Tertiary Period

Introduction
Tertiary environment
- Paleogeography
- Paleoclimate
Tertiary life
- Life on land
  - Flowering plants and grasses
  - Birds
  - The rise of mammals
    - Mammalian migration from Eurasia to North America
    - Mammalian migration between North and South America
    - Primates
- Life in the oceans
  - Marine extinctions and recovery
  - Radiation of invertebrates
  - Large marine animals
  - Foraminiferans
Tertiary rocks
- Major subdivisions of the Tertiary System
- Occurrence and distribution of Tertiary deposits
  - Volcanism and orogenesis
  - Sedimentary sequences
- Establishing Tertiary boundaries
- Correlation of Tertiary strata

References & Edit History Related Topics

Images & Videos

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At a Glance

Tertiary Period summary

Related Questions

How did Charles Lyell divide the Tertiary Period in 1833?
How did corals recover after the extinction of reef-building rudists?
How did grasslands influence mammal evolution during the Miocene Epoch?
How did mammals change during the Tertiary Period?
How did the Isthmus of Panama enable the Great American Interchange?
How did the closure of the Tethys seaway affect marine organisms?
How did the extinction at the Cretaceous-Paleogene boundary affect dinosaurs?
How do Global Boundary Stratotype Sections and Points help geologists correlate rocks worldwide?
How do magnetic reversals preserved in rocks help build the geologic time scale?
How do the Paleogene and Neogene periods relate to the former Tertiary Period?
How quickly did Atlantic water refill the Mediterranean basin after the Messinian salinity crisis?
What evidence shows that Alaska and the Arctic had subtropical conditions during the early Eocene?
What major extinction marked the beginning of the Tertiary Period?
When did Antarctic ice sheets begin to form?
When did large ice sheets first form in the Northern Hemisphere?
Where is the Global Boundary Stratotype Section and Point for the Cretaceous-Paleogene boundary?
Where is the Global Boundary Stratotype Section and Point for the Oligocene-Miocene boundary?
Where is the Global Boundary Stratotype Section and Point for the Paleocene-Eocene boundary?
Which era included the traditional Tertiary Period?
Which events may have caused the mass extinction at the Cretaceous-Paleogene boundary?
Which five epochs made up the traditional Tertiary Period?
Who introduced the name Tertiary in 1760?
Why did many grazing mammals develop high-crowned teeth during the Miocene Epoch?
Why did the end of the Thulean Land Bridge separate mammal evolution in Europe and North America?

Science Earth Science, Geologic Time & Fossils Fossils & Geologic Time

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Tertiary Period

geochronology

Written by

Warren D. Allmon

Director, Paleontological Research Institution, Ithaca, N.Y.

Warren D. Allmon

Fact-checked by

Britannica Editors

Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....

Britannica Editors

Last updated

Sep. 29, 2026 •History

Tertiary Period, former official interval of geologic time lasting from approximately 66 million to 2.6 million years ago. It is the traditional name for the first of two periods in the Cenozoic Era (66 million years ago to the present); the second is the Quaternary Period (2.6 million years ago to the present). The Tertiary has five principal subdivisions, called epochs, which from oldest to youngest are the Paleocene (66 million to 55.8 million years...

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