Paleoproterozoic

  1. Adjective.  (geology) Of a geologic era within the Proterozoic eon; comprises the Siderian, Rhyacian, Orosirian and Statherian periods from about 2500 to 1600 million years ago, when cyanobacteria increased the amount of oxygen in the atmosphere and changed life on Earth for ever.
  2. Proper noun.  (geology) The Paleoproterozoic era.

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