Oliocene Series

Read about the Oligocene Series

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• Cenozoic Erathem
  • Quaternary System
    • Holocene Series
    • Pleistocene Series
  • Tertiary System
    • Eocene Series
    • Miocene Series
    • Oligocene Series
    • Paleocene Series
    • Pliocene Series

There are currently no known geologic units of Oliocene age in Illinois.