Abstract The Congo (CC) and the São Francisco (SFC) cratons were joined at about 2.05 Ga; northern parts of Palaeoproterozoic basement subsequently underwent extension at about 1 Ga, forming intracratonic basins. Neoproterozoic metasedimentary rocks in these basins yield detrital zircons as young as 630 Ma. The Brasiliano and Pan-African ( c. 620–580 Ma) assembly of West Gondwana extensively altered this system. The Sergipano domain occurs north of the SFC, and the comparable Yaoundé domain occurs north of the CC. Crust north of the Sergipano domain comprises the Pernambuco–Alagoas (PEAL) domain. The NE–SW-striking Tcholliré–Banyo fault in Cameroon may extend southwestwards between the PEAL and Sergipano domains, defining northern limits of abundant SFC/CC basement. The Adamawa–Yadé domain in Africa does not appear to extend into Brazil. The Transverse domain of Brazil is a collage of Palaeoproterozoic crustal blocks, the 1.0 Ga Cariris Velhos orogen (CVO), late Neoproterozoic basins, and Brasiliano granites. The CVO extends ENE for more than 700 km in Brazil, but eastern continuation into Africa has not been identified. North of the Transverse domain contiguous c. 2.15 Ga gneisses comprise basement of Rio Grande do Norte and Ceará domains, which continue eastwards into western Nigeria and western Sahara.

Abstract The Neoproterozoic successions of the São Francisco Craton are primarily represented by the Bambuí and Una groups, deposited in cratonic epicontinental basins, and by the Vazante and Vaza Barris/Miaba groups, which accumulated on passive margins on the edges of the craton. The epicontinental basins comprise three megasequences: glaciogenic, carbonate platform (marine) and dominantly continental siliciclastics. Possible correlative sequences are observed in the passive margin deposits. At least two major transgressive–regressive sea-level cycles occurred during the evolution of the carbonate megasequence, which lies above glaciomarine diamictites of probable early Cryogenian (i.e. Sturtian) age. C, O, Sr and S isotope trends from analyses of well-preserved samples, together with lithostratigraphic observations, provide reasonable correlations for most of the Neoproterozoic successions of the São Francisco Craton. The 87 Sr/ 86 Sr record of these successions, ranging from 0.70769 to 0.70780, supports the proposed correlation with the Bambuí, Una and Vaza/Barris successions, and with the basal units of the Vazante Group. In addition, C-isotope positive excursions ranging from +8.7 to +14‰ and negative excursions from –5.7 to –7‰ VPDB in the Bambuí, Una and Vaza-Barris successions provide key markers for correlations. The precise ages of the sedimentation in these successions remains a matter of debate, but organic shales of two units of the Vazante Group have been dated by Re–Os techniques in two different laboratories, both yielding Mesoproterozoic ages. The Neoproterozoic and Mesoproterozoic successions preserve significant glaciogenic deposits.

Abstract A combination of seismic reflection and gravimetric imagery has been used to map four sectors of proto-oceanic crust along conjugate segments of the West African and Brazilian margins. These form corridors isolating oceanic crust, produced about the post-118 Ma pole of rotation, from continental crust. Seaward of the proto-oceanic crust/oceanic crust boundary, relatively uniform, thin oceanic crust (4.2–6.5 km thick) has been generated at the paleo-Mid-Atlantic Ridge. Structural variability is limited largely to fracture zones. Proto-oceanic crust in the northern sectors ( i.e. , Kribi, Mbini, and Ogooue) is up to 10 km thick, block-faulted, compartmentalized, and seismically layered. These sectors of proto-oceanic crust likely were generated by slow spreading, as the relative plate motions evolved from left-lateral dislocation along the Sergipe-Alagoas transform to full-fledged spreading. Thus, proto-oceanic crust in the north is the product of a leaky transform fault and records the evolution from disorganized to organized spreading under a changing stress regime. Proto-oceanic crust in the southern sector, the Gabon sector, may consist of slivers of lower crustal or upper mantle rocks emplaced along detachments and unroofed as the Gabon upper plate detached from the Brazil lower plate. The ocean-continent boundary marks the transition from deeply-subsided proto-oceanic crust to relatively elevated continental crust. Merging the mapped oceanic crust/proto-oceanic crust boundaries from the conjugate margins results in a rigid closure model at about 118 Ma for this part of the Atlantic. Merging the mapped ocean-continent boundaries ( i.e. , removing proto-oceanic crust) produces a Neocomian rigid closure fitting the continental sectors of the African and South American plates. Prior to this stage, and beginning in earliest Neocomian, continental deformation was dominated by sinistral shear along the Sergipe-Alagoas transform, parallel to the West African margin between 3° north–1° south (or parallel to the Brazilian margin between 8°–13° south). Shear along the transform produced a complex swath of transcurrent fault branches, relays, pull-apart basins, and transpressional ridges. Conjugate fits of paired seismic lines from the two margins indicate the South American plate moved more than 100 km southwest relative to the African plate, prior to a 40° change in plate motion direction leading to genesis of proto-oceanic crust. Dislocation along the transform obliquely extended both the Gabon rift zone to the south of the transform, and the Jatobá-Tucano-Recôncavo rift zone marking the western boundary of the Sergipe microplate. Conjugate seismic pairings across the adjoined Brazil and Gabon rift zone margins show that a simple shear mode of extension developed in this area as dislocation along the transform progressed. The low-angle main décollement dips toward the Gabonese side and deepens beneath it, dividing a narrow band of abruptly extended São Francisco cratonic crust (lower plate) from a broad zone of extended Congo fold belt rocks (upper plate). With the 40° change in plate motion direction and the onset of seafloor spreading, extension of the Gabon rift zone ceased and the Jatobá-Tucano-Recôncavo rift zone became an aulacogen. The plate closure scenarios presented here have an important bearing on matching rock units and basins from the two margins, particularly in an exploration context. The scenarios also explain why previous attempts to pair apparent conjugate seismic lines from offshore Brazil and West Africa have been unable to consistently match both continental and oceanic crustal sectors.