bluuebunny/crossref_metadata_2025 huggingface dataset:
Feições sedimentológicas e geomorfológicas do ambiente de deglaciação das geleiras Wanda e Ecology, ilha Rei George, Antártica
Authors: ROSA Kátia Kellem da , VIEIRA Rosemary , SIMÕES Jefferson Cardia , FERRANDO Francisco José
Published: April 2019

Um estudo comparativo da evolução dos ambientes de deglaciação foi realizado nas geleiras Wanda e Ecology, ilha Rei George, Antártica para a análise dos processos erosivos e deposicionais subglaciais destes ambientes. Os dados para a reconstrução da deglaciação resultam da interpretação geomorfológica e de fotogramas aéreos, juntamente com análise de imagens de satélite SPOT tomadas em diversos anos. Os processos subglaciais foram investigados por meio de análises granulométricas e morfoscópicas dos sedimentos coletados durante a estação de verão e co-variância entre os índices RA (porcentagem de clastos angulosos) e C40 (porcentagem de clastos com razões c:a ≤ 0,4). Desde 1956 essas geleiras estão recuando rapidamente, sem períodos de reavanço. No entanto, é possível observar diferenças nos processo de deglaciação entre elas; na geleira Ecology ocorreu maior perda de área (1,35 km2 ) do que na geleira Wanda (0,64 km2 ) em cinco décadas. A retração da geleira Ecology, nesse período, foi maior na parte norte da zona proglacial; já ao sul observam-se morainas frontais não muito elevadas, o que indica pouco tempo de estabilização da frente de gelo. Durante as distintas fases de recuo da geleira Wanda ocorreram mudanças na orientação principal do fluxo de gelo, concomitante com a diminuição da sua espessura. Como resultado destas retrações, tem-se a exposição de várias geoformas e depósitos proglaciais, tais como flutes, terraços de kame, cordões morâinicos, pavimentos de clastos, rochas estriadas e eskers. Nos dois ambientes sedimentares estudados predominam sedimentos desgastados e transportados subglacialmente, com a presença de água de degelo. O grande volume de sedimentos de grãos finos, rochas estriadas, pavimentos de clastos, blocos stoss in lee e depósitos subglaciais indica que as duas geleiras têm regime termal basal temperado.
O complexo Dadoxylon-Araucarioxylon, Carbonífero e Permiano do Gondwana: estudo taxonômico do gênero Dadoxylon
Authors: KURZAWE Francine KURZAWE , MERLOTTI Sheila
Published: April 2019

A flora do Paleozóico Superior da Província Gondvânica encontra-se dividida em dois grupos principais, de acordo com sua posição taxonômica, um característico do Carbonífero Superior e outro típico do Permiano. O primeiro era composto por licópsidas, pteridospermas, cordaitales e ginkgoales, e o segundo tinha Glossopteris Brongniart constituindo o gênero mais típico, além de ser composto por muitas espécies bastante diferenciadas ecologicamente. Esta flora encontra-se hoje representada no registro fossilífero por folhas e órgãos reprodutivos preservados por impressão / compressão carbonosa e por lenhos permineralizados. Estes têm sido descritos desde meados do século dezenove principalmente como Dadoxylon Endlicher e Araucarioxylon Kraus. Entretanto, desde suas definições originais, pouco precisas, estes nomesgenéricos têm sido aplicados indiscriminadamente para diferentes tipos lenhosos, transformando- se em verdadeiro complexo taxonômico, englobando formas não necessariamente relacionáveis entre si. Na primeira parte desta reavaliação taxonômica serão analisadas as espécies de Dadoxylon com base nas novas propostas estabelecidas por diferentes autores e nas regras do CINB (Código Internacional de Nomenclatura Botânica). Como resultado do presente estudo, das 20 espécies identificadas na literatura, três foram recombinadas no gênero Dammudoxylon (Maheshwari) Maheshwari: Dammudoxylon arberi, D. waltonii e D. sp. (D. australe?); nove foram consideradas inválidas: Dadoxylon cf. D. indicum, D. cf. Eristophyton, D. kumarpurensis, D. sp. Arber, D. sp. Walton, D. sp. Moonje, D. sp. Jacob, D. sp. Narasimhan e D. sp. Seward; cinco não foram passíveis de transferência devido a ausência de características diagnósticas preservadas:Dadoxylon angustum, D. binneyi, D. brisbanense, D. maitlandi e D. williamsoni; e três necessitam ser enquadradas em novos gêneros: Dadoxylon butiense, D. sudanense e D. tordoxyloïdes.
Associações de foraminíferos e composição textural da região próxima ao emissário submarino de esgotos domésticos de Cigarras, Canal de São Sebastião, SP, Brasil
Authors: TEODORO Andreia , DULEBA Wânia , LAMPARELLI Cláudia
Published: April 2019

O objetivo do presente estudo foi caracterizar por meio da integração de estudos da composição textural e das associações de foraminíferos a região próxima ao emissário submarino de esgotos domésticos de Cigarras, localizado no Canal de São Sebastião, município de São Sebastião, São Paulo, Brasil. A malha de amostragem, com 10 estações, foi posicionada em região circunjacente aos difusores do emissário submarino. Foram realizadas análises granulométricas, do conteúdo de matéria orgânica e das associações de foraminíferos. Os resultados das análises granulométricas e análises tafonômicas e morfométricas realizadas nas carapaças dos foraminíferos (tanatocenoses) indicam que a área de estudo é ambiente de fraco hidrodinamismo, o que possibilita a deposição de elevada concentração de matéria orgânica. Asbaixas riquezas, diversidades específicas e equitabilidades, observadas nas biocenoses, são indicativas de estresse ambiental, o qual pode ser associado ao enriquecimento orgânico que há na região. Ammonia tepida é a espécie predominante em todas as estações analisadas.
Registros Palinológicos Inéditos nas Formações Teresina e Rio do Rasto (Permiano, Grupo Passa Dois, Bacia do Paraná) Implicações Biocronoestratigráficas e Paleoambientais
Authors: NEREGATO RODRIGO , SOUZA PAULO ALVES DE , ROHN ROSEMARIE
Published: April 2019

The Pennsylvanian-Permian interval of the Paraná Basin is relatively well-known on its palynological content. However, little has been published from the Permian Serra Alta, Teresina and lower Rio do Rasto formations (Passa Dois Group). A total of thirty seven core samples were collected along a vertical range of 600 meters of these units in two boreholes in the Congonhinhas Municipality, northeastern Paraná State, South Brazil, but only the Teresina Formation and the lower part of the Serrinha Member of the Rio do Rasto Formation yielded identifiable palynomorphs. Of the thirty recorded species, ten species are registered for the first time in the basin, three are probably new, and five were previously documented at stratigraphic levels below the units of the present study. Assemblages are assigned to the Lueckisporites virkkiae Zone, regarded as Middle Permian (Guadalupian) in age, as suggested by other fossil and radiometric data. According to the relative abundance of some spore species, it is possible to discriminate two intervals: the first characterized by the predominance of Laevigatosporites vulgaris (from the Teresina Formation to the basal Serrinha Member), and the second dominated by Thymospora (in higher stratigraphic levels). The great abundance of fern spores in these assemblages is amazing because lycophyte stems are the best represented macrophytofossils of the Teresina Formation, similarly as glossopterid leaves and sphenophyte stems in the Rio do Rasto Formation. These aspects are discussed in the scope of lithofaciological and other paleontological data.
Minerais Pesados dos Depósitos Aluviais do Rio Paraná e sua Implicação Paleohidrológica
Authors: SANTOS MANOEL LUIZ DOS , GASPARETTO NELSON VICENTE LOVATTO
Published: April 2019

Heavy-mineral analyses have been widely used in order to study the origin of sediments. Although it is not often used in stratigraphic studies, heavy minerals may be very important to correlate events, and facies associations in sedimentary basins. In this study, the rate-of-occurrence analysis of these accessory minerals and their texture intends to correlate the related fluvial deposits with both the present and the past channel of the Paraná River, and those deposits occurring in its hydrografic basin. Thirty samples were collected from the Paraná River deposits and its slopes, from Paranaíba (MS) to Porto Rico (PR) areas. The assembly of transparent heavy minerals is formed by zircon, tourmaline, staurolite, kyanite, epidote, rutile, sillimanite, andalusite, garnet, pyroxene, and amphibole. The analysis of the mineralogical and textural maturity of this assembly have shown a significant differentiation between the deposits of the Paraná river alluvial system and, it proved to be a useful tool for paleohydrological studies.
Propriedades Sísmicas Anisotrópicas Derivadas da Orientação Cristalográfica Preferencial de Muscovita-Quartzo Milonitos
Authors: MORALES LUIZ , FERNANDES LUÍS
Published: April 2019

Seismic wave propagation in organized matter usually results in azimuthal variations of longitudinal waves (Pwaves), as well as the effect of birefringence in transversal waves (S-waves), which results in two orthogonal shear waves with contrasting velocities. In this paper we present the results of the anisotropic seismic properties of five samples of muscovitequartz mylonites collected in different parts of a fold in the Saas Fee region, Western Internal Alps. The P-wave velocities in these rocks varies from 5.73 to 6.32 km/s, whereas the high-velocity shear wave (S1) varies from 3.82 to 4.22 km/s and the low velocity (S2) from 3.73 to 4.09 km/s. The anisotropy in these rocks is relatively high and reaches values from 9.5% for P-waves, and almost 11% for shear wave splitting. Both anisotropy and propagation directions seem to be related to from the strong preferred orientation of quartz and muscovite but also depend of muscovite modal content within the different specimens. Development of preferred orientation of minerals destroys and disperses the single crystal seismic properties, which causes a decrease of wave velocities and a dispersion of propagation directions, of both compressional and shear waves. Since the preferred orientation of quartz and muscovite can be directly related to the main macroscopic structures in these rocks (foliation, lineation, and pole of foliation) and the anisotropic seismic properties are related to the preferred orientation, it is possible to determine the propagation directions in terms of these structures. Due to the relatively high muscovite content, many of the maximum propagation velocities are parallel/subparallel to the foliation and some parallel to the lineation of the reference frame. On the other hand, directions of minimum propagation cannot be directly related to the foliation pole. The presence of folds in the mid-to lower crust can exert changes in the propagation directions due to the foliation variation around such structures, mainly in the P-waves.
Evolução Tectono-Estratigráfica e Paleoclimática da Formação Maricá (Escudo Sul-Rio-Grandense, Brasil): um Exercício de Geologia Histórica e Análise Integrada de uma Bacia Sedimentar Neoproterozóica
Authors: DE BORBA ANDRÉ , MARASCHIN ANDERSON , MIZUSAKI ANA MARIA
Published: April 2019

Significant improvement in the knowledge concerning the Neoproterozoic Maricá Formation of the Sul-riograndense Shield, southern Brazil, was obtained in the latest years. This contribution synthesizes recent data obtained though an integrated analysis of the lowermost unit of the “Camaquã Basin”. Stratigraphic and paleocurrent analyses, petrography, Sr and Nd isotope geology, U-Pb SHRIMP geochronology and Ar-Ar dating were applied to the sedimentary and volcanogenic record of the Maricá Formation in order to better constrain its depositional evolution. The Maricá Formation was deposited within a coastal to shallow marine setting, its detrital load being derived from the weathering of granite-gneissic, paleoproterozoic (1.76 to 2.37 Ga) source rocks, possibly located in the western La Plata craton. A syn-depositional, partially explosive, volcanic event was recognized and dated by U-Pb SHRIMP at 630.2 ± 3.4 Ma, positioning the inception of the “Camaquã Basin” at the end of the Cryogenian. Thus, the deposition of the Maricá Formation post-dates the global-scale Marinoan glaciation (660-635 Ma), possibly recording greenhouse paleoclimatic conditions. Field, petrographic and isotopic evidence supports this interpretation. The evolution of the Maricá Formation started during the collisional climax of the Brasiliano II orogenic system (Dom Feliciano orogen), thus the analyzed sedimentation could represent the infilling of a foreland basin. It is possible that correlative portions of the foreland system may be preserved in other sedimentary or metamorphic successions of the Mantiqueira Province, such as the Fuente del Puma (Lavalleja), Porongos, Brusque, Abapã (Itaiacoca), Cerro da Árvore and Passo da Capela units. The 507.3 ± 1.8 and 506.7 ± 1.4 Ma Ar-Ar step-heating ages obtained in K-feldspars from volcanogenic samples of the Maricá Formation are most likely associated with uplift and cooling below ca. 200ºC, possibly during the inception of the rift where the Camaquã Group (Santa Bárbara and Guaritas formations) accumulated.
Caracterização da Alteração Hidrotermal Micácea do Tipo Greisen e dos Reequilíbrios de Baixa Temperatura em Áreas Graníticas: o Exemplo do Distrito Estanífero de Encruzilhada do Sul, RS
Authors: TEIXEIRA ROBERTO DOS SANTOS , FRANTZ JOSÉ CARLOS , MEXIAS ANDRÉ SAMPAIO , CHARÃO MARQUES JULIANA , COSTA JORGE ALBERTO
Published: April 2019

The hydrothermal alteration associated with the tin mineralization in the Encruzilhada do Sul Tin District is characterized by zones with different compositions. The most important of these hydrothermal zones are the phyllic and the argillic. The first one is composed mainly by white mica and quartz with tourmaline. The argillic alteration is composed by kaolinite. The phyllic zones represent associations with greisens and disseminated pervasive white mica on the granitic wall rocks. The argillic zones are constrained to the top zones of some granitic intrusions associated with greisens and quartz-veins in the stockworks. The hydrothermal fluids associated with the alteration show homogenization temperatures ranging from about 450˚C to 120˚C. The first temperature is the upper limit for the hydrothermal system, related with the white mica high temperature alteration. The second temperature is the lower limit of the argillic alteration under the hydrothermal conditions. The white mica related with the phyllic alteration range from phengite to muscovite. The argillic alteration has the presence of halloysite, probably as a weathering product.
Análise Estatística da Concentração de Potássio Obtida por Aerolevantamentos Geofísicos em Diferentes Formações Geológicas na Região de Santa Maria (RS)
Authors: PEREIRA JOÃO EDUARDO DA SILVA , DA SILVA JOSÉ LUIZ SILVÉRIO , STRIEDER ADELIR JOSÉ , PIRES CARLOS ALBERTO DA FONSECA
Published: April 2019

The present work was developed in outcrops of Santa Maria region, southern Brazil, Rio Grande do Sul State. Statistic evaluations were applied in different rock types. The possibility to distinguish different geologic units, sedimentary and volcanic (acid and basic types) by means of the statistic analyses from the use of airborne gamma-ray spectrometry integrating potash radiation emissions data with geological and geochemistry data is discussed. This Project was carried out at 1973 by Geological Survey of Brazil/Companhia de Pesquisas de Recursos Minerais. The Camaquã Project evaluated the behavior of potash concentrations generating XYZ Geosof 1997 format, one grid, thematic map and digital thematic map files from this total area. Using these data base, the integration of statistics analyses in sedimentary formations which belong to the Depressão Central do Rio Grande do Sul and/or to volcanic rocks from Planalto da Serra Geral at the border of Paraná Basin was tested. Univariate statistics model was used: the media, the standard media error, and the trust limits were estimated. The Tukey’s Test was used in order to compare mean values. The results allowed to create criteria to distinguish geological formations based on their potash content. The back-calibration technique was employed to transform K radiation to percentage. Inside this context it was possible to define characteristic values from radioactive potash emissions and their trust ranges in relation to geologic formations. The potash variable when evaluated in relation to geographic Universal Transverse Mercator coordinates system showed a spatial relation following one polynomial model of second order, with one determination coefficient. The statística 7.1 software Generalist Linear Models produced by Statistics Department of Federal University of Santa Maria/Brazil was used.
Structural Constraints on Paraná Basalt Volcanism and their Implications on Agate Geode Mineralization (Salto do Jacuí, RS, Brazil)
Authors: STRIEDER ADELIR JOSÉ , HEEMANN ROBERTO
Published: April 2019

The Paraná-Etendeka Continental Flood Basalt province hosts world-class agate and amethyst geode deposits in Rio Grande do Sul (Brazil; Serra Geral Fm.). Salto do Jacuí Mining District (Rio Grande do Sul, Brasil) has different types of agate geode hosted in vesicular basalt. A series of structural features has recently been investigated in the Salto do Jacuí Mining District, and indicates at least two volcanic episodes: i) normal tholeiitic basalt and dacite eruption, and ii) vesicular basalt and dacite intrusions as sills and dikes. These structural features include: basalt and aeolian sandstone xenoliths in vesicular basalts, vesicular basalt apophyses in massive basalts, sandstone and basalt breccias, sandstone dikes cutting across vesicular lavas and connected to mixed sandstone-agate geodes, sandstone assimilation by vesicular lava, and mixed sandstone and agate geodes. These features show that agate geodes were formed by melting of Botucatu sandstone xenoliths. High density contrast between vesicular basalt and Botucatu sandstone melts makes them immiscible during flow. Botucatu sandstone xenoliths melting is favored by degasing of intrusive volatile-rich basalts. The high-silica globs crystallize dynamically in a closed-system environment, giving rise to agate banding and fibrosity.
O Método Radiométrico Rb-Sr Aplicado em Rochas Sedimentares o Exemplo da Bacia do Paraná, Brasil
Authors: DA SILVA DIOGO RODRIGUES ANDRADE , MIZUSAKI ANA MARIA , DOS ANJOS SYLVIA MARIA COUTO , CONCEIÇÃO ROMMULO VIEIRA
Published: April 2019

The Rb-Sr method has been successfully applied to argillaceous sedimentary rocks in order to supply parameters for the definition of their depositional ages. In many studied cases, despite the geologically significant results, there are doubts concerning the interpretation of the obtained data and their limitations. This happens because sedimentary rocks are considered to be the mixture of detrital fragments of diverse sources, and therefore is the possibility of contain an isotopic record of their source rocks. The Rb-Sr method, when applied to mudrocks, allows constraining absolute depositional ages, owing to the resetting of the isotopic Rb/Sr system during deposition. This process is called isotopic homogenization in the depositional environment. Some special care must be taken with respect to sampling, sample grain size, depositional setting, and mineralogical composition. Nevertheless, questions still remain when concerning this methodology, particularly on the real occurrence and extent of the isotopic homogenization in the sedimentary environments. In the present work, the Rb-Sr method has been applied to samples of sedimentary rocks collected from different units representing several depositional settings from the Paraná Basin. The parameters responsible by the isotopic homogenization of Sr have been evaluated. The obtained results allowed the improvement of the application of the Rb-Sr method to sedimentary rocks, and significant results concerning depositional ages were obtained.
A Fonte dos Metais da Mina de Ouro do Schramm, Santa Catarina: Evidências de Dados de Isótopos de Pb e Elementos Terras Raras
Authors: DA ROCHA FLÁVIO FRANÇA NUNES , NETO ARTUR CEZAR BASTOS , REMUS MARCUS VINÍCIUS DORNELLES , PEREIRA VITOR PAULO
Published: April 2019

The source of the ore elements in the Schramm gold mine, localized in central part of Santa Catarina shield, has been constrained based on lead isotope composition of galena and sulfosalts, and the rare earth element (REE) patterns of the ore. The Pb207/ Pb206 model age obtained in galena and lillianite-gustavite series from the mineralization yields an age of 1.88 Ga. It is higher than the estimated age of the deposit (» 534 Ma). The Pb isotopic composition obtained in these minerals indicates that the age of Schramm mine source is similar to that of the galena of the Ribeirão da Prata mine (Pb-Zn-Cu-Ag). This mine is located 25 Km southwest of the Schramm gold mine witch is hosted in the tension fracture zone conjugated with the first order shear zone that contains the Ribeirão da Prata deposit. The similarities between Pb-isotope compositions of both deposits could indicate that they were contemporaneous and derived from the same regional lead source. The REE patterns of the ore samples of Schramm mine are similar to that of the pyroxenites and banded iron formations from the Archean Santa Catarina Granulitic Complex that host the Schramm gold mine. They present low REE contents with flat patterns and lack Eu anomalies. The comparison among the isotopic data from this mine with those from other places indicates that the banded iron formation and mafic-ultramafic granulitic gneisses are the source of the gold mineralization. This evidence agreed with the hypothesis that the ore fluids were derived from retrogressive metamorphism reactions of Santa Catarina Granulitic Complex in the shear zones during the final stage of Brasiliano orogenic cycle.
O Emprego de Minerais Pesados como Indicador da Proveniência da Cobertura Pedológica do Arenito Caiuá na Região Noroeste do Paraná
Authors: GASPARETTO NELSON VICENTE LOVATTO , DOS SANTOS MANOEL LUIS
Published: April 2019

This paper aims the identification of the translucent heavy minerals that occur in the pedological covering at the northwestern region Paraná state (Brazil), and compare them to the minerals observed in the Caiuá sandstone that orverlies it. The origin of the pedological covering is controversial because many researches consider it to be colluvium, originated during a semi-arid climate that occurred in the Quaternary. To reach the proposed goals, morphological descriptions along the top sequences were done and samples from different profiles of the trenches were collected. A slight mineralogical diversity was observed at the pedological covering and at the Caiuá sandstone, where the main minerals are staurolite, rutile, tourmaline and zircon, followed by lower amounts of garnet, kyanite and dumortierite. This assemblage of minerals suggests a high textural and mineral maturity of the studied materials. It is an important argument concerning the origin of the pedological covering, suggesting that it was derived from the alteration processes of the overlaying sandstone, thus, confirming the residual characteristics of said materials in northwestern Paraná state.
Estratigrafia Química (COT, δ13C, δ18O) e Nanofósseis Calcários na Passagem Pliensbaquiano–Toarciano no Perfil de Peniche (Portugal): Resultados Preliminares
Authors: DE OLIVEIRA LUIZ CARLOS VEIGA , DUARTE LUIS VITOR , PERILLI NICOLA , RODRIGUES RENÉ , LEMOS VALESCA
Published: April 2019

The marl-limestone succession that encompasses the Pliensbachian–Toarcian Stage Boundary (Lower Jurassic) and crops out at Peniche (Lusitanian Basin, Portugal), was chosen as one of the candidates for the establishment of Toarcian GSSP. Chemostratigraphy analyses, of the Upper Pliensbachian (spinatum Zone)-Lower Toarcian (levisoni p.p. Zone) portion, were based on total organic carbon (TOC) (68 samples), the isotope carbon (δ13C) and oxygen (δ18O) (38 samples) on the whole rock sample. Presenting an absolute variation of around -2.0‰, the δ13C and δ18O values decrease from the middle part up to the uppermost part of spinatum Zone, with smaller values in the lowermost part of the polymorphum Zone. In the Lower Toarcian the δ13C data shows a positive trend (spread of + 2.0‰) with a maximum value in the middle-upper portion of the polymorphum Zone and a minimum in the lowermost part of the levisoni Zone. The δ18O values show a general tendency to decrease within the polymorphum Zone, with the smallest values observed in the lower portion of the levisoni Zone. In general the TOC values are low, around 0.2%, in the spinatum Zone, upwards they increase to 0.5% in the polymorphum Zone, whilst they decrease again to 0.2% in the lowermost levisoni Zone. Calcareous nannofossils assemblages were investigated in 12 slides of marly samples collected around the Pliensbachian – Toarcian Stage Boundary that, according to the adopted zonation, proposed for NW European, lies in the NJ5b biozone. Abundant and well preserved nannofossils assemblages comprise 12 genera and 18 species. The genera Schizosphaerella and Lotharingius are dominant. Calcivascularis jansae, a characteristic taxon of the Lower Jurassic tethyan nannofossils assemblages, is abundant in the whole investigated interval. Biscutum grande is the other tethyan taxon present in studied succession. The occurrences of C. jansae and B. grande support the tethyan affinity of the calcareous nannofossils assemblages recovered from the Pliensbachian – Toarcian transition sampled at Peniche section.
Recognition of Environmentally Vulnerable Depositional Facies in the Chacahua Lagoon, Oaxaca, Mexico
Authors: RÍOS FELIPE , SANDOVAL GELIA , FRÍAS ALFREDO
Published: April 2019

Over the years, human activity and environmental problems have impacted the Chacahua Lagoon in the State of Oaxaca, Mexico. In an attempt to gain more insight into the current environmental conditions of this lagoon, twenty-eight bottom sediment samples were collected in August 2003. Using depth, physical properties (grain-size and texture) and biological characteristics (organic matter and CaCO3 contents) of sediments as environmental indicators, three depositional facies were identified implementing cluster analysis, each facies seems to be under the influence of different processes. In terms of environmental concern, it was determined that the central part of the lagoon presents a high potential of pollutant sorption, thus this sector should be closely monitored.
Aspectos Geoquímicos de Silicificações em Rochas Sedimentares no Rio Grande do Sul, Brasil
Authors: DA SILVA JOSÉ LUIZ SILVÉRIO , MENEGOTTO EGYDIO
Published: April 2019

Some exposures of silicified sedimentary rocks and duricrusts occur in the central Depressão Periférica along the edge of the Paraná Basin in Rio Grande do Sul State, in southern part of Brazil. These silicified materials were firstly studied in the petrographic aspects by Silvério da Silva & Menegotto (2002). This paper presents geochemical results of the analysis on samples of sedimentary rocks and silica duricrusts collected in two profiles (Santa Maria and Cachoeira do Sul). The relationships between the sedimentary rocks and the duricrusts, as well their probable provenance and genesis, are discussed. Silicification occurs as lenses, concretions, nodules and pedotubules, in the Mesozoic sedimentary rocks of these profiles. Micro quartz predominates and forms the most part of the matrix. Fibrous chalcedony and mega quartz were present in minor amounts filling vughs. Three types of silicification were recognized: silcretes (SiO2>87%), silica rich concretions (SiO2 from 76.10 % to 86.76% SiO2) and sedimentary rocks with few silica cement. Gresen′s mass balance is presented to point out the gain of SiO2. The silica source is related to weathering processes of the minerals of the sedimentary rock and added to the groundwater.
Elementos Arquiteturais do Substrato da Lagoa dos Patos Revelados por Sísmica de Alta Resolução
Authors: WESCHENFELDER JAIR , CORRÊA IRAN , ALIOTTA SALVADOR
Published: April 2019

A high-resolution seismic survey was performed on the Lagoa dos Patos, southern Brazil. The survey was conducted aboard the research vessel LARUS of the Fundação Universidade Federal do Rio Grande. The seismic profiles were obtained using a 3.5 kilohertz frequency, which provided a rather good penetration depth and resolution of the records. Results of the seismic records allowed the determination and mapping of seismic facies and seismic sequences, as well as related architectural elements, which were identified basically through the configuration patterns of the seismic reflectors. The analysis of the seismic records allowed the identification of the architectural elements that build up the sedimentary pile accumulated in the coastal prism of the State of Rio Grande do Sul, contributing to a better understanding of the geological evolution of the southern Brazilian coastal plain during the Quaternary period.
Geoquímica das Rochas Máficas Toleíticas da Suíte Pós-Colisional Paulo Lopes, Neoproterozóico do Sul do Brasil
Authors: FLORISBAL LUANA MOREIRA , NARDI LAURO , BITENCOURT MARIA DE FÁTIMA , BETIOLLO LEANDRO MENEZES
Published: April 2019

The Paulo Lopes Suite (SPL), composed of the Paulo Lopes Granite (GPL), Garopaba Granitoids (GG) and Silveira Gabbro (GS), is an association of contemporaneous acid and basic rocks, comprising monzo and syenogranites associated to basic dikes, with abundant mafic microgranular enclaves, interpreted as co-mingling products. The contacts between the granitoids and the basic rocks are evidences of coeval and interactive magmas. The Silveira Gabbro occurs in the study area as a main body and several narrow dikes of NNE orientation. Field relations define a chronological order of magmatic events, where the GPL is the first magmatic pulse and, while steel partially crystallized, was intruded by mingled magmas, represented by the GG and the GS. The basic components are medium-grained, equigranular rocks, with subophitic and ophitic textures. The centre of the main body contains medium- to coarse-grained, equigranular rocks, where agglomerates of early-formed clinopyroxene and plagioclase crystals are found. In the chilled margins, they are microporphyritc rocks of aphanitic groundmass, indicative of rapid crystallization. The Silveira Gabbro rocks are composed of labradorite-andesine, orthopyroxene, augite, pigeonite, olivine (occasionally serpentinized), Fe-hornblende and magnesian hornblende, red biotite, magnetite, ilmenite, apatite, and baddeleyite. The composition is tholeiitic, similar to the high-Ti-P basalts of the Serra Geral Formation. Their high contents of K, Rb, Sr and Ba, as well as negative anomalies of Nb and Ta in multielemental diagrams are similar to the ones observed in magmatic rocks from mature arcs or post-collisional environments. The Neoproterozoic basic rocks may be discriminated from the ones belonging to the Cretaceous Serra Geral Formation by their higher contents of alcalis, Cs, U, Th, and by their fractionated REEpatterns, expressed in the La/LuN ratio. The associated granitoids are structural and compositionally compatible with the ones found in post collisional settings, which indicates that the SPL magmatism developed in such environment.
Aplicação do Diagrama de Pejrup na Interpretação da Sedimentação e da Dinâmica do Estuário da Baía de Marajó-PA
Authors: CORRÊA IRAN CARLOS STALLIVIERE
Published: April 2019

From statistical parameters of the bottom morphology and of the application of the diagram proposed by Pejrup(1988) it was possible to characterize the dynamic and sedimentary processes that occur in the estuary of the Marajó bay. The sediments that recover the bottom of the studied area are formed by medium to very fine sands that grade to coarse to fine silt in direction to the continental shelf. The hydrodynamic of the area is dominated by the tidal and fluvial currents as well, partly due the action of winds which influence these currents. These factors associated with the estuarine circulation, are responsible for the transport, redistribution and deposition of the sediments in the study area.
Um Novo Horizonte de Correlação para o Triássico Superior do Rio Grande do Sul
Authors: RUBERT ROGÉRIO ROQUE , SCHULTZ CESAR LEANDRO
Published: April 2019

A new biozone - called Ictidosaur Assemblage Zone - is proposed to the Upper Triassic Caturrita Formation from Southern Brazil, based on the discovery of a distinct tetrapod association characterized by the presence of little non-mammalian cinodonts including Riograndia guaibensis, Brasilodon quadrangularis and Brasilitherium riograndensis. Besides, the advanced procolophonid Soturnia caliodon, the dinosaur Guaibasaurus candelariensis, the dicynodont Jachaleria candelariensis, indeterminated phytosaurs and sphenodontids were also found in this association. The new biozone overlies the Rhynchosaur Assemblage Zone and encloses the “Jachaleria Level” usually cited for these layers. Stratigraphical sections, as well as facies analysis, facies associations and architectural elements confirms that the new biozone is clearly included in a distinct stratigraphical level, which reflects a marked change in the fluvial pattern of the sequence. The anastomosed/meandering pattern associated to the underlying Rhynchosaur Assemblage Zone turns to a braided to low confinement fluvial system with unconfined flows. The faunal and faciological changes may have been caused by a combined action of climatic, base level and floral changes, probably reflecting the global tendency to an increasing aridity towards the end of the Triassic. It is presumed an early Norian age for the new biozone on basis on its faunal content, on its stratigraphic placement, recovering the Carnian rhynchosaur assemblage and also on the presence of woods, leafs and reproductive structures of conifers, whose morphological pattern is exclusively Triassic.
Determination of Net Sediment Transport Patterns in Lirquén Harbor, Chile, Through Grain-size Trend Analysis: A Test Of Methods
Authors: RÍOS FELIPE , ULLOA RAÚL , CORRÊA IRAN CARLOS STALLIVIERE
Published: April 2019

During June 1997, bottom sediment samples were collected at 76 stations on a rectangular grid in a small port (Lirquén Harbor, south-central Chile) facing siltation problems. The spatial changes in grain-size parameters, analyzed by using three different methodologies to infer net sediment transport paths, are compared with the measured water circulation of the study area and sediment dispersal patterns on aerial photographs. A Geographical Information System (GIS) is used to determine the degree of similarity between the results of the three grain-size trend methodologies. The results of this study confirm that because of its formulation and underlying assumptions, the McLaren-Bowles methodology tends to confuse the space-scale of sediment transport processes. In this way, the obtained transport patterns are in poor correlation with the observed hydrodynamics and aerial photographs and they seem to represent a combination of the spatial macroscale and mesoscale sediment transport processes existing in Concepcion Bay and in Lirquén Harbor, respectively. On the contrary, because the results yielded by the Gao-Collins and Le Roux methodologies correlate well with these studies, it is suggested that both methodologies be applied in combination to allow a better representation of local net sediment transport patterns, especially in estuarine environments where multiple sediment sources exist. Spatial analysis suggests that transport pathways obtained through these two methodologies represent the mesoscale sediment circulation existing in Lirquén Harbor. This study also emphasizes the importance of applying a statistical test to the transport trend vectors obtained using the GSTA program of Gao (1996), as these may erroneously reflect sediment transport direction. Lastly, the analyzed data and the results of the models are combined to determine the sediment transport regime existing in Lirquén Harbor.
Primeira Notícia da Descoberta de Waimirita e Atroarita, Dois Novos Minerais na Mina de Pitinga, AM, Brasil
Authors: MINUZZI ORLANDO RENATO RIGON , FERRON JOSÉ MAXIMINO TADEU MIRRAS , BASTOS NETO ARTUR CEZAR , PEREIRA VITOR PAULO
Published: April 2019

Waimirite and Atroarite are associated with the core of the albite-granite from the Madeira Granite and occur in different places as thin veins. Waimirite is a yttrium fluoride that macroscopically form massive and white rounded aggregates. Atroarite is a alumino-fluoride and macroscopically form dark grey octahedral crystals. The DRX analyses confirm that they are new minerals.
Foram os Bivalves do Grupo Passa Dois (Exclusive Formação Rio do Rasto), Neopermiano, Invertebrados Tipicamente Dulcícolas?
Authors: GHILARDI RENATO PIRANI , SIMÕES MARCELLO GUIMARÃES
Published: April 2019

During the Late Permian Paraná Basin was a huge epeiric sea in which salinity deviated from either normal marine or freshwater, particularly in marginally environments. Sedimentological, geochemical, petrographic data and associated micro- and microflora have been used to identify such variations. Although shell morphology (paleoautoecology) and preservation (taphonomy) of bivalve mollusks could be used as an additional tool, these have been fully neglected. Previous authors based on the occurrence of charophyte oogonia in rocks of the Terezina/Corumbataí Formations (Passa Dois Group) and coeval occurrences outside the Brazilian portion of the basin, interpreted the fauna (Pinzonella illusa and Pinzonella neotropica assemblages) as typically freshwater. However, morphologic and taphonomic evidences do not corroborate this assumption: a- assimetrical sculptures and radial ornamentation found in shells of the genera Cowperesia and Ferrazia are absent in freshwater bivalve shells; b- anteriorly expanded shells (e.g., Runnegariella fragilis) are not present in mollusks that colonized freshwater environments, and c- lunule (e.g., Pinzonella, Itatamba, and Plesiocyprinella) is rare or absent in freshwater bivalves. Additionally, typical morphological features (e.g., claustrun, tubercles, shell torsion) exhibited by freshwater bivalves were not observed in the studied fauna. Assemblages including high proportion of shells with extensive solution pits concentrated in the umbonal region are common in bivalves that suffered prolonged exposures to freshwater conditions. These features have never been observed in the studied fossil record. Our data highly suggest that the reconstruction of Passa Dois Group paleosalinity must be done using a “myriad” of stratigraphic, sedimentologic, paleobiologic and taphonomic information. At this moment, we can only affirm that they were not typical freshwater mollusks. Probably, they lived in shallow water habitats, frequently affected by storms, and punctuated by episodes of intense evaporation and hypersalinity with influence of local freshwater inputs, configuring an situation of high environmental stress.
Aplicação da Estratigrafia de Seqüências para Caracterização em Multiescala de Reservatórios no Grupo Guatá (Eopermiano da Bacia do Paraná) na Região de São Gabriel - RS, Brasil
Authors: KÜCHLE JULIANO , HOLZ MICHAEL
Published: April 2019

Detailed stratigraphic analysis of the Early Permian Rio Bonito and Palermo Formations of the intracratonic Paraná Basin in the region of São Gabriel County has been used for a study on reservoir characterization of paralic sandstones. Two main depositional systems were recognized, a fluvial-dominated delta system at the base and a wavedominated barrier island system at the top, with an intervening succession characterized by a delta system with alternated wave and fluvial influence. The succession is divided in two third-order depositional sequences, enclosing thirteen fourthorder parasequences. This high-resolution stratigraphic framework was the base for a multiscale approach on reservoir characterization of the paralic sandstone bodies of the two sequences. Reservoir heterogeneities are discussed, starting from the scale of depositonal sequence (heterogeneity level 1), passing down to heterogeneity at the scale of systems tracts (heterogeneity level 2) and finalizing with an approach at parasequence scale (heterogeneity level 3). Main control on heterogeneity at the first level - depositional sequences - is base-level variation as generating mechanism for unconformities (sequence boundaries) and the sediment type and rate. At the second level -systems tracts - the reservoir heterogeneity is controlled by the lateral and vertical variations in thickness of particular systems within the different systems tracts and by the stratigraphic signatures of the bounding surfaces (sequence boundaries, transgressive surfaces and flooding surfaces), and at the third level the minor flooding surfaces control internal heterogeneity, reservoir continuity and connectivities between reservoirs. At this scale, five paralic reservoir bodies were recognized, with thickness range from 5 to 25 meters. The study has a twofold importance: it is useful as a predictive tool for similar geologic settings in producing oil fields, and may also be used for geologic characterization of the aquifer in the study area.
Aproveitamento Industrial do Mármore da Sequência Metavulcano-Sedimentar Marmeleiro, Rio Grande do Sul, Brasil. Dados Petrográficos e Químicos
Authors: SIVIERO ROSEMERI SOARES , PULZ GÊNOVA MARIA
Published: April 2019

This study presents chemical and petrographic properties of marble of the Marmeleiro metavolcano-sedimentary sequence, Southern Brazil. This rock is characterized by 80% of the pure calcite, 48 to 53.3 wt.% of CaO, 0.32 to 0.86 wt.% of MgO and neutralizing value between 75 and 91%. The elevated loss on ignition this rock makes possible the production of considerable amounts of CaO after calcinations. These characteristics are adequated for manufacture of Portland lime, as well as for agricultural lime.
Morfodinâmica da Praia do Cassino, RS
Authors: TOZZI HEITOR AUGUSTO DE MORAES , CALLIARI LAURO JULIO
Published: April 2019

The Cassino beach morphodynamic oscillates between the dissipative and intermediate states, accumulating sediments in the primary dunes and in long shore bars of combat to South Atlantic Western coastal storms. Approximately five years (1991-1996) of daily littoral environmental observations of wind, waves, long shore currents and beach width allied to coastlines transverse topographical profiles promoted a qualitative methodology which determined the physical agent's regime and its influences in the sedimentary beach stock and morphodynamic states. Three main incidence angles, South. Southeast (perpendicular to the coastline) and East were characterized in relation to the following factors: wave regime. omega parameter (W = Hb/Tp.Ws) and the mean sea level oscillations. The meteorological tides (storm surges) condition the destruction of the close bars to the beach face and occasionally the frontal dunes. These high wave energy events (hangover) are frequent for the South quadrant (12% a year). The Southeast quadrant (42% occurrences) presents conditions of swell which determine times of dynamic balance of the morphology. These conditions facilitate the development of an intermediary state with long shore bars troughts smaller variations in the sedimentary stock but significant alterations in the bars form. The East quadrant (46% a year) constantly governed by moderate winds and local waves with rare events of swell favours the enlargement to the backshore and coalition of the first bar with the beach face, typical intermediate state of beach in construction. The constructive intermediary state facilitates the largest beach sedimentary variation volume as it becomes more susceptible to strong storms (autumn storms). The dissipative state presents smaller mobility trought the soft slope, leaving the concave beach face, concentrating the storm effect in the surf zone and frontal dunes. We characterized periods of constructive and destructive beach profiles. where the omega parameter evidenced oscillations among the dissipative modal state, of larger frequency in the autumn and winter, and secondary intermediate states in the spring anti summer.
Arcabouço Cronoestratigráfico do Eopermiano da Bacia do Paraná na Região Centro-Oeste do Rio Grande do Sul
Authors: ELIAS ANDRÉIA REGINA DIAS , GARCIA ANTÔNIO JORGE VASCONCELOS , LAVINA ERNESTO LUIZ
Published: April 2019

The chronostratigraphic framework of the Rio Bonito and Palermo formations (Artinskian-Kungurian) of the Paraná Basin in Southern Brazil presented here was based on the Sequence Stratigraphy approach. This interval was subdivided into four 3rd order (2-3Ma) depositional sequences (A, B, C and D). these sequences, as a whole, include facies associations interpreted as transitional depositional systems (lowstand systems tract) which were progressively overlain by shallow marine systems (transgressive systems tract) until a relative stability was achieved and deeper marine conditions were established (highstand systems tract). All depositional sequences are bounded by unconformities which are related to the glacioeustasy with some local tectonic influence. Third order transgressions were probably superimposed to a larger scale basement rocks, during the deposition of the middle portion of depositional sequence C.
Indicatives of ancient conditions of sea level stability on the southern Pernambuco continental shelf
Authors: MICHELLI MAXIMILIANO , ARAÚJO TEREZA , MAIDA MAURO , VITAL HELENICE
Published: April 2019

The continental shelf in southern Pernambuco State (Brazilian Northeast) is characteristically narrow, and breaks around 32km from the actual coastline, in depths of 50 to 60m. The sediments on this shelf are similar in their constitution to the rest of the Brazilian Northeastern shelf, showing a prevailing fraction of coarse carbonatic sands. There is also a significant input of terrigenous material, which may be found mainly up to 20m deep. Regarding it’s geomorphology, Pernambuco’s southern shelf presents a soft slope, with long and smooth surfaces, sometimes crossed by meandering channels which show more frequently next to river mouths. Indicatives of sea level change like the presence of beach rocks and paleochannels occur along the shelf. The main interest of the present work lies on the location and characterization of the submerged beachrocks on the southern portion of Pernambuco State continental shelf. The area was investigated using sonographic techniques. Data analysis allowed to identify indicatives of ancient conditions of sea level stability on the shelf. The first evidence was found at a depth of 20m, where a beachrock of a triangular shape and rounded top with 136m wide and 6m height, was identified. The second evidence was registered at 40 to 50m depth also represented by a beachrock. Geomorphologically this second feature presents a relatively flat top, 209m of width and 4m height. Another structure indicative of sea level change identified was a paleochannel, which started at 30m depth and followed the direction northwest-southeast on the shelf.