I'll open this up to discussion as you had the misfortune of being water logged in the brain.
"In such cases, we can date the fossil-bearing layers relative to one another using other lines of evidence and reasoning. For example, in the vast majority of strata studied, rock layers containing ammonite fossils are found beneath rock layers containing dinosaur fossils. Because of this, scientists are quite confident that ammonites died out before dinosaurs arose."
What are ammonite fossils? They're marine fossils.
Where's
Grumblenuts? What's his explanation from the 60s?