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

(Chart)

• Eocene
• Paleocene
• Black line: Carbon isotope
• Increase of carbon in the sea and atmosphere = greenhouse effect.
• Yellow line: Oxygen isotope
• Climate warming.
• Horizontal axis: Warming – Pre-warming
• Left image: Shell corroded by ocean acidification.
• Right image: Shell in good condition. It managed to survive the meteorite extinction but went extinct at the PETM.