Global Warming and Equatorial Atlantic Paleoceanographic Changes During Early Eocene Carbon Cycle Perturbation V

Abstract A series of transient global warming events (“hyperthermals”) in the early Eocene is marked by massive environmental and carbon cycle change. Among these events, the impacts of the Paleocene Eocene Thermal Maximum (∼56 Ma), Eocene Thermal Maximum 2 (∼54 Ma) and Eocene Thermal Maximum 3 (∼53 Ma) are relatively well documented. However, much less is known about the many subsequent hyperthermals that apparently occurred on orbital eccentricity maxima until at least the end of the Early Eocene Climatic Optimum (EECO; ∼53–49 Ma). Ocean Drilling Program (ODP) Site 959 (Equatorial Atlantic Ocean), we report a large negative carbon isotope excursion (CIE) in both organic and carbonate substrates that we correlate to the “V” event sensu Lauretano et al. (2016), https://doi.org/10.1127/nos/2016/0077 (or C22nH1 sensu Sexton et al. (2011), https://doi.org/10.1038/nature09826 ) at ∼49.7 Ma, following combined bio‐ and chemostratigraphic constraints. Through TEX 86 paleothermometry, we reconstruct a sea surface temperature rise of 1.3–2.0°C associated with this CIE, which, combined with evidence for warming from the deep sea, implies that this event indeed represents a transient global‐scale warming episode like the earlier hyperthermals. Organic walled dinoflagellate cyst assemblages indicate a productive paleoceanographic background setting, likely through regional upwelling, which alternated with episodes of stratification. Warming reconstructed across V at Site 959 is relatively similar to the higher‐latitude‐derived deep ocean reconstructions. However, the presence of upwelling and its variable intensity across the event compromises the use of the reconstructed warming as an estimate for the complete tropical band.