Abstract The synrift and breakup stages of the Pelotas basin in southeast Brazil are characterized by scarce siliciclastic deposits and widespread volcanism in the form of seaward-dipping reflectors (SDRs). Using high-quality seismic reflection and refraction profiles integrated with gravity, magnetics, and exploratory boreholes, a volcanostratigraphic analysis has been undertaken to understand the geological processes observed during the rifting and breakup stages of this segment of the South Atlantic continental margin. Ten volcanic units have been identified and mapped within the extended continental crust and into the transitional and oceanic crusts. The magmatic cycle began during the early synrift stage, with alkaline, high TiO 2 basalts produced at 125 Ma. This was followed by the formation of a series of voluminous tholeiitic, high TiO 2 SDR wedges during the late synrift and breakup stages. The end of the breakup process was marked by flat-lying, late synrift/early postrift, tholeiitic, low TiO 2 basalts at 118 Ma. During the Late Cretaceous and Early Paleogene, the magmatic activity continued only in the oceanic crust, forming igneous intrusions (volcanic cones or seamounts). A comparison between the Pelotas basin and the Lüderitz and Walvis basins offshore Namibia is discussed by integrating regional geological maps, potential field methods, seismic data, and results of exploratory drilling. The SDR province in the Pelotas basin coincides geographically with the Paraná basin continental flood basalts onshore Brazil, which crop out near the coastline. This makes the Pelotas basin an ideal place to understand the relationships between the tectonic-magmatic events that preceded and continued during the Gondwana breakup, which resulted in the development of continental margin rift basins and the formation of the South Atlantic Ocean.

Abstract This study focuses on a regional comparison of interpretations from selected 2D seismic transects between large salt and salt-free basins offshore southern Brazil (Espirito Santo basin, Campos basin, Santos basin, and Pelotas basin) and southwest Africa (Kwanza basin, Benguela basin, Namibe basin, and Walvis basin). Based on tectonostratigraphic analysis of megasequences and first-pass geometric reconstructions of synrift settings, including sedimentary decompaction and isostatic correction, it provides a comprehensive basin-to-basin documentation of the key geological parameters controlling asymmetries in basin evolution. The diversity in the tectonic and stratigraphic architecture of the conjugate margin basins reflects variations in the interplay of a number of controlling factors, of which the most important are: (A) the structural configuration of each margin segment at the time of break up; (B) the postbreakup subsidence/uplift history of the respective margin segment; (C) variations in the type, quantity, and distribution of margin sediment (including salt); (D) the evolution of the large salt basins during sag to postsag stages; and (E) sea-level changes.

Abstract Geological reconstructions in the last two years involving the elements and processes of the petroleum systems across the southern South Atlantic rifted margins of Namibia and Brazil show evidence of great similarities in the geochemical affinity of petroleum systems in the conjugate margin basins, although some differences are present in their structural and stratigraphic framework. The results of three deep water wells drilled in 2013, in the Walvis and Orange basins, offshore Namibia, showed the presence of at least three prolific active petroleum systems; an early Barremian lacustrine saline, a Barremian marine siliciclastic, and a Cenomanian–Turonian marine anoxic, all of which are characterized by expressive correlations with world-class lacustrine and marine source rock entities. The occurrence of marine anoxic source rocks deposited in Barremian times suggests that sea incursions, in the synrift occurred earlier in the Namibian coast when compared with their Brazilian counterparts where the present of Late Aptian salt is observed (Santos and Campos basins). The recovery of a marine light oil (41° API), for the first time, offshore Namibia, tested from Barremian turbidite sandstones in the Wingat-1 well in the Walvis basin, together with the penetration of at least three source rock systems intervals in the Wingat-1, Murombe-1, and Moosehead-1 wells, confirmed the oil-charged character of a new underexplored petroliferous basin in the deep water province of Namibia.