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, but much less is known on the many later hyperthermals
that apparently occurred on orbital eccentricity maxima until at least
the end of the Early Eocene Climatic Optimum (EECO;
~53–49 Ma). Here, at 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) (or C22nH1
sensu Sexton et al. (2011)) at ~49.7 Ma, following
combined bio- and chemostratigraphic constraints. Through TEX86
paleothermometry, we reconstruct a sea surface temperature rise of
1.1–1.9 ºC associated with this CIE, which, combined with evidence for
warming from the deep sea, implies that this event indeed represents a
transient global 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.