Not the dreaded creationist biostratigraphy argument again!
Don't creationists ever come up with anything original?  I will
simplify the reasoning behind biostratigraphy so that even our
creationist friends can understand it.

       1. We radiodate a rock.
       2. The rock comes from a given stratum of the geological record.
       3. The rock contains certain fossils.
       4. Other rocks in the same stratum contain the same fossils.
         5. We radiodate these other rocks.
       6. These other rocks are the same age.
       7. We find rocks in a different stratum.
       8. These rocks don't have the same fossils in them.
       9. We radiodate these other rocks.
      10. They are not the same age as our previous set of rocks.
      11. Radiodating a rock takes a lot of time and money.
      12. Oil men and women probably don't like to waste time and money.
      13. Fossils can be used to quickly estimate the age of a rock.

Get it?  Got it?  Good.

>We know the age of the rock because we find a fossil in it that our
>"theory" believes is 250 m.y. old therefore our rock MUST be 250 m.y.
>old.

Oh, you still don't get it.  Darn, and I thought I had done a pretty
good job making things simple.

Our rock is 250 MY old because other rocks in the same strata were
radiodated to that age.  Furthermore, for some darn strange reason
we keep on finding only a certain group of fossils in those rocks.
Amazingly, we never find human and trilobyte fossils in the same
strata.  Golly gee, I wonder why that is.

>Please try harder.

I'm trying as hard as I can.  You can't possibly understand how
difficult it is to explain simple logic to a creationist.