Gamman 100 dating
We scientists who measure isotope ages do not rely entirely on the error estimates and the self-checking features of age diagnostic diagrams to evaluate the accuracy of radiometric ages.
Whenever possible we design an age study to take advantage of other ways of checking the reliability of the age measurements.
Dating schemes based on rates of radioactivity have been refined and scrutinized for several decades.
The latest high-tech equipment permits reliable results to be obtained even with microscopic samples.
Radiometric dating is self-checking, because the data (after certain preliminary calculations are made) are fitted to a straight line (an "isochron") by means of standard linear regression methods of statistics.
The slope of the line determines the date, and the closeness of fit is a measure of the statistical reliability of the resulting date.
Radioactive decay rates have been measured for over sixty years now for many of the decay clocks without any observed changes.
The use of different dating methods on the same rock is an excellent way to check the accuracy of age results.
If two or more radiometric clocks based on different elements and running at different rates give the same age, that's powerful evidence that the ages are probably correct.
In the particular case that Morris highlighted, the lava flow was unusual because it included numerous xenoliths (typically consisting of olivine, an iron-magnesium silicate material) that are foreign to the lava, having been carried from deep within the Earth but not completely melted in the lava.
Also, as the authors of the 1968 article were careful to explain, xenoliths cannot be dated by the K-Ar method because of excess argon in bubbles trapped inside [Dalrymple2006].