Stratigraphic Analysis of the Rift and Post-Rift Sections in the Mundau Sub-basin, Ceará Basin, Brazilian Equatorial Margin
Sequence Stratigraphy; Ceara Basin; Rift Basin; Seismic Stratigraphy; Tectomic System Tracts
The discoveries of oil fields in the African Equatorial Margin combined with the drilling of wells such as Pecém and Pitu in the Ceará and Potiguar basins, respectively, reinforce the necessity for studies which aim to better understand the evolution of the sedimentary basins within the Brazilian Equatorial Margin (BEM), emerging as a new frontier for hydrocarbon exploration. The tectonic-structural complexity of the Equatorial Margin is discussed in several works, which classify this region as a transforming passive margin. However, there is a gap in the research of this basins when it comes to the concepts of Sequence Stratigraphy. The Ceará Basin is placed in the continental shelf of the Equatorial Margin and its origin is connected to the Gondwana’s breakup process during the Lower Cretaceous, resulting in the Equatorial Atlantic opening. The basin is limited to the southeast by the Fortaleza High, to the west by the Tutóia High, to the north by the southern part of the Romanche Fracture Zone, and to the south by the crystalline basement. Due to the distinct tectonic aspects and different structural framework, The Ceará Basin can be divided into four sub-basins, from west to east: Piauí-Camocim, Acaraú, Icaraí and Mundaú. The tectonic-sedimentary evolution of the Mundaú Sub-basin is composed by three super sequences: rift, post-rift and drift. In lithostratigraphic terms, the rift and post-rift stages correspond to the Mundaú and Paracuru formations, respectively, which were studied in this work from the well data, allowing the elaboration of 1D diagrams with lithofaces, cycles, sets of cycles and depositional sequences. The seismic stratigraphic analysis was carried out from 2D seismic lines, and consisted of characterizing seismic facies, reflectors terminations and bounding surfaces. The integration of these data and interpretations allowed the separation of the studied section in terms of tectonic systems tratcs and seismic stratigraphic units. Therefore, a model for the tectonic stratigraphic evolution of the basin was proposed.