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| Opening of the South Atlantic | |
|---|---|
| Name | Opening of the South Atlantic |
| Date | Mesozoic–Cenozoic |
| Location | South Atlantic Ocean, Gondwana margins |
| Outcome | Continental breakup; formation of South Atlantic Ocean basin |
Opening of the South Atlantic
The Opening of the South Atlantic describes the continental breakup and seafloor creation that separated southwestern Gondwana into what became the South Atlantic Ocean. The event links plate reorganizations involving the African Plate, South American Plate, Antarctic Plate, and associated microplates, and it profoundly influenced the tectonics of Brazil, Argentina, Namibia, South Africa, Uruguay, Angola, Gabon, Bolivia, Paraguay, Chile, Peru and Antarctica. Its study integrates evidence from marine geophysics collected by institutions such as the Lamont–Doherty Earth Observatory, Institute of Oceanography (Portugal), and surveys by navies and petroleum companies including Royal Dutch Shell and ExxonMobil.
The South Atlantic opening represents a classical example of passive margin formation that developed following the breakup of the supercontinent Gondwana. Interpretations draw on seismic reflection profiles from the South Atlantic Ocean and magnetic anomaly mapping first applied in studies by researchers at Scripps Institution of Oceanography and British Geological Survey. Continental rifting linked to hotspot activity associated with the Tristan da Cunha region and the Walvis Ridge–Rio Grande Rise volcanic system established the stage for seafloor spreading recognized in magnetic isochrons correlated with work at Columbia University and the National Oceanography Centre.
Rifting initiated along pre-existing Proterozoic and Paleozoic structures including the Benguela and Sao Francisco cratonic margins and exploited Proterozoic mobile belts such as the Kaapvaal Craton margin and the Congo Craton edge. Plate reconstructions employ kinematic models developed by groups at Purdue University and University of Oslo and use restoration tools from the Paleomap Project and the GPlates community. The evolving plate boundary reorganized slip partitions among the South American Plate, African Plate, and minor plates like the Scotia Plate and the South Sandwich Plate, while interactions with mantle structures linked to the Tristan hotspot and the Saint Helena hotspot influenced magmatic emplacement.
Seafloor spreading commenced diachronously, beginning in the Central South Atlantic during the Late Jurassic to Early Cretaceous and propagating northward and southward through the Early to Late Cretaceous. Chronostratigraphic frameworks rely on magnetic anomaly identifications first documented in the work of Marie Tharp and Bruce Heezen and later refined by teams at Geological Survey of Brazil and Instituto Nacional de Pesquisas Espaciais. Reconstructions reference magnetic chrons like Chron M0 and marine biostratigraphy from planktonic foraminifera studied by laboratories at Scripps Institution of Oceanography and Smithsonian Institution. Kinematic links to the opening of the Central Atlantic Ocean and the motion of the Farallon Plate are considered in global plate circuit analyses by researchers at University of Cambridge.
Volcanism associated with continental breakup produced large igneous province deposits, including flood basalts along the Parana Basin and the Etendeka Province, spatially associated with the Tristan da Cunha plume track and the emplacement of the Walvis Ridge. Petrographic and geochemical investigations have been led by teams at Bremen University and University of Cape Town, employing isotopic systems such as Sr-Nd-Pb measured in laboratories at Max Planck Institute for Chemistry. The end-member styles range from volcanic margins with seaward-dipping reflectors identified in seismic profiles collected by Petrobras to non-volcanic margins documented offshore Uruguay and Argentina, reflecting variable lithospheric thinning before the onset of steady-state spreading.
Continental rift basins evolved into passive margin depocenters including the Santos Basin, Campos Basin, Kwanza Basin, Namibe Basin, and the Malvinas Basin. Sediment infill records syn-rift lacustrine and fluvial systems followed by thermal subsidence during drift stages; datasets derive from stratigraphic wells drilled by BP and TotalEnergies and seismic sequence stratigraphy studies by groups at University of Texas at Austin. Turbidite systems sourced from Patagonia and the Brazilian Highlands shaped continental slope architecture, while synchroneity with the Cretaceous Normal Superchron influenced biostratigraphic calibration.
The opening reconfigured paleocirculation patterns by establishing the proto-South Atlantic Gyre and ultimately influencing the development of the Antarctic Circumpolar Current via later separation of South America and Antarctica. Changes in ocean gateways modulated nutrient distribution and climate feedbacks during the Cretaceous greenhouse and the Cenozoic cooling studied by paleoceanographers at Woods Hole Oceanographic Institution and Alfred Wegener Institute. Paleogeographic reconstructions by teams at Paleomap Project and University of Edinburgh integrate fossil distributions documented in collections at the Natural History Museum, London and the Museu Nacional (Brazil).
The passive margins created prolific hydrocarbon provinces explored by companies such as BP, Chevron, and Equinor with major discoveries in the Santos Basin pre-salt plays and analogous systems in the Kwanza Basin. Mineral resources associated with continental breakup, including placer deposits on continental shelves and seafloor massive sulfides proximal to paleo-rifts, have been targeted by mining consortia linked to Angola and Brazil. Paleontological finds, including marine reptiles and continental vertebrates recovered from rift and post-rift strata, have been described by paleontologists at University of Buenos Aires and Museu de História Natural e Jardim Botânico da UFRJ, providing biogeographic evidence for Mesozoic dispersal pathways across Gondwana.
Category:Geology of South America Category:Geology of Africa Category:Plate tectonics