How did geologist know that cretaceous geological time ended 65 millions years ago?

Question

I know that geologist use fossils records to date the time, but how did they know that fossils were from estimated 65 millions years ago.

An immidiate answers would be helpful

Answer 1

scientificalcation proofizioid.

Answer 2

There are lots of cross references including nuclear isotope decay clocks. Cosmic rays build up tracks in crystals.

Fossils aren't the only record of time. The Cretaceous and date has been estimated by many different methods and they all agree within a few 1000 years.

note: Carbon dating can not be used for things older than a few thousand years.

Answer 3

carbon dating in rocks, fossils