Late Cretaceous changes in continental configuration: toward a better-ventilated ocean?
Abstract
Oceanic anoxic events (OAEs) are large-scale events of oxygen depletion in the deep ocean that happened dur-
ing pre-Cenozoic periods of extreme warmth. Last global OAE occurred at the Cenomanian-Turonian boundary
(OAE2) prior to the Late Cretaceous long term cooling. Ever since, and despite the occurrence of warming events,
Earth no more experienced such large-scale anoxic conditions. Here we explore the role of major continental
configuration changes occurring during the Late Cretaceous on oceanic circulation modes through numerical sim-
ulations using a General Circulation Model (GCM), that we confront to existing neodymium isotope data (
"
Nd).
Except from a continuous deep-water production in the North Pacific, the simulations at 95 Ma and 70 Ma reveal
major differences marked by a shift in the southern deep-water production sites from South Pacific at 95Ma to
South Atlantic and Indian oceans at 70Ma. Our modelling results support an intensification of southern Atlantic
deep-water production as well as a reversal of the deep-water fluxes through the Caribbean Seaway as the main
causes of the decrease in
"
Nd values recorded in the Atlantic and Indian deep waters during the Late Cretaceous.
We conclude that the change from a sluggish to a much more active circulation depicted by the model in the
Atlantic from 95Ma to 70Ma may have driven the disappearance of OAEs after the Late Cretaceous.