Produção Nacional
Volcanic Structures as Indicators of Aptian and Albian Tectonism in the Sergipe Sub-Basin, Offshore Brazil
2022; RELX Group (Netherlands); Linguagem: Inglês
10.2139/ssrn.4237717
ISSN1556-5068
AutoresMariana Meirelles Lima da Silva, Delzio de Lima Machado, Celso Moura Jardim, Fabio Soares de Mendonça, Mirela Paula de Paula Ribas, Júlio Almeida, Mônica Heilbron,
Tópico(s)Geological and Geophysical Studies
ResumoDetailed seismic interpretation reveals the presence of abundant magmatism in deep and ultradeep waters of the Sergipe sub-basin, represented mainly by Seaward Dipping Reflectors (SDRs). Most SDRs terminate on faults that limit basement highs, suggesting a tectonic influence during their development. Other structures, such as seamounts, lava deltas and volcanoes occur preferentially covering basement highs indicating periods of relative tectonic stability. The general pattern of eastwardly shifted volcanic stacking indicates progressive volcanic rejuvenation to the east. Ages obtained in two borehole samples, together with the seismostratigraphic correlation, locate these magmatic events as having occurred from the Late Aptian to Early Cenomanian. Geochemistry indicates an alkaline composition and a within plate tectonic environment fed by a fertile asthenosphere. The magmatism therefore occurred in an anomalous zone of extended continental crust where differential extension was enabled by two faults resulting from basement shear zones reactivation (São Miguel do Aleixo and Vaza Barris faults) and by Sergipe Fracture Zone (SFZ), that acted as a dextral strike-slip/transform fault during final rifting. Structural lows would have originated from unsuccessful attempts at oceanic crust inception in Late Aptian that jumped eastward throughout the transform fault (SFZ) until reaching the location where the rupture effectively occurred and where the Continental-Oceanic crusts Boundary (COB) can be traced. After breakup, magmatism continued locally, such as in the São Francisco Volcanic Field and its continuation in the oceanic crust in the alignment of volcanoes known as the Bahia Seamounts. Understanding the processes and controls on volcanism formation enabled us (1) to define the age of effective continental breakup at the end of the Albian when the last fault-controlled SDR was identified and (2) to locate the COB that limits this anomalous segment of extended continental crust.
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