Abstract:The São Miguel do Tapuio Circular Structure (SMTCS) is one of the largest recognized in the Phanerozoic sedimentary rocks of the Parnaiba Basin, in Piauí (PI), Brazil. Research works on the genesis of the SMTCS consider either an endogenetic origin or meteoritic impact formation. The present study is based on bibliographic survey, fi eldwork and laboratory analyses (remote sensing). The SMTCS superfi cial morphological features, their organization, total diameter, multi-directional pattern and high density of lineaments inside the structure were characterized by remote sensing. Also, the morphostructural units such as the outer margin, intermediate ring, annular depression and a central topographic high were defi ned. The fi eldwork allowed identifying a variable thermal metamorphism in the Keywords:Bacia do Parnaíba; Astroblemas; Sensoriamento Remoto. 764Martins J. A. et al. Rev. Bras. Geomorfol. (Online), São Paulo, v.17, n.4, (Out-Dez) p.763-781, 2016 sandstones that formed the SMTCS. The metamorphism grade increased clearly from the margin to the center, with the presence of highly recrystallized and consolidated metasandstones around the center of the structure. Finally, the geomorphic characterization and the geometric signature obtained for the SMTCS seem to correspond to those of complex impact structures (presence of a central uplift). Moreover, the identifi cation of macro and microscopic deformation structures in the sandstones (while not typical of shock origin) may be more conclusive of a meteoritic origin, and the lack of evidence of igneous activity might explain the observed thermal metamorphism. Resumo:A estrutura circular de São Miguel do Tapuio (ECSMT) corresponde a uma das maiores do gênero registrada em rochas sedimentares fanerozoicas da Bacia do Parnaíba, Estado do Piauí, Brasil. As pesquisas considerando a gênese da ECSMT dividem-se entre uma origem endógena e uma através de impacto meteorítico. No presente estudo foram realizados trabalhos envolvendo o estágio do conhecimento atual, campo e laboratoriais (sensoriamento remoto). Os trabalhos de sensoriamento serviram para delinear a confi guração morfológica superfi cial, o diâmetro total e compartimentos, bem como o padrão multidirecional e alta densidade dos lineamentos no interior da estrutura. Puderam ser defi nidas unidades morfoestruturais como a borda externa, o anel intermediário, a depressão anelar e um alto topográfi co central. Os trabalhos de campo evidenciaram uma intensidade de metamorfi smo termal variável observado nos arenitos interiores à ECSMT. Da borda para o centro observa-se nítido aumento no grau de metamorfi smo nos arenitos, caracterizando metarenitos intensamente recristalizados e consolidados no entorno do centro da estrutura. Finalizando, a caracterização morfológica superfi cial e a assinatura geométrica obtida para a ECSMT são semelhantes e condizentes com várias estruturas de impacto do tipo complexa (presença de um núcleo soerguido). Somado a estes fatos temos a presença de estruturas deformaci...

In this comment, we showed that the Dirac equation in the screw dislocation space-time also carries a term that represents the torsion of such topological defect, given by Kµ. Therefore, the Dirac equation worked by Wang et al. is incomplete since such a term was ignored in your equation (what cannot happen). In other words, it is only possible to work with the Dirac equation in the form presented by Wang et al. if the space-time is torsion-free, which is obviously not the case.

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Summary The Ceará Basin is a deepwater exploration frontier basin that comprises part of the Brazilian equatorial margin. This basin has been receiving renewed attention from the petroleum industry since the discovery of important deepwater oil fields in its African counterpart. However, detailed seismic stratigraphic, depositional, and structural frameworks for the Ceará Basin are still lacking in the literature. We have analyzed a series of 2D seismic data sets and stumbled into the pitfalls of migration artifacts (i.e., multiples) ultimately realizing that reprocessing was the best option to avoid the mistake of interpreting these artifacts as geologic features. Multiples can be difficult to identify in seismic data in which they mimic the true geology of the region, and they often present a pitfall for less experienced interpreters. Indeed, the identification and removal of multiples is crucial because they do not reflect the true geology in the subsurface and may otherwise lead to incorrect business decisions. Geological feature: Stratigraphy of the Ceará Basin, offshore Brazil Seismic appearance: Strong seismic horizons mimicking geological layering Alternative interpretations: Multiples arising from poor seismic migration processing Features with similar appearance: Strong seismic horizons reflecting basement and carbonates Formation: Rift sequence of the Ceará Basin Age: Cretaceous Location: Ceará Basin, offshore Brazil Seismic data: Obtained by the Brazilian National Petroleum Agency and reprocessed by the authors Analysis tool: Reprocessing