第だい三さん紀き

noun

Tertiary period

Geological term for the period from about 66 million to 2.6 million years ago. Now often replaced by Paleogene and Neogene in modern classification, but still used in general contexts.

• 第だい三さん紀きの化か石せきがこの地ち域いきで見みつかった。

  Fossils from the Tertiary period were found in this area.