Since most rocks on the surface of the Earth are sedimentary, early
geologists used them to look for answers to the age of the Earth. The
birth of stratigraphy has its roots in scientists trying to
determine the age of the Earth. They made simple predictions by looking
at sedimentary processes going on today.
Geologists started to realize that you can trace certain strata by
comparing the fossils that it contains. The use of fossils became an
important tool to unravel the history of the Earth.
Deposition of fossils and sediment
Sedimentary layers with fossils