Arcabouço geofísico, isostasia e causas do magmatismo cenozóico da província Borborema e de sua margem continental (Nordeste do Brasil)

The Borborema Province (BP) is a geologic domain located in Northeastern Brazil. The BP is limited at the south by the São Francisco craton, at the west by the Parnaíba basin, and both at the north and east by coastal sedimentary basins. Nonetheless the BP surface geology is well known, several key aspects of its evolution are still open, notably: i)its tectonic compartmentalization established after the Brasiliano orogenesis, ii) the architecture of its cretaceous continental margin, iii) the elastic properties of its lithosphere, and iv) the causes of magmatism and uplifting which occurred in the Cenozoic. In this thesis, a regional coverage of geophysical data (elevation, gravity, magnetic, geoid height, and surface wave global tomography) were integrated with surface geologic information aiming to attain a better understanding of the above questions. In the Riacho do Pontal belt and in the western sector of the Sergipano belt, the neoproterozoic suture of the collision of the Sul domain of the BP with the Sanfranciscana plate (SFP) is correlated with an expressive dipolar gravity anomaly. The positive lobule of this anomaly is due to the BP lower continental crust uplifting whilst the negative lobule is due to the supracrustal nappes overthrusting the SFP. In the eastern sector of the Sergipano belt, this dipolar gravity anomaly does not exist. However the suture still can be identified at the southern sector of the Marancó complex arc, alongside of the Porto da Folha shear zone, where the SFP N-S geophysical alignments are truncated. The boundary associated to the collision of the Ceará domain of the BP with the West African craton is also correlated with a dipolar gravity anomaly. The positive lobule of this anomaly coincides with the Sobral-Pedro II shear zone whilst the negative lobule is associated with the Santa Quitéria magmatic arc. Judging by their geophysical signatures, the major BP internal boundaries are: i)the western sector of the Pernambuco shear zone and the eastern continuation of this shear zone as the Congo shear zone, ii) the Patos shear zone, and iii) the Jaguaribe shear zone and its southwestern continuation as the Tatajuba shear zone. These boundaries divide the BP in five tectonic domains in the geophysical criteria: Sul, Transversal, Rio Grande do Norte, Ceará, and Médio Coreaú. The Sul domain is characterized by geophysical signatures associated with the BP and SFP collision. The fact that Congo shear zone is now proposed as part of the Transversal domain boundary implies an important change in the original definition of this domain. The Rio Grande do Norte domain presents a highly magnetized crust resulted from the superposition of precambrian and phanerozoic events. The Ceará domain is divided by the Senador Pompeu shear zone in two subdomains: the eastern one corresponds to the Orós-Jaguaribe belt and the western one to the Ceará-Central subdomain. The latter subdomain exhibits a positive ENE-W SW gravity anomaly which was associated to a crustal discontinuity. This discontinuity would have acted as a rampart against to the N-S Brasiliano orogenic nappes. The Médio Coreaú domain also presents a dipolar gravity anomaly. Its positive lobule is due to granulitic rocks whereas the negative one is caused by supracrustal rocks. The boundary between Médio Coreaú and Ceará domains can be traced below the Parnaíba basin sediments by its geophysical signature. The joint analysis of free air anomalies, free air admittances, and effective elastic thickness estimates (Te) revealed that the Brazilian East and Equatorial continental margins have quite different elastic properties. In the first one 10 km < Te < 20 km whereas in the second one Te ≤ 10 km. The weakness of the Equatorial margin lithosphere was caused by the cenozoic magmatism. The BP continental margin presents segmentations; some of them have inheritance from precambrian structures and domains. The segmentations conform markedly with some sedimentary basin features which are below described from south to north. The limit between Sergipe and Alagoas subbasins coincides with the suture between BP and SFP. Te estimates indicates concordantly that in Sergipe subbasin Te is around 20 km while Alagoas subbasin has Te around 10 km, thus revealing that the lithosphere in the Sergipe subbasin has a greater rigidity than the lithosphere in the Alagoas subbasin. Additionally inside the crust beneath Sergipe subbasin occurs a very dense body (underplating or crustal heritage?) which is not present in the crust beneath Alagoas subbasin. The continental margin of the Pernambuco basin (15 < Te < 25 km) presents a very distinct free air edge effect displaying two anomalies. This fact indicates the existence in the Pernambuco plateau of a relatively thick crust. In the Paraíba basin the free air edge effect is quite uniform, Te ≈ 15 km, and the lower crust is abnormally dense probably due to its alteration by a magmatic underplating in the Cenozoic. The Potiguar basin segmentation in three parts was corroborated by the Te estimates: in the Potiguar rift Te ≅ 5 km, in the Aracati platform Te ≅ 25 km, and in the Touros platform Te ≅ 10 km. The observed weakness of the lithosphere in the Potiguar rift segment is due to the high heat flux while the relatively high strength of the lithosphere in the Touros platform may be due to the existence of an archaean crust. The Ceará basin, in the region of Mundaú and Icaraí subbasins, presents a quite uniform free air edge effect and Te ranges from 10 to 15 km. The analysis of the Bouguer admittance revealed that isostasy in BP can be explained with an isostatic model where combined surface and buried loadings are present. The estimated ratio of the buried loading relative to the surface loading is equal to 15. In addition, the lower crust in BP is abnormally dense. These affirmations are particularly adequate to the northern portion of BP where adherence of the observed data to the isostatic model is quite good. Using the same above described isostatic model to calculate the coherence function, it was obtained that a single Te estimate for the entire BP must be lower than 60 km; in addition, the BP north portion has Te around 20 km. Using the conventional elastic flexural model to isostasy, an inversion of crust thickness was performed. It was identified two regions in BP where the crust is thickened: one below the Borborema plateau (associated to an uplifting in the Cenozoic) and the other one in the Ceará domain beneath the Santa Quitéria magmatic arc (a residue associated to the Brasiliano orogenesis). On the other hand, along the Cariri-Potiguar trend, the crust is thinned due to an aborted rifting in the Cretaceous. Based on the interpretation of free air anomalies, it was inferred the existence of a large magmatism in the oceanic crust surrounding the BP, in contrast with the incipient magmatism in the continent as shown by surface geology. In BP a quite important positive geoid anomaly exists. This anomaly is spatially correlated with the Borborema plateau and the Macaú-Queimadas volcanic lineament. The integrated interpretation of geoid height anomaly data, global shear velocity model, and geologic data allow to propose that and Edge Driven Convection (EDC) may have caused the Cenozoic magmatism. The EDC is an instability that presumably occurs at the boundary between thick stable lithosphere and oceanic thin lithosphere. In the BP lithosphere, the EDC mechanism would have dragged the cold lithospheric mantle into the hot asthenospheric mantle thus causing a positive density contrast that would have generated the main component of the geoid height anomaly. In addition, the compatibility of the gravity data with the isostatic model, where combined surface and buried loadings are present, together with the temporal correlation between the Cenozoic magmatism and the Borborema plateau uplifting allow to propose that this uplifting would have been caused by the buoyancy effect of a crustal root generated by a magmatic underplating in the Cenozoic

Arquitetura deposicional e evolução tectono-estratigráfica das sequências pré-rifte e rifte, na porção central do Vale do Cariri, Bacia do Araripe, NE do Brasil

A complex depositional history, related to Atlantic rifting, demonstrates the geological evolution during the late Jurassic and early Neocomian periods in the Araripe Basin NE Brazil. Based on outcrop, seismic and remote sensing data, a new model of the tectono-stratigraphic evolution of the section that covers the stages Dom João, Rio da Serra and Aratu (Brejo Santo, Missão Velha and Abaiara formations) is presented in this paper. In the stratigraphic section studied, ten sedimentary facies genetically linked to nine architectural elements were described, representing depositional systems associated with fluvial, aeolian and deltaic environments. Based on the relationship between the rates of creation of accommodation space and sediment influx (A / S) it was possible to associate these depositional systems with High and Low accommodation system tracks. These system tracks represent two tectono-sequences, separated by regional unconformities. The Tectono-sequence I, which includes lithotypes from the Brejo Santo Formation and is related to the pre-rift stage, is bounded at the base by the Paleozoic unconformity. This unit represents only a High Accommodation System Track, composed by a succession of pelitic levels interbedded with sandstones and limestones, from a large fluvial floodplain origin, developed under arid climatic conditions. The Tectono-sequence II, separated from the underlying unit by an erosional unconformity, is related to the rift stage, and is composed by the Missão Velha and Abaiara Formation lithotypes. Changes in depositional style that reflect variations in the A / S ratio, and the presence of hydroplastic deformation bands, make it possible to divide this tectonosequence into two internal sequences. Sequence IIA, which includes the lower portion of the Missão Velha Formation and sequence IIB, is composed by the upper section of the Missão Velha and Abaiara Formations The Sequence IIA below, composed only by the Low Accommodation System Track, includes crossbedding sandstones interbedded with massive mudstones, which are interpreted as deposits of sandy gravel beds wandering rivers. Sequence IIB, above, is more complex, showing a basal Low Accommodation System Track and a High Accommodation System Track at the top, separated by an expansion surface. The lower System Track, related to the upper portion of the Missão Velha Formation, is composed by a series of amalgamated channels, separated by erosion surfaces, interpreted as deposits of a belt of braided channels. The High Accommodation System Track, correlated with the Abaiara Unit, is marked by a significant increase in the A / S, resulting in the progradation of a system of braided river deltas with aeolic influence. Regarding tectonic evolution, the stratigraphic study indicates that the Tectonosequence Rift in the Araripe basin was developed in two phases: first characterized by a beginning of rifting, related to Sequence IIA, followed by a phase of syndepositional deformation, represented by sequence IIB. The first phase was not influenced by the development of large faults, but was influenced by a sharp and continuous decrease of accommodation space that permitted a change in depositional patterns, establishing a new depositional architecture. In turn, the stage of syndepositional deformation allowed for the generation of enough accommodation space for the preservation of fluvial-lacustrine deposits and conditioned the progradation of a braided river-dominated delta system.

Sobrevida e morbidade em prematuros com menos de 32 semanas de gestação na região central do Brasil

OBJETIVO: Avaliar a sobrevida e complicações associadas à prematuridade em recém-nascidos com menos de 32 semanas. MÉTODOS: Estudo prospectivo do tipo coorte. Foram incluídos os nascidos vivos, com idade gestacional entre 25 semanas e 31 semanas e 6 dias, sem anomalias congênitas admitidos em UTI Neonatal, entre 1º de agosto de 2009 e 31 de outubro de 2010. Os recém-nascidos foram estratificados em três grupos: G25, 25 a 27 semanas e 6 dias; G28, 28 a 29 semanas e 6 dias; G30, 30 a 31 semanas e 6 dias, e acompanhados até 28 dias. Foram avaliadas a sobrevida aos 28 dias e a morbidade associadas à prematuridade. Para análise dos resultados, utilizou-se o teste do c², análise de variância, teste de Kruskal-Wallis, razão de risco com intervalo de confiança (IC) e regressão logística múltipla, com significância em 5%. RESULTADOS: A coorte compreendeu 198 prematuros, sendo G25=59, G28=43 e G30=96. O risco de óbito foi significativamente maior em G25 e G28, em relação ao G30 (RR=4,1; IC95% 2,2-7,6 e RR=2,8; IC95% 1,4-5,7). A sobrevida encontrada foi, respectivamente, 52,5, 67,4 e 88,5%. A partir da 26ª semana e peso >700 g, a sobrevida foi superior a 50%. A morbidade foi inversamente proporcional à idade gestacional, exceto para enterocolite necrosante e leucomalácia, que não diferiram entre os grupos. A análise de regressão logística mostrou que a hemorragia pulmonar (OR=3,3; IC95% 1,4-7,9) e a síndrome do desconforto respiratório (OR=2,5; IC95% 1,1-6,1) foram fatores independentes de risco para óbito. Houve predomínio das lesões cerebrais hemorrágicas graves em G25. CONCLUSÕES: Sobrevivência superior a 50% ocorreu a partir da 26ª semana de gravidez e peso >700 g. A hemorragia pulmonar e a síndrome do desconforto respiratório foram preditores independentes de óbito. Há necessidade de identificar e instituir práticas para melhorar a sobrevida de prematuros extremos.

Estrutura em quilha Brasil central, uma feicao fundamental na geologia de Goias e Tocantins

The older Precambrian geological setting of north Goias/south Tocantins includes three areas of granite-greenstone terrains formed of medium-grade gneisses with associated greenstone belts and nepheline syenitic gneisses, separated by two orogenic belts composing a crustal-scale pop-up structure. The movements were firstly oblique towards NW along the northwestern NNE-SSW-trending Porto Nacional suture, and afterwards of essentially frontal type towards ESE along the southeastern Ceres suture of curved geometry with N-S direction at north and WNW-ESE at the south. The Porangatu block, limited by these sutures, was upthrusted over the neighbouring underthrusted blocks. Three principal kinematic phases are recognized along the orogenic belts. -from English summary

Hacia un desarrollo sustentable e integrado de la Amazonía: los corredores de transporte en la cuenca amazónica central-occidental y sus afluentes principales en Brasil, Colombia, Ecuador y Perú

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Paleosuperfícies e perfis bauxíticos no Planalto de Poços de Caldas, São Paulo/Minas Gerais, Brasil

This work has the objective of correlating altitude with the bauxite profiles in the Poços de Caldas Plateau in order to identify paleosurfaces. Then, bauxite profiles found in the Plateau have been classified and mapped through DEM. Three different types of bauxite profiles are highlighted in the area: (1) Rim Profiles which are well-developed and thick and are located in the areas of highest altitude in the Plateau; (2) Plateau Profiles which are not very thick and very clayey, normally appear in the lower portion of the landscape; (3) Reworked Profiles, characterized by bauxite reworked fragments composed by similar materials found in the tops of Rim and Plateau Profiles. After relating altitude to the constituting materials of the bauxite profiles, it is noticed that there are occurrences of Rim Bauxite Profiles located in altitudes of Plateau Profiles and Reworked Profiles located over Rim Profiles, above 1,400 meters of altitude. In the opposite direction, tops of the same elevation are found, where there should be Rim Profiles, there are rocky outcrops observed in field, without any evidence of laterite profiles. It is concluded, therefore, that the elevation rates by themselves, at least in this area, are not good enough references to determine the existence and distribution of paleosurfaces.

Prevalência de Oestrus ovis (Diptera: Oestridae) em ovinos da região Central de São Paulo, Brasil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Brasil: ¿cómo reaccionan los mercados financieros ante los anuncios de política monetaria del banco central en un esquema de metas de inflación?

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Banco Central do Brasil: institucionalidade, relações com o estado e com a sociedade civil, autonomia e controle democrático

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Identificação das raias-viola Rhinobatos horkelii, Rhinobatos percellens e Zapteryx brevirostris (Chondrichthyes, Rhinobatidae) na costa central e sul do Brasil utilizando marcadores moleculares

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Área de vida da choca-do-planalto Thamnophilus pelzelni Hellmayr, 1924 (Passeriformes: Thamnophilidae) na estação ecológica de Jataí, Luiz Antônio, SP

Pós-graduação em Ciências Biológicas (Zoologia) - IBRC

Padrões de infecção por helmintos em comunidades de lagartos do Brasil central

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo evolutivo do sistema morfoclimático e morfotectônico da bacia do Rio Verde (MG), sudeste do Brasil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desempenho e comportamento de vacas nelores e suas crias puras ou mestiças no Brasil Central

Pós-graduação em Zootecnia - FMVZ

Composição e riqueza de espécies de anfíbios anuros em três diferentes habitat em um agrossistema no Cerrado do Brasil central

A plasticidade adaptativa tem sido postulada como um fator importante para explicar a distribuição e abundância de espécies em habitat com diferentes níveis de variação ambiental e a heterogeneidade ambiental tem sido apontada como responsável pela manutenção, aumento ou diminuição da diversidade. Neste trabalho, determinamos o efeito da periodicidade e estrutura do habitat sobre a riqueza e composição de espécies em três diferentes habitat: córrego (P1), poças temporárias (P2) e represa permanente (P3) em um agrossistema no Cerrado do Brasil central. Nove expedições de campo foram realizadas entre outubro de 2005 e abril de 2007. Os métodos de amostragem por encontro visual e procura auditiva foram utilizados para o registro das espécies. Foram registradas 19 espécies de anuros pertencentes a quatro famílias: Bufonidae (uma espécie), Hylidae (nove espécies), Leptodactylidae (cinco espécies) e Leiuperidae (quatro espécies). Maior riqueza e a abundância foram registradas nas lagoas temporárias (P2), que diferiram significativamente do córrego (P1) e da represa permanente (P3). Dendropsophus nanus, Hypsiboas raniceps e Leptodactylus chaquensis apresentaram forte associação com o sítio P2. Os sítios P2 e P3 apresentaram maior diferenciação entre si na composição de espécies, do que quando comparados ao sítio P1. Apesar dos corpos d'água estudados estarem inseridos em área de intensa agricultura e sofrerem elevado grau de perturbação antrópica, esses ambientes apresentam elevada riqueza de espécies, constituindo-se como importantes refúgios para anurofauna da região. Entretanto, as espécies registradas são associadas a áreas antropizadas ou fitofisionomias abertas sendo favorecidas com a criação de ambientes artificiais como os observados no presente estudo.