The Eocene-Oligocene extinction
As the ice arrives, warm-water marine life is culled worldwide and tropical forests retreat toward the equator.
- When
- —
- Duration
- 500 thousand years
- Known to
- ± 300 thousand years
- Era
- Oligocene, Cenozoic
The onset of Antarctic glaciation coincides with a substantial extinction, especially among warm-adapted marine groups: nummulite foraminifera, many molluscs, and the reef systems built for a hotter ocean. Sea surface temperatures drop sharply and the latitudinal temperature gradient steepens, compressing the tropical belt. On land, closed forest gives way to more open, seasonal vegetation across the mid-latitudes. It is not one of the big five, but it is the sharpest ecological reorganisation between the asteroid and the Pleistocene.