Salt beds and vanishing seas
Repeated sea-level swings evaporate whole basins, leaving kilometre-thick deposits of salt.
- When
- Known to
- ± 3 million years
- Era
- Silurian, Paleozoic
In the Michigan Basin and elsewhere, extreme oscillations in sea level alternately flood and isolate shallow seas, producing bursts of pinnacle reef growth followed by thick evaporite deposits of halite and gypsum. These sequences record a carbon cycle in repeated upheaval, and the salt they left is still mined today.