PETM IN THE ZUMAIA FLYSCH

The red clays of Itzurun Beach leave no room for doubt. The foraminifera living on the seabed became extinct, the water became warmer and more acidic, and erosion increased on the continents. Zumaia is one of the most widely studied records of the PETM in the world.

¹³C and ¹⁸O isotopes

The main anomaly of the PETM is the negative 13C and 18O isotopes trapped in the sediments and shells of the Zumaia flysch.

Aberrant shapes

Acidification of the water hindered the formation of foraminifera shells during and after warming, decreasing their size and resulting in anomalous shapes.

• During warming
• Before warming

The clues

• Sharp decline in 13C and 18O isotopes.
• Mass extinction of organisms living on the seabed.
• Calcium carbonate-free area.
• Kaolinite ore.

What happened?

• Methane emission and greenhouse warming began.
• Ocean acidification.
• Shells dissolved by acidified water.
• Increased erosion on continent.