The attempt to abuse the meaning of a single contrived date -- which was produced only by a sample selection geared to dating a different event, and only for samples whose results were known by Austin in advance -- says a lot more about the level of competence or honesty in this creation "science" research program, than it says about the validity of isochron dating methods.
Even if given credit for discovering this case (which he clearly doesn't deserve, as his use of Leeman's data proves), Austin has only managed to "call into question" a particular sampling technique.
That data is lacking from Austin's published works.
Besides, this line of argument does not address the fact that the result is a known and expected behavior of isochrons.
He didn't pretend that the age of the flows was the expected result, and he didn't make the false claim that his result was sufficient to call all isochron dating into question.
However, problems remain in the interpretation of the measured Pb isotopic ratios to transform them into ages.As discussed above, whole-rock samples of multiple flows yields the time since their common source was isotopically homogeneous.It also be the age of the flows, but it does not have to be.There are a number of lava flows on the plateau that the canyon is cut into (yellow in Figure 1, above).
These lava flows are Cenozoic in age, and some of them spill into the canyon.
One particular Precambrian layer known as the Cardenas Basalt has been dated by radiometric methods to about 1.1 billion years in age.