Irreconcilable disagreement within and between the methods is the norm, even at the outcrop scale.
This is a devastating "blow" to the long ages that are foundational to uniformitarian geology and evolutionary biology.
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.
In Grand Canyon, the "date" of metamorphism of the basalt lavas to form these Brahma amphibolites has been determined as 1690-1710 Ma (million years ago), based on U-Pb dating of minerals in the overlying Vishnu Schist and underlying Rama Schist that formed during the metamorphism.Furthermore, the seven samples from the small amphibolite unit near Clear Creek, which should all be the same age because they belong to the same metamorphosed basalt lava flow, yielded K-Ar model ages ranging from 1060.4±28 Ma to 2574.2±73 Ma.This includes two samples only 0.84 meters apart that yielded K-Ar model ages of 1205.3±.2±73 Ma.These included seven samples from a 150 meter long and 2 meter wide amphibolite body outcropping just upstream from the mouth of Clear Creek at river mile 84 (measured from Lees Ferry).All 27 samples were sent to two well-credentialed internationally-recognized, commercial laboratories for radioisotope analyses—potassium-argon (K-Ar) at a Canadian laboratory, and rubidium-strontium (Rb-Sr), samarium-neodymium (Sm-Nd), and lead-lead (Pb-Pb), at an Australian laboratory.