Um novo peixe euteleósteo do Cretáceo Inferior da Bacia do Tucano, Nordeste do Brasil

A new euteleostean fish, Britoichthys marizalensis gen. and sp.nov. is described from the Lower Cretaceous of Tucano basin, North-eastern Brazil, based on various almost complete and articulate specimens preserved in a yellowish siltstone yielded from Marizal Formation. This taxon is recognised by an unique combination of characters: an ethmoidean commissure on rostrodermethmoid bone; well- developed premaxilla with fang-like teeth; presence of a sinuous maxilla with oral border garnished of aligned conical teeth; massive mandible with straight oral border; reduced orbit bordered by large infraorbital bones; seven branchiostegals rays; three uroneurals, the first not extending forward beyond the preural centrum 1; ural centra not fused; membranous outgrowth (stegural) of first uroneural; leaf- like plates of bone associated with rudimentary neural arches of the first preural and ural vertebrae; non bifurcate epineurals, pattern 2 supraneurals, cycloid scales, and 36 vertebrae. The reduced number of vertebrae and branchiostegal rays, premaxilla shape, caudal endoskeleton pattern, simple epineurals, supraneural type, and the presence of a retroarticular in the corner of the lower jaw suggest affinities with euteleostean fishes. In so far as known, Britoichthys is unique in its combination of features and cannot be included in any known family.Um novo peixe euteleósteo, Britoichthys marizalensis gen. e sp.nov., é descrito do Cretáceo Inferior da Bacia do Tucano, Nordeste do Brasil, com base em espécimes praticamente completos e articulados preservados em um siltito amarelado produzido na Formação Marizal. Esse táxon é reconhecido por uma combinação única de caracteres: comissura etmoideana no rostrodermetmóide; pré-maxilar bem desenvolvido e com dentes agudos; presença de um maxilar sinuoso provido de dentes cônicos alinhados; mandíbula bem ossificada e com bordo oral reto; órbita reduzida e margeada de grandes ossos infraorbitais; sete raios branquiostégios; três uroneurais, o primeiro não se estendendo adiante além do primeiro centro preural; centros urais não fusionados; projeção membranosa (estegural) do primeiro uroneural; lâminas ósseas em forma de folha associadas com arcos neurais rudimentares dos primeiros centros pré-ural e ural; epineurais simples (não bifurcados); padrão tipo 2 de supraneurais; escamas ciclóides; e trinta e seis vértebras. O reduzido número de vértebras e raios branquiostégios, o formato do pré-maxilar, o padrão do endoesqueleto caudal, epineurais simples, o padrão de supraneural, e a presença de um retroarticular no canto da maxila inferior sugerem afinidades com peixes euteleósteos. Até onde se sabe, Britoichthys é único em sua combinação de caracteres e não pode ser incluído em qualquer família conhecida

A New Chanidae (Ostariophysii: Gonorynchiformes) from the Cretaceous of Brazil with Affinities to Laurasian Gonorynchiforms from Spain

Based on specimens originally referred to as “Dastilbe minor”, a nomem-nudum, we describe a new genus of Chanidae †Nanaichthys longipinnus nov. gen. and sp. which exhibits several diagnostic characters such as the absence of orbitosphenoid and basisphenoid, anteriorly displaced quadrate-mandibular articulation, laterally expanded supraneurals, an acute angle between the preopercular limbs, expansion at the angle between the preopercular limbs, and a curved maxillary articular process. Its occurrence and supposed relationship within the Chanidae reinforce the influence of the Mediterranean Tethys over the Gondwanan main rift system prior to the Aptian/Albian highstands

Interpretation of the gravity anomalies of Bahia state Brazil

This thesis describes the gravity interpretation of Bahia State, Brazil, which comprises the northern Sao Francisco craton, the Upper Proterozoic fold belts and the basins adjacent to the continental margin. The study centres on the isostatic analysis of the region and on the interpretation of large and high amplitude negative anomalies which occur over the Precambrian and the sedimentary basins. The isostatic analysis of the northern Sao Francisco craton was carried out using the isostatic response function technique. Taking into account subsurface loads, an elastic plate with a minimum effective thickness of 20-40 km explains the observed isostatic response function. The subsurface loads are (l) a slight thickening of the crust under the Espinhaco Fold System and (2) five to ten kilometres of low density rocks in the upper crust. A large and high amplitude ( - 50 mGal ) negative anomaly of shallow origin, centred near the western border of the Paramirim complex and parallel to the Espinhaco fold belt, is interpreted as caused by a large and mainly unexposed granite batholith. The granite substantially underlies the fold belt and extends towards the centre of the Paramirim complex. The minimum density contrast between the granite and the country rocks is estimated to be -0.06 g cm(^-3). The thickness of the granite is 8 to 13 km for density contrasts of -0.15 g cm(^-3) to -0.10 g cm(^-3). A series of high amplitude negative anomalies (50 to 100 rrGal), without flanking positive anomalies, characterizes the onshore Reconcavo, Tucano and Jatoba basins, which were ail formed in connection with the South Atlantic opening. The gravity interpretation indicates up to 7 km of sediments infilling these basins and no significant Mo ho upwarp beneath. In contrast, the gravity anomalies over the offshore Jacuipe and Sergipe-Alagoas basins are explained by a thick accumulation of sediments on a strongly attenuated crust. The onshore basins show short-lived subsidence ( < 25 Ma) with little, if any thermal subsidence. Syn-rift and post-rift (thermal) sedimentation is observed only in the continental margin basins. A mechanism in which upper crustal extension in one region (onshore basins) is compensated and balanced against lower extension in another region (offshore basins), through a detachment fault, may explain the way these basins formed

Digital image processing and enhancement of gravity data as an aid to the definition of the structural framework of the north Tucano-Jatobá basins, Northeastern Brazil

Técnicas de processamento digital de imagens foram aplicadas a dados gravimétricos visando melhorar definição das principais feições estruturais na porção norte do Rift Recôncavo-Tucano-Jatobá. Os processamentos utilizados incluíram: (a) conversão de dados Bouguer e residual-Bouguer, no formato de grids, em imagens realçadas; (b) geração de composições falsa cor híbridas e (c) geração de modelos de elevação digital com visão em perspectiva. A análise integrada desse conjunto de dados permitiu reconhecer feições lineares e sutis variações espaciais nos dados gravimétricos, as quais foram associadas a unidades tectónicas no contexto do rift, tais como: plataformas em rampa, baixos e altos estruturais, horsts, grabens e falhas de borda.Digitally processed and enhanced gravity data in raster format were used to improve the definition of the main structural features in the northern part of the Reconcavo-Tucano-Jatoba Rift. Image processing techniques included: (a) conversion of Bouguer and residual-Bouguer gridded data into contrast-enhanced gray-level images; (b) generation of enhanced hybrid pseudo-color composites; and (c) generation of a gravity digital elevation model in perspective views. The integrated analysis of this dataset permitted the recognition of subtle trends and intensity-related spatial variations in gravity data, tentatively related to the following tectonic units of the RTJ Rift: ramp platforms, structural lows and highs, along-length horsts, grabens, faulted borders and extensional faults

Spectral remote sensing for onshore seepage characterization: A critical overview

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOIn this article, we overview the application of spectral remote sensing data collected by multi-, and hyperspectral instruments in the visible-near infrared (VNIR), short-wave infrared (SWIR), and longwave infrared (LWIR) wavelengths for characterization of seepage systems as an exploration indicator of subsurface hydrocarbon (HC) accumulations. Two seepage systems namely macro-, and microseepage are recognized. A macroseepage is defined as visible indications of oil and gas on the surface and in the air detectable directly by a remote sensing approach. A microseepage is defined as invisible traces of light HCs in soils and sediments that are detectable by its secondary footprints in the strata, hence an indirect remote sensing target. Based on these broad categories, firstly, a comprehensive set of well-described and reliable remote sensing case studies available in the literature are thoroughly reviewed and then systematically assessed as regards the methodological shortcomings and scantiness in data gathering, processing, and interpretation. The work subsequently attempts to go through seminal papers published on microseepage concept and interrelated geochemical and geophysical techniques, exhumed HC reservoirs, lab-based spectroscopic analysis of petroleum and other related disciplines from a remote sensing standpoint. The aim is to enrich the discussion and highlight the still unexplored capabilities of this technique in accomplishing exploration objectives using the concept of seepage system. Aspects of seepage phenomenon in environmental pollution and uncertainties associated with their role in global warming are also underlined. This work benefits from illustrative products generated over two study areas located in the Ventura Basin, State of California, USA and the Tucano Basin, State of Bahia, Brazil known to host distinctive macro-, and microseepage systems, respectively. In conclusion, we recommend further research over a diverse range of seepage systems and advocate for a mature conceptual model for microseepage phenomenon1684872FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2015/06663-

Reconstructing fluvial bar surfaces from compound cross-strata and the interpretation of bar accretion direction in large river deposits

The interpretation of fluvial styles from the rock record is based for a significant part on the identification of different types of fluvial bars, characterized by the geometric relationship between structures indicative of palaeocurrent and surfaces interpreted as indicative of bar form and bar accretion direction. These surfaces of bar accretion are the boundaries of flood-related bar increment elements, which are typically less abundant in outcrops than what would be desirable, particularly in large river deposits in which each flood mobilizes large volumes of sediment, causing flood-increment boundary surfaces to be widely spaced. Cross-strata set boundaries, on the other hand, are abundant and indirectly reflect the process of unit bar accretion, inclined due to the combined effect of the unit bar surface inclination and the individual bedform climbing angle, in turn controlled by changes in flow structure caused by local bar-scale morphology. This work presents a new method to deduce the geometry of unit bar surfaces from measured pairs of cross-strata and cross-strata set boundaries. The method can be used in the absence of abundant flood-increment bounding surfaces; the study of real cases shows that, for both downstream and laterally accreting bars, the reconstructed planes are very similar to measured bar increment surfaces.Sao Paulo Research Foundation (FAPESP)CAPESCNPqLiliane JanikianUniv Sao Paulo, Inst Energia & Ambiente, Av Prof Luciano Gualberto 1289,Cidade Univ, BR-05508900 Sao Paulo, SP, BrazilUniv Sao Paulo, Inst Geociencias, Rua Lago 562,Cidade Univ, BR-05508900 Sao Paulo, SP, Brazil|Univ Fed Itajuba, Inst Recursos Nat, Av BPS 1303, BR-37500903 Itajuba, MG, BrazilCPRM Geol Survey Brazil, Rua Costa 55, BR-01304010 Sao Paulo, SP, BrazilUniv Fed Sergipe, Dept Geol, Av Marechal Rondom S-N, BR-49100000 Sao Cristov, SE, BrazilUniv Fed Sao Paulo, Campus Baixada Santista, BR-11030400 Santos, SP, BrazilUniv Fed Sao Paulo, Campus Baixada Santista, BR-11030400 Santos, SP, BrazilFAPESP: 2009/53363-8FAPESP: 2009/52807-0FAPESP: 2009/51766-8FAPESP: 2010/51103-6FAPESP: 2010/51559-0FAPESP: 2013/01825-3FAPESP: 2014/16739-8CAPES: PROEX-558/2011CNPq: 301774/2012-9Liliane Janikian: 301775/2012-5Web of Scienc

Stratigraphy of the Southern part of the Sergipano Belt, NE Brazil : tectonic implications

A Faixa Sergipana (NE, Brasil) é uma cunha orogenética de direção geral ESE-WNW e que foi polideformada/metamorfisada em consequencia da colisão entre o Macifo Pernambuco- Alagoas, a norte, e o Cráton de São Francisco, a sul, no Ciclo Brasiliano, há cerca de 700-600 Ma, A partir de estudos anteriores em escala regional a faixa e dividida, de sul para norte, em tres domínios litotectônicos longitudinals, respectivamente assemelhados a pilhas de rochas sedimentares e vulcanicas construidas em ambiente cratdnico, miogeoclinal e eugeoclinal separados por falhas reversas, em geral de alto angulo, que indicam transporte de topo para SSW com transcorrgncia associada. Na parte norte da faixa são ainda individualizados dois outros domfnios de rochas fgneas e um domfnio de migmatitos e gnaisses. Modelos divergentes de evolução tectônica foram produzidos para a faixa, com base em interpretações a favor e contra a continuidade lateral entre os metasedimentos. Estudos litoestratigrdficos-estruturais realizados em escala de detalhe (1987-1995) em drea de 4000km2 circundando dois domos gnáissicos de embasamento e englobando a interface entre o craton, miogeoclinal e eugeoclinal, na parte sul da faixa Sergipana, revelam: (1) uma nova litoestratigrafia das rochas depositadas nos dois domínios mais a sul, distinta daquela dos estudos anteriores; (2) evidencias sedimentológicas, estruturais, metamórficas e geofísicas inequívocas a favor da continuidade entre os três domínios, através das suas falhas de borda; (3) a parte superior da seção da cobertura cratonica compreende uma sequencia de argilito, siltito, arenito, arcósio e grauvação lítica, com granulometria crescente para o topo; esta seção passa gradativamente a metasiltito e filito depositados na bacia, onde ocorre sobreposta ao grupo basal e sotoposta a diamictitos e carbonates do grupo superior, todos depositados em tomo dos domos de embasamento que ocupam o nucleo de antiformes regionais; (4) as caracteristicas sedimentológicas e o posicionamento estratigráfico inequívoco da sequência de granulometria crescente para o topo descartam modelos tipo bacia foreland anteriormente adotados para explicar o topo da seção da cobertura cratônica adjacente a Faixa Sergipana. Os dados permitem interpretar que o preenchimento da bacia precursora se deu em regime de sedimentação controlada por tectônica, no qual os domos de embasamento provavelmente atuaram como paleo-altos e as falhas regionais limitantes dos domínios (meta)vulcano-sedimentares sao provdveis falhas normals originais, que foram positivamente invertidas na fase de fechamento da bacia. A origem da parte superior da cobertura cratônica, cuja deve ser atribuída ao soerguimento e erosao de fonte a sul, e os controles tectonicos da sedimentacao, implicam consideravelmente para a evolução da Faixa Sergipana e do Cráton de São Francisco. _________________________________________________________________________________ ABSTRACTThe Sergipano Belt (NE Brazil) is a ESE-WNW trending volcano-sedimentary wedge polydeformed and metamorphosed (700-600Ma) due to the collision of the Pernambuco-Alagoas Massif, to the north, with the São Francisco Craton, to the south, during the Pan-African/Brasiliano orogeny. According to previous, regional-scale studies, the belt comprises three longitudinal lithotectonic domains with cratonic, miogeoclinal and eugeoclinal affinities, respectively from S to N, separated by regional, WNW-ESE trending, generally high-angle thrust-strike slip faults. Divergent tectonic evolution models were produced based on interpretations for and against the lateral continuity between these domains. Detailed stratigraphic-structural analysis from a 1:50,000 scale mapping carried out (1987-1995) in a 4000km2 area encompassing the interface between the three domains and surrounding two basement gneiss domes in the southern part of the belt, revealed: (1) the lithostratigraphy of the rocks deposited in the cratonic and miogeoclinal segments; (2) innequivocal evidence for the sedimentological, structural and metamorphic continuity across the domains boundary faults; (3) the upper section of the sediments deposited in the cratonic domain records the deposition of coarsening-upwards mudstones, siltstones, arkosic sandstones and lithic wackes that spreaded from the craton, to the south, across the craton-basin interface and graded into metasiltites and phyllites towards the miogeoclinal basin, where they occur in the core of a major basement-cored antiform and are overlain by a distinct diamictite formation, thus building up a siliciclastic mcgascquence. The sedimentological characteristics and innequivocal stratigraphic position of these arkosic sandstones and lithic wackes do not fit in previously suggested thrust-fold belt/foreland basin models; (4) very strong evidence for the miogeoclinal and eugeoclinal domains being also continuous across their boundary faults, allowing to erect a new stratigraphic template for the Sergipano Belt. The data allow to interpret that sedimentation was tectônicaly controlled by the basement domes and normal faults likely to have been inverted during the closure of the basin. The origin of the upper section of the sediments deposited in the cratonic domain and the tectonic controls of the sedimentation have relevant implications for the evolution of both the Sergipano Belt and the São Francisco Craton

A geological and geophysical study of the Sergipe-Alagoas Basin

Extensional stresses caused Africa and South America to break up about 130 Million Years. When Africa rifted away from South America, a large onshore triple junction began at about 13° S and propagated northward. This triple junction failed and created the Reconcavo-Tucano-Jupato rift (R-T-J), located in northeastern Brazil (north of Salvador). The extensional stress that created this rift was caused by a change in the force acting on the plate during the Aptian. A series of offshore rifts also opened at this time, adjacent to the R-T-J rift; this series of basins are referred to as Jacuipe, Sergipe, and Alagoas (J-S-A). The basins are separated by bathymetric highs to the north and the south of the Sergipe-Alagoas basin. The Sergipe-Alagoas basin has a Bouguer gravity anomalies more negative than -35 mGal, and the other two basins have values more negative than -100 mGal; the total magnetic intensity is also about 60-80 nT higher in the Sergipe-Alagoas basin than the surrounding basins. The gravity and magnetic values in the Sergipe-Alagoas basin, when compared to the Jacuipe and the Sergipe-Alagoas basins, indicate that the depositional history and/or the formation of the Sergipe-Alagoas basin is different from the other two basins. This study was done by analyzing the gravity and magnetic anolamies in the region, and comparing these anomalies to the stratigraphy of the basin. This research has allowed the stratigraphy and structures of the Sergipe-Alagoas basin to be better understood - the location of the Sergipe fracture zone will also be outlined. This study provides a comprehensive view of the Sergipe-Alagoas basin and outlines a method for using Gravity and Magnetics to better understand the stratigraphy and structure of the Sergipe-Alagoas basin