Using index fossils helps scientists determine the relative age of rock strata.
Here is an example of how valuable index fossil are when trying to relatively date some rock strata.
Layer 10 represents a fault, in this case a normal fault caused by tension.
The slate itself cannot be radiometrically dated, so can only be bracketed between the ages of the granite and the pegmatite.
The candy should be poured into a container large enough for them to bounce around freely, it should be shaken thoroughly, then poured back onto the paper so that it is spread out instead of making a pile.
Rock correlation is matching exposed layers in one area to exposed layers in another area.
Index fossils are used to connect and prove that these layers are the same.