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 Ar·chae·an /ɑrˈkiən/
 (a.)太古化的

 Ar·chæ·an a.  Ancient; pertaining to the earliest period in geological history.

 Ar·chæ·an, n. Geol. The earliest period in geological period, extending up to the Lower Silurian. It includes an Azoic age, previous to the appearance of life, and an Eozoic age, including the earliest forms of life.
 Note: ☞ This is equivalent to the formerly accepted term Azoic, and to the Eozoic of Dawson.
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 archaean
      adj : used of the earliest known rocks [syn: archean]