Navegando por Assunto "Barreiras Formation"

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Acesso aberto (Open Access)
Avaliação das influências espaço-temporais e de maré nas concentrações de metais em água e sedimentos estuarinos no entorno de um polo industrial amazônico
(Universidade Federal do Pará, 2025-04-25) FERREIRA, Johnata Azevedo; AMADO, Lílian Lund; http://lattes.cnpq.br/3382900147208081; https://orcid.org/0000-0001-7693-8191
Formed by the Tocantins River and smaller tributaries such as the Guamá and Capim rivers, the Pará River Estuary is an important ecosystem, serving as a shelter and reproduction site for many fish species and contributing to nutrient recycling in the aquatic environment. However, this area suffers from constant discharges of domestic and industrial effluents. The town of Barcarena, located in Pará and approximately 40 km from the state capital (Belém), plays a significant role in the state’s economy by hosting an industrial hub focused on the aluminum, kaolin, and steel industries. This study aims to characterize the temporal and spatial variation in the presence of metals and metalloids in both surface water (total, dissolved, and particulate fractions) and sediment across various points with differing levels of urban and industrial influence in Barcarena, PA. Water and sediment samples were collected during different seasonal periods throughout 2023 and 2024. During the sampling period, several phenomena were observed, particularly those related to the El Niño–Southern Oscillation (ENSO). The year 2023 was marked by the occurrence of La Niña, while 2024 was characterized by El Niño conditions. Sampling was performed in triplicate during both low and high tides at each site. Ten different metals (Al, Ba, Cd, Fe, Pb, Mn, Ni, Cr, As, and Hg) were analyzed in both water and sediment samples using Atomic Absorption Spectrometry with Flame Atomization, Graphite Furnace, Cold Vapor Mercury, and Hydride Generation techniques. The results showed no statistically significant differences between the different tidal conditions (high and low tide). Overall, the metals that exhibited higher concentrations across the sites were Al, Fe, Mn, and Ba, in both environmental matrices. This outcome was expected, as these elements naturally occur at high concentrations in the area's geological formation (Barreiras Formation). Although the region presented high metal concentrations, this pattern is most likely related to the local geology. However, anthropogenic factors may also contribute to elevated metal levels, as observed at certain highly impacted sites characterized by poor basic sanitation and direct discharge of domestic effluents and contamination from open-air dumps. These residues ultimately become sources of metal and metalloid input into the environment, especially for elements such as Pb, Hg, and As, in both water and sediment. These elements are often associated with domestic sewage, improper solid waste disposal, and open dumpsites. Our results also highlight important conclusions regarding the influence of ENSO on metal distribution in water and sediment in the Amazon region. Higher metal concentrations in both water and sediment were observed during the El Niño period compared to the La Niña period. Therefore, we conclude that environmental assessments in the Amazon region especially those involving metal monitoring in environmental matrices, should carefully consider the natural background input of these elements into abiotic compartments in order to accurately identify potential contamination arising from anthropogenic activities such as urbanization and industrialization.
Acesso aberto (Open Access)
O Neógeno da Plataforma Bragantina e da parte leste da Bacia do Marajó, norte do Brasil: Paleoambiente, Proveniência e relação com a evolução do Proto-Amazonas
(Universidade Federal do Pará, 2021-11-16) BAIA, Lohan Barbosa; SILVA JUNIOR, José Bandeira Cavalcante da
During the lower Miocene, tectonic stability on the Bragantina Platform favored the accumulation of carbonate deposits, later suppressed by a siliciclastic system associated with the Barreiras Formation. Previous works suggest that this one came from the sedimentary plume of the proto-Amazonas, while others indicate an independent evolution. Based on the above, this study applied provenance techniques to indicate the tectonic compartments that contributed as source rocks of the Barreiras Formation, discuss the influence of the proto-Amazonas in the suppression of the carbonate platform and understand the paleogeographic context. The study area covers the municipalities of Ourém (OU), Capanema (CA), Castanhal (CS), Santa Isabel do Pará (SI), Outeiro (OT), Mosqueiro island (IM), Salinópolis (SA), Aricuru (AR) and Mocooca (MO). Facies analysis techniques were performed with paleocurrent measurements, and 12 samples were collected, containing around 500 g of sediment each. Clasts were collected for morphological characterization in Ourém and Mosqueiro island. For the unconsolidated sediment, sieving was performed targeting the 250 - 125 µm and 125 - 63 µm fractions. Oxalic acid (50 g.L-1) was applied to these fractions and the light and heavy minerals were separated by density in bromoform (2.8 g/ml). Twenty-four petrographic thin sections of light minerals were prepared for cathodoluminescence (CL) and 24 thin sections of heavy minerals for identification of the mineralogical assembly, analysis of shape and elaboration of graphs. From the results of heavy minerals, it was possible to group the values with data from previous studies and apply the Inverse Distance Weighting method. The results indicate the presence of 10 facies, which were grouped into two associations, covering conglomerates, sandstones and pebbles. The clasts presented exclusively quartzous composition, predominating subangular to rounded shapes. The CL indicates a predominance of 45% of quartz with dark blue luminescence, 28% with light blue luminescence and 26% with violet luminescence. The results of heavy minerals indicate the presence of staurolite (54.45%), zircon (20.29%), tourmaline (10.02%), kyanite (7.19%), rutile (5.37%) and sillimanite (2.67%). Values above 50% of the sum of the percentages of zircon, tourmaline and rutile indicate an increase in maturity towards the coastal portion, while the distribution maps show a predominance of staurolite in the Bragantina Platform and an increase in kyanite values following those of tourmaline and zircon in the Marajo Basin. From the faciological interpretations, we were able to improve paleoenvironmental reconstruction consisting of alluvial fans, intertwined and meandering rivers, sandy plains, muddy plains and mangroves. The CL values and the high concentration of staurolite reflect sources of metamorphic rocks for the Bragantina Platform that come from southeastern Pará, possibly from the Gurupi Belt and São Luís Craton; while the CL values for the Marajó Basin, linked to the values of kyanite, zircon and tourmaline, indicate a strong influence of plutonic and metamorphic sources from southern Pará, such as the Tocantins-Araguaia Belt, Grajaú Basin and Sub -Cametá Basin. In general, the proto-Amazonas had no influence on carbonate suppression, the main phenomenon being responsible for the progradation of sediments, from metamorphic rocks with smaller contributions of plutonic and volcanic rocks, from the evolution of tectonics in the south and southeast of Pará.
Acesso aberto (Open Access)
O Neógeno da Plataforma Bragantina e da parte leste da Bacia do Marajó, norte do Brasil: Paleoambiente, Proveniência e relação com a evolução do Proto-Amazonas
(Universidade Federal do Pará, 2021-11-16) BAÍA, Lohan Barbosa; SILVA JUNIOR, José Bandeira Cavalcante da; http://lattes.cnpq.br/8615194741719443
During the lower Miocene, tectonic stability on the Bragantina Platform favored the accumulation of carbonate deposits, later suppressed by a siliciclastic system associated with the Barreiras Formation. Previous works suggest that this one came from the sedimentary plume of the proto-Amazonas, while others indicate an independent evolution. Based on the above, this study applied provenance techniques to indicate the tectonic compartments that contributed as source rocks of the Barreiras Formation, discuss the influence of the proto-Amazonas in the suppression of the carbonate platform and understand the paleogeographic context. The study area covers the municipalities of Ourém (OU), Capanema (CA), Castanhal (CS), Santa Isabel do Pará (SI), Outeiro (OT), Mosqueiro island (IM), Salinópolis (SA), Aricuru (AR) and Mocooca (MO). Facies analysis techniques were performed with paleocurrent measurements, and 12 samples were collected, containing around 500 g of sediment each. Clasts were collected for morphological characterization in Ourém and Mosqueiro island. For the unconsolidated sediment, sieving was performed targeting the 250 - 125 μm and 125 - 63 μm fractions. Oxalic acid (50 g.L-1) was applied to these fractions and the light and heavy minerals were separated by density in bromoform (2.8 g/ml). Twenty-four petrographic thin sections of light minerals were prepared for cathodoluminescence (CL) and 24 thin sections of heavy minerals for identification of the mineralogical assembly, analysis of shape and elaboration of graphs. From the results of heavy minerals, it was possible to group the values with data from previous studies and apply the Inverse Distance Weighting method. The results indicate the presence of 10 facies, which were grouped into two associations, covering conglomerates, sandstones and pebbles. The clasts presented exclusively quartzous composition, predominating subangular to rounded shapes. The CL indicates a predominance of 45% of quartz with dark blue luminescence, 28% with light blue luminescence and 26% with violet luminescence. The results of heavy minerals indicate the presence of staurolite (54.45%), zircon (20.29%), tourmaline (10.02%), kyanite (7.19%), rutile (5.37%) and sillimanite (2.67%). Values above 50% of the sum of the percentages of zircon, tourmaline and rutile indicate an increase in maturity towards the coastal portion, while the distribution maps show a predominance of staurolite in the Bragantina Platform and an increase in kyanite values following those of tourmaline and zircon in the Marajo Basin. From the faciological interpretations, we were able to improve paleoenvironmental reconstruction consisting of alluvial fans, intertwined and meandering rivers, sandy plains, muddy plains and mangroves. The CL values and the high concentration of staurolite reflect sources of metamorphic rocks for the Bragantina Platform that come from southeastern Pará, possibly from the Gurupi Belt and São Luís Craton; while the CL values for the Marajó Basin, linked to the values of kyanite, zircon and tourmaline, indicate a strong influence of plutonic and metamorphic sources from southern Pará, such as the Tocantins-Araguaia Belt, Grajaú Basin and Sub -Cametá Basin. In general, the proto-Amazonas had no influence on carbonate suppression, the main phenomenon being responsible for the progradation of sediments, from metamorphic rocks with smaller contributions of plutonic and volcanic rocks, from the evolution of tectonics in the south and southeast of Pará.