Geology and tectonics of the South Atlantic Brazilian salt basins
Published:January 01, 2007
Ian Davison, 2007. "Geology and tectonics of the South Atlantic Brazilian salt basins", Deformation of the Continental Crust: The Legacy of Mike Coward, A. C. Ries, R. W. H. Butler, R. H. Graham
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This paper first reviews the salt basins and depositional ages in the South Atlantic salt province. This comprises a series of salt basins separated by basement highs, deep graben (that never dried up), later volcanic highs and subaerial ocean spreading ridges. Initial halite and anhydrite deposition occurred first in the Sergipe-Alagoas Basin of NE Brazil at c. 124.8 Ma, and was closely followed by deposition in the Kwanza Basin, Angola between 124.5 and 121 Ma. The later potassium-magnesium-rich salts were deposited in the Sergipe-Alagoas and Gabon-Congo basins before 114.5 Ma. The age of the main Santos-Campos salt is not known precisely, but the latest anhydrites deposited on the southern margin of the Santos Basin post-date volcanic rocks dated at 113.2 Ma. The paper then compares the salt tectonics of the wide Campos-Santos Basin segment with the narrow South Bahia basins segment. Sediment loading in the Santos Basin produced a landward-dipping base salt, which led to the development of counter-regional faults, and inhibited downslope sliding, and enhanced later contractional effects caused by either gravity spreading or regional tectonic compression. Folding occurred in simultaneous pulses across the Santos Basin, suggesting that regional tectonic compression occurred. The narrow salt basins of South Bahia have a steeply dipping base salt horizon (4°) and pronounced folding, which initiates at the oceanward pinch-out of the salt and propagates back up the slope. The topographic highs, above fold anticlines, are rapidly eroded on narrow margin slopes, which allows the folds to grow more easily to large amplitudes at the top salt horizon.
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Deformation of the Continental Crust: The Legacy of Mike Coward
This Special Publication, in memory and celebration of the work of Professor Mike Coward, is about the deformation of the continental lithosphere. The collected papers discuss geometry, structural principles, processes and problems in a wide range of tectonic settings and thereby reflect the breadth of Coward's interests. They encompass the evolution of Precambrian basement gneiss terrains, the geometry and evolution of thrust systems, basement involvement and structural inheritance in basins, syn-orogenic extension, salt tectonics, the implication of structural evolution on hydrocarbon prospectivity and structural controls on mineralization. Examples are drawn from the Lewisian and Moine Thrust Belt of NW Scotland, the Italian Apennines, NW Himalayas, the Cyclades, Oman, Zagros Mountains, Colombian Cordillera, Carpathians, North Sea, offshore Brazil, regional studies of the Irumide Belt (central Africa), Taurus Mountains (Turkey), greater South America, and from the Witwatersrand Basin of South Africa and the Antler Orogeny of SW USA.