Seismic characteristics of the onshore Abrolhos magmatism, East-Brazilian continental margin

A 3D seismic volume was interpreted in order to study the extension of the Abrolhos magmatism in the onshore portion of the Mucuri Basin, East-Brazilian continental margin. The effusive rocks were divided into two volcanic-sedimentary cycles that encompasses at least three igneous pulses, which were recognized in the well analyses. The seismic boundary between the volcanic-sedimentary cycles is marked by a strong negative amplitude reflector associated to the Lower Eocene Unconformity surface. Diffuse features similar to hydrothermal vents were also described, which would have been responsible for paleo-seepages in the marine Eocene sediments. The paleo-surface coincident with the top of these structures is directly related to the top of the first cycle of the onshore Abrolhos magmatism and, consequently, to the Lower Eocene Unconformity. The second volcanic-sedimentary cycle onlaps onto the mounds of the previews cycle and is limited at the top by the Pre-Upper Eocene Unconformity. The seismic analyses presented herein suggest that the relationship between the Cenozoic magmatism, associated to the Abrolhos Formation, and the Paleogene-Neogene sequences would not be restricted only to the offshore portion of the basin, but would also have related deposits in the onshore portion of the Mucuri Basin.