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ESTRUTURA E EVOLUÇÃO DAS BACIAS MESOZÓICAS EMERSAS DA MARGEM CONTINENTAL BRASILEIRA
ESTRUTURA E EVOLUÇÃO DAS BACIAS MESOZÓICAS EMERSAS DA MARGEM CONTINENTAL BRASILEIRA
Autor
OJEDA Y OJEDA, HILDEBERTO A.
Institución
Resumen
The basic structural framework of the onshore Mesozoic Brazilian marginal basins is preferencially constituted by antithetic andsynthetic tilted faulted blocks. Occasionally, less subsident blocks form intrabasinal highs, which some times arepetrolíferous. Thecomplement of this framework is composed by shallow platforms, hinges andregional homoclínes, as well as salt diapirs, shale incipient domes and growth faults with rollover. The stratigraphic columnof the basins is generally composed by a basal section of Paleozoic sediments, unconformably covered by Late Jurassic-Barly Cretaceous continental deposits of the Dom João Stage. Conformably overlie Early Cretaceous (Rio da Serra to Jiquiá stages) fluvial-deltaic lacustrine sediments interbedded with syntectonic conglomerares. Unconformably overlie Early Cretaceous (Alagoas Stage) evaporitic or fluvial-lacustrine sequences. ln the top of the column there are Albian-Tertiary marine-non marine sequences, which arecomposed by deltaic deposits, platform carbonates and slope carbonates, and clastics, Continental late Tertiary-Quaternary sediments as well as eruptive igneous rocks complete the stratigraphic section of the basins. The geologic evolution of the focused basins retlects the events of the tectonic-sedimentary development of the Brazilian continental margin. Four principal phases were distinguished: intumescence, in the Late Jurassic-Early Cretaceous, with crustal uplift, development of peripheric basins and deposition of the Dom João Stage; rift, in the Early Cretaceous (Neocomian to Aptian), when rift valleys and antithetic and synthetic tilted fault blocks systems were formed, and the Rio da Serra Jiquiá stages and a part of the Alagoas stage were deposited; transition, in the Early Cretaceous (Alagoas Age), when the first marine transgressions and deposition of evaporitic sequences occurred in some basins. ln other basins, fluvial-deltalc-lacustrine sedimentation happened; and migration, in the Late Cretaceous (Albian)-Quaternary, when a generalized synthetic tilting and development of homoclinal structures (filled by and deposition of thick wedge of clastic-carbonatic-non marine and oceanic deposita) took place, and adiastrophic structures were formed. Resumo indisponível.