A better-ventilated ocean triggered by Late Cretaceous changes in continental configuration.

Yannick Donnadieu,Mathieu Moiroud,Emmanuelle Pucéat,Jean- François Deconinck,François Guillocheau

doi:10.1038/ncomms10316

Abstract

Oceanic anoxic events (OAEs) are large-scale events of oxygen depletion in the deep ocean that happened during pre-Cenozoic periods of extreme warmth. Here, to assess the role of major continental configuration changes occurring during the Late Cretaceous on oceanic circulation modes, which in turn influence the oxygenation level of the deep ocean, we use a coupled ocean atmosphere climate model. We simulate ocean dynamics during two different time slices and compare these with existing neodymium isotope data (ɛNd). Although deep-water production in the North Pacific is continuous, the simulations at 94 and 71 Ma show a shift in southern deep-water production sites from South Pacific to South Atlantic and Indian Ocean locations. Our modelling results support the hypothesis that an intensification of southern Atlantic deep-water production and a reversal of deep-water fluxes through the Caribbean Seaway were the main causes of the decrease in ɛNd values recorded in the Atlantic and Indian deep waters during the Late Cretaceous.

Highlights

Oceanic anoxic events (OAEs) are large-scale events of oxygen depletion in the deep ocean that happened during pre-Cenozoic periods of extreme warmth
It has been suggested that Late Cretaceous changes in climate and continental configuration[6,7,8], namely the widening of the Atlantic Ocean and the deepening of the Central Atlantic (CA) gateway[9], could have induced major changes in oceanic circulation that may have had an impact on the general oxygenation state of the oceanic basins and contributed to the conclusion of these large-scale anoxic events in the deep ocean[10,11]
The experiments conducted here emphasize the potentially important role of land–sea configuration as a preconditioning factor that affects the ease with which OAEs can develop

Summary

Introduction

Oceanic anoxic events (OAEs) are large-scale events of oxygen depletion in the deep ocean that happened during pre-Cenozoic periods of extreme warmth. To assess the role of major continental configuration changes occurring during the Late Cretaceous on oceanic circulation modes, which in turn influence the oxygenation level of the deep ocean, we use a coupled ocean atmosphere climate model. It has been suggested that Late Cretaceous changes in climate and continental configuration[6,7,8], namely the widening of the Atlantic Ocean and the deepening of the Central Atlantic (CA) gateway[9], could have induced major changes in oceanic circulation that may have had an impact on the general oxygenation state of the oceanic basins and contributed to the conclusion of these large-scale anoxic events in the deep ocean[10,11]. Our simulations highlight an evolution from a sluggish circulation in the South and CA using a Cenomanian/Turonian land–sea mask towards a much more active circulation in these basins with an early Maastrichtian land-sea mask

Methods

Results

Conclusion