Radiometric dating proved wrong
The K-Ar clock works primarily on igneous rocks, i.e., those that form from a rock liquid (such as lava and granite) and have simple post-formation histories.
It does not work well on sedimentary rocks because these rocks are composed of debris from older rocks.
Some of the methods have internal checks, so that the data themselves provide good evidence of reliability or lack thereof.
Commonly, a radiometric age is checked by other evidence, such as the relative order of rock units as observed in the field, age measurements based on other decay schemes, or ages on several samples from the same rock unit.
The point is that not all methods are applicable to all rocks of all ages.
One of the primary functions of the dating specialist (sometimes called a geochronologist) is to select the applicable method for the particular problem to be solved, and to design the experiment in such a way that there will be checks on the reliability of the results.
The main point is that the ages of rock formations are rarely based on a single, isolated age measurement.
Some of the isotopic parents, end-product daughters, and half-lives involved are listed in Table 1.
Sometimes these decay schemes are used individually to determine an age (e.g., Rb-Sr) and sometimes in combinations (e.g., U-Th-Pb).