The Paleocene and Eocene epochs (65-34 Ma) were peppered with global warming events called “hyperthermals”. Sedimentary records of the largest hyperthermal, the Paleocene-Eocene Thermal Maximum (PETM), suggest that a massive amount of carbon was released into the atmosphere, causing ocean acidification, warming, and widespread extinction of deep-sea organisms. Records of the surface ocean carbon system derived from boron-based foraminifer proxies are providing a new constraint on the size and magnitude of the ocean acidification that occurred and by extension the amount of carbon that was released. I will present new calibrations for the planktic foraminiferal B/Ca proxy that we have created by growing living foraminifera in seawater chemistry analogous to that of the Paleogene. In particular, we have tested the influence of seawater [B], [Ca], and the Mg/Ca ratio on the sensitivity of B/Ca to the carbon system. In contrast to experiments with inorganic calcites, our data show that crystal growth rate as driven by CaCO3 saturation state is not a major control on planktic foraminiferal B/Ca. I will discuss the best way to apply these new calibrations from modern species to now-extinct Paleogene foraminifera and will show how our calibrations shed new light on the size and source of the PETM ocean acidification event.
Environmental Geology & Geochemistry Seminar (EGGS) Seminar
Thu, Sep 19, 2019, 12:30 pm to 1:30 pm