Paleogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: Paleotopographic and geodynamic implications

Abstract

International audienceThe geodynamic processes that control the opening of the central segment of the South Atlantic Ocean (between the Walvis Ridge and the Ascension FZ) are debated. In this paper, we discuss the timing of the sedimentary and tectonic evolution of the Early Cretaceous rift by drawing eight paleogeographic and geodynamic maps from the Berriasian to the Middle-Late Aptian, based on a biostratigraphic (ostracodes and pollen) chart recalibrated on absolute ages (chemostratigraphy, interstratified volcanics, Re-Os dating of the organic matter). The central segment of the South Atlantic is composed of two domains, with a two phases evolution of the pre-drift ("rifting") times: a rift phase characterized by tilted blocks and growth strata, followed by a sag basin. The southern domain includes the Namibe, Santos and Campos Basins. The northern domain extends from the Espirito Santo and North Kwanza Basins, in the south, to the Sergipe-Alagoas and North Gabon Basins to the north. Extension started in the northern domain during the Late Berriasian (Congo-Camamu Basin to the Sergipe- Alagoas-North Gabon Basins) and migrated southward. At that time, the southern domain was not a subsiding domain (emplacement of the Parana-Etendeka Trapp). Extension started in this southern domain during the Early Barremian. The rift phase is shorter in the south (5-6 Ma, Barremian to base Aptian) than in the north (19 to 20 Myr, Upper Berriasian to base Aptian). The sag phase is of Middle to Late Aptian age. In the northern domain, this transition corresponds to a hiatus of Early to Middle Aptian age. From the Late Berriasian to base Aptian, the northern domain evolves from a deep lake with lateral highs to a shallower organic-rich one with no more highs. The lake migrates southward in two steps, until the Valanginian at the border between the northern and southern domains, until the Early Barremian, north of Walvis Ridge

Biogeochemical sulfur cycling during Cretaceous oceanic anoxic events: A comparison of OAE1a and OAE2

“…The onset of heterogeneous δ 34 S SO4 profiles occurs at~115 Ma, indicating that low sulfate concentrations could have been established 15-20 Ma prior to OAE2. This timing is consistent with recent age estimates of 114-116 Ma for the deposition of South Atlantic evaporites [Chaboureau et al, 2013] and previous estimates of 110-119 Ma [Karner and Gambôa, 2007]. This evaporite burial event could have severely decreased the size of the marine sulfate reservoir [Wortmann and Chernyavsky, 2007].…”

“…δ 34 S SO4 determined from marine barite are from ODP site 766 in the Northeast Indian Ocean (grey diamonds; [ Paytan et al, ] with revised dating from Prokoph et al []; because GTS2012 ascribes an age of 126.3 Ma to the base of M0 versus an age of 125 Ma for GTS2004, data has been adjusted to GTS2012 by adding 1.3 Ma to the ages of Prokoph et al []). The purple bar indicates timing of evaporite burial event [ Chaboureau et al, ]. The lower and upper black bars indicate the timing of OAE1a and OAE2, respectively [ Ogg et al, ].…”

“…References: 1, Neal et al []; 2, Eldholm and Coffin []; 3, Kerr et al []; 4, Turgeon and Creaser []; 5, DuVivier et al []; 6, Weissert []; 7, Weissert []; 8, Weissert and Lini []; 9, Haq []; 10, Jorgensen []; 11, Canfield et al []; 12, Chaboureau et al []; 13, Wortmann and Chernyavsky []; 14, Larson []; 15, Tejada et al [].…”

Paleogeographic and structural evolution of northwestern Africa and its Atlantic margins since the early Mesozoic

“…The NE-trending Tacutu rift continues to be filled with continental sediments after its initiation in the Late Jurassic (Vaz et al, 2007b). The future South Atlantic domain consists in a wide rift system preserving nonmarine sediments (de Matos, 1992;Chaboureau et al, 2013). It is mostly located in intracontinental South America and interacts with ENE-trending transfer faults (future transforms) reactivating Pan-African shear zones (e.g., Popoff, 1988).…”

Tectonic control of the oil-rich large igneous-carbonate-salt province of the South Atlantic rift

“…The apparent absence of rift sediments below the basalts gives the impression that before and during early basalt volcanism this area was thermally elevated and rifted only afterwards Chaboureau et al, 2013;Stica et al, 2013) in contrast to the north (Recôncavo, Tucano, Sergipe basins) where rifting started about 10 Ma earlier. 6.…”