Oligocene(redirected from Oligocene System)
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of, denoting, or formed in the third epoch of the Tertiary period, which lasted for 10 000 000 years
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The third oldest of the seven geological epochs of the Cenozoic Era, beginning 34 million years ago and ending 24 million years ago. It corresponds to an interval of geological time (and rocks deposited during that time) from the close of the Eocene Epoch to the beginning of the Miocene Epoch.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.