Oceanic Anoxic Event 2
At the Cenomanian-Turonian boundary the oceans go anoxic again, and a fifth of marine genera die.
- When
- —
- Duration
- 300 thousand years
- Known to
- ± 200 thousand years
- Era
- Cretaceous, Mesozoic
Around 94 million years ago the Bonarelli Event lays a distinctive black shale across ocean basins worldwide, driven by a large pulse of volcanic carbon — the Caribbean and Kerguelen provinces are the leading candidates. Surface waters warm, oxygen minimum zones expand and euxinic conditions reach into the shelf seas. Roughly a quarter of marine invertebrate genera are lost, with deep-water and reef organisms hardest hit. It is the sharpest of the Cretaceous ocean crises and the best studied, precisely because its black shale is such an unmistakable marker.