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 Plate tectonic reconstructions and geophysical interpretations across the southern South Atlantic Ocean suggest geodynamic relationships between Brazilian and West African continental margin basins, particularly the correlation of synrift basins, transform faults, fracture zones, salt basins, and other geological markers. The analysis indicates a diversity of basin characteristics (rift and drift systems) on both sides of the South Atlantic that define them as different stratigraphic, structural, and geochemical entities. Marked differences are observed between the basins north and south of the Florianópolis (Rio Grande) Fracture Zone in Brazil and the Walvis Ridge in Africa, which are clearly expressed in the regional deep seismic profiles recently obtained in the conjugate margins. However, in terms of petroleum systems, the basins are characterized by several geochemical similarities in source rocks deposited during a continental, lacustrine synrift sequence. This interpretation has been overlooked by several previous works comparing the South Atlantic margins, but it has been recently applied to the delineation of several exploratory targets in the southern Angola, Namibian, and South Africa offshore basins. Two end-end member basins have been suggested north and south of the Walvis Ridge–Florianópolis Fracture Zone, which experienced a different structural and stratigraphic evolution as a consequence of their geodynamic models. The southern African basins (located south of the Walvis Ridge), as well as the conjugate Pelotas Basin offshore Brazil, and the offshore Uruguay and Argentina basins, have been associated with the development of volcanic margins, formed during the emplacement of the Tristan da Cunha mantle plume. Due to the lack of significant hydrocarbon discoveries in the southernmost South Atlantic, doubts have been cast on the presence of the prolific Lower Cretaceous lacustrine source rock systems south of the Walvis Ridge, which occur in the northern basins (particularly in the Greater Campos basin) and are overlain by the massive salt offshore Angola. This work reports the comparison of the geological, geophysical, geochemical and consequently the petroleum system features of the Namibian and South African basins (Walvis, Lüderitz, and Orange) with the basins offshore Brazil, Uruguay, and Argentina. The results of seismic, potential field, and geochemical analyses of oil samples recovered from offshore wells in the South Atlantic conjugate margins endorse the application of a unified model for source rock and petroleum system assessment in the offshore basins, heralding the existence of a new frontier for the petroleum exploration offshore Namibia, possibly containing giant lacustrine oil and gas reserves.

Abstract Tectonic reconstructions made across the southern South Atlantic Ocean indicate a diversity of rift and drift basin characteristics on the conjugate margins that define them as different stratigraphic and structural entities. In terms of petroleum systems, the basins are not as unlike as some characteristics suggest. Given the lack of significant hydrocarbon discoveries to date south of the Walvis Ridge, doubts have been cast on the presence in this area of the prolific Lower Cretaceous lacustrine and marine source rock systems, which are well known in the Greater Campos Basin and offshore Angola. Oils and condensates from the basins south and north of the Walvis Ridge exhibit geochemical similarities suggesting that comparable source rock systems are present in both areas. The condensate geochemical analysis results from the Kudu Field in Namibia are compared with oils from marine and lacustrine sources in Brazil, indicating that the Kudu condensates are derived from at least two different source rocks. These results suggest that the underexplored basins offshore Namibia contain thermally mature Lower Cretaceous lacustrine and marine source rocks, offering a new frontier for petroleum exploration in Africa's southern South Atlantic.

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.