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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".
This proposal seeks to answer first order questions about the tectonic, climatic and biotic evolution of the EquatorialAtlantic 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-riserdrilling in the vicinity of the Pernambuco Plateau, part of the northeastern Brazilian continental shelf. This region waschosen to satisfy two key constraints that other regions in Equatorial Brazil could not meet: first, Aptian-Albian agedsediments, that record the main phases of the South Atlantic marine incursion, are present at depths shallow enough to berecovered 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 providewell-preserved organic biomarkers and calcareous microfossils for multi-proxy studies of greenhouse climate states. Newrecords in this region will allow us to address major questions within four key themes: A) The early rift history of theEquatorial Atlantic; B) Biogeochemistry of the restricted Equatorial Atlantic; C) The long-term paleoceanography of theEquatorial 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-terminteractions between tectonics, oceanography, ocean biogeochemistry and climate, and the functioning of tropicalecosystems and climate during intervals of extreme warmth.
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