1,133 research outputs found
Erratum
No full textvan Gils PF, Lambooij MS, Flanderijn MHW, van den Berg M, de Wit GA, Schuit AJ, Struijs JN. Willingness to participate in a lifestyle intervention program of patients with type 2 diabetes mellitus: a conjoint analysis. Patient Prefer Adherence. 2011;5:537–546.Dr B van den Berg was mistakenly removed from the list of authors of this paper.Read the original article
Avaliação da qualidade de vida de pacientes com acne vulgar antes e após o tratamento com isotretinoína oral.
No full textTrabalho de Conclusão de Curso - Universidade Federal de Santa Catarina. Curso de Medicina. Departamento de Clínica Médica
Recherche de traces de vie primitive dans des forages de séquences sédimentaires archéennes (Craton des Pilbara, Australie et Chaîne de Barberton, Afrique du Sud)
No full textLe craton des Pilbara en Australie occidentale et la chaîne de roches vertes de Barberton en Afrique du Sud contiennent les microfossiles les plus vieux et mieux préservés du monde. En 2004, dans le cadre d’une collaboration franco-australienne (IPGP/GSWA, Pilbara Drilling Project), deux niveaux stratigraphiques du Craton des Pilbara ont été forés: le Dresser à 3,5 Ga et le Tumbiana à 2,7 Ga. Un nouveau forage a été réalisé en août 2008 dans la chaîne du Barberton à la base du groupe du Fig Tree (3,25 Ga) dans le cadre d’une collaboration franco-sudafricaine (IPGP/AEON, projet ! Khure Africa, Barberton Barite Drilling Project). L’analyse des carottes collectées représente une opportunité unique pour contraindre le cadre environnemental des écosystèmes microbiens archéens. Il s’agit, en particulier, d’y rechercher les traces des premiers métabolismes microbiens et d’établir le lien avec l’évolution des compositions chimiques et isotopiques de l’atmosphère primitive et des premiers océans et continents.The Pilbara Craton of Western Australia and the Barberton Greenstone Belt of the Kaapvaal Craton, South Africa, contain some of the oldest and best preserved Archaean rocks and microfossils in the world. Two stratigraphic horizons in the Pilbara Craton were drilled as part of a collaborative effort between France and Australia (the Pilbara Drilling Project) during August 2004, including the 3481 Ma Dresser Formation (Warrawoona Group) and 2724 Ma Tumbiana Formation (Fortescue Group). A new diamond drill hole was cored in August 2008 through part of the ∼3250 Ma Fig Tree Group in the Barberton Greenstone Belt as part of a joint project between France and South Africa. These pristine diamond drill cores present a unique opportunity to constrain the chemistry of the earliest ocean, the composition of the atmosphere, and the settings and types of microbial ecosystems spanning the Archean Eon. These drill core samples can also provide new clues on the earliest metabolic pathways.</p
Paleogeography and tectono-stratigraphy of carboniferous-Permian and Triassic "Karoo-like" sequences of the congo basin
No full textInternational audienceThe Congo Basin is a large Phanerozoic sedimentary basin with up to 3–6 km of Carboniferous to Triassic sequences, comparable to those of the Karoo Basins of southern Gondwana. Here, we present a substantially revised stratigraphy for the Congo Basin, based on new field observations, seismic and borehole data, together with paleontology and new geochronology. In the center of the basin, the deepest boreholes intercept 3 to 4 km thick successions of conglomerates and red sandstones that overlie carbonate rocks, which correlate to deformed upper Neoproterozoic (Pan African) platform sequences extending beyond the Congo Basin into the Pan African orogenic zones (e.g. the West Congolian Group). The overlying sequences are dated biostratigraphically to be Carboniferous-Permian (the Lukuga Group) and Triassic (the Haute Lueki Group) in age. A regional erosion surface separates these two groups, possibly related to late Paleozoic intracontinental deformation associated with the Mauritanian-Variscan and Cape-de la Ventana orogens flanking the northwestern and southern margins of Gondwana, respectively. This change in basin paleogeography is consistent with detrital zircons dated from these sequences that suggest the ca. 1.4 Ga Kibaran Belt along the eastern margin of the Congo Basin stopped acting as a major source during the early Mesozoic
U–Pb detrital zircon dates and source provenance analysis of Phanerozoic sequences of the Congo Basin, central Gondwana
No full textInternational audienceThe Congo Basin (CB) is the largest sediment sink of central Gondwana, built on a mosaic of Precambrian crustal blocks amalgamated during the mid-Paleoproterozoic (Eburnian; 2.1–1.8 Ga), late Mesoproterozoic (Kibaran; 1.4–1.0 Ga), and late Neoproterozoic–early Cambrian (Pan African; 750–500 Ma). Sporadic uplift, tilting and erosion of these Precambrian terrains form the source regions for the sedimentary sequences that fill the CB. We investigate the Phanerozoic successions in the field and along four historic deep boreholes drilled in the center of the basin, and date detrital zircons from the main stratigraphic groups to characterize their provenance ages and reconstruct the paleogeographic evolution of the CB during amalgamation and break-up of the Gondwana supercontinent. Sedimentological data show that the oldest, upper Neoproterozoic–lower Paleozoic Redbeds (the Inkisi, Aruwimi and Biano Groups) were derived from the north. Zircons from these sequences have two dominant age-populations of 1100–950 Ma and 800–600 Ma, likely sourced from Kibaran and Pan African terrains within the Oubanguides (e.g. the Central Saharan Belt) and parts of the North African Shield (e.g. Darfour). The overlying Carboniferous–Permian glacial and deglaciation sequences (the Lukuga Group) have similar peaks, as well as abundant zircons of 2.05–1.85 Ga and a subordinate number dated at 1.42–1.37 Ga. The latter are from Eburnian and Kibaran sources in east-central Africa, consistent with west-facing glacial paleo-valleys preserved along the eastern margin of the CB. The succeeding Triassic (the Haute–Lueki Group) and Jurassic–Cretaceous (the Kwango Group) fluvial and aeolian red sandstones were again derived from the north. Their range of zircon dates has two main peaks at 1000 Ma and 600 Ma, but also contain small younger grains of 290–240 Ma and 200–190 Ma. We interpret these younger zircons to be derived from volcanic dust that originated during late Paleozoic–Jurassic magmatism of the Choiyoi and Chon Aike Provinces flanking the Andean subduction margin of Gondwana. By contrast, the uppermost Cenozoic alluviums of the CB (the Kalahari Group) contain diamond concentrates and large zircon fragments dated at 3–2.5 Ga, derived from the Kasai and Cuango Cratons, to the south, which host Cretaceous diamondiferous kimberlites
Old, strong continental lithosphere with weak Archaean margin at - 1.8 Ga, Kaapvaal Craton, South Africa
No full textLow elastic strength of ancient lithosphere based on flexural analyses has been interpreted to reflect elevated regional geothermal gradients in response to higher global heat production in the past. Here we present a flexural analysis of Archean/Palaeoproterozoic sediment cover along the western margin of the Archaean Kaapvaal craton based on seismic stratigraphy. Our results show that between ~1.93 and ~1.75 Ga, the Archaean margin of the craton had an effective elastic thickness of 7.5 to 10km compared to its present day value of 60 to 70km. Because the Kaapvaal craton had already stabilized by ~2.7 Ga and was underlain by 150 to 300km thick strong mantle lithosphere, it is unlikely that the relatively thin elastic thickness along this old margin reflects a change in secular cooling of the Earth. Instead, we interpret the low elastic strength to be a transient marginal tectonic effect similar to that recorded along modern continental margins
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