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This includes two samples only 0.84 meters apart that yielded K-Ar model ages of 1205.3±.2±73 Ma.
The computer program Isoplot was used to plot isochrons and calculate isochron ages from the other radioisotope analyses.
Twenty-seven Brahma amphibolite samples were collected from various Inner Gorge outcrops as part of the RATE (Radioisotopes and the Age of The Earth) project.
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).
Among these metamorphosed volcanic strata are amphibolites, belonging to the Brahma Schist.