IODP Expedition 388: Equatorial Atlantic Gateway

Our IODP proposal, led by Tom Dunkley-Jones, to drill the Equatorial Atlantic, off the Brazilian Pernambuco Plateau has been successful and is now scheduled to sail in August/September 2020 as IODP Expedition 388 "Equatorial Atlantic Gateway".


Abstract

This proposal seeks to answer first order questions about the tectonic,
climatic and biotic evolution of the Equatorial
Atlantic Gateway (EAG). We propose to target sequences of Late
Cretaceous and Cenozoic sediments offshore NE Brazil,
just south of the theorized final opening point of the EAG.
These sequences are accessible to conventional non-riser
drilling in the vicinity of the Pernambuco Plateau, part of
the northeastern Brazilian continental shelf. This region was
chosen to satisfy two key constraints that other regions in
Equatorial Brazil could not meet: first, Aptian-Albian aged
sediments, that record the main phases of the South
Atlantic marine incursion, are present at depths shallow enough to be
recovered by non-riser drilling; second, Late Cretaceous
and Paleogene sediments preserved on the Pernambuco Plateau,
are close enough to the continental margin, and at
shallow enough paleo water depths (<2000 m) to provide
well-preserved organic biomarkers and calcareous microfossils
for multi-proxy studies of greenhouse climate states. New
records in this region will allow us to address major
questions within four key themes: A) The early rift history of the
Equatorial Atlantic; B) Biogeochemistry of the restricted
Equatorial Atlantic; C) The long-term paleoceanography of the
Equatorial Atlantic Gateway; and, D) the limits of tropical
climates and ecosystems under conditions of extreme warmth.
Tackling these major questions with new drilling in the
EAG region will advance our understanding of the long-term
interactions between tectonics, oceanography, ocean
biogeochemistry and climate, and the functioning of tropical
ecosystems and climate during intervals of extreme warmth.

Scientific objectives

i) Determine the dynamics and paleoenvironments of the Cretaceous Gondwana triple junction rift systems, including the localisation of rifting, passive margin formation, magmatism and depositional environments

ii) Document the transition from breakup to mature spreading: ocean water chemistry, age of oceanic crust, gateway formation, contribution to the knowledge of rift diachronism

iii) Determine the post rift evolution & deep earth Dynamics

iv) Investigate how volcanism, ocean circulation, temperature, nutrient availability, and ecosystem compositions interact to both trigger and end Ocean Anoxic Events

v) Investigate the role of tropical young ocean basins within the global carbon cycle and how this is amplified during times of global temperature perturbations, such as OAEs

vi) Test the effects of extreme low oxygen concentrations and high temperatures on the ecological and biogeochemical processes operating within marine basins

vii) Determine the impact of EAG opening on the evolution of global ocean circulation

viii) Determine if there are negative feedbacks that limit tropical temperatures in greenhouse climate states