Tiny fossils crack a Cretaceous cold case
Northwestern University researchers have linked a 113-million-year-old mass extinction event to ocean acidification caused by massive volcanic eruptions. By analyzing calcium isotopes in ancient fossils, the team confirmed that CO2-induced acidification hindered shell-building organisms.
Why it matters
This study provides a historical precedent for how modern human-generated CO2 emissions may impact current ocean chemistry and marine ecosystems.
Ancient ocean acidification triggered one of the ocean’s most severe extinctions
EMBARGOED UNTIL 2 P.M. EDT (U.S.) ON THURSDAY, JULY 30, 2026
EVANSTON, Ill. — A 113-million-year-old marine murder mystery may finally be solved.
Using chemical clues locked inside microscopic fossils, Northwestern University scientists found evidence that ocean acidification drove one of the largest extinction events in the history of planktic foraminifera — tiny shell-building organisms that help regulate Earth’s carbon cycle.
The scientists attribute the acidification to the eruption of the Kerguelen Plateau, a massive volcanic province in the southern Indian Ocean. During the Early Cretaceous period, the volcanic province spewed vast quantities of carbon dioxide (CO2) into the atmosphere. As the oceans absorbed that CO2, seawater became more acidic, making it more difficult for marine organisms to build and maintain their shells.
The study will be published on Thursday (July 30) in the journal Science.
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