Proterozoic

  1. Adjective.  (geology) Of, or relating to the geologic eon from about 2,500 to 570 million years ago; comprises the Paleoproterozoic, Mesoproterozoic and Neoproterozoic eras; marked by the build up of oxygen in the atmosphere and the emergence of primitive multicellular life.
  2. Proper noun.  (geology) The Proterozoic eon.

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This entry was last updated on RefTopia from its source on 3/20/2012.