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| Sergipe-Alagoas Basin | |
|---|---|
| Name | Sergipe-Alagoas Basin |
| Country | Brazil |
| State | Sergipe; Alagoas |
| Onshore offshore | onshore and offshore |
| Age | Paleozoic–Cenozoic |
| Basin type | pull-apart; passive margin |
Sergipe-Alagoas Basin is a rift-to-passive-margin sedimentary province located along the Brazilian eastern margin in the states of Sergipe and Alagoas. It preserves a long stratigraphic record from Paleozoic through Cenozoic and hosts significant hydrocarbon accumulations that have driven exploration by companies such as Petrobras, Shell plc, and Statoil. The basin links regional tectonics involving the South American Plate, the African Plate, and the breakup of Gondwana during Mesozoic rifting.
The basin's stratigraphy records deposition across Cambrian–Ordovician continental sequences correlated with the São Francisco Craton margin, Permian–Triassic sequences tied to the Paraná Basin, and extensive Jurassic–Cretaceous rift-related successions contemporaneous with the South Atlantic opening and the Walvis Ridge–Rio Grande Rise hotspot track. Reservoir intervals include Itaparica Formation, Riachuelo Formation, and Albian shallow-marine sandstones, whereas sealing intervals include shale-rich members analogous to the Santos Basin and the Campos Basin source–seal couples studied by ANP. Stratigraphic frameworks have been refined using data from wells drilled by Halliburton, Schlumberger, and the multidisciplinary teams from Universidade Federal de Sergipe and Universidade Federal de Alagoas.
Rifting initiated in the Early Jurassic associated with the breakup of Gondwana and transform faulting linked to the Falklands/Malvinas Plateau–Northeast Brazil differential motion. The basin evolved through synrift subsidence, post-rift thermal sag, and passive-margin subsidence influenced by the South Atlantic opening and magmatic events connected to the Paraná-Etendeka flood basalts and the Trindade Island hotspot track. Structural styles include half-grabens, listric normal faults, and salt-controlled mini-basins comparable to adjacent basins studied by teams from Universidade de São Paulo and the Brazilian Geological Survey. Regional inversion related to the Andean orogeny and Cenozoic compressional pulses reactivated older faults.
Hydrocarbon systems in the basin comprise marine source rocks of the Riachuelo Formation and lacustrine organic-rich intervals analogous to source rocks of the Pelotas Basin and the Recife Basin, with maturation influenced by burial, heat-flow variations, and magmatic intrusions studied in collaboration with TotalEnergies and Chevron Corporation. Reservoirs include fluvial–deltaic sandstones, carbonate buildups, and turbiditic fans comparable to reservoirs in the Espírito Santo Basin; traps include structural closures associated with growth faults and stratigraphic pinch-outs akin to plays in the Campos Basin. Major exploration wells drilled by Petrobrás and international partners documented oil shows and commercial accumulations leading to production fields managed under concession rounds regulated by Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP). Enhanced recovery studies involve techniques promoted by Schlumberger and research partnerships with Federal University of Rio de Janeiro.
Sedimentary facies span fluvial conglomerates and sandstones, lacustrine shales, carbonate platforms, and marine siliciclastic successions reflecting changes in relative sea level, climate shifts associated with Cretaceous Thermal Maximum events, and sediment supply from the São Francisco Craton and Gondwanan hinterland. Deltaic systems show distributary-mouth bars and mouth-bar deposits comparable to models from the Niger Delta and the Mississippi Delta, while carbonate ramps exhibit bioclastic grainstones studied using methods from the Geological Society of America and the Society of Economic Paleontologists and Mineralogists. Sediment provenance studies use detrital zircon geochronology linked to laboratories at Lamont–Doherty Earth Observatory and University of Oxford collaborators.
Fossil assemblages include ammonites, bivalves, foraminifera, ostracods, and trace fossils used for biostratigraphic correlations with the Tethyan and South Atlantic faunal provinces. The Riachuelo sequence preserves rich marine faunas comparable to those described by paleontologists at the Smithsonian Institution and the Natural History Museum, London, while microfossil zonations (planktonic foraminifera, nannofossils) tie to global chronostratigraphic frameworks such as the Geologic Time Scale updates by International Commission on Stratigraphy. Vertebrate remains, including crocodilian and dinosaur fragments, have been reported in proximal successions and studied with institutions like Museu Nacional (Brazil) and Universidade Federal do Rio de Janeiro.
Petroleum production and exploration have driven regional development involving multinational operators (ExxonMobil, Equinor) and national entities (Petrobras), influencing state revenue for Sergipe and Alagoas and infrastructure projects supported by the Brazilian Development Bank (BNDES). Hydrocarbon activities spurred port upgrades at Port of Aratu, gas pipeline proposals connected to the Northeast Gas Pipeline network, and local employment in collaboration with universities including Universidade Federal de Pernambuco. Mining of associated minerals and aggregate resources has local economic impact, while tourism linked to coastal geology involves agencies such as Embratur.
Environmental challenges include offshore oil spill risk, produced water disposal, coastal erosion affecting São Cristóvão and Maceió, and biodiversity impacts on zones protected under the Chico Mendes Institute for Biodiversity Conservation and state environmental agencies. Management responses involve contingency planning by ANP and environmental licensing by Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (IBAMA), along with environmental impact assessments conducted with universities such as Universidade Federal de Alagoas and international partners including UNECLAC and World Wildlife Fund. Mitigation strategies emphasize best practices from industry groups like the International Association of Oil & Gas Producers and monitoring programs coordinated with municipal authorities.
Category:Geology of Brazil Category:Oil fields of Brazil