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Seismic Stratigraphy of the Onshore Portion of Pernambuco Basin, Evidence of Break-up During Middle Albian for the South Atlantic Rift in Northeast Brazil


It was previously proposed that the prolongation of the Atlantic rift beyond the Late Aptian in the eastern Portion of Northeast Brazil. This marginal region encompasses the Pernambuco, Paraíba and the Natal Platform Basins. This proposition was mainly based due the absence of Aptian-Albian sedimentary sequences over the coastal zone to the North of Pernambuco Basin. The Pernambuco Basin records the last rift phase pulse of South Atlantic which also involved the Sergipe-Alagoas Basin. A reassessment of three 2D seismic sections, as well as the record from the only deep stratigraphic well drilled in the coastal zone of the Pernambuco Basin, shows that the rift in this region begun in the Aptian and ended in the Mid-Albian. The seismic stratigraphic interpretation showed that there is a initial Aptian rift phase, dominated by aluvial systems (Cabo Formation), which caused the rapid opening of the basin. At the top of this sequence there is an unconformity caused by a second rift phase, which began in the Lower Albian and is characterized by less deformation, and was dominated by fluvial and volcaniclastic systems (Suape Formation). The poor biostratigraphic data suggested that the break up unconformity, which marks the end of second rift phase, which occurred in the Mid-Albian. Overlying the break up unconformity there is a sequence of Upper Albian deposits (Paraíso Formation) with some evidence of marine influence, as indicated by unidentified dinoflagelates and palinoforaminifers. This unit represents the first post-rift sequence, which remained influenced by continental deposition due the isolation of the proximal region caused by an external high in the platform. At the end of the Albian another unconformity was established, over which the Cenomanian-Turonian deposits of the Estiva Formation were deposited, marking the shallow marine influence caused by a major transgression over the proximal region. Another important observation is that some stratigraphic relations show that the Albian magmatic event, which affected the basin probably, began in the Lower Albian. This finding is important for understanding the magmatic influence in the rift process, for which existent data suggests that the main pulse occurred during the Late Albian. This new proposal for the basin stratigraphy is important because it could have a positive impact the regions petroliferous potential, as well as assisting correlations with the African Conjugate Margin.