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| South American continental margin | |
|---|---|
| Name | South American continental margin |
| Location | South America, Atlantic Ocean, Pacific Ocean |
| Length | approx. 14,000 km (coastline extent) |
| Type | continental margin |
| Major regions | Falkland Islands, Patagonia, Brazilian Highlands, Guiana Shield, Andes Mountains, Amazon Basin |
| Notable features | Brazilian continental shelf, Argentine Basin, Peru–Chile Trench, Benguela Current (note: Benguela is Atlantic adjacent to Africa), Carnegie Ridge, Nazca Plate, South American Plate |
South American continental margin is the coastal and submarine transition zone between the South American Plate and the adjacent ocean basins, comprising a mosaic of shelves, slopes, and rises along the eastern and western littorals of Argentina, Brazil, Uruguay, Venezuela, Colombia, Chile, Peru, Ecuador, Guyana, Suriname, and French Guiana. The margin records interactions among major tectonic entities such as the Nazca Plate and features prominent sedimentary systems fed by drainage from inland provinces like the Amazon Basin and the La Plata Basin, and hosts diverse economic activities centered on hydrocarbon provinces like Santos Basin and Golfo San Jorge Basin.
The margin extends from the southern tip of Tierra del Fuego and the Strait of Magellan northward along the Atlantic Ocean to the Caribbean margin adjoining the Lesser Antilles arc, and westward along the eastern flank of the Pacific Ocean from Cape Horn to the equatorial margin adjacent to Panama. Along the western margin, the margin is narrow off Chile and Peru adjacent to the Peru–Chile Trench, while the eastern margin off Brazil and Argentina is broad, featuring the Brazilian continental shelf, the Plata Shelf, and abyssal plains such as the Argentine Basin and Santos Basin. The margin interfaces with offshore plateaus and ridges including the Walvis Ridge (across the Atlantic) and the Carnegie Ridge near Galápagos Islands.
The western margin is an active convergent margin dominated by subduction of the Nazca Plate beneath the South American Plate producing the Andes Mountains and the Peru–Chile Trench, with seismicity concentrated near megathrusts like the source of the 1960 Valdivia earthquake and historic events cataloged by institutions such as the United States Geological Survey. The eastern margin is a passive margin formed during breakup of Gondwana and the opening of the South Atlantic Ocean involving the separation of Africa and South America and features rifted continental blocks including the Recôncavo-Tucano-Jatobá Basin and transform systems linked to the Romanche Fracture Zone and Vema Fracture Zone. The margin’s evolution is recorded in accretionary prisms, forearc basins such as the Pisco Basin, and hinterland drainage reorganizations tied to orogenic events like the Andean orogeny and paleogeographic changes recorded in formations such as the Solimões Formation and the Miocene Paraná Basin deposits.
Morphologically, the margin comprises continental shelves, steep continental slopes, submarine canyons such as the Amazon Canyon and the La Plata Canyon, and abyssal plains with sediment drifts like the Buenos Aires abyssal plain. Sediment supply is dominated by fluvial sources from the Amazon River, Orinoco River, Paraná River, and Magdalena River, with terrigenous clastic deposition, deltas (for example the Amazon Delta), turbidite systems, contourite drifts influenced by currents like the Brazil Current and Humboldt Current, and authigenic mineral precipitation on the continental slope. Sedimentary sequences include thick post-breakup siliciclastic wedges, carbonate platforms off northeastern Brazil, and hydrocarbon-bearing source and reservoir rocks within basins such as the Campos Basin and the Neuquén Basin.
Oceanographic regimes shaping the margin include the warm southward-flowing Brazil Current on the western flank of the South Atlantic Gyre and the cold northward-flowing Humboldt Current (also called the Peru Current) along the west, which modulate upwelling off Peru and Chile and influence primary productivity and fisheries such as the Anchoveta fishery. Interannual climate variability driven by El Niño–Southern Oscillation and teleconnections to the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation alter precipitation across the Amazon Basin, coastal wind regimes, and sediment flux to the margin. Atmospheric systems including the South Atlantic Convergence Zone, the Intertropical Convergence Zone, and seasonal migrations of the South American Monsoon System control river discharge, while oceanographic fronts such as the Subtropical Convergence and eddies spawned by the Brazil–Malvinas Confluence influence nutrient transport.
The margin sustains ecosystems from temperate kelp forests off Patagonia to tropical coral and mangrove systems near Venezuela and the Guianas, and productive pelagic zones supporting schools exploited by fleets from Peru and Chile. Benthic communities on the continental shelf and slope include cold-water coral assemblages, chemosynthetic faunas at cold seeps and methane hydrate sites, and benthic megafauna cataloged in research by institutions such as the Consejo Nacional de Investigaciones Científicas y Técnicas and Instituto Nacional de Pesca. Iconic species include Lama guanicoe along coasts, migratory populations of Chelonia mydas and Eretmochelys imbricata using nesting beaches, and commercially important taxa like Engraulis ringens and Trachurus murphyi.
The margin hosts prolific hydrocarbon provinces including the Santos Basin, Campos Basin, Golfo San Jorge Basin, and frontier plays along the Brazilian pre-salt provinces with reservoirs overlain by thick evaporites such as the Açu Formation. Major fisheries off Peru and Chile underpin national economies and international trade linked to markets in United States and China, while mineral resources include manganese nodules on abyssal plains and placer deposits along the Guiana Shield continental shelf. Offshore infrastructure is developed by companies like Petrobras, Yacimientos Petrolíferos Fiscales (YPF), and international contractors, with ports such as Santos (port), Valparaíso, Callao and Buenos Aires serving as logistics hubs.
Hazards include megathrust earthquakes and tsunamis exemplified by the 1960 Valdivia earthquake, submarine landslides generating paleo-tsunami deposits, and slope instabilities affecting infrastructure. Environmental concerns encompass oil spills (notable incidents prompting responses by organizations like the International Maritime Organization), overfishing affecting stocks managed under regimes such as the Regional Fisheries Management Organization frameworks, coastal erosion exacerbated by sea-level rise linked to IPCC assessments, and habitat loss impacting protected sites such as Galápagos Islands and Maracanã-region coastal reserves. Conservation and management efforts involve multilateral agreements such as the Convention on Biological Diversity and regional research collaborations spanning universities and agencies across Argentina, Brazil, Chile, Peru, and Colombia.
Category:Geology of South America Category:Oceanography of South America