Miocene
Americanadjective
noun
adjective
noun
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The fourth epoch of the Tertiary Period, from about 24 to 5 million years ago. During this time the climate was warmer than it had been in the Oligocene, and kelp forests and grasslands first developed. With the isolation of Antarctica, a circumpolar ocean current was established in the southern Hemisphere, reducing the amount of mixing of cold polar water and warm equatorial water and causing a buildup of ice sheets in Antarctica. The African-Arabian plate became connected to Asia, closing the seaway which had previously separated Africa from Asia. Mammalian diversity was at its peak.
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See Chart at geologic time
Other Word Forms
Etymology
Origin of Miocene
First recorded in 1825–35; mio- (from Greek meíōn “less”) + -cene
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
During the Miocene, the area experienced warm and wet rainforest conditions.
From Science Daily • Apr. 23, 2026
Surrounding rock layers suggest that the fossils date to the Early Miocene, approximately 21 million years ago.
From Science Daily • Dec. 12, 2025
The Tatacoa Desert is home to rich deposits of fossils from an epoch known as the Middle Miocene.
From BBC • Jul. 22, 2025
For prehistory fans, the Miocene, with its fantastic mammal life, is an immensely attractive period.
From Salon • Feb. 17, 2025
All had died from some mysterious cataclysm just under twelve million years ago in the time known to geology as the Miocene.
From "A Short History of Nearly Everything" by Bill Bryson
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
