The computer program Isoplot was used to plot isochrons and calculate isochron ages from the other radioisotope analyses.
The best isochron plots, where all the variation from the line of best fit to the data incorporates all the analytical errors, yielded an Rb-Sr isochron age of 1240±84 Ma, an Sm-Nd isochron age of 1655±40 Ma, and a Pb-Pb isochron age of 1883±53 Ma.
These were originally basalt lava flows several meters to tens of meters thick.
In some outcrops pillow structures have been preserved, testimony to the basalt lavas having originally erupted and flowed under water onto the Creation Week ocean floor.
Both laboratories use standard, best-practice procedures on state-of-the-art equipment.
The model K-Ar ages for each of the samples ranged from 405.1±10 Ma to 2574.2±73 Ma.
It is also claimed that the original basalt lavas were erupted between 17 Ma, based on U-Pb dating of "original" zircon grains in metamorphosed felsic (granitic) volcanic layers within the Brahma and Rama Schists.
Obviously, if radioisotope decay was accelerated, say during the Genesis Flood, then the radioisotope decay "clocks" could never be relied upon to "date" rocks as many millions of years old.
Most people believe that when the different radioisotope dating methods are used on the same rock unit they all yield the same age.
However, the radioisotope dating of these Grand Canyon rocks clearly demonstrates that the disagreement, or isochron discordance, is pronounced.
Even when the calculated error margins are taken into account the different radioisotope dating methods yield completely different "ages" that cannot be reconciled—1240±84 Ma (Rb-Sr), 1655±40 Ma (Sm-Nd), and 1883±53 Ma (Pb-Pb) (see diagram).
None of the obtained isochron "ages" corresponds to the "date" for any recognized event, neither the original lava eruptions nor the subsequent metamorphism.