First, it provides no evidence whatsoever to support their claim that the earth is very young.
The results of the Manson Impact/Pierre Shale dating study (Izett and others 1998) are shown in Figure 1.
There are three important things to note about these results.
The Pierre Shale also contains volcanic ash that was erupted from volcanoes and then fell into the sea, where it was preserved as thin beds.
These ash beds, called bentonites, contain sanidine feldspar and biotite that has been dated using the 40Ar/39Ar technique.
Not only that, they have to show the flaws in those dating studies that provide independent corroborative evidence that radiometric methods work.
This is a tall order and the creationists have made no progress so far.
It will probably fail, but what would a reasonable person conclude from that? All they indicate is that the methods are not infallible.
Those of us who have developed and used dating techniques to solve scientific problems are well aware that the systems are not perfect; we ourselves have provided numerous examples of instances in which the techniques fail.
Scientists who use radiometric dating typically use every means at their disposal to check, recheck, and verify their results, and the more important the results the more they are apt to be checked and rechecked by others.
As a result, it is nearly impossible to be completely fooled by a good set of radiometric age data collected as part of a well-designed experiment.
We often test them under controlled conditions to learn when and why they fail so we will not use them incorrectly. For example, after extensive testing over many years, it was concluded that uranium-helium dating is highly unreliable because the small helium atom diffuses easily out of minerals over geologic time.