Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact

While the synchronicity of both Deccan volcanism and the Chicxulub bolide impact with mass extinction at the Cretaceous-Paleogene (K-Pg) boundary is increasingly clear, empirical evidence is still lacking for how either of these factors could have driven observed extinction patterns and carbon cycle perturbations. Here, using boron isotopes in foraminifera, we document for the first time a geologically rapid surface-ocean pH drop following the Chicxulub impact, demonstrating impact-induced ocean acidification was a key mechanism behind ecological collapse in the marine realm. Surface water pH then rebounded sharply with the extinction of marine calcifiers and imbalance in the global carbon cycle. Reconstructed water-column pH gradients and earth-system modelling indicate partially reduced marine primary productivity after impact, followed by protracted inefficiency in carbon export to the deep sea. In sum, our findings provide new insights into the drivers of the last mass extinction, the recovery of marine carbon cycling in a post-extinction world, and how the activity of marine life imprints its isotopic signal onto the geological record.