Ordovician

The Ordovician is a geological period from about 485 to 443 million years ago, marked by major marine diversification and ending in a mass extinction.

Ordovician biodiversification: A major increase in the diversity and ecological complexity of marine life during the Ordovician. Expanding marine ecosystems define the period’s most conspicuous biological change.
Geologic time scale: A chronological framework dividing Earth's history into eons, eras, periods, and smaller units. The Ordovician is one period in this nested chronology.
Burgess Shale: A fossil deposit in British Columbia famous for exceptionally preserved Cambrian marine organisms. It offers a celebrated earlier snapshot for comparison with Ordovician fossil communities.
Ordovician-Silurian extinction event: A mass extinction around 444 million years ago that eliminated many marine species. Researchers still debate how glaciation, sea-level change, and ocean chemistry combined.
Ordovician glaciation: A major glaciation near the end of the Ordovician, centered on Gondwana. The cooling and falling sea levels helped drive the period’s terminal extinction.
Paleozoic: The geologic era from about 539 to 252 million years ago, preceding the Mesozoic. The Ordovician occupies the middle of this broader era.
Fezouata Shale: An Early Ordovician fossil deposit in Morocco preserving soft-bodied marine organisms. Its fossils reveal animals that rarely survive in the ordinary rock record.
Ordovician climate: The range of climatic conditions on Earth during the Ordovician, including Late Ordovician cooling. Reconstructing climate shifts is essential to explaining both diversification and extinction.
Great Ordovician Biodiversification Event: A prolonged rise in marine diversity and ecological structure during the Ordovician. This named interval captures the period’s extraordinary expansion of marine life.
Cambrian: The geological period preceding the Ordovician, beginning about 539 million years ago. Its earlier animal diversification provides the baseline for Ordovician marine ecosystems.

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