Validity of Radiometric Dating

You say:
"The fact is that all the other dating methods do give good collaboration of potassium-argon dating. The other radiometric methods involve very different parent chemical elements, different daughter elements, and different stages of intermediaries. All of these different method usual yield essentially the same ages for the same minerals and individual rocks, and different methods used in different parts of the world yield consistent dates when correlated with such things as index fossils."I understand the sense of correlating the different dating methods with "index fossils", but how are the index fossils dated?

I get the impression relative ages of strata are generally more relevant and useful to geologists than absolute ages.