determining the age at which a geomorphic surface was created (exposure dating), or at which formerly surficial materials were buried (burial dating).
Biostratigraphy does not directly provide an absolute age determination of a rock, but merely places it within an interval of time at which that fossil assemblage is known to have coexisted.