Abstract Glaciogenic deposits of the Jequitaí Formation (Fm.) are well exposed along the margins of the Serra do Cabral on the São Francisco Craton, southeastern Brazil. The Jequitaí Formation is thin (0–150 m thick), lenticular and overlies the Espinhaço Supergroup on a discrete unconformity. Sandstones show subglacial erosional structures such as grooved and striated pavements oriented ENE–WSW. The Jequitaí Fm. consists of massive and stratified diamictites with granules, pebbles and boulders of gneiss, granite, quartzite and carbonate. At the base, the diamictites are massive, whereas the upper part contains many alternating beds of clast-rich and -poor diamictites. They also contain discontinuous, fine-grained sandstones and a few laminated siltstone–mudstone intercalations. This diamictite association indicates glaciomarine sedimentation. The Jequitaí Fm. covers the São Francisco cratonic domain and its equivalent extends eastward over the Araçuaí fold belt where it is part of the metasedimentary Macaúbas Group, a thick Neoproterozoic unit with metadiamictites, quartzites and schists. The diamictite–turbidite association of the Macaúbas Group was deposited on the border of the Pan-African–Brasiliano rift as gravity flows.

Abstract The Cretaceous actinistian Mawsonia is represented by more than 360 dissociated, but well-preserved, bones obtained from the Areado Group in the Sanfranciscana Basin of Minas Gerais, Brazil. These are among the oldest records of Mawsonia (Berriasian, Lower Neocomian) and include previously undescribed or poorly known skeletal elements (e.g. splenial, dentary, autopalatine, zygals). The new material is referred to the type species, M. gigas . Morphological variation in the sample blurs some of the distinctions formerly drawn between nominal species of Mawsonia , and species level diversity in the genus is difficult to establish. Mawsonia ubangiensis , M. libyca , and M. brasiliensis are considered to be junior subjective synonyms of M. gigas. Mawsonia gigas probably appeared prior to the separation of S America and Africa and became widespread throughout much of western Gondwana (including parts of Africa), even surviving briefly on both continents following their separation. Mawsonia tegamensis is a morphologically distinctive Late Cretaceous African species with no evident fossil record in Brazil and which probably arose by vicariant speciation following isolation of a local Mawsonia population during the later stages of rifting between Northern Africa and the rest of Western Gondwana. Similarities between Axelrodichthys , Lualabaea (here regarded as Early Cretaceous in age) and recently described fossils from Morocco, Niger, and Madagascar suggest the presence of a second endemic Cretaceous mawsoniid lineage in northeastern Brazil and Africa.

Abstract Satellite-derived gravity anomalies were used to map the location and distribution of rift subbasins comprising the Campos and Santos Basins of the southeastern Brazilian continental margin. Free-air and crustal Bouguer gravity anomalies define several features. A negative–positive gravity gradient along the southeastern Brazilian margin correlates generally with termination of oceanic fracture zones, the boundary of synrift evaporites, and an abrupt change in anomaly trends from east-west to margin-parallel. The gravity gradient thus defines the location of the ocean–continent boundary and suggests that much of the São Paulo Plateau is underlain by thinned continental crust. Second, a major offshore tectonic hinge zone, consisting of a series of short-segment, en echelon, high-standing blocks subparallel to the Brazilian margin demarcates the western limit of significant continental extension. The Badejo High of the Campos Basin is part of this hinge zone trend. The Serra do Mar and Serra da Mantiqueira mountains represent an onshore hinge zone. Third, a series of major rift subbasins exist seaward of both the Campos and Santos hinge zones. These have limited along-strike continuity, implying that synrift lake communication, water chemistry, and possibly source quality and preservation were restricted to each subbasin. Extension between west Africa and Brazil occurred during the Early Cretaceous as a series of rift pulses that culminated in the initiation of sea floor spreading. The Congo–Cabinda margin of west Africa and the Camamu–Almada margin of eastern Brazil are characterized by a common tripartite rift history: Berriasian–Hauterivian, Hauterivian–middle Barremian, and late Barremian–early Aptian. Early depth-independent, broadly distributed, and increasingly focused brittle deformation (rift phases I and II) was replaced by depth-dependent deformation dominated by plastic thinning of the lower crust and lithospheric mantle (rift phase III). The nonmarine part of the Lagoa Feia Formation correlates with rift phase II while the “transitional” part is associated with rift phase III. The intervening pre-Alagoas unconformity is equivalent to the pre-Chela unconformity on the Congo margin. The possibility of a mid-crustal detachment beneath the Brazilian margin active during rift phase III has profound implications for the hydrocarbon maturation history of the margin. Seismic reflection data from the São João da Barra Low (Campos Basin) have helped define an early synrift depositional package that likely equates with rift phase I.