Programa de Pós-Graduação em Geologia e Geoquímica - PPGG/IG
URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2603
O Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA) surgiu em 1976 como uma necessidade de desmembramento do então já em pleno desenvolvimento Curso de Pós-Graduação em Ciências Geofísicas e Geológicas (CPGG), instalado ainda em 1973 nesta mesma Universidade. Foi o primeiro programa stricto sensu de Pós-Graduação (mestrado e doutorado) em Geociências em toda Amazônia Legal. Ao longo de sua existência, o PPGG tem pautado sua atuação na formação na qualificação de profissionais nos níveis de Mestrado e Doutorado, a base para formação de pesquisadores e profissionais de alto nível. Neste seu curto período de existência promoveu a formação de 499 mestres e 124 doutores, no total de 623 dissertações e teses.
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Item Acesso aberto (Open Access) Acúmulo e exportação de carbono, nitrogênio, fósforo e metais em canais de maré dos manguezais de Marapanim, Costa Norte Brasileira(Universidade Federal do Pará, 2020-12-18) MATOS, Christiene Rafaela Lucas de; SILVA, José Francisco Berrêdo Reis da; http://lattes.cnpq.br/1338038101910673; https://orcid.org/0000-0002-8590-2462; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228In this study, we assessed the potential of intertidal mudflat sediments along mangrove forest to accumulate and export carbon, nutrients (N and P) and metals (Fe and Mn), in addition to examine the influence of the Amazonian seasonal rainfall patterns on the physicochemical conditions, diagenetic processes and exchange of nutrients and metals along the sediment-water interface (SWI) in intertidal mudflats fringed by pristine mangroves. The study was carried out in the Marapanim River estuarine system (northern Brazil), which is fringed by extensive areas of well-developed mangroves, part of the largest continuous and best preserved mangrove forest in the world, located approximately 200 km from west of the mouth of the Amazon River. The results of this work are presented in two articles. The first deals with the potential of stocks and accumulation of COT, NT and PT in intertidal mudflat sediments, in addition we investigate the potential sources of sedimentary organic matter (OM). The second assesses the influence of seasonal rainfall pattern on physicochemical properties, the diagenetic processes and the diffusive fluxes of nutrients at the SWI in the Marapanim mangrove creeks. During wet season the salinity values decreased as a consequence of the increase in rainfall, with a dilution-mixing zone in the top sediment (<15 cm). In the dilution-mixing zone, Fe (III) and Mn (IV) reduction are the dominant anaerobic respiratory processes in the sediments. The redox zonation of sediments oscillated in response to the rainfall patterns, with the highest concentrations of Fe2+ and Mn2+ in deeper sediment layers during the dry season. Under suboxic conditions, the mudflat sediments act as a source of Fe2+, Mn2+, NH4 +, and PO4 3- to the water column, and these fluxes were driven by rainfall. The results indicated that mangrove-fringed mudflats are quite effective in retaining carbon, nutrients and iron in sediment solid phases than exporting to the coastal waters, while can potentially be a significant contributor to the oceanic Mn cycle. The potential of these mangrove creeks to accumulate these elements is directly related to grain size, sources and susceptibility of OM degradation. In addition, temporal variability in pyrite formation revealed that the solid phase retention mechanisms are also susceptible to seasonal effects, with lower concentrations of chromium-reducible sulfur (CRS, mainly pyrite fraction) during the dry season. Therefore, we show that these seasonal variabilities implied substantial changes of physicochemical properties and the diagenetic processes, affecting the release of metals and nutrients from the SWI and their accumulation in the sediment.Item Acesso aberto (Open Access) Alteração hidrotermal e potencial metalogenético do vulcanoplutonismo paleoproterozoico da região de São Félix do Xingu (PA), Província Mineral de Carajás(Universidade Federal do Pará, 2015-08-27) CRUZ, Raquel Souza; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983The region of Sao Felix do Xingu, south-central Pará, exposes a volcano-plutonic system exceptionally well preserved and grouped in the Sobreiro and Santa Rosa formations, in which hydrothermal alteration and mineralization associated were recognized. The Sobreiro Formation consists of lava facies flow of andesitic, basaltic andesite, and dacitic composition, according to the proportions or absence of clinopyroxene and/or amphibole phenocrysts. Volcaniclastic facies is genetically associated and is represented by mafic crystals tuff, lapilli-tuff, and massive polymictic breccia. Santa Rosa Formation is fissure-contolled and composed of lava flow facies and associated volcaniclastic facies of felsic crystal tuffs, ignimbrites, lapilli-tuff, and massive polymictic breccia. Part of this system is interpreted as ash-flow caldera partially eroded and developed in several stages. Conventional petrography, X-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy show hydrothermal alteration paragenesis occurring in these rocks. In general, the alteration minerals develop subeuhedral anhedral crystals and replace magmatic minerals. The types of hydrothermal alteration identified are incipient the pervasive and are distinguished propylitic, sericitic, intermediate argillic, and potassic, which overlap, and fracture-controlled silicification associated with hematite and carbonate. Propylitic alteration, prevalent in Sobreiro Formation, presents both pervasive and fracture-controlled styles. The paragenesis consists of epidote + chlorite + carbonate + quartz + sericite + clinozoisite ± albite ± hematite ± pyrite, which is overlapped by pervasive potassic alteration or fracture-controlled, mainly represented by potassic feldspar + biotite ± hematite. Locally, fracture is filling with prehnite-pumpellyite association that suggests geothermal low-grade metamorphism conditions. The sericitic alteration is marked by the occurrence of mainly sericite + quartz + carbonate ± epidote ± chlorite ± muscovite. It is manifested mainly in mafic crystal tuff. However, the overlap of these types of changes is evidenced by relics of propylitic chlorite alteration and textures of rocks, partially obliterated, in which there were only pseudomorphs of sericitized plagioclase. In the Santa Rosa Formation the sericitic alteration is pervasive and characterized by the occurrence of sericite + quartz + carbonate. Also presents fracture-controlled, which is represented by sericite + quartz. It is the main type of change identified in this unit by assigning the whitish rocks. SEM data show that, associated with the sericitic alteration occur lead phosphate, gold, rutile, and barite. The potassic alteration is more subordinate, generally associated with granitic porphyry and locally to rhyolites. Paragenesis is given by microcline + biotite + chlorite + carbonate + sericite ± albite ± magnetite. The intermediate argillic alteration was recognized in rhyolites and possibly corresponds to the final stages of hydrothermal alteration. It is characterized by the presence of montmorillonite + illite + chlorite + sericite ± kaolinite ± halloysite ± quartz ± hematite, which were identified by infrared spectroscopy and XRD. It gives whitish to whitish pink to the rocks. The hydrothermal alteration types were mainly controlled by temperature, fluid composition, and fluid/rock ratios. They are compatible with thermal anomalies related to magma, and possible temperature decrease due to mixing and neutralization with meteoric water, similar to that described in low- and intermediate-sulfidation mineralization. Gold identification and compatible accessories phases provide important information for prospective studies in the region, especially for potential intermediate- and low-sulfidation epithermal deposits of precious metals (gold and silver) in volcano-plutonic systems with related ash flow calderas, as well the Au(Cu) and Mo porphyry-type deposits.Item Acesso aberto (Open Access) Alterações hidrotermais associadas às rochas máfico-carbonatíticas do depósito de fosfato Serra da Capivara, região de Vila Mandi (PA), extremo sul do Cráton Amazônico.(Universidade Federal do Pará, 2019-07-14) VIEIRA, Danilo Amaral Strauss; FERNANDES, Carlos Marcello Dias; http://lattes.cnpq.br/9442875601862372Near the border of the states of Pará and Mato Grosso, in the Amazonian Craton, about 90 km west of the Vila Mandi district, Santana do Araguaia (PA) city, there is an unprecedented volcano–plutonism named Santana mafic-carbonatitic Complex. It is formed by a lower maficultramafic member with plutono–volcanic and other volcaniclastic lithofacies; besides an upper carbonatitic member with plutonic, effusive, and volcaniclastic lithofacies originated in a volcanic caldera environment with large areas of hydrothermal alterations and genetically related circular structures. The severe Amazon weathering partially affected this cluster, producing the Serra da Capivara Phosphate deposit supergenically. Although speculative, the Santana mafic-carbonatitic Complex is Paleoproterozoic in age, because it invades the Paleoproterozoic volcano-plutonic sequences Cinco Estrelas and Vila Mandi formations (1980–1880 Ma) and it is capped by sedimentary rocks from the same Era. The lower maficultramafic member has lithofacies with slabs of pyroxenite, and minor isolated metric blocks of ijolite and apatitite. They are medium-grained ceylonite-bearing (MgAl2O4) pyroxenites with augite (~ 90% vol.), magnesio-riebeckite, and olivine crystals replaced by clay minerals (saponite). The ijolite is composed of clinopyroxene and nepheline phenocrysts immersed in a fine-grained groundmass with nepheline, calcite, and interstitial magnetite. Apatitite blocks are composed of medium-grained apatite grains (~ 98% vol.) and calcite. The volcanic rocks of this lithofacies comprise isolated metric blocks of alkali basalt and rare associated outcrops of finegrained apatitite. This basalt rock presents plagioclase-rich groundmass and acicular augite phenocrysts as essential mineralogy. Aphyric samples have primary spherules filled with calcite and quartz, besides interstitial pyrite, iron oxides, apatite, barite, rutile, celestine, and monazite. This textural feature suggests silicate and carbonatitic melts immiscibility process. An explosive to autoclastic mafic volcaniclastic lithofacies encompasses poor sorting deposits of massive polymictic breccia, lapilli-tuff, crystal-rich tuff, and ash tuff. The autoclastic rocks reveal volcaniclastic texture comprising centimetric angular clasts sourced from autofragmentation of the mafic-plutonic plutono–volcanic lithofacies. Epiclastic sedimentary volcanogenic deposits usually cover all previous lithofacies. The upper carbonatitic member reveals coarse-grained carbonatite (sövite) lithofacies comprising reddish-yellow sövite (calcite carbonatite) composed of subhedral to euhedral calcite (85–90% vol.), with variations to magnesium-ferriferous calcite and dolomite. Primary accessories are magnetite, hematite, potassic feldspar, and pyrite. These lithotypes show hydrothermalized medium- to fine-grained carbonatite veins. Rare coarse-grained apatitite bodies occur associated with this lithofacies, which represents part of the proto-ore. An effusive carbonatite (alvikite) lithofacies reveals finegrained calcite-rich (80–85% vol.) to porphyritic alvikite, besides hematite, magnetite, potassic feldspar, and pyrite. Fragment-rich explosive carbonatitic volcaniclastic lithofacies encompassing poor sorting and texturally variable massive crystal-rich tuff, lapilli-tuff, and massive polymictic breccia formed by angular clasts sourced from host rocks and the complex. Syenitic stocks and dikes invade these rocks. The main hydrothermal magmatic alteration of the complex is represented by hydrothermalized carbonatitic rocks of reddish, brownish, and yellowish colors. The mineral paragenesis found was barite + fluorapatite + dolomite ± quartz ± rutile ± chalcopyrite ± pyrite ± monazite ± magnetite ± hematite. This alteration occurs in three distinctive ways; 1) in the deeper zones, where the minerals found were barite, fluorine apatite, and dolomite in pervasive to fracture-controlled alteration associated with deep fine carbonatites. 2) In the sövite, of weak interstitial form with mineralogy similar to the deep alterations. 3) in the alvikite with intense interstitial changes and formation of hydrothermal quartz associated with barite, fluorapatite, dolomite, monazite, celestine, and rutile. The mineral assemblage of the deeper alterations suggests initially sulphate-rich, magnesium, phosphorus, and CO2 fluids with possible transitional source between the late magmatic and the hydrothermal stages. In transition to more superficial phases of the volcanism, there was an assimilation of SiO2 from the country rocks evidenced by the formation of fine interstitial quartz crystals in alvikite. The interpreted environment of volcanic caldera occurs in the interception of regional NE-SW and NW-SE faults with up to 40 km of extension and that served as deep conduit of the precursor magma of the complex. The root of the system is represented by maficultramafic rocks and plutonic carbonatites. The pre-caldera phase involved intense degasification and hydrothermal activities as a function of magmatic evolution, and ascending by lithic faults and placing on the surface of large volume of carbonate lava (alvikites) that built the extinct volcanic building. The collapse of this structure and the topographic landslide coincided with explosive volcanism and formation of the volcanoclastic lithotypes, representing the intra-caldera filling. The late syenites may represent the post-caldera phase and sealing of these structures. The hydrothermal paragenesis identified in the Santana maficcarbonatitic Complex shows important metallogenetic potential for rare earth elements and phosphate and represents a prospective guide on Proterozoic terrains of the Amazonian Craton, like other areas of the planet.Item Acesso aberto (Open Access) Ambiente geológico e mineralizações associadas ao granito Serra Dourada (extremidade meridional) Goiás(Universidade Federal do Pará, 1983-08-29) MACAMBIRA, Moacir José Buenano; VILLAS, Raimundo Netuno Nobre; http://lattes.cnpq.br/1406458719432983The Serra Dourada granite belongs to a set of domic structures, generally mineralized in cassiterite, located in the center-east of Goiás, where rocks of the Uruaçu and Brasília folding belts and the Goiás median massif dominate. In order to contribute to the petrological, metallogenetic and stratigraphic knowledge of these granitic rocks, the southern tip of Serra Dourada was selected for this study. The methodology adopted was mapping at a 1:45,000 scale, petrographic, minerographic and geochronological studies, in addition to the determination of the contents of major elements in rocks and some minerals, and of trace elements in rocks. The granitic rocks of Serra Dourada were classified as syenogranites, presenting three varieties: amphibole-biotite granite, muscovite-biotite granite and biotite granite, the latter being dominant. The K-Rb graph indicates an advanced degree of fractionation for these rocks and suggests a trend that starts from granite to amphibole and ends in muscovite. In turn, the systematic variation of the contents and ratios of some trace elements reveals an intimate relationship between these varieties, meaning multiple intrusions that correspond to different degrees of partial fusion of the original material. In attempts at dating by the Rb-SR method, it was observed that the phenomena subsequent to the initial lodging in the crust introduced possible isotopic rejuvenations. However, these granitic rocks provided maximum conventional ages close to 2 b.a. The last magmatic phases of the Serra Dourada granite were the pegmatites which, in the core of the batholith, are zoned and contain aquamarine, while at the edge they bear tantalite-columbite, emerald, muscovite and monazite. Then, large amounts of hydrothermal solutions enriched in Sn and F reached both the granite and its host, changing them to greisens. Upon contacting the enclaves, the solutions precipitated cassiterite, magnetite, fluorite and sulfides. Veins with wolframite and rutile lodged in the nearest enclaves. At lower temperatures, these solutions generated kaolin when reaching the pegmatites of the contact range. Several types of enclaves have been identified in the granite: biotitite, soda-gneiss, xenoliths of schists and quartzites, and amphibolites. The soda-gneiss enclaves are trondhjemitic in nature and also have amphibole and biotite, biotite and biotite and muscovite varieties. The similarity of the assemblage and chemistry of some mineralogical phases suggests a consanguinity between soda-gneiss and granite, with the possibility that they are partially intact fragments of the rocks that gave rise, by anatexia, to the granitic material. On the other hand, the contents and anomalous ratios of some elements of soda-gneiss indicate reaction with magma, which is emphasized by the position of these rocks in the K-Rb graph. This reaction certainly affected the isotopic ratios, allowing only to suggest an Archean age. In turn, the biotites are possibly restricted. The sequence where the Serra Dourada granite was lodged is composed of intercalations of schists and quartzites from the Serra da Mesa Group. The typical mineralizations of acid magmatism, greissens, pegmatites and granitic sills in the metasediments, in addition to xenoliths from the enclosing rocks and pronounced foliation at the edges of the body, testify to the intrusive character of the granite in these metamorphites, whose late-syntectonic event is associated with the formation of the brachyanticlinium, which agrees with the regional structural pattern. Through the mineralogical assemblage of these rocks, conditions of low amphibolite facies were attested for its formation, where pressures above 4.5 Kb and temperatures around 550°C.Item Acesso aberto (Open Access) Análise comparativa hidroambiental das bacias do Una e da Estrada Nova, em Belém-PA, e suas implicações socioeconômicas(Universidade Federal do Pará, 2015-03-26) LEÃO, Eduardo Araujo de Souza; ABREU, Francisco de Assis Matos de; http://lattes.cnpq.br/9626349043103626To evaluate the effectiveness of public interventions in relation to changing social dynamics and improve the quality of life of a population is necessary to the built and application of social indicators in monitoring public management, especially when dealing with large environmental interventions. As much as these indicators are mapped, the vast majority of environmental studies where these interventions occur, the government has dedicated itself or if it does not perform and monitor efficiently the behavior of these indicators over time. In Belém, the floods in urban areas pose a serious problem for most of the municipality, especially when involving densely occupied areas, at which generate considerable damage and often irreparable, even with losses of human lives. Flooding has been a problem during periods of frequent rainfall, both in the oldest areas of the city and consolidated, as in the areas of urban sprawl, a fact compounded by soil sealing, occupation of wetlands and removal of riparian vegetation, which hinders the infiltration rainwater. Due to these environmental factors and the inattention of government in providing social amenities and physical interventions in the area of the metropolis, populations that occupy the most vulnerable parts of the city of Belém, in general have a poor quality of life, as regards the issue of the environment in which they live. In order to comparatively evaluate two different realities and really consider whether public intervention was effective and efficient and from the same include as practical application of social indicators in monitoring the public administration, was used as case for this research performed by government intervention state in the basin of Una, where he was executed the deployment of Macro Drainage Basin of Una and services contemplated drinking water supply, sewerage, storm water drainage and road system, compared with the intervention of the municipal government to bowl Estrada Nova, running, with the deployment of these services. To develop the research, the study gathered data and information collected in the basin of Una and projected future scenarios for the basin of Estrada Nova, using the same indicators. These indicators in this study were also addressed and strengthened with a hydrogeological assessment of the two basins, the analysis of quality of surface and groundwater, consideration of the incidence of waterborne diseases, the vulnerability of aquifers, configured together in a GIS specifically built for it, with the aim of evaluating the criticality of spatialization basins and identify which areas need more attention or have the best results. The study demonstrated that the physical and socioeconomic study of the two basins are similar and after the intervention in the basin of Una, any kind of indicator was monitored with a view to demonstrate the effectiveness of the intervention. The study also showed that health indicators linked to waterborne (why the intervention was also made) chosen for monitoring before and after the intervention, have partially direct connections to the environmental quality of the basin, but many indicators not could be chosen by the lack of government data. The vulnerability of the aquifer top is also concern in some quarters, in that much of the population obtains its supplies from this aquifer, which has its recharge provided, in part, by draining channels of Belém, known holders of very bad quality indices its waters and can even be characterized as true open sewers. The drainage channels and creeks of Belém, are thus responsible for directing this excess sewage into the Bay of Guajará and river Guamá through interconnection with those that have physiographic elements. Because the city has much of its area located in quotas of up to 4 meters, which is also the average annual tidal amplitude regional, these areas are subject to flooding. By way of consequence throughout the upper aquifer is vulnerable to infiltration of contaminated water channels, which in times of floods are dammed increasing the residence time in them,. The research now being evaluated scenarios and presentation indicators, this reality, leaving open the need to be constructed and monitored indicators other than the act of evaluating the effectiveness of public intervention can be more consistent. Finally the study also notes that several indicators could not be considered in the study due to insufficient and the quality of data provided by the government.Item Acesso aberto (Open Access) Análise da dinâmica da cobertura e uso do solo na bacia hidrográfica dos lagos Bolonha e Água Preta, Belém, Pará.(Universidade Federal do Pará, 2024-12-20) BARROS, Jackison Mateus Lopes; SOUZA FILHO, Pedro Walfir Martins e; http://lattes.cnpq.br/3282736820907252; https://orcid.org/0000-0003-0252-808XThe increase in the urban population in the world has impacted river basins that supply water to cities, including the treatment and distribution of drinking water for domestic, industrial and commercial use. One example is the Bolonha and Água Preta Lakes Hydrographic Basin (BHLBA) in the Belém Metropolitan Region (RMB), the second largest urban agglomeration in the Brazilian Amazon, with 2.3 million inhabitants. One of the best ways to monitor the dynamics of river basins is through remote sensing techniques with orbital images, due to the quality of the spatio-temporal data. This work aims to analyze the changes in land cover and use in the last four decades in the BHLBA, through images from the Landsat satellite series from the years 1984, 1989, 1994, 1999, 2004, 2008, 2018, 2021 and 2023, using a geographic object-oriented image analysis (GEOBIA) methodology. Thus, the classes of lakes (L), urban area (AU), aquatic macrophytes (MA), arboreal vegetation (VA) and pasture (P) were evaluated. The overall accuracy of the images showed values around 90%, with the main error being allocation errors. Changes that occurred over the years were identified, such as the significant growth of macrophytes on the water surface of the Bolonha and Água Preta lakes, which decreased by approximately 3.7%. A 13.4% increase in arboreal vegetation in the BHLHA was also recorded, evidencing a forest recomposition. A 3.2% growth in urban areas around the BHLBA was also observed, which is worrying because human influence can put the health of the water supply sources of the RMB at risk. The GEOBIA methodology proved to be adequate for the study and we recommend that monitoring be continued due to the socio environmental importance of the area under study.Item Acesso aberto (Open Access) Análise da dinâmica morfo-sedimentar da praia da Marieta – Ilha do Marco-Maracanã (NE do Pará)(Universidade Federal do Pará, 2010-04-19) GUERREIRO, Juliana de Sá; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429This study aims the investigation of the morphological and sedimentological variations occurred in Marieta’s Beach- Marco Island (NE of Pará) during the rainy season (March) and rainyless season (November) of 2007, seeking to identify the main factors responsible by these variations. The Marieta’s beach has 3 km long, with NW-SE direction, and is supported by the sediments of the Barreiras Group, Post-Barreiras and the recent sediments that provide much of the sediment at the mouth of the estuary Urindeua. Topographic profiles were conducted in June in the following subdivisions Beach Marieta: Sector sandy spit - profiles I and II (tgβ = 0.0015); central section - profiles III, IV (tgβ = 0.0017) and NW sector - and V profiles VI (tgβ = 0.005). We applied the following morphological beach models: Inmam & Guza (1975), Sandy Spur - in the rainy season in the rainyless period, Sector Central - 12 in the rainy season during rainyless. These results show a strong reflection with some dissipation, characterized as Intermediate Bar and Longitudinal with the NW sector, which indicated a Dissipative behavior during the two periods studied, According to Wright & Short (1984) had a whole beach Dissipative behavior during the two periods studied - in the rainy season in the less rainy period; And following Masselink & Short (1993) showed the profiles to be modified by tides, with dissipative bars RTR = 4 in the rainy season and RTR= 3.6 in the rainyless period. The beaches are predominantly covered by very fine sand, very well selected and moderately selected, with mesocurtic and platicurtic kurtosis and negative asymmetry at the supratidal zones during the rainy season and in areas of infratidal in the rainyless season in other areas of the beach Marieta were approximately symmetrical and positive asymmetries. The Marieta’s beach has been profiled morpho-sedimentary influenced by the displacement of the Convergence Zone Inter-Tropical (ITCZ) in the rainy season (1736.6 mm) and at rainless (2.4 mm). The speed of the wind was weaker during the rainy season with an average of 6.7 nodes while in the less rainy period the average speed was 11.3 knots with preferential direction NE, and therefore, buckled with higher energy (Hb = 1 , 5 m in the rainy season in March). Coupled with an amplitude of 5.5 m tide reaching the innermost areas of the beach. In the less rainy period, the waves were smaller, compared to the rainy season, which reached 1.2 m combined with an amplitude of 4.8 m tide. Through these parameters showed that the major changes in the beach profile were associated mainly to the interaction of the effects of winds, waves and tides, showing the strong relationship between the shape and orientation of the beach and the incidence of these agents.Item Acesso aberto (Open Access) Análise de imagens de sensores remotos orbitais para mapeamento de ambientes costeiros tropicais e de índices de sensibilidade ambiental ao derramamento de óleo no Golfão Maranhense(Universidade Federal do Pará, 2006-04-18) TEIXEIRA, Sheila Gatinho; SOUZA FILHO, Pedro Walfir Martins e; http://lattes.cnpq.br/3282736820907252The oil spills in Brazil are more and frequents, causing several impacts on environments and biological communities. Envronmental sensitivy index maps of oil spils are indispensbles components of contingency and emergency answer plans for this tpe of accident. These maps present a system of classification based on geomorphologic characteristics of the áreas, which are defined by the following factors: wave and tidal energy exposure relative degree, shoreline slope and substrate type, and also, the easiness to clean and remove the oil impacted áreas. In this contect, the “Golfão Maranhense” region, located on Northern “Maranhão” State, was chosen in order to map and analyze the environmental sensitivity indexes (ESis) of oil spills on coastal environments, for in this área, we find the second largest port in draught of the world, the Porto f “Itaqui”. Moreover, this region is the route of six hundred oil tankers per year, which are potential agents that cause the oil spill. The methodological approach for creating the maps of environmental sensitivity index included the integrated analysis of coastal environments based on digital image processing from remote optical sensores, in this case, Landsat-4TM, CBERG-2 CCD and SPOT-2 HRV, SAR (Synthetic Aperture Radar) images from RADARSAT-1 Wide 1, SRTM (Shuttle Radar Topography Mission) elevation data, geographic information system and Field surveys related to geomorphology, topography and sedimentology. Using the aforementioned methods, the coastal environments recognized in “Golfão Maranhense” were grouped according to their envronmental sensitivity index: 1 – Solid men-made structures (ESI 1B); 2- Cliffs (ESI 1C); 3 – Fine grained sand beaches and móbile dunes (ESI 3ª); 4- Tidal sandflats (ESI 7); 5- Mixed intertidal Banks, tidal mudflats and ebb-tidal delta (ESI 9ª); 6- Supratidal sandflat (ESI 9C); 7- Saltmarshes (ESI 10ª); 8- Fresh marhes and intermittent lakes (ESI 10B) and 9- Mangrove (ESI 10C). This approach is efficient to recognize and analyze coastal environments and, therefore, it pernitted the sensivity index attribution for the oil spill on yhese environments, in a georefenced data base, which allows making faster e more efficiently decisions in case oil spills come to happen.Item Acesso aberto (Open Access) Análise de imagens Landsat ETM, Radarsat-1 e modelos numéricos de terreno para o mapeamento dos índices de sensibilidade ambiental ao derramamento de óleo na costa de manguezais do nordeste do Pará(Universidade Federal do Pará, 2006) BOULHOSA, Messiana Beatriz Malato; SOUZA FILHO, Pedro Walfir Martins e; http://lattes.cnpq.br/3282736820907252Accidents related to exploration and oil transport are a threat to coast zones araund the world. Oil spills are an ecological disaster that may cause irreparable damage to the environment affecting living beings that live in these coast zones and also the local economy. Characterizing coast environments is very complex because of the many limiting factors during the mapping process. When it comes to humid tropical environment, like in Pará northeast coast, it gets worse because this area is typically dominated by macro tide. First of all, the macro tide plain creates low areas where informations about the relief are, most of times, scarce and the plain metric representation is dominant. Secondly, the tide variations with its vertical and horizontal moving produces strong changes on the sediment coast environment limits. Thirdly, the geomorphological modifications in the coast areas are intense and fast. Towards this context, the objective of this master’s degree dissertation is to create a map of the coast environment and a rating map of the environmental sensitivity about the oil spills in a certain part of Pará state northeast coast. The methodology consisted on processing digital images from remote sensors in the range of optical (Landsat ETM +7) and microwave (RADARSAT–1 Wide-1) associated to data from the SRTM (shuttle radar topographic mission) digital model of elevation, and to the field data collected in SIG (geographical information system) environment, providing an integrated analysis of the spectral, geomorphological, altimetrical and sedimentological characteristics of the coastal environments in cartographic georeferenced bases. The most important results of this dissertation allowed: 1) The evaluation of the potential of the images Landsat ETM +7, RADARSAT-1 and of the multi sensors fusion products used for identifying the coastal environment and the Environment Sensitivity Rates (ISA) of oil spills in this areas 2) Recognizing and describing five main morphological unities and fourteen sub unities: Coastal Plateau, Tide Plain, Coastal Plain and Alluvial Plain 3) Identifying and classifying eight unities of Environmental Sensitivity Rates (ISA) for the Amazon coast zone which are: ISA 1B – support wall; ISA 3B – exposed scarps with declivity to the sand; ISA 9B – sand bank and plains of tidal vegetable mudflats; ISA 9C – hypersalt herbaceous fields, ISA 10A – salt and salobre herbaceous fields; ISA10C – Mangrove; ISA 10D – Lea; 5) creation of the Environmental Sensitivity Rates map to oil spill of the studied area. The using of remote sensors techniques and SIG proved to be an important tool for recognizing and analyzing coast environments and for generating maps to coast environments and to environmental sensitivity rates to oil spills in the northeast coast of Pará.Item Acesso aberto (Open Access) Análise do padrão espectro-temporal de ambientes costeiros com imagens Landsat, Ilha de Marajó/PA.(Universidade Federal do Pará, 2010-10-06) CARDOSO, Gustavo Freitas; SOUZA JUNIOR, Carlos Moreira de; http://lattes.cnpq.br/2090802631407077; SOUZA FILHO, Pedro Walfir Martins e; http://lattes.cnpq.br/3282736820907252Knowledge of spatial and temporal distribution and monitoring of its dynamic evolution are the most important factors for the study and management of wetlands. The aim of this study was to characterize, to map, to compare the spectral response of coastal wetlands, as well as detect the changes on the eastern shore of Marajo, State of Pará, using images from TM Landsat-5 reflectance. To this end, the images were geometrically and radiometrically corrected. Were collected in the reference image (2008), at least 20 polygonal samples (5x5 pixels) for each type of land cover. The analysis of variance (ANOVA), Tukey HSD Test and an index of spectral separability of pairs of regions of interest (ROIs) were calculated. The mapping was generated from the supervised classification Spectral Angle Mapper, and validating data, outlined by the Confusion Matrix. Thus were recognized the following units: MAN - mangrove, MAD - degraded mangrove, PRD – beaches and dunes, VSI – initial secondary vegetation, VSA - advanced secondary vegetation, ACS – water with sediment, ASS - water without sediment, OCH - human occupation and CAM – marshes. The result of ANOVA showed that there are significant differences between the average reflectance in all classes and at least one pair of means, for all bands (1-5 and 7) image. The Tukey HSD test found that the smallest difference between two means of bands 1 and 2 occurs in pair VSAMAN, the band 3, VSI-MAN, the band 4, OCH-MAN, the band 5, OCH-PRD, and band 7, ASS-ACS. The function of spectral separability of pairs of ROIs highlighted a low value for the pair of classes OCH-CAM. The calculation accuracy of the mapping showed acceptable values. Was also applied the technique of spectral mixture model to determine the fractions – green vegetation, water and/or shade, soil and vegetation not photosynthetically active – in reflectance images in years from 1988, 1994, 1998, 2004, 2006 and 2008. The detection of changes over the years was done with the help of the tri-linear diagram of Thompson, used to analyze the evolution of Mangrove environments, Salt Marshes with a predominance of soils, Grassland Salt Marshes, Beaches and Dunes, Wet Sediment, Water with Sediment and Water without Sediment. The results showed that 80% of the samples from mangrove environment, maintained their spectral characteristics, ie, the environment has not changed over time, and that 15% of possible paths indicated a gradual change for the formation of mangrove until 2008. Of the total number of pixels analyzed for this environment, 93% corresponded to the actual mangrove, confirming a relative stability of this environment in the study area. Salt Marshes showed an unusual condition in the analysis of the image of the reference year (2008), with spectral response similar to the soil characteristics, this is not checked in years gone by. In recent years, there was a predominance of Grassland Salt Marshes. As for the environment Beaches and Dunes revealed a considerable increase of its surface (66.7%) in the 20-year period (1988-2008). Overall, the results suggest that the study area has undergone the process of progradation of sediments along the shoreline and stabilization in the increase of surface Mangrove since 2006. For the Salt Marshes detect the variations in the abundance values among the three fractions (Green Vegetation, Shade/Water, Non-photosynthetically Active Vegetation and Soil) generated by the spectral mixture model, mainly due to seasonal climate in the region. The method of change detection applied fostered the development of a model spectral dispersion diagram for coastal wetlands. This model should assist in future research about the monitoring of the impacts of the humid coastal environments from the increase in sea level, the location and spectral characterization, and change detection.Item Acesso aberto (Open Access) Análise espaço-temporal dos manguezais degradados de Bragança, com base em imagens de satélite e modelos de elevação digital(Universidade Federal do Pará, 2022-02-22) MOLANO CÁRDENAS, Sergio Mauricio; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228The Bragança Peninsula occurs at the northern littoral of Brazil, in the state of Pará. It is characterized by the largest continuous mangrove belt in the world. The construction of the PA- 458 road in the ‘70s changed the hydrodynamics of the peninsula, causing the degradation of a considerable portion of the mangroves in the central region of the peninsula. Recently, degraded areas are being colonized by mangrove trees, mainly by the Avicennia germinans specie. This study intends to identify changes in the degraded areas of the tidal flats in topographically higher sectors during the last 35 years. To reach that objective, we used the following techniques: a) manual mapping of the degraded areas with mid spatial resolution satellite imagery; b) object-based classification of the degraded areas and mangrove species, using high spatial resolution satellite imagery; c) photogrammetry of drone imagery; d) digital elevation models; and e) topographic validation with theodolite and GNSS GPS “Antenna Catalyst”. From 1986 to 2019, there was a reduction in the degraded areas of 247.96 ha according to the mid-resolution “dataset” quantification. However, high-resolution data showed a reduction in the degraded areas of 211.65 ha between 2003 and 2019. The degraded areas quantification presents fluctuations in the regeneration trend; it is related to significant climatic phenomena such as “El Niño” and “La Niña”, accompanied by periods of drought and high rainfall, respectively. Overall accuracy and Kappa index values for the high-resolution data generally exhibited values above 0.9. Producers’ and users’ accuracy and Kappa per class values showed the difficulties separating mangrove species due to the lack of radiometric resolution of the analyzed images. The digital terrain model representing the tidal flat showed two topographically differentiated regions in the degraded areas, separated by the PA-458 road, which are mainly influenced by the Caeté’s and Taperaçú’s characteristics. This same difference was found in the vegetation height model, where the largest trees are located toward the SE side of the road, reaching 25 m, while at the NW side of the road, the tree heights oscillated mainly between 5 and 15 m. The sea-level rise specifically controls regeneration rates. This relocated the intertidal zone to topographically higher areas, increasing tidal flushing processes, essential for the mangrove forests development.Item Acesso aberto (Open Access) Análise faciológica da formação Codó (Aptiano superior) na Região de Codó (MA), leste da Bacia do Grajaú(Universidade Federal do Pará, 2000-09-11) PAZ, Jackson Douglas Silva da; ROSSETTI, Dilce de Fátima; http://lattes.cnpq.br/0307721738107549The Codó Formation, focused in this paper, is exposed in the adjacencies of Codó town, eastern Maranhão State, where it consists of intergraded shales, limestones and evaporites, laterally continuous, forming shoaling-upward successions averaging 2.5 m in thickness. Sedimentological features, the abundance of freshwater ostracodes and Charophyte algae, as well as the absence of any marine fauna, characterize this unit as a dominantly lacustrine unit, which can be described by three broad facies associations, attributed to: 1. central lake; 2. transitional lake; and 3, marginal lake. The central lake facies association represents the base of the shoaling upward successions and consists of two facies: a) black shale; and b) evaporite. The dominance of shale beds in this association indicates sedimentation in low energy depositional settings, typical of central lake areas, where the abundance of pyrite and the bituminous composition point to highly reducing conditions. The scarcity of infauna is indicated by the complete absence of bioturbation, which is consistent with anoxia. The evaporite facies point to a highly saline lake setting. The transitional facies association consists of: a)laminated argillite; hb)lime- mudstone; c)peloidal limestone (mudstone to packstone); and d)meso-crystalline limestone. These deposits, between central lake and marginal lake facies associations, own in the middle portion of the shoaling upward cycles, consistent with a transitional lacustrine setting. The marginal lake facies association represents the top of the shoaling upward successions and consists of a variety of intergrading lithofacies: ajmassive pelite; b)calcite-arenite; Cc) ostracodal limestone (wackestone to grainstone); d) pisoidal limestone (packstone) ; e)gipsite-arenite; £f) tuffa; and 9) rhythmite. These deposits show an abundance of sedimentary features (i.e., paleosoil, karstic surface, fenestrae) typical of subaerial and/or meteoric exposure, which is consistent with their interpretation as marginal lake deposits. A lacustrine facies model with ramp margin and low energy flow is proposed for the study area, taking into account the following characteristics: 1) low rates of sediment supply; 2) presence of areas with low relief around the lacustrine basin; 3) abundance of sedimentary features recording episodes of subaerial and/or meteoric exposure; and 4) prevalence of marginal facies. This interpretation is further suggested by: 1) the small thickness of the depositional cycles, which is attributed to decreased accommodation; 2) absence of turbiditic deposits, which are typical in lacustrine settings with pronounced slope break; and 3) absence of resedimented deposits, which are also common in bench margin lacustrine settings. The abundance of black shales and evaporites suggests a hydrologically closed lacustrine basin with stratified and saline water column for the study area. The depositonal cycles identified reveal a regressive character for this lacustrine succession. Three types of cycles were recognized: 1) complete shoaling-upward cycle; 2) incomplete shoaling-upward cycle; and 3) flooding-upward cycle. The origin of these cycles is attributed to tectonism, based on the assymetrical vertical stacking pattern. This interpretation is corroborated by the presence of sin- sedimentary deformational features related to sin- depositional sismic activity. The faciological, palaeontological and geochemical data presented in this work suggested on show that the Late Aptian marine transgression recorded in the northern portion of the São Luís-Grajaú Basin did not reach the Codó area.Item Acesso aberto (Open Access) Análise faciológica das formações Poti e Piauí (carbonífero da Bacia do Parnaíba) na Região de Floriano-PI(Universidade Federal do Pará, 2000-07-20) RIBEIRO, Cleive Maria Monteiro; GÓES, Ana Maria; http://lattes.cnpq.br/2220793632946285Item Acesso aberto (Open Access) Análise faciológica e aspectos estruturais da formação Águas Claras, região central da Serra dos Carajás-PA(Universidade Federal do Pará, 1995-01-31) NOGUEIRA, Afonso César Rodrigues; TRUCKENBRODT, Werner Hermann Walter; http://lattes.cnpq.br/5463384509941553Item Acesso aberto (Open Access) Análise integrada da morfologia e sedimentologia do baixo curso do rio Xingu(Universidade Federal do Pará, 2019-01-28) SILVA, Ariane Maria Marques da; ASP NETO, Nils Edvin; http://lattes.cnpq.br/7113886150130994The Xingu River is an important tributary of the Amazon River, contributing with 5% of its total water discharge. Nevertheless, it does not contribute substantially with sediment load. The lower reaches of the Xingu River correspond to a Ria, as a result of the Holocene sea-level rise. It is also classified as a tidal river, where tides reach over 1 m at its confluence with the Amazon River. This study evaluated the morphology and sedimentology of the area, correlating it with hydrodynamics, aiming to understand the still ongoing infilling process of the Xingu Ria. The study area encompasses a stretch of about 180 km, from the Xingu-Amazon river confluence upward to the narrowing of the channel, near the city of Vitória do Xingu. During the maximum sediment discharge of the Amazon River (i.e., feb/2016) 109 bottom sediment samples were collected, whereas 11 of the sampling sites were re-sampled during the minimum water discharge period of both rivers (i.e., nov/2016). During the maximum water discharge period of the Amazon River (i.e., jun/2018), additional water level measurements were undertaken simultaneously in several locations along the Xingu River, as it was also performed during the other campaigns. The morphology was evaluated on the basis of the bathymetric surveys of the Brazilian Navy (CLSAOR/DHN), including about 20,000 points. The results showed that the infilling process of the ria lake has taken place from both ‘ends’ of the area- from the Xingu River itself, forming a prominent bay-head delta, as well as from the Xingu-Amazon River confluence, where tides have transported Amazon River sediments upstream into the Xingu Ria. Furthermore, there is a central portion of the ria lake with large cross-sectional areas, reached only by relatively small amounts of sediments, being a quiescent environment within muddy sedimentation. In a transversal perspective, sands seem to prevail along the margins, where local wave action seem to result in bluff erosion. Longitudinally, sands are substantially more frequent at the bay-head delta area, and at the confluence area, where cross-sections are clearly narrower. Results also suggest that the sediment input from the Amazon River into the Xingu ria has reduced over time, whereas the combination of cross-section area variation and the Xingu River water discharge itself reduce the sediment flux from the Amazon River into the Xingu River.Item Acesso aberto (Open Access) Análise integrada da paisagem para avaliação da vulnerabilidade à perda de solo das margens da Baía de Marajó, estado do Pará(Universidade Federal do Pará, 2011-11-30) GUIMARÃES, Ulisses Silva; COHEN, Marcelo Cancela Lisboa; http://lattes.cnpq.br/8809787145146228Marajó Bay is part of the Coastal Zone in the Amazon estuary, and it constitutes a form of "V" with intensive processes of erosion and progradation. The bay shores are the object of this study, from the west coast, represented by the west coast by Salvaterra and Soure municipalities, to the east coast of Mosqueiro Island. The purpose is to analyze the coastal environments adjacent to the Marajó Bay, with a systemic and integrated approach using thematic databases (geology, geomorphology, pedology, climatology and Use and Land Cover) and remote sensing images (Landsat TM 5 and MDE SRTM) to prepare maps syntheses of landscape units and vulnerability to loss of soil as a subsidy to coastal management. The main steps of this methodology are: i) atmospheric correction by dark-object subtraction, geometric correction by orthorectification, with supervised classification algorithm Spectral Angle Mapper (SAM) through training samples to map the Use and Land Cover; ii) compilation, adaptation and classification to improve data of morphology; iii) development of derivatives geomorphometric; and, iv) integration of the thematic basis for map algebra, with an overlap equation for synthesis of the landscape units maps and another equation for the preparation of the arithmetic average map of vulnerability to loss of soil. The Marajo Bay shores have mostly the unit of Fields with 17.61% of the study area (50,483.16 ha), maximum altimetry of 58 m, the topography is flat and smooth, the relief were overwhelmingly straight and planar. The integrated data indicate that the pedogenetic processes prevail in only 3.58% (10,231.38 ha) of the study area. The areas in balance between morphogenic and pedogenetic processes correspond to 3.75% (10,737.63 ha), while morphogenesis is prevalent in 42.40% (121,317.39 ha). The superiority of morphogenic units shows the hazard of coastal environments per surface mechanisms, how substrate desegregation and erosion by processes of runoff and mass displacement.Item Acesso aberto (Open Access) Análise morfoestratigráfica do estuário do Rio Marapanim - NE do Pará(Universidade Federal do Pará, 1998-12-20) SILVA, Cléa Araújo da; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429The estuary of Marapanim River is developed on tertiary-quaternary sediments of Barreiras and Pós-Barreiras Formation. It is inserted on "Littoral of Rias" of Pará northeast, which from High Pleistocene was submitted to marine transgression that drowned coastal paleolines and, in the maximum of Holocene Transgression, reached the coastal plateau. This portion of coast is strongly influenced by dynamic macrotides (5,3m) and salt wedge with mear salinity of 8%0 (high tide — Marudazinho) and 3%0 (low tide — Marapanim). So that, on outer funnel (Marudá) the salinity is 35°/00, representing no influente of mouth river discharge. Geomorphology of the area is subdivided in three morphologic domains: (1) Coastal Plain, constituted by strand plain, paleodune, coastal dune, salt marsh, tidal flat (sand flat and mangrove swamp), recurved spit, lake and palco tidal creek; (2) Estuarine Plain, constituted by estuarine channel (subdivided in estuarine funnel segment, sinuous meandering segment, cuspidate meandering segment and upstream channel), tidal creek and floodplain (salt marsh and fresh water marsh) and; (3) Alluvial Plain constituted by meandering channel (chute cutoff), channel deposits (channel lag deposits), overbank deposits (natural levee, crevasse-splay deposits and floodplain) and channel-fill deposits. Fourteen morphostratigraphic units was identified: floodplain, levee, chute cutoff, fresh water marsh, mudflat, channel bar, point bar, strand plain, paleodune, coastal dune, recurved spit, sand flat and salt marsh. Six stratigraphic facies are also present: point bar sand and mud, marine sands, estuarine sand and mud, estuarine muds, fluvial sands and motled sand. Stratigraphical analysis permitted recognize stratigraphic sequences: Basal Marine Transgressive (Si) with fluvial, salt marsh and shoreface environments; Marine Regressive (S2) with fluvial, fresh water marsh, tidal flat, salt marsh and strand plain environments and; Recent Marine Transgressive (S3) with estuarine (channel bar and point bar) and littoral environments (recurved spit, strand plain and coastal dune). Geological evolution of the estuary of Marapanim River is associated with sea levei oscillations that occurred during progradation and regressive cycles on Later Holocene, which in the maximum of the Holocenic Transgression eroded the highland (coastal plateau). In stillstand sea levei conditions occurred marine regressive and mud flat progradation over marine sand deposits. In present time, sand sheets are deposited over mud ilat providing partia! filling in the mouth of estuary by sand bars.Item Acesso aberto (Open Access) Análise palaeoambiental e caracterização dos Folhelhos Negros da Formação Barreirinha utilizando análises Multiproxy(Universidade Federal do Pará, 2025-06-04) CARVALHO, Wivian Maria Rodrigues; BRITO, Ailton da Silva; http://lattes.cnpq.br/9873489431846769; HTTPS://ORCID.ORG/0000-0001-9224-5563; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131The initial sedimentation phase of the Barreirinha Formation was associated with a rapid relative sea-level rise during a significant marine transgression event that flooded the Amazon Basin. These organic-rich shales outcrop along a narrow yet extensive belt located on the southern margin of the Amazon Basin. Few studies have specifically addressed the potential paleoenvironmental variations linked to the deposition of these shales. This is mainly due to the relative lithological uniformity of these rocks—composed predominantly of fine-grained sediments—and their economic relevance, which has directed most research toward the maturation of organic matter. To investigate the paleoenvironmental variations during the deposition of these fine sediments—focusing on sedimentary dynamics, the origin, and provenance of the organic matter—a multiproxy approach was applied, combining various quantitative, semi-quantitative, and qualitative techniques. The analyzed stratigraphic succession is mainly composed of gray to black shales, exhibiting facies variations related to coarse terrigenous input and episodes of bioturbation. These features suggest a deep, distal, anoxic marine depositional environment, with no evidence of carbonate sedimentation, typical of the Abacaxis Member of the Barreirinha Formation. Mineralogical cluster analyses indicate a dominance of kaolinite, characterizing the Kaolinite Facies, with subordinate quartz, sulfates, and sulfides in the lower portions. The base of the succession includes massive fine-grained sandstones with cross-bedding, correlated with the Ereré Formation, interpreted as deltaic to inner shelf deposits. The transition to laminated shales interbedded with sandstones and siltstones marks the onset of the Devonian (Frasnian) transgression, with substantial continental input evidenced by heavy minerals, pyritized plant remains, and tasmanites. The presence of dumpstones suggests glacial influence and ice-rafted debris deposition. Upper levels show more homogeneous shales, enriched in organic matter, lacking bioturbation and detrital minerals, indicating maximum anoxia during the peak of the transgressive event in the Amazon Basin. Diagenetically, the shales underwent compaction, fracturing, mineral substitution, oxidation, and intense pyritization, mainly as framboidal pyrite—typical of reducing marine environments. The mineralogy is dominated by kaolinite and quartz, with accessory minerals indicating alteration processes and possible Jurassic-Triassic igneous intrusions (Penatecaua magmatism), which contributed to increasing the thermal maturity of the kerogen. Rock-Eval pyrolysis and biomarker analyses reveal Type II-III kerogen with gas-generating potential, ranging from immature to post-mature depending on proximity to igneous intrusions. These findings reflect a transgressive system strongly influenced by environmental controls and regional thermal input.Item Acesso aberto (Open Access) Análise paleoambiental da Formação Pirabas no litoral do Maranhão, Brasil(Universidade Federal do Pará, 2011-06-03) OLIVEIRA, Samantha Florinda Cecim Carvalho de; ROSSETTI, Dilce de Fátima; http://lattes.cnpq.br/0307721738107549The Pirabas Formation is a geological unit known for its abundant fossil content, which includes a large number of invertebrate and vertebrate groups. This unit is exposed in the north and northeast coast of Brazil, in the States of Para, Maranhão and Piaui. The majority of the studies focusing the fossils of the Pirabas Formation emphasized initially, invertebrates. However, studies using ichthyoliths have been increasingly emphasized in the last years, which is due to their resistance to dissolution, transportation and deposition. Moreover, the small size favors their continuous recovery along different stratigraphic levels, allowing their use as an additional tool in paleoenvironmental interpretations. This work aimed to prospect ichthyoliths of the Pirabas Formation exposed along the coast of the State of Maranhão, as well as their identification and integration with facies analysis. This study area is part of the São Luís Basin, which is filled with a 4,000 m-thick sedimentary succession represented mainly by Cretaceous rocks, with a thin Cenozoic cover, the latter represented by the Pirabas and Barreiras Formations deposited mostly in the Miocene. The exposures studied occur along various cliffs between the towns of Alcantara and Guimarães. Miocene carbonates with ichthyoliths record in this location are occasional, occurring as thin layers up to 2 m thick, which are laterally and vertically intergraded with siliciclastic deposits. These strata occur as three stratigraphic units, with the second one documenting fossiliferous carbonates related to the Pirabas Formation. The cliffs studied include the ones in the localities of Canelateua, Mamuna Grande, Peru and Base. We analyzed 16 thin sections sampled from these localities, which resulted in description of four carbonate microfacies, and one of mudstone. The samples provided 30 ichthyoliths, which were photographed, identified and described under a scanning electron microscope. In addition to the ichthyoliths, the petrographic study recorded the presence of other fossils, including bryozoans, foraminifera, gastropods, bivalves, algae, and echinoids. The integration of paleontological data and microfacies is consistent with deposition in carbonate paleoenvironments predominantly with low energy, reducing conditions and subjected to the frequent introduction of siliciclastic grains. These characteristics, added to the low fossil frequency in most of the samples, corroborate previous interpretations that the deposition of these strata occurred in paralic, probably estuarine palaeoenvironments. However, the abundance of marine fossils in some samples, associated with the presence of ichthyological elements common in environments with normal salinity, shows periodic introduction of saline inflows. Therefore, we can conclude that the strata analyzed were deposited in association with an estuarine system, but representing more distal facies of this system, representative environments more exposed to marine influence.Item Acesso aberto (Open Access) Análise tafonômica da ostracofauna do testemunho 1AS-5-AM: contribuição para a interpretação paleoambiental dos depósitos neógenos da Formação Solimões, AM, Brasil.(Universidade Federal do Pará, 2019-11-01) SANTOS, Katiane Silva dos; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936The Solimões Formation corresponds to the miocenic sedimentation from the Solimões Basin; it is constituted, essentially by mudstone, siltstone and fine sandstone, poorly consolidated, interspersed by lignite and carbonate levels, whose deposition took place in a fluvial and fluvio-lacustrine environment. Among the invertebrates from Solimões Formation the ostracode stand out for their abundance and diversity. Initially, the studies on those microcruteacea focused mainly on taxonomy. Subsequently, contributions on the bioestigraphy field suggest Early Miocene - Late Miocene age for this unit; while geochemical and paleontological analysis point to predominantly freshwater environmental conditions, with sporadic marine influence. However, taphonomic studies with emphasis on ostracode from Solimões Formation have not yet been performed. Taphonomic analysis of fossil concentrations can provide important data on paleoenvironmental hydrodynamics, sediments geochemistry, sedimentation rates and diagenetic processes. This paper deals with the biostratinomy and fossildiagenesis of ostracodes from Solimões Formation, as well as the mineralogical composition and sedimentological aspects of lithotypes. The material analyzed comes from thecore 1AS-5-AM, drilled in the village Cachoeira, near the Itacuaí river, Amazonas State. According to lithological characteristics, types of preservation and occurrence of ostracodes it was possible to individualize three intervals along the analyzed core. The interval I (284.50-119.30 meters) corresponds to the lower portion of the core. In this, the ostracofauna is poorly preserved, occurring only few juveniles (A-2, A-3 stages) and adults, with strong dissolution process. The lithology of this interval comprises solid, dark greenish gray to black mudstone, with rich organic matter content. The Interval II (116.70-107.10 meters) presents a higher occurrence of ostracodes in excellent preservation state and several ontogenetic stages, higher occurrence of closed carapaces and low degree of dissolution (occurs partially and punctually), suggesting a rapid burial event and little influence of methanogenesis on the lower organic matter content of the samples. The lithology of these layers are the same from interval I, however the organic matter content is fewer. Interval III (106.90-41.00 meters) has a moderate preservation stage, where the highest dissolution rate is associated to oxidation of monosulfides and iron sulfides that occurs adherent to the specimens surface, which were exposed by bioturbating organisms of sediments. The predominance of juvenile ostracodes in this interval indicates high mortality in ontogeny probably due to environmental stress. The lithology of this interval is made up of light to medium solid greenish gray, locally siltitic and lignite. Bioturbations (Skolitos) were recorded only at this interval. Organic matter content varies from low to moderate. Related to the color change of the ostracodes, opaque white valves were recorded in interval I more frequently; in II predominate black, dark gray, white and in smaller quantity, amber and hyaline colored valves; while in the III predominate reddish brown specimens, followed by light gray and opaque white. The taphonomic analysis of the ostracodes allowed to verify carapaces/valves with original chemical composition preserved, however, contaminated by chemical elements from the siliciclastic sediments and thin mineral layers adhered to its surface. The following types of preservation were identified: 1) ostracode valves and carapaces covered by thin mineral layers of iron monosulfide, iron phosphate, iron and thallium sulfide; 2) preserved in iron oxides; 3) recrystallized; and 4) pyritized molds. Preservation types identified predominantly reflect conditions of early (thin mineral layers mineralization and mold formation), and late (recrystallization, oxide formation) diagenesis. Fossildiagenetic alterations correspond to mineral filling of carapaces by pyrite, dissolution, color change and recrystallization. The first is related to iron phosphate present in sediments and rapid burial events. The dissolution resulted from the oxidation of the thin mineral layers adherent in the valves and the organic matter content; while carapaces/valves with alterations to reddish brown, dark gray, black and amber reflect the deposition of thin mineral layer on the specimens surface, opaque white valves result from partial dissolution. The punctual recrystallization of few valves reflects the mineral stability of the low magnesian calcite, the main constituent of ostracod carapace. The biostratinomic alterations identified are equivalent to fragmentation, disarticulation (from death, ecdysis and transport of ostracodes), bioerosion (due to chitinolytic bacteria) and transport. In interval I juvenile allochthonous ostracodes suggest postmortem transport. In interval II the predominance of native fauna shows low energy environment. Allochthonous and autochthonous (predominant) ostracodes of interval III reflect energy variation in scenery near the coastal lake zone. Based on the types of preservation and lithological characteristics, the environment was interpreted as lacustrine, with low to moderate energy. The absence of evaporitic minerals and dispersed pyrite in sediments attest to the low salinity of the environment.