How does radiometric dating help determine the age of fossils

how does radiometric dating help determine the age of fossils - For example, if they believed it would take 200 million years for an ammonite (somehow) to turn gradually into say a dog, then all rocks containing fossil ammonites (the “index fossil”) would be given an “age” 200 million years older than rocks containing fossils of dogs:“… the geological column and approximate ages of all the fossil-bearing strata were all worked out long before anyone ever heard or thought about radioactive dating … there are so many sources of possible error or misinterpretation in radiometric dating that most such dates are discarded and never used at all, notably whenever they disagree with the previously agreed-on [index fossil] dates. A number of processes could cause the parent substance to be depleted at the top of the magma chamber, or the daughter product to be enriched, both of which would cause the lava erupting earlier to appear very old according to radiometric dating, and lava erupting later to appear younger. But even if it is true that older radiometric dates are found lower down in the geologic column (which is open to question), this can potentially be explained by processes occurring in magma chambers which cause the lava erupting earlier to appear older than the lava erupting later. Any radiometric dates that show a supposedly “old” rock to be young are rejected for no other reason:“few people realize that the index fossil dating system, despite its poor assumptions and many problems, is actually the primary dating tool for geologic time.

How Does Radiocarbon Dating Work? - Instant Egghead #28

How do scientists determine the age of fossils that have been under the surface of the earth for thousands of years? Scientific ...