Figura 1 - uploaded by Paulo Sergio Gomes Paim
Content may be subject to copyright.
Mapa geológico simplificado do Brasil, com indicação de bacias rifte Paleo-Mesoproterozoicas descritas no texto. Segundo Schobbenhaus et al (1984) e Schobbenhaus & Brito Neves (2003).
Source publication
No Brasil destacam-se dois crátons brasilianos - o Amazônico, na região norte, e o do São Francisco, que ocorre na região centro-leste. Bacias rifte Paleo (2,5-1,6 Ga) e Mesoproterozoicas (1,6-1,0 Ga) compreendem depósitos vulcano-sedimentares sub-horizontais ou deformados, situadas no interior destes crátons. No Cráton Amazônico destacam-se as cob...
Similar publications
En las geografías políticas de Venezuela y la República Cooperativa de Guyana son inevitables las referencias a sus históricas controversias relacionadas con las indefinidas delimitaciones fronterizas. Es un tema complejo puesto que trasciende el reclamo venezolano sobre una extensión territorial de 159.500 km2 y abarca un conjunto de componentes,...
The Neotropical genus Polychrus contains seven species of arboreal lizards. The type species for the genus is the widespread Polychrus marmoratus. We compared a few populations of P. marmoratus using 16S and COI mitochondrial gene sequences (1,035 bp total) and found several lineages existing under the name Polychrus marmoratus. Working backwards,...
Here we report on a ceramic assemblage excavated from the middle Berbice region of Guyana, and dated to the mid-Holocene. The results of a techno-functional ceramic attribute analysis, along with the contexts from which they were recovered are discussed in order to shed new light on the timing and location of early agricultural mound builders and c...
Citations
... In the Espinhaço Supergroup, two rifting processes related to the Statherian and Calymmian periods have been identified and are known as Tuxás and Tupinaés events, both associated with intracontinental extension (Danderfer et al., 2015;Costa et al., 2018). The Espinhaço Basin outcrops in three geographic regions known as Serra do Espinhaço Meridional (Southern Espinhaço range), Serra do Espinhaço Setentrional (Northern Espinhaço range), and Chapada Diamantina (Diamantina Plateau) (Schobbenhaus and Brito Neves, 2003;Uhlein et al., 2015).) (Figs. ...
The tectonostratigraphic evolution of the intracontinental Natividade Basin is evaluated by zircon U/Pb analysis of one sample of acidic metavolcanic rock observed at the bottom of the depositional succession and three samples of metasedimentary rocks collected at different stratigraphic levels. The metavolcanic sample yielded a 1824 Ma zircon U–Pb age, and the youngest detrital zircon grains from the metasedimentary sequence resulted in a maximum depositional age of 1776 Ma for the paleobasin. The isotopic data associated with the analysis of stratigraphy, paleogeography, and sedimentary environments converge to the interpretation that the Natividade Group evolved from the late Paleoproterozoic (Statherian), possibly entering the early Mesoproterozoic. The sedimentation is interpreted to have occurred between the deposition of the Araí and the Traíras/Serra da Mesa groups. This understanding is due to the absence of continental sediments in the Natividade Basin (which could corroborate the correlation with the Araí Basin) and the absence of detrital zircon grains younger than 1.5 Ga (which would support the correlation with the Traíras/Serra da Mesa groups). The metavolcanic rocks are observed only locally and are interpreted as the result of melting by crustal rifting that was greatest in the south, related to the Araí Group, and decreased northwards of the study region. The mechanical subsidence responsible for the deposition of the Araí Group continental sediments was not observed in the Natividade Basin. The thermo-flexural subsidence responsible for the Natividade basin evolution allowed the deposition of complex sedimentary environments related to mixed siliciclastic platforms and shallow water turbidite facies. Based on bibliographic studies and fieldwork data, our geological model suggests that the Almas Block was possibly a high paleorelief area, separating the Araí Basin to the south and the Natividade Basin to the north. This assertion is based on the following facts for the study area: i) there is no occurrence of the Veadeiros Supergroup sediments; ii) Nowadays in the region, there are many high relief areas related to quartzite layers and several granitic units that are resistant to denudation processes; iii) deposition of the shallow water turbidite present at the Natividade Group needed elevated source areas to control the sedimentation; iv) The predominance of carbonates and mass flow deposits in the southern portion of Natividade Group, near to Almas Block, suggests a lower depth of the sea to the south of the basin. Further north, the predominance of fine-grained terrigenous deposits suggest a deeper basin; v) it is common in rift-sag environments the preservation of elevated blocks as an isostatic compensation mechanism. The integrated analysis conducted allowed the following conclusions: the Natividade Basin evolution is not coeval with the Araí or the Traíras/Serra da Mesa basins and is classified as a sag-type basin in which the sedimentary environments resulted in massive carbonate accumulation in a complex platform controlled by the basement paleorelief.
... A single age determination has been published for the sequence, which proposes a maximum deposition age of 1779 ± 6 Ma (Silva et al., 2005) calculated with the youngest detrital zircon grains via U-Pb method. This unit has been preliminarily correlated to the Paleo-Mesoproterozoic rift and sag systems in the São Francisco Craton western margin (Veadeiros Supergroup, Brasília Belt) and eastern margin (Espinhaço Supergroup, Araçuaí Belt) (Gorayeb et al., 1988;Hasui et al., 1990;Silva et al., 2005;Uhlein et al., 2015;Martins-Ferreira et al., 2018a). However, the sets of rocks present in different stratigraphic arrangements, the different depositional systems and the lack of comprehensive geochronological data hinder this correlation. ...
Download at: https://authors.elsevier.com/c/1csLf_KNqlezyI The Natividade Group is a Paleo-Mesoproterozoic metasedimentary sequence outcropping in the external zone of the Northern Brasília Belt, western margin of the São Francisco Craton, Brazil. The present study delimited eleven sedimentary rock types grouped into four rock assemblages: i) Sand-Silt-Carbonate; ii) Sand-Conglomerate; iii) Sand, iv) Silt-Clay. A geological map for the region was produced, and six stratigraphic columns were composed. Based on the descriptions of rock types and on lateral variation of rock assemblages, it was possible to establish four depositional environments for the Natividade Group, including mixed platform (siliciclastic-carbonate deposition), internal siliciclastic platform, open-marine siliciclastic platform, and a shallow water turbidite (mass flow slope deposition). The mixed platform was controlled by the basement paleogeography, which allowed the deposition of carbonates in warm, agitated, and clean, shallow water conditions in parallel to deposition in deeper water setting, where thin siliciclastic sediments were deposited. The siliciclastic internal platform consists mostly of quartzite, originating from sandy sediments, probably indicating deposition dominated by bedload currents under shallow water shoreface conditions. The open-marine siliciclastic platform is dominated by fine-grained sediments, indicating deepening water conditions under lower shoreface conditions below the fair-weather wave base. Shallow water turbidite occurs in the southern parts of the study area. The elevated paleorelief in the southeast of the Natividade basin is considered as the provenance area providing suitable slope environments for density flow initiation. The basin was shallower in the southern portion with a predominance of carbonate and gravitational flux deposits and deeper to the north, evidenced by the northward predominance of fine-grained sediments. Finally, the study shows that the Natividade Group was deposited in a basin controlled by thermo-flexural subsidence.
... Sucessões sedimentares pré-cambrianas representam parte do registro de preenchimento de antigas bacias. Em geral, a caracterização desses pacotes permite inferir sobre o sítio tectônico que acolheu a sedimentação e o regime tectônico predominante no local (p.ex., Danderfer e Dardenne 2002;Costa, 2013;Guadagnin et al., 2015;Uhlein et al., 2015). No entanto, são raras as vezes em que se utiliza o registro estrutural para fundamentar a interpretação da tectônica formadora de uma bacia sedimentar, sobretudo nos casos em que ela experimentou deformação durante processos orogênicos. ...
Na região norte da faixa Araçuaí, no domínio fisiográfico do Espinhaço Central, existem registros de bacias sedimentares superpostas instaladas sobre o embasamento do cráton São Francisco. Nesse contexto, a morfoestrutura da Serra Central, norte de Minas Gerais, é sustentada por uma sucessão siliciclástica do Supergrupo Espinhaço superposta a oeste por diamictitos da base do Grupo Macaúbas, representando os registros de rifteamento superpostos ao final do Esteniano e do Toniano Superior, respectivamente. No bordo oeste da Serra Central, são descritas estrias de média a alta obliquidade desenvolvidas sobre os planos de acamamento da sucessão do Grupo Sítio Novo, incompatíveis com a tectônica compressional Brasiliana, que afeta essas rochas. Essas estrias são associadas a degraus e definem vetores de deslizamento interestratais indicativos de movimentação normal a normal destral. Associados a essas lineações, ocorrem veios que também apontam para a atuação de um campo de esforço extensional, com componente destral associada. A análise cinemática e dinâmica dessas estruturas permitiu a interpretação de um regime tectônico distensivo de natureza transtrativa destral e, possivelmente, relacionado ao evento de rifteamento Macaúbas. Nesse cenário, o bloco de capa regional do rifte Macaúbas, representado pela sucessão esteniana do Grupo Sítio Novo, foi deformado sob a atuação de um cisalhamento antitético, com desenvolvimento de um rollover associado. No flanco frontal do rollover, as camadas experimentaram significativa magnitude de rotação, revelando elevado mergulho próximo à borda de falha e favorecendo o desenvolvimento do deslizamento interestratal.
... Este último evento, denominado Ventuari-Tapajós (ou Tapajós-Parima) e de ocorrência restrita ao cráton Amazônico, é contemporâneo ao processo de aglutinação de blocos crustais que formaram uma parte significativa do supercontinente Columbia (Figura 3A), o qual também ganhava contornos finais neste momento (Bizzi et al., 2003, incluindo a lista de referências desta obra; Hou et al., 2008). Merecem destaque o plutonismo e o vulcanismo intraplaca (SLIP) desenvolvidos em boa parte do cráton Amazônico por volta de 1,9 Ga, conhecidos no Brasil como Evento Uatumã, seguidos pelo desenvolvimento de bacias sedimentares, no norte e no sul da Amazônia, com centenas de milhares de quilômetros quadrados de extensão (localmente, espessuras superiores a 3.000 m) no total, em ambiente continental a marinho raso (Bizzi et al., 2003, incluindo a lista de referências desta obra; Uhlein et al., 2015). ...
Resumo: Sob a luz dos processos tectônicos intraplaca e orogênicos vigentes durante a transição Orosiriano (2,05-1,80 Ga)-Estateriano (1,80-1,60 Ga), é apresentada, neste artigo, uma tentativa de reposicionamento dos proto-crátons sul-americanos Amazônico, São Francisco, Rio de la Plata e São Luís, no supercontinente Columbia, utilizando dados geológicos, geocronológicos e paleomagnéticos de Províncias Ígneas Gigantes (Large Igneous Provinces-LIP) e de Províncias Ígneas Gigantes Silícicas (Silicic Large Igneous Provinces-SLIP) disponíveis na literatura. Uma possível junção tríplice pode ser reconstruída, dentro da qual as respectivas LIP e SLIP são acomodadas no tempo e no espaço, com o proto-cráton Rio de la Plata virado de cabeça para baixo e posicionado entre o proto-cráton Amazônico e o bloco Báltica e, ainda, por meio de rotação no sentido horário de cerca de 90 graus do proto-cráton Amazônico em relação à sua posição atual, colocando-o lado a lado com o proto-cráton São Francisco. Um cenário geológico coerente com a Tafrogênese do Estateriano, que marca o início da quebra de Columbia, é remontado a partir do ensaio geotectônico aqui proposto. Palavras-chave: LIP. Columbia. América do Sul. Reconstrução tectônica. Orosiriano-Estateriano. Abstract: Based on the orogenic and intraplate tectonic processes existing during Orosirian (2,05-1,80 Ga)-Statherian (1,80-1,60 Ga) transition, this article is an attempt to reposition the South American proto-cratons Amazon, São Francisco, Rio de la Plata and São Luís in Columbia supercontinent using geological, geochronological and paleomagnetic data of Large Igneous Provinces (LIP) and Silicic Large Igneous Provinces (SLIP) available in the literature. With the proto-craton Rio de la Plata turned upside down between Amazon and Baltica and through a clockwise rotation of about 90 degrees of the proto-craton Amazon in relation to its current position by placing it side by side with proto-craton San Francisco, a possible triple junction can be reconstructed, in which their LIP and SLIP are accommodated in time and space. A geological setting consistent with the Statherian Taphrogenesis, which marks the beginning of the Columbia breakup, is reconstructed from the tectonic evaluation here proposed.
In this expanded abstract, we have studied the airborne magnetic data on the Caiabis Basin, Mato Grosso State, Brazil. Using processing techniques like regional-residual separation by spectral analysis, anomaly centralization by vertical integration and estimative of magnetic source depth by Werner Deconvolution, we have proposed that the magnetic anomalies from Caiabis Basin may be related to: basement; lineaments; manganese ore and; sediments/basement interface in the Porto dos Gauchos seismic zone. In this last case, we also verified that the magnetic source depth estimates provided by Werner solutions are agreement with other depth estimates given in seismic studies.
