Artigos Científicos - FAGEO/IG

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Riscos socioeconômicos e ambientais em municípios banhados pelos afluentes do Rio Amazonas
(Universidade Federal do Pará, 2017-10) COUTINHO, Eliane de Castro; ROCHA, Edson José Paulino da; LIMA, Aline Maria Meiguins de; RIBEIRO, Hebe Morganne Campos; GUTIERREZ, Lucy Anne Cardoso Lobão; BARBOSA, Ana Julia Soares; PAES, Gleicy Karen Abdon Alves; BISPO, Carlos José Capela; TAVARES, Paulo Amador
Municipalities in the Amazon are constantly affected by droughts and floods, and these socioeconomic and environmental risks mainly affect the local population. These precipitation extremes cause severe changes in rivers' hydrology, on both a temporal and a spatial scale. The intended objective of this study therefore was to determine the socioeconomic and environmental risk of municipalities affected by the tributaries and by the main channel of the Amazon River in relation to extreme precipitation events. We used monthly and annual precipitation data from 1982 to 2012 and social data from 2010 (urban, elderly, female and child populations, income and education level) for 47 localities in the Amazon Basin. We concluded that the risk was highest during flood events, particularly in smaller states (Acre and Roraima), and that vulnerability was greater in larger states (Amazonas and Pará). However, the population in the municipalities along the Amazon River have moderate to very strong socioeconomic and environmental risk because of the vulnerability associated with high urbanization and poverty, and threat of floods and droughts ranging from moderate to high.
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Avaliação tecnológica de cerâmicas tradicionais incorporadas com rejeito do minério de manganês
(2014-12) RODRIGUES, L. dos S.; SILVA, J. C.; ANGÉLICA, Rômulo Simões; RABELO, A. A.; FAGURY, Renata Lilian Ribeiro Portugal; FAGURY NETO, Elias
The ceramic industry has a great environmental role when it comes to recycling waste. The industrial production that has been developed in the Northern Region of Brazil makes room for use of waste as a substitute raw material in the production of ceramics. This substitution in addition to the environmental advantage also provides interesting physical characteristics in the ceramics produced. This work aimed to study the effects caused by the incorporation of manganese ore tailings in formulations of ceramic clay, to examine the extent to which it is possible to incorporate this waste without prejudice to the product properties. It was proposed some formulations containing varying amounts of tailings. The ceramic bodies were shaped and sintered at 1000 ºC to 1200ºC for 2 h. Results demonstrated that the material showed a decreasing in the porosity and water absorption, and an increasing in the bending strength as a result of the densification promoted by the tailing incorporation which acts as fluxing agent.
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Estratigrafia da faixa de dobramentos Paraguai-Araguaia no centro-norte do Brasil
(1997-12) HASUI, Yociteru; ABREU, Francisco de Assis Matos de; SILVA, José Maurício Rangel da
The Paraguai-Araguaia Fold Belt, constituted during the Brasiliano Cycle, extends to the north of Bananal Island, with submeridian trend. Between the 9º 30'S and 3º30'S parallels, the fold belt is represented by the Baixo Araguaia Group, an ophiolitc belt, some granitic bodies and by the Rio das Barreiras Formation. The Baixo Araguaia Group comprises three formations named, from the bottom to the top, Estrondo, Couto Magalhães and Pequizeiro, the latter one being of magmatic-sedimentary characted related to the ophiolitic belt. The ophiolitic belt is associated to the Tocantins-Araguaia geosuture, which seems to be manifested at the surface only in the northern region by a thrust fault, where glaucophanitic greenschist facies rocks have been recognized. The fold belt evolution shows a western trending polarity for the geosynclinal phenomena, except for the basic-ultrabasic magmatism.
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Considerações filogenéticas e biogeografia histórica dos malacostráceos (decápodes e isópodes) cenozóicos do Brasil
(2010-03) TÁVORA, Vladimir de Araújo; PAIXÃO, Gleicy Mara Carvalho; SILVA, Fabrício Araújo da
This work deals the analysis of the Historical Biogeography of the brazilian cenozoic paleocarcinofauna, recorded in the Maria Farinha, Tremembé and Pirabas formations. This taxa has affinity with the tethian carcinofaunas and modern aspect. The paleobiogeographic setting allows to situate their biological events of the origin, dispersional and irradiation trends in the tethian, south high latitude and amphitropical origins. The majority of the brazilian carcinofauna has affinity with the tethian faune, that migrate in two seaways, west and east. The phylogenetic relationships suggest appearence of the Thalassinoidea group from the Caridea infraordo. The Retroplumidae family (genus Costacopluma) recorded at Maria Farinha Formation is directed related with the cenozoic ocypodid (i.e. genus Uca at Pirabas Formation, living in the same ecological niches and environmental tolerances. Also, the morphological similarities between Xanthoidea and Portunoidea in the Paleocene, suggest monophyletic relationships with Goneplacidae and Hexapodidae. The detailed phylogenetic studies in Goneplacidae family reveals that Glyphithyreus genus is related with Eucratopsinae subfamily.
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Sedimentação coluvial pleistocênica na região de Presidente Figueiredo, nordeste do estado do Amazonas
(2009-06) SARGES, Roseane Ribeiro; NOGUEIRA, Afonso César Rodrigues; RICCOMINI, Claudio
This paper describe Upper Pleistocene colluvial deposits in the Presidente Figueiredo region, northestern State of Amazonas, Brazil. Outcrop-based sedimentologic and stratigraphic study, integrated with geomorphologic analysis and optically stimulated luminescence dating, allowed to characterize the architecture and lithofacies of these sedimentary successions and provided information about the denudation history and landscape changes in the central Amazonian region during the Pleistocene. The colluvial deposits consist of sands and mainly matrix-suppported gravels with massive beddding, locally with inverse grading, suggestive of deposition by gravitaty and torrential flows. Two types of colluvial deposits were identified: Colluvial deposits 1, dated at 57.000±5.000 years BP, constituted of gravels and sands with fragments of pelite, lateritic crusts and ferruginous sandstone, overlying Early Paleozoic rocks; and Colluvial deposits 2, yielding 22.100±2.600 years BP, consisting of gravels with fragments of semi-flint kaolin and lateritic crust, overlying Cretaceous kaolinic silciclastic deposits of the Alter do Chão Formation. The types of fragments indicate as sources Phanerozoic weathered rocks and lateritic bauxitic and ferruginous laterites which were removed during denudation of plateau. The two colluvial events described here seem to confirm that the main phases of geomorphogenesis are correlated with periods of forest retreat related to the two dry climatic events recorded during the Upper Pleistocene in Amazonia.
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Granitóides proterozóicos como marcadores da evolução geotectônica da região nordeste do Pará, Brasil
(2009-12) PALHETA, Edney Smith de Moraes; ABREU, Francisco de Assis Matos de; MOURA, Candido Augusto Veloso
Granitoids cropping out inside Phanerozoic sedimentary cover in northeast Pará, Brazil (Gurupi region), records the geotectonic evolution of this region. 207Pb/206Pb single zircon evaporation ages were obtained for different granitoid bodies of the region, besides Sm-Nd isotopic studies. Almost all the plutons are genetically related with regional geological processes operative during this crustal segment formation, which includes the São Luís Craton. Such processes are associated with amalgamation of island arcs and Archean nuclei during the Palaeoproterozoic (2.15 to 2,07 Ga). The reworking of the southwestern margin of the São Luís Craton at the end of the Neoproterozoic formed the Gurupi Belt and is recorded by the occurrence of a granitic pluton of 549 ± 4 Ma.
Acesso aberto (Open Access)
Evolução geológica das sequências do embasamento do Cinturão Araguaia na região de Paraíso do Tocantins (TO), Brasil
(2013-09) ARCANJO, Silvia Helena de Souza; ABREU, Francisco de Assis Matos de; MOURA, Candido Augusto Veloso
Isotopic studies based on single zircon Pb-evaporation and Sm/Nd (whole rock) methodologies, allowed advances at the lithostratigraphic scene and geologic evolution of basement, in the south segment of Araguaia Belt. The identified geological processes took place from the Achaean (2.6 Ga and TDM ages varying between 2.78 and 3.25 Ga) through Neoproterozoic Era. The Paleoproterozoic ortognaisses, represented by Rio dos Mangues Complex, are placed between 2.05 and 2.08 Ga, and they were formed from a mantellic and youthful source, with a small crustal contribution where TDM ages are 2.35 e 2.21 Ga. At the end of the Paleoproterozoic, a strong crustal shortening happened, and a partial melting of isolated and thickening compartments were facilitated, generating some igneous bodies (1.85 and 1.82 Ga) and Serrote Granite (1.86 Ga), that comes from sources situated between 2.50 and 2.43 Ga. At the end of the Mesoproterozoic, the region was marked by taphrogenetic processes, evidenced by the appearance of alkaline magmatism (1.05 Ga), beyond depositional basins, amongst which the one that received the sediments that had originated the supracrustals of Araguaia Belt. Through the inversion in the geodynamic conditions, in the Neoproterozoic, a process of horizontal shortening with crustal thickening and distinct volumetric and spatial melting occurred, which may have generated Matança and Santa Luzia Granites. The Araguaia Belt was built from this tectonic motion. The tectonic mass transport in the Amazonian Craton might have occurred, resulting in the current architecture in the form of imbricate fans.
Acesso aberto (Open Access)
A seção-tipo da Formação Serra do Quilombo, Grupo Araras, Neoproterozoico da Faixa Paraguai Norte, Mato Grosso
(2013-06) MILHOMEM NETO, João Marinho; NOGUEIRA, Afonso César Rodrigues; MACAMBIRA, Moacir José Buenano
After the last Cryogenian glaciation (ca. 635 Ma), large carbonate platforms were developed in several cratonic regions of the Earth and, despite the intense dolomitization of these deposits, paleoceanographic and paleoenvironmental pieces of information are preserved. One of the most important examples of this period in Brazil are the dolostones of Serra do Quilombo Formation, which belong to the upper portion of the Araras Group, exposed in the northern Paraguay Belt, south of the Amazonian Craton. The stratigraphic revaluation of this formation in its type-section and in a reference section in the Nobres region, based on facies and stratigraphic analyses, allowed to enlarge the paleoenvironmental interpretations and to propose a depositional model. The study succession of 140 m thick includes Serra do Quilombo Formation in sharp basal contact with the limestones of Guia Formation and the gradual contact, to the top, with the sandy dolostones of Nobres Formation, at the top. Serra do Quilombo Formation comprises a shallowing upward succession, which includes two facies associations: 1) deep to moderately shallow carbonate platform, composed of laminated dolostone rich in organic matter and a massive to laminated dolostone; and 2) storm influenced shoreface, consisting of hummocky/swaley to planar stratified sandy dolostone, sandy/oolitic dolostone with wave cross laminations and matrix-supported dolomitic breccias. Serra do Quilombo Formation represents the progradational record of a high-stand system tract, in a homoclinal carbonate ramp, installed on the southern part of the Amazonian Craton during the Ediacaran.
Acesso aberto (Open Access)
Retenção do dimetoato e sua relação com pH e teores de argila e matéria orgânica nos sedimentos da zona não-saturada de uma microbacia no nordeste paraense
(Instituto Nacional de Pesquisas da Amazônia, 2007-06) LIMA, Lilianne Maia; SOUZA, Eliene Lopes de; FIGUEIREDO, Ricardo de Oliveira
On smallholder farms of eastern Amazonia, in particular the northeast of the Pará state, heavy by pesticide applications at industrial half-perennial crops are very common. Due to their large use, mainly the dimethoate, in the catchment of the Cumaru stream, Igarapé-Açu county, we evaluated the retention process of this compound in samples of the non saturated zone, as well as verified the effects of soil pH and clay and organic mater contents in this process. Among the main pesticides the farmers use in this region, dimethoate was selected for this study, due to its larger leaching potential according to the GUS (Groundwater Ubiquity Score) index. A sorption experiment was carried out to evaluate the retention of the dimethoate in sediments in the non saturated zone. The experiment showed that the sorption of the dimethoate varied from 2.5% to 36.2% (initial concentration of 20 mg.l-1) and from 6.2% to 31.0% (initial concentration of 10 mg.l-1). These data demonstrate a high contamination potential of the groundwater by this compound, mainly due to its high mobility and low retention capacity. The dimethoate sorption rates were positively related to organic matter content in the sediments. On the other hand, values have an inverse relationship with the sorption rates of dimethoate, while clay content did not produce any effect on its retention.
Acesso aberto (Open Access)
Synthesis and characterization of zeolite NaP using kaolin waste as a source of silicon and aluminum
(2014-08) HILDEBRANDO, Edemarino Araujo; ANDRADE, Christiano Gianesi Bastos; ROCHA JUNIOR, Carlos Augusto Ferreira da; ANGÉLICA, Rômulo Simões; DIAZ, Francisco Rolando Valenzuela
The synthesis of zeolite NaP using kaolin waste, from the Amazon region, as a predominant source of silicon and aluminum has been studied. The zeolitisation process occurred in hydrothermal conditions using static autoclaving and the effects of time, temperature, and the Si/Al ratio were investigated. The starting material and the phases formed as reaction products were characterized by XRD, SEM and FTIR. The results showed that pure zeolite NaP is hydrothermally synthesized, at 100 °C for 20 hours, using metakaolin waste material in alkaline medium in presence of additional silica. The XRD and SEM analyses indicate that the synthesized zeolite presents good crystallinity.
Acesso aberto (Open Access)
Application of bauxite waste from amazon region in the heavy clay industry
(2013-12) HILDEBRANDO, Edemarino Araujo; SOUZA, José Antônio da Silva; ANGÉLICA, Rômulo Simões; NEVES, Roberto de Freitas
In this work, a method was developed for the application of red mud, an alkaline leaching waste, from a bauxite processing plant located in northern Brazil (Amazon region) as starting material for heavy clay products. Samples were prepared by pressing blends of red mud and clay, which were then fired at temperatures from 900 ºC to 1190 ºC. Characterization was carried out by chemical analysis, differential thermal analysis (DTA) and X-ray diffraction (XRD), and the following ceramic properties were evaluated: water absorption, linear shrinkage and flexural strength. In order to evaluate the Na+ stability in the dense ceramic, leaching tests were also carried out on the specimens after sintering process. Results indicated that samples with 50 and 70 wt% of red mud are proper for being used in the production of ceramic bodies, due to its excellent properties, mainly high mechanical resistance and low water absorption, showing thus, an option to minimizing the environmental impacts caused by the aluminum industry.
Acesso aberto (Open Access)
Facies analysis of the Codó formation (Late Aptian) in the Grajaú area, Southern São Luís-Grajaú Basin
(2004-12) ROSSETTI, Dilce de Fátima; PAZ, Jackson Douglas Silva da; GÓES, Ana Maria
Facies descriptions of the Codó Formation in the Grajaú area are provided for the first time, and its sedimentary characteristics compared to those from the Codó area to allow paleoenvironmental reconstructions. Deposits in the Grajaú area include evaporites, limestones and argillites bearing features indicative of a shallow, low energy, subaqueous, saline environment exposed to meteoric and/or capillary conditions. Floodingevaporative concentration-desiccation cycles suggest a saline pan complex surrounded by extensive evaporitic mudflats. The location of the system, whether coastal or inland, is a matter open for debate. However, the later hypothesis is favored considering: 1. Sr isotopic data, with values higher than those expected for Late Aptian marine waters; 2. calcitic composition of limestones (instead of dolomitic and/or magnesitic as expected in coastal settings); and 3. presence of continental ostracods and lack of marine fauna. This interpretation is consistent with that proposed for UpperAptian deposits of the Codó area, but the depositional system there was one dominated by more stable, well-stratified, anoxic waters and evaporite precipitation in central lacustrine areas, while in the Grajaú area the salt pan was more oxygenated and ephemeral, with salt precipitation mainly in marginal areas or along surrounding mudflats.
Acesso aberto (Open Access)
Proveniência de arenitos albianos (Grupo Itapecuru), borda leste da bacia de São Luís-Grajaú, Maranhão, usando análise de minerais pesados e química mineral
(2009-04) MENDES, Anderson Conceição; TRUCKENBRODT, Werner Hermann Walter
Albian deposits from the São Luis-Grajaú Basin, formerly recognized only in the subsurface, have been recently found along the Itapecuru river, eastern part of this basin. These deposits consist of red, gray to greenish mudstones, cross-bedded and massive sandstone and subordinately limestones, interpreted as deposits of a to ENE/E and ESE prograding delta connected to a restricted platform. In order to understand the provenance of Albian sandstones, 18 samples were collected for heavy mineral analysis (fraction 0,062-0,125 mm) using a conventional petrographic microscope and scanning electron microscope. The sandstones have been classified as moderately to well sorted, dolomite-cemented quartz-arenites whose heavy-mineral suite consists of zircon (4-70%), garnet (12-74%), tourmaline (3-20%), staurolite (1-9%), rutile (1-8%) and baryte (0-55%), while kyanite, anatase (authigenic), calcic-amphibole, andalusite, sillimanite, spinel and ilmenite occur more rarely. The majority of the grains is angular irregular, but well rounded grains, particularly tourmaline and zircon, are also present. Surface textures include conchoidal fractures, percussion marks in V and diminute pits, the latter in rounded tourmaline and zircon grains, while corrosion features are mainly present in baryte (rhombic cavities), kyanite, staurolite (surface mammillae) and garnet (well-formed etch-facets). Zircon grains, with oscillatory zoning textures, U/Th ratio ≥ 0,5 and mean Zr/Hf ratio of 29, are mainly derived from granites and probably migmatites. Plots on Zr/Hf-Y and Hf-Y-Nb diagrams show that this mineral can be related to at least two different sources. The tourmaline types, determined as dravite and schorl, indicate provenance mainly from aluminous and/or Al-poor metapelites and metapsammites with smaller contribution from granitic and meta-ultramafic rocks. Garnet is rich in almandine and has relatively low spessartine, grossular and pyrope contents whose potential source rocks are low- to medium-grade metamorphic rocks and granites. Based on their heavy-mineral suite and the progradation of the delta system to ENE/E and ESE, the most likely source areas of the studied Albian sandstones are the São Luís Craton, the Neoproterozoic Araguaia and Gurupi belts as well as the Paleozoic Parnaíba Basin, the latter supplying sediments of rounded grains.
Acesso aberto (Open Access)
Estratigrafia da sucessão sedimentar Pós-Barreiras (Zona Bragantina, Pará) com base em radar de penetração no solo
(2001-08) ROSSETTI, Dilce de Fátima; GÓES, Ana Maria; SOUZA, Lena Simone Barata
Ground penetrating radar (GPR) is a geophysical method that consists in the emission of electromagnetic waves of high frequency (between 10-2500 Mhz). This equipment has been increasingly applied for mapping of physical properties and chemical compositions of rocks at shallow depth, as well as for stratigraphic and facies analysis. The application of this methodology in Brazil is still reduced to a few studies, mostly emphasizing soil stratigraphy and eolian paleoenvironments. However, previous studies undertaken in northern Brazil have demonstrated that, in combination with traditional studies using outcrop data, the GPR might be a powerful additional tool to help correlating sedimentary successions and reconstruct depositional environments throughout the Neogene in the Bragantina Zone. In this paper, we will document a pioneer investigation applying a SYR-2 GPR system (Geophysical Survey Systems Inc.) in the Praia do Atalaia area, Salinópolis, northern Brazil, which allowed us to characterize, for the first time, facies and stratigraphy of the deposits known informally as Pós-Barreiras Sediments (Pliocene and younger). The equipment was operated using a 200 Mhz monostatic antenna in continuous mode. The acquired sections were processed using the RADANWIN software in order to increase the reflection resolution and thus allow a refined interpretation of the sections. Based on this procedure, it was noticed that the studied sedimentary succession overlies unconformably the Miocene basement, represented by the Pirabas/Barreiras formations. Three stratigraphic units were also distinguished. The lowermost Unit 1 consists of an interval up to 6 m thick dominated by poorly-defined, low amplitude reflections, which intergrade with medium-scale, tangential oblique and hummocky reflections. This unit revealed to be discontinuous throughout the studied radar sections, occurring mainly where the Miocene basement is depressed. The middle Unit 2 is circa 9 m thick and mostly includes large-scale oblique reflections varying in style from parallel, tangential, sigmoidal to sigmoidal complex. The two latter ones might reach up to 7 m thick. A strong, high amplitude and laterally continuous reflection marks the top of Unit 2, forming a bounding surface having local depressions of up to 40 m in relief. The uppermost Unit 3 corresponds to an interval ranging from 3.5 to 9 m thick, which is dominated by hummocky reflections, followed by medium-scale oblique, parallel to sub-parallel and cut and fill reflections. The GPR data allows the interpretation that the Pós-Barreiras Sediments were unconformably deposited over the Miocene deposits, as revealed by the mapping of an erosional bounding surface at the base of Unit 1. In addition, the analysis of internal reflection configurations and reflection geometries led us to propose that the Pós-Barreiras Sediments is more variable in terms of facies than previously thought, including eolian deposits (coastal dunes), as well as beach ridge, tidal flat, channel and mangrove deposits. Furthermore, the mapping of the three stratigraphic units described above is important to unravel the complexity of sedimentation versus erosion during the latest Neogene in northern Brazil. The conclusions obtained from the GPR data lead to suggest a drop in relative sea level after the end of the Miocenelower Pliocene in the Bragantina Zone, which was followed by a transgression and deposition of Unit 1 along embayments and adjacent eolian dunes and/or beach ridges. Renewed phase of relative sea level drop took place, which led to erosion of the uppermost portions of Unit 1, forming a bounding surface that is locally cut by fluvial channel scouring. Large-scale eolian dunes laterally intergraded with tidal flat, filling the depressions formed by channel erosion during a subsequent transgressive phase. At least one more drop in relative sea level appears to have taken place in the study area, as revealed by the discontinuity surface between units 2 and 3, which is in turn mantled by modern sedimentation along mangroves, tidal channels and coastal dune environments.
Acesso aberto (Open Access)
Araçatuba formation: palustrine deposits from the initial sedimentation phase of the Bauru Basin
(2003-06) FERNANDES, Luiz Alberto; GIANNINI, Paulo César Fonseca; GÓES, Ana Maria
The Bauru Basin (Upper Cretaceous) accumulated an essentially sandy continental sedimentary sequence. In a first desertic phase the basaltic substratum was covered by a widespread and homogeneous aeolian sand unit with minor loess intercalations. The substratum relief favored the formation of an endorheic drainage system under semi-arid climate, a process that started the development of the Araçatuba Paleoswamp. The palustrine deposits (Araçatuba Formation) comprise siltstone and tipically greenish gray narrow tabular strata of sandstone cemented by carbonate. Moulds and gypsite and dolomite pseudomorphs were identified. The moulds seem to be genetically associated with desiccation cracks, root marks and climbing ripple lamination levels, that, on the whole, indicate calm shallow saline waters undergoing phases of subaerial exposition. At the boundaries of the study area, sand units may exhibit sigmoidal features and convolute bedding structure, which is characteristic of marginal deltaic deposits. TheAraçatuba Formation is enclosed in and later overlaid by the aeolian deposits of the Vale do Rio do Peixe Formation.
Acesso aberto (Open Access)
Heavy mineral as a tool to refine the stratigraphy of kaolin deposits in the Rio Capim Area, Northern Brazil
(2007-09) GÓES, Ana Maria; ROSSETTI, Dilce de Fátima; MENDES, Anderson Conceição
Studies of heavy minerals in kaolin deposits from the Ipixuna Formation in the Rio Capim area (Northern Brazil) showed a mature to super mature assemblage dominated by zircon and tourmaline, and subordinately rutile, kyanite and staurolite. These minerals do not change much throughout the whole section; however, each kaolin unit displays a particular signature, defined by differences in the proportions of the whole assemblage of heavy minerals, as well as of their textural characteristics. This work revealed that the lower and upper kaolin units can be definitely considered as distinct depositional sequences. A higher proportion of opaque minerals and higher zircon values characterize the lower unit. The higher volumes of anhedric, rounded to sub-rounded grains of zircon and tourmaline in the upper unit suggests that this includes grains that were undergone to a higher degree of reworking. The increased volume of unaltered staurolite and kyanite in the upper unit leads to conclude that, even considering sediment reworking, a distinct source must be invoked. The results also show that the characteristics of the heavy mineral assemblage from the intermediate unit are comparable with those from the upper unit, which suggests they might record a same stratigraphic sequence.
Acesso aberto (Open Access)
Mineralogia e química dos sedimentos de fundo do médio e baixo Madeira e de seus principais tributários: Amazonas - Brasil
(Instituto Nacional de Pesquisas da Amazônia, 2011) QUEIROZ, Maria Mireide Andrade; HORBE, Adriana Maria Coimbra; MOURA, Candido Augusto Veloso
This study reports the granulometric, mineralogic and chemical analyses, including Pb isotope, carried out on the bottom sediments of the Madeira River, whose headwaters are in the Andes Mountain, and its tributaries that come from the cratonic region, in order to investigate the compositional variation of the sediments transported by the major rivers of the Amazon. The analytical data show that the bottom sediments of the Madeira River have higher amounts of sand and quartz, and lower contents of Al2O3, Fe2O3, K2O, MgO, Na2O, PF, TiO2O, P2O5, MnO and trace elements, and the maturity increases toward downstream. Among the tributaries, the bottom sediments from Machado and, secondarily, Marmelos rivers are those that more closely match the composition of the sediments of Madeira River. The sediments of Jamari River, with higher proportion of Ti2O, Zr, Y, Nb, Ga, Hf, U, Ta and REE, are quite distinct. In spite of the intense weathering and erosion, in humid tropical conditions, that the rocks drained by the Madeira river basin have been submitted, the Th/Co, Th/Pb, Th/Yb, Al/Pb, Zr/Co ratios and Pb isotope data indicate that different sources contributed to the bottom sediments. It is suggested that mafic rocks are the main source of the sediments of the Madeira River, while felsic rocks are the source of the tributaries.
Acesso aberto (Open Access)
Hidroquímica do rio Solimões na região entre Manacapuru e Alvarães: Amazonas - Brasil
(Instituto Nacional de Pesquisas da Amazônia, 2009) QUEIROZ, Maria Mireide Andrade; HORBE, Adriana Maria Coimbra; SEYLER, Patrick Thierry; MOURA, Candido Augusto Veloso
The present study evaluated the physical and chemical characteristics of the water of the rivers Solimões, Purus and their tributaries, collected in November of 2004 in the State of Amazonas between the cities of Manacapuru and Alvarães and Anamã and Pirarauara. Physical-chemical analyses (temperature, pH, electrical conductivity, turbidity, Ca2+, Na+, K+, Mg2+, HCO3-, SO42-, Cl-), and trace-elements (Li, B, Al, Sc, V, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Rb, Sr, Mo, Cd, Sb, Cs, Ba, Pb, La, Ce e U) and Sr isotopes were accomplished. The analyzed parameters and the chemical composition show that the waters of the rivers and tributaries of the central region of the Amazonia are chemically distinct between them. The white waters of Solimões are calcium-bicarbonate and of Purus are bicarbonates, and the respectives tributaries are sodium-potassium-bicarbonate and sodium-potassium-sulphate. This causes the white poorly acided waters to the neutrals and more conductives, while the black ones are less mineralized, more acids, mainly of Purus. The Ba, Sr, Cu, V e As in highest levels differentiate the Solimões white waters of the Purus`s waters, well as the tributaries of the first related to the second. This complex of caracteristics indicates that the Solimões as the Purus and their respectives tributaries are submitted to geological/ambiental distinct conditions. The influence of arrives in port of sediments of Andes is diluted at the currency of basin of the Solimões and it reflects on formation of fertile valleys Solimões and Purus. By another view, the crust rocks, represented by the Shields of the Guianas and Brasileiro both contribute, but in a reduced proportion.
Acesso aberto (Open Access)
Evaluation of two genera of benthic foraminifera for down-core paleotemperature studies in the western south atlantic
(2006) COSTA, Karen Badaraco; TOLEDO, Felipe Antonio de Lima; PIVEL, María Alejandra Gómez; MOURA, Candido Augusto Veloso; CHEMALE JUNIOR, Farid
In this study we have compared the oxygen isotopic composition of two genera of benthic foraminifera (Uvigerinaand Cibicidoides) from core-top samples with modern oxygen isotopic composition of seawater (d18O). Based on a new relationship between d18O and salinity for the mid-latitude western South Atlantic, we estimated the isotopic composition of equilibrium calcite (d18Oeq) using two different equations: (1) O'Neil et al. (1969), modified by McCorkle et al. (1997) and (2) Kim & O'Neil (1997). When using (1), the small difference between d18Oeq and d18O of Uvigerina suggests that this genus precipitates its shell close to equilibrium with ambient seawater. The d18OCibicidoides data are 0.82 ‰ lower than the predicted (equilibrium) oxygen isotopic composition. Conversely, using (2) the Cibicidoides d18O data show excellent agreement with the oxygen isotopic composition predicted from d18O and water temperature while Uvigerina d18O data are 0.69 ‰ higher than predicted oxygen isotope equilibrium values. Based on the evidences presented here and on the results from previous studies we suggest using the genus Cibicidoides and applying Kim & O'Neil's (1997) equation for down-core paleotemperature investigations. In the absence of enough Cibicidoides specimens we suggest using Uvigerina d18O data and applying a correction factor of -0.69 ‰.
Acesso aberto (Open Access)
Determinação da composição isotópica de estrôncio em águas naturais: exemplos de sua aplicação em águas subsuperficiais da zona costeira na região Bragantina-PA
(2007) BORDALO, Adriana Oliveira; MOURA, Candido Augusto Veloso; SCHELLER, Thomas
Analytical procedures used for determining the concentrations and isotope composition of strontium in subsurface waters, by mass spectrometry, are described. Sampling was performed in coastal plateaus, salt marsh and mangrove environments in the coastal region of Pará. Coastal plateau waters have δ87Sr between 1.51 and 6.26‰ and Sr concentration bellow 58 ppb. Salt marsh waters show δ87Sr between 0.55 and 0.90‰ and Sr concentration between 93 and 114 ppm, while mangrove waters have δ87Sr around zero and Sr concentration above 15 ppm. Differences in the 87Sr/86Sr ratio in these subsurface waters are detected, as well as seasonal variations in the coastal pleteau waters.