Large Igneous Province Control on Ocean Anoxia and Eutrophication in the North Sea at the Paleocene–Eocene Thermal Maximum

The Paleocene–Eocene Thermal Maximum (PETM) was a global hyperthermal event ∼56 Ma characterized by massive input of carbon into the ocean–atmosphere system and global warming. A leading hypothesis for its trigger is the emplacement of the North Atlantic Igneous Province (NAIP), with extensive extrusion/intrusion of igneous material into nearby sedimentary basins, forcing local uplift and warming-inducing carbon emissions. It remains unclear if oceanographic changes in the North Sea–Norwegian Sea–Arctic basins, such as anoxia and productivity, were causally linked to local NAIP uplift/activity, and at what time scales these perturbations occurred. To test mechanisms and time scales, we present geochemical proxies (XRF analysis, clay mineralogy, molybdenum isotopes, and pyrite framboid size distribution) in undisrupted marine sediment core E−8X located in the central North Sea. We find evidence for a rapid onset of anoxia/euxinia at the negative carbon isotope excursion from redox proxies, followed by a gradual drawdown of molybdenum/total organic carbon (Mo/TOC) during the PETM main phase indicative of tectonically-restricted basin likely from NAIP uplift. A short-lived increase in Mo, pyrite and TOC occurred during a precursor event associated with a sedimentary mercury pulse indicative of volcanic activity. We suggest thermal uplift and flood basalt volcanism tectonically restricted the North Sea and tipped it into an euxinic state via volcanic emission–oceanographic feedbacks inducing eutrophication. This fine temporal separation of tectonic versus climatic geochemical proxies, combined with pulsed NAIP volcanism, demonstrates that Large Igneous Province emplacements can, at least locally, result in ocean biogeochemical feedbacks operating on relatively short timescales.