地ち質しつ時じ代だい

noun

geological age; geological era

Technical term used in geology and earth science to refer to a division of geologic time.

• 恐きょう竜りゅうが絶ぜつ滅めつしたのは中ちゅう生せい代だいという地ち質しつ時じ代だいだ。

  The dinosaurs went extinct during a geological era called the Mesozoic.

• この化か石せきはどの地ち質しつ時じ代だいのものですか。

  Which geological age does this fossil belong to?