Navegando por Autor "OLIVEIRA, Camila Vilar de"

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Ambiente flúvio-deltáico influenciado por maré e tempestade da Formação Rio Maria, leste da Província Carajás (SE) do Cráton Amazônico
(2012-12) NASCIMENTO, Marivaldo dos Santos; OLIVEIRA, Camila Vilar de; ALTHOFF, Fernando Jacques
The Rio Maria Formation is a siliciclastic sedimentary sequence deposited in an eiperic sea formed along of eastern edge of the Carajás Province – the oldest Archean province of the Amazonian Craton – being intruded by rapakivi-type granite (1.88 Ga). Four facies associations have been recognized: prodelta-distal bar, delta-front/shoreface, delta-plain/distributaries and fluvial channels. Large-scale hummocky-swaley cross-stratifications (> 1 m) attest storm waves-influenced in upper shoreface deposits (tempestites). Bipolar cross-beddings with drape and reactivation surfaces reflect tidal-influence. Quartzarenite, sublitharenite and subarkose modal frameworks indicate stable continental block (craton interior) source. Heavy-minerals assemblages (e.g. zircon, tourmaline, staurolite, epidote, etc.) provide evidence of contribution from felsic plutonic igneous and metamorphic rocks. Well-rounded zircon grains can be associated to reworked sediments or metamorphic sources. These litotypes can be related to Rio Maria Block, which includes granitoid and metassedimentary rocks of the Rio Maria granite-greenstone terrain (3.0 – 2,86 Ga).
Acesso aberto (Open Access)
Geocronologia U-Pb em zircão detrítico aplicada ao estudo de proveniência dos arenitos do Grupo Canindé, borda leste da bacia do Parnaíba
(Universidade Federal do Pará, 2015-10-13) OLIVEIRA, Camila Vilar de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
The U-Pb dating by LA-ICP-MS of detrital zircons from Canindé Group allowed the establishment of a direct link between the ages of zircon grains from sandstones of the eastern edge of the Parnaiba sedimentary basin and the rock units in distal and/or proximal source areas, and showed that this technique is an indispensable tool for sedimentary provenance investigation. The studied siliciclastic succession are composed of diamictic, intraformational breccias, fine to coarse sandstones and, fine to very fine sandstones which are interdigitated with pelites and mudstones. This sedimentary sequence is represented by seven facies associations: a) the basal unit corresponds to lower offshore-shoreface deposits (Af1) of Pimenteiras Formation; b) gradually westward, crop out rocks of Cabeças Formation represented by subglacial deposits (Af2) intercalated with, and in erosive character, distal deltaic front deposits (Af3) - these deposits exhibit more proximal features in the northern, highlighted by sigmoidal lobes (Af4); c) the Longá Formation exposure is narrower, featuring deposits of distal deltaic front (Af5); d) the top unit, represented by the Poti Formation, shows deposits with offshore-shoreface marine features (Af6) in the northwestern portion, and more continental, with channel bar deposits (Af7), in the southwestern. The imaging of internal structure of 318 zircon grains of these sedimentary successions, by Scanning Electron Microscope with Cathode- Luminescence (SEM-CL), revealed four major populations: a) grains with concentric zoning (Zr1); b) homogeneous grains (Zr2); c) grains with convoluted zoning or recrystallized rims (ZR3); d) metamític or fractured grains with exsolved rims (ZR4). The density distribution diagrams (relative and cumulative probability) of the U-Pb ages, and the percentages of these ages in pie charts, show clear heterogeneous distribution of the zircon age spectrum. Paleoproterozoic zircon population (mainly Orosirian) predominates over Mesoarchean and Mesoproterozoic ones. In addition, important contribution of Neoproterozoic (largely Tonian) and Cambrian zircon populations shows up in most of the samples. The K-S test suggests strong similarity between the sources of Cabeças and Longá formations (p = 0.385) and, a clear difference of the provenance patterns between the Pimenteiras and Poti formations (p = 0). Paleocurrent measurements of the fluvial sandstones and of the unimodal deltaic sigmoids have shown that, during the deposition of Canindé Group, the source areas were located to the south and southeast of the current border of the Parnaíba basin. These areas include the west sector of the Borborema Province (BP) and the São Francisco Craton (SFC) with its surrounding Braziliano belts (Brasília and Rio Preto). Thus, it is suggested that the sediments of the eastern portion of the Parnaíba Basin, derived from the northern segment of the SFC (Sobradinho block) and the Central and South subprovinces of the BP. For the latter, the probable candidates would be the Alto Pajeú tarrain (Cariris Velho – sensu stricto) and the Riacho do Pontal belt. The sediment supply was fully controlled by marine incursions (transgressions and regressions) recorded from the Mesodevonian to the Eocarboniferous.
Acesso aberto (Open Access)
Proveniência dos arenitos dos grupos Canindé, bacia cratônica do Parnaíba, por termocronologia e geocronologia em zircão detrítico.
(Universidade Federal do Pará, 2023-11-27) OLIVEIRA, Camila Vilar de; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
Before the most severe Late Paleozoic Ice Age, the Western Gondwana was affected by short-lived glaciations recorded in several intracratonic basins from Northern South Amer ica. The Famenian-Tournasian coastal marine successions exposed in the Sulamerican plat form represent a window of opportunity to unravel the different source lands using U-Pb ages of detrital zircon grains during the icehouse and greenhouse conditions. The Famenian Tournasian Cabeças Formation in the intraplate Parnaiba basin, Northern Brazil, represents a glaciomarine system of the ice contact delta developed at the Western Gondwana Margin. Preglacial deltaic deposits indicate two significant U-Pb age peak ranges of 768-448 Ma and 1175-937 Ma, suggesting drainage from the East of Western Gondwana. In contrast, U-Pb age peak ranges of 1998-1731 Ma and 1079-894 Ma show sources from the South supplying the northwestern glacier advance on the coastal-marine settings. During the initial greenhouse phase, the ice-melt deltaic system provided zircon ages of 1093-817 Ma, indicating the retak ing of the preglacial source lands. The sampling for age acquisition combined with precise paleoenvironmental interpretation offers, for the first time, high-resolution information that supports a most robust paleogeographic reconstruction of the Western Gondwana during the Late Paleozoic. Additionally, the use of Hf isotope and fission track proxies linked to a sys tematic morphological description, internal structure, and Th/U ratio applied to Mesoprotero zoic-Tonian detrital zircons, focused on the main detrital age spectra of glacial deposits, al lowed reveals the discrimination of competing sedimentary source land regions and recogniz ing detrital contributions from the provenance dynamic of ancient orogenic settings, such as the West Gondwana and Araçuai-West Congo orogens.