Radiometric dating has not been applied to just a few selected rocks from the geologic record.
Literally many tens of thousands of radiometric age measurements are documented in the scientific literature.
The third approach, and the one that scientists think gives the most accurate age for the Earth, the other planets, and the Solar System, is to determine model lead ages for the Earth, the Moon, and meteorites.
The rocks in these shields are mostly metamorphic, meaning they have been changed from other rocks into their present form by great heat and pressure beneath the surface; most have been through more than one metamorphism and have had very complex histories.An outline of the geology of Australia, with palaeontological notes by Smith, E. efore analyzing the arguments advanced by creation “scientists” for a very young Earth, I here summarize briefly the evidence that has convinced scientists that the Earth is 4.5 to 4.6 billion years old.” The answer to this question was provided by radiometric dating and is now known to within a few percent.
Three basic approaches are used to determine the age of the Earth.Although early stratigraphers could determine the relative order of rock units and fossils, they could only estimate the lengths of time involved by observing the rates of present geologic processes and comparing the rocks produced by those processes with those preserved in the stratigraphic record.