The early Oligocene glacial maximum
Antarctic ice reaches its greatest extent yet and sea level drops further than at any other point in the Cenozoic.
- When
- —
- Duration
- 800 thousand years
- Known to
- ± 300 thousand years
- Era
- Oligocene, Cenozoic
For roughly a million years after the Oi-1 step, the East Antarctic Ice Sheet holds close to its modern volume or more, and global sea level falls to its lowest stand of the era — the largest drop of the whole Tertiary. Continental shelves are exposed worldwide, river systems cut down into them, and shallow marine habitats are drastically reduced. It is the first time since the Permian that a large ice sheet has governed global sea level, and the mechanism that will drive the Quaternary is now switched on.