Most physical dating methods are based on processes that are strictly a function of time or that contain a prominent time-dependent component. This is especially true for the radiometric methods. Even with these methods, however, derivations from the siderial time-scale sometimes occur as a result of processes not taken into consideration by the assumptions of the model (Fig. 2.1). Such processes can be geochemical or geophysical, e.g., diagenetic mobilization of parent or daughter nuclides in a mineral or rock system, the occurrence or annealing of radiation damage, isotope fractionation, or long-term fluctuations in the production of cosmogenic radionuclides.
KeywordsZircon Lithium Boron Radium Fractionation
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