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archean, archaean | [in geology] of or relating to the earliest known rocks formed during the Precambrian Eon | |
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Archean, Archean eon, Archean aeon, Archeozoic, Archaeozoic, Archeozoic eon, Archaeozoic aeon | the time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life |