Plankton and benthic foraminiferal dataset for the study of the Eocene-Oligocene transition

The Eocene–Oligocene transition (EOT) was the crucial turning point when Earth’s climate shifted to its current cool state. Understanding how life responded to this “warmhouse-to-icehouse” shift was limited by the absence of high-resolution fossil data. Here, we use a novel AI algorithm to construct a 28-myr-long species richness history of foraminifera with ~26,000-year resolution. A significant richness decline occurred during the EOT, eliminating 74% of species. Planktonic and larger benthic foraminiferal extinctions are associated with rapid cooling, sea-level fall, and positive carbon isotopic excursion. However, small benthic foraminifera in deep oceans experienced a two-phase biocrisis coinciding with changes in food supply and volcanic activity. These findings reveal complicated, ecologically differentiated environment-life processes and the need to reconsider other major bioevents in deep time.