Such failures may be due to laboratory errors (mistakes happen), unrecognized geologic factors (nature sometimes fools us), or misapplication of the techniques (no one is perfect).
These ash beds, called bentonites, contain sanidine feldspar and biotite that has been dated using the 40Ar/39Ar technique.
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.
Only rarely does a creationist actually find an incorrect radiometric result (Austin 1996; Rugg and Austin 1998) that has not already been revealed and discussed in the scientific literature.
The creationist approach of focusing on examples where radiometric dating yields incorrect results is a curious one for two reasons.