Role of Basement in the Evolution of Sedimentary Basins: Examples from Brazil's Cratonic Basins and Continental Margin
Abstract
The role of basement in the evolution of sedimentary basins in Brazil was first studied systematically in 1984 through the cooperation of Petrobras exploration geologists with eminent specialists of Proterozoic at the Brazilian universities. The aim of this pioneering project was to better understand the main structural features recognized in Brazil's Phanerozoic basins and evaluate the degree to which preexisting Precambrian features controlled their position and evolution. The project integrated geochronological mapping of Brazil's outcropping basement with the tectonic framework of all sedimentary basins, its results being applied since as a basic tool of planning petroleum exploration. The results obtained in 1984 were reviewed in 2018-2019 using more recent information.
For the cratonic syneclises, large areas of subsidence and sedimentation during much of the Paleozoic and Mesozoic, the existence of a fragmented basement and its zones of discontinuities made up of cratonic blocks, mobile belts, orogenic sutures and major faults, appear to account for the location of sedimentary depocenters and the main structural trends of these basins. Several of these basement discontinuities that were episodically reactivated in Phanerozoic stress fields provided the initial subsidence for the successive sequences that filled the cratonic basins. The propagation of the South Atlantic rift was strongly dependent on crustal structure. When going through cratonic areas, rupture encountered much greater resistance so that deformation took place by trial and abandoning, locally producing aborted rift branches such as Reconcavo-Tucano-Jatobá; a more favorable option for continental rupture was found in such case. Conversely, where crossing orogenic belts especially in a direction favored by its strong mechanical anisotropy, rifting was easier, creating wide extended basins like those along the São Paulo Plateau. The various segments of the South Atlantic Rift, produced by geotectonic processes active for almost 100 Ma, may thus serve as a giant laboratory suitable for testing the effects of tectonic inheritance.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T43E0499S
- Keywords:
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- 8105 Continental margins: divergent;
- TECTONOPHYSICS;
- 8107 Continental neotectonics;
- TECTONOPHYSICS;
- 8109 Continental tectonics: extensional;
- TECTONOPHYSICS;
- 8169 Sedimentary basin processes;
- TECTONOPHYSICS