EM - Escola de Minas
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6
Notícias
A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.
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2 resultados
Resultados da Pesquisa
Item Evaluation of distinct soft-sediment deformation triggers in mixed carbonate-siliciclastic systems : lessons from the Brazilian Pre-Salt analogue Crato Formation (Araripe Basin, NE Brazil).(2022) Varejão, Filipe Giovanini; Warren, Lucas Veríssimo; Simões, Marcello Guimarães; Cerri, Rodrigo Irineu; Alessandretti, Luciano; Santos, Mauricio Guerreiro Martinho dos; Assine, Mario LuisSoft-sediment deformation structures (SSDSs) are ubiquitous in several depositional sedimentary environments and can be triggered by autogenic- and allogenic-related mechanisms. SSDSs identification in the geological record is more frequent in siliciclastic deposits, from which the most accepted models were developed. Given the fact that carbonate rocks have rapid diagenesis, which results in changes in the rheological behavior of defor- mational processes in short time, these are excellent facies for exploring past deformational mechanisms in a given sedimentary basin. Here, we describe distinct SSDSs developed in mixed carbonate-siliciclastic successions deposited in an Early Cretaceous lacustrine depositional system (carbonate-dominated) subjected to recurrent epicontinental marine ingressions (siliciclastic-dominated). Deformation occur in some siliciclastic intervals but it is more common in carbonate beds. Facies associations analysis combined with detailed outcrop description of the SSDSs allowed the recognition of seismic- and non-seismic-generated structures. Two km-scale, laterally continuous carbonate beds, characterized by deformation-bearing horizons, are interpreted to be the result of seismic shocks. Conversely, most of the recognized SSDSs cannot be confidentially interpreted as seismites. Autogenic triggers and criteria for accessing the origin of deformation mechanisms in both carbonate- and siliciclastic-dominated settings are alternatively proposed. Assessing such criteria is fundamental for differ- entiatte the timing and range of deformation and are here discussed in the context of the offshore petroleum reservoirs in the Brazilian Pre-Salt successions, where lacustrine carbonates were probably subjected to a similiar superposition of syn-sedimentary seismicity and later events of salt-tectonics and hydrotermalism.Item Shaking a methane fizz : seismicity from the Araguainha impact event and the Permian–Triassic global carbon isotope record.(2013) Tohver, Eric; Cawood, Peter Anthony; Riccomini, Claudio; Lana, Cristiano de Carvalho; Trindade, Ricardo Ivan Ferreira daThe Late Permian and Early Triassic periods are marked by large fluctuations in the carbon isotope record, but the source(s) of the disturbance to the global carbon cycle and the link to the end-Permian mass extinction arewidely debated. This contribution explores the possible isotopic effects of an impact event into the hydrocarbon-rich rocks of the Paraná–Karoo Basin. Recent U–Pb and 40Ar/39Ar dating of the 40 km Araguainha impact structure of central Brazil reveals an age of 254.7 ± 2.5 Ma (2σ error) for this event. The calculated energy (10^5–10^6 MT of TNT equivalent) released by this impact is less than threshold values of 10^7–10^8 MT TNT equivalent for global mass extinctions. Thus, the Araguainha crater is unlikely to have been the cause of the end-Permian biotic crisis. However, the combined seismic effects from the impact itself and the post-impact collapse of the 20–25 km diameter transient crater to its present 40 km diameter would result in large magnitude earthquakes (Mw 9.3–10.5) and tsunamis in the shallow marine Paraná–Karoo Basin. Slope failure and sediment liquefaction are predicted to have occurredwithin a 700–3000 km radius of the crater, causing large-scale release of methane from organic-rich sediments of this basin, including the oil shale horizons of the Iratí Formation. New geological evidence for seismicity in the Paraná Basin at the time of impact is presented, together with a compilation of existing carbon isotope data from the Paraná Basin, which demonstrate a widespread pattern of disturbance consistent with the release of methane. These two datasets suggest that both seismicity and methane release took place within ca.1000 km of the impact site, with mass balance calculations suggesting ca. 1600 GT of methane were released into the atmosphere at this time. Methane release at this scale would have significant climate effects and would contribute to a sharp (<1 ka) negative shift in δ^13 C values at the time of the impact, which should be distinguishable from the more gradual shift over 0.5–1 Ma caused by contemporaneous intrusion of the Siberian traps.