This epoch is part of theTertiary period and the
The Eocene Epoch is a period of time that extends from about 36 million to 58 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified, but the exact dates of the start and end of the period are slightly uncertain. The name Eocene refers to the dawn of modern ('new') mammalian faunas that appeared during the epoch. The Eocene follows the Paleocene Epoch and is followed by the Oligocene Epoch. The Eocene is the second epoch of the Tertiary Era.
The start of the Eocene is marked by the emergence of the first modern mammals. The end is set at a major extinction event that may be related to the impact of (a) large extraterrestrial object(s) in Siberia and/or near Chesapeake Bay.
The Eocene is usually broken into Lower and Upper subdivisions. The Faunal stages from youngest to oldest are:
- Ypresian/(Lower Claiborne)
- Lutetian/(Lower Claiborne)
- Bartonian/Auversian (Upper Claiborne)
- Priabonian/Jackson (Upper Claiborne)
During the Eocene plants and marine faunas became quite modern. The first Charcharinid sharks appeared as did early marine mammals. On land, early forms of many modern mammalian orders appeared including ungulates, bats, probiscidians, primates, and rodents. Older forms declined. Many modern orders of birds first appear in the Eocene.
- See also: Geologic Time Scale