Sentence Examples

  • The Proterozoic formations are unconformable on the Archean in most places where their relations are known.
  • Proterozoic, Widespread unconformity.
  • Prolerozoic (Algonkian) Systems.The Proterozoic group of rocks (called also Algonkian) includes all formations younger than the Archean and older than the Palaeozoic rocks.
  • The Proterozoic formations have a wide distribution.
  • In some places this is because the regions where they occur have net been carefully studied since the subdivision into Archeozoic and Proterozoic was made, and in others because of the inherent difficulty of separation, as where the Proterozoic rocks are highly metamorphosed.