The Tertiary is a term for a geologic period 65 million to 1.8 million years ago.
The Tertiary covered the time span between the superseded Secondary period and the Quaternary.
The period began with the demise of the non-avian dinosaurs in the Cretaceous–Tertiary extinction event, at the start of the Cenozoic era, spanning to the beginning of the most recent Ice Age, at the end of the Pliocene epoch.