All these labors have not led to a single unexpected finding such as a human fossil from the time of the dinosaurs, or a jurassic dinosaur in the same rocks as silurian trilobites.
Repeated recalibrations and retests, using ever more sophisticated techniques and equipment, cannot shift that date.
In the past 150 years they have not found any fossils that darwin would not have expected.
This is because new sediments are always laid down on top of sediments that have already been deposited.
So, when looking at the history of a cliff face, it is important to read the story it tells from the bottom layer up.
Simply stated, each bed in a sequence of sedimentary rocks (or layered volcanic rocks) is younger than the bed below it and older than the bed above it.