Ian McDougall, 1978. "Potassium-Argon Isotopic Dating Method and Its Application to Physical Time-Scale Studies", Contributions to the Geologic Time Scale, George V. Cohee, Martin F. Glaessner, Hollis D. Hedberg
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Advantages and disadvantages of the potassium-argon (K-Ar) isotopic dating method are discussed in relation to its application to the accurate calibration of the physical time scale for the Phanerozoic. The method is best applied to the dating of igneous rocks but authigenic glauconite in sedimentary rocks also is amenable to dating. In physical time-scale studies, the ideal situation is that of volcanic rocks datable from sequences for which there is good stratigraphic and biostrati- graphic control. Ages determined on intrusive rocks in a biostratigraphically well-controlled sequence are useful in providing a younger limit to the age of the sediments. As with all dating methods, it is of utmost importance to measure ages on several samples in known stratigraphic relation in order to evaluate and test the assumptions underlying the K-Ar method, in particular those involving closed-system behavior and the possible effect of later events.