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Dissertações em Geologia e Geoquímica (Mestrado) - PPGG/IG

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2604

O Mestrado Acadêmico pertence ao Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).

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Acesso aberto (Open Access)
As águas subterrâneas de Belém e adjacências: influência da Formação Pirabas e parâmetros físico-químicos para medidas de qualidade
(Universidade Federal do Pará, 1996-04-08) SAUMA FILHO, Michel; LIMA, Waterloo Napoleão de; http://lattes.cnpq.br/1229104235556506
In the Metropolitan Region of Belém (PA) the water supply to the population comes from springs (physiographic area of Utinga) and from a network of positional tube wells, in general, in more remote urban areas or where pumping is precarious. This work evaluates the groundwater used in the Metropolitan Region of Belém, correlating data of physical, physical-chemical and chemical parameters, in an attempt to compose an understandable picture about the quality of these waters, and to verify the influence that they suffer from the geological units in which they are located. the aquifers that preserve them are located. To carry out the work, water samples were collected in two different seasonal periods: dry and rainy. After exhaustive consultation of the files of companies, institutions and researchers, 17 tubular wells were selected, 9 in Belém, 5 in Icoaraci, 2 in Mosqueiro and 1 in Ananindeua (Annex A). The most frequent turbidity indices were between 9 and 14 units (ppm of SiO2), but some wells showed higher values (33, 41 and 71 ppm of SiO2. Only in some cases, this turbidity can be immediately correlated with the silica content obtained by chemical analysis. The most frequent color measurements are in the range from zero to 7.5 U.C., with the zero index predominating. However, some wells showed a value above 100 U.C. and others, less frequent, with indices varying between 20 and 60 U.C. The pH and electrical conductivity were quite different parameters. Thus, the highest pH and electrical conductivity indices were verified in the aquifers of the Pirabas Formation. In these cases, the pH was around 6 .4 to 7.6 and conductivity between 231 and 362 µS/cm, with a discontinuity at 87.5 µS/cm, also attributed to a well associated with the aforementioned Formation. More acidic waters (pH below 6.38 and above of 4.01) are certainly attributed to the aquifers of the Barreiras and Post-Barreiras Group. The chemical constituents, notably the contents of Ca2+, Mg2+, Na+ and K+, are consistent with the interpretation of the numerical values of pH and electrical conductivity. Without exception, the concentrations of Ca2+ are higher than those of the other cations, establishing a decreasing order according to Ca2+> Mg2+> Na+>K+, with some inversion between Na+ and Mg2+. The highest concentrations of Ca2+ (soon followed by Mg2+) result from the dissolution of carbonates present in the Pirabas limestone. In fact, confirming this assertion, the concentrations of HCO-3 are also much higher than the concentrations of Cl- and SO2-4. It is to be expected, therefore, that the dissolution of Pirabas sediments produces higher concentrations of Ca2+ and HCO-3. The silica and iron contents also discriminate such waters. In general, higher silica contents correspond to greater depths, as would be expected, taking into account the action of chemical weathering on silicate minerals. As for iron, this constitutes a differentiating parameter of the waters of the Pirabas Formation, almost always at much lower levels than the corresponding values associated with the Barreiras and Post-Barreiras aquifers, with, however, exceptions, in which appreciable indices of iron related to Pirabas sediments. It should be noted that the Pirabas Formation appears in the Metropolitan Region of Belém almost always at depths greater than 100 m, although there are records of smaller depths, but these are apparently rarer situations, as is the case with well number 3. , on the University Campus, near the Guamá River, with a depth of 76 m, and the 94 m well of the Museu Paraense Emílio Goeldi, in the central area of the city (Annex A). The exhaustive consultation of the aforementioned archives of institutions, companies and researchers led to the realization that many tubular wells installed in the urban area use water associated with the Barreiras and Post-Barreiras aquifers, where the pH values are almost always, below 6 units, and electrical conductivity measurements rarely reach 100 µS/cm. Finally, it appears that there is a need for greater investments in order to increase the prospection and use of groundwater in the region, as these, in addition to dispensing with treatment prior to distribution, are still a source of resources, not dimensioned, but of great potential.
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/1345968080357131
The 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.
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/0307721738107549
The 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.
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/4546620118003936
The 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.
Acesso aberto (Open Access)
Análise tafonômica de Eremotherim laurillardi (Lund, 1842) dos depósitos pleistocenos, município de Itaituba, Pará
(Universidade Federal do Pará, 2008-08-18) FERREIRA, Denys José Xavier; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936
The present work deals with the taphonomic study of Eremotherium laurillardi (Lund, 1842), a ground sloth found within a Pleistocene depositional site in Itaituba town, State of Pará. The samples comprise approximately eight hundred skeletal fragments and complete pieces of this specie deposited in the Paleontological Collection of Museu Paraense Emílio Goeldi. Taphonomy is the post mortem history of fossils, the study of processes that influence preservation of potential fossils. It consists of two major aspects: biostratinomy, the study of processes affecting organism remains prior to burial and fossil diagenesis affecting potential fossils after burial. The biostratinomic study showed that the skeletal remains had a loose packing and were poorly sorted, indicating deposition in situ. Moreover, the biostratinomic study revealed that the taxonomic composition of the skeletal fragments is monotypical and monospecific related to catastrophic death (non-selective) by abrupt burial which occurred before necrolysis. Traces of abrasion and reworking during transport of the skeletal remains are insignificant and/or non-existent. Bioerosion facies have not been identified too. The non-preservation of soft parts shows that the necrolysis occurred in an aerobic environment. However, the partial presence of pyrite in the foramina and channels of ribs and teeth analyzed point to localized reducing micro environment. The skeletal remains show their morphological structures, both external and internal, well preserved suggesting that they were not exposed to the exogenous cycle, due to the quick burial. The fossildiagenetic study, conducted on samples of ribs, teeth and vertebrae, using both optical and scanning electron microscopy, revealed that both the bone and dental structures, known as Havers` channels and dentinal tubules, respectively, remained well – preserved. Additionally EDS Analysis (Energy Dispersive Spectroscopy) carried out on these components showed a nearly unaltered chemical composition relating to Ca, P, Mg, K and Na contents.
Acesso aberto (Open Access)
Avaliação dos impactos da ocupação urbana sobre as águas da bacia hidrográfica do igarapé Mata Fome, Belém-PA
(Universidade Federal do Pará, 2001-05-17) GASPAR, Marcia Tereza Pantoja; SOUZA, Eliene Lopes de; http://lattes.cnpq.br/2060516413833723
The watershed of the Mata Fome stream, with 6 km2, is located to the north of the Metropolitan Region of Belém. It is the pilot area for the implementation of the UN's Urban Management Program (PGU), which has among its objectives the environmental recovery of this area. The present study, inserted in the above mentioned program, evaluates alterations related to the anthropic occupation of the basin, through hydrogeological and water quality data from the stream and the free aquifer. In the analyzes of the waters carried out in the dry (November) and rainy (April) periods of 2000, the nitrogen components (NH4+, NO2-, NO3-), dissolved oxygen (OD), total dissolved solids (STD), fecal coliforms and total values, pH and electrical conductivity (EC). The hydrological regime of the stream was evaluated through discharge measurements and readings of limnimetric rulers, which were installed in an intensely occupied area, at the mouth of the stream, under the influence of the tides (station 1), and at its source, relatively preserved and without tidal influence (station 2). The stream showed a regime characterized by 9 hours of low tide and 4 hours of high tide, reaching higher water level heights in the rainy season (January-June), in the high tide, with a maximum height of about 3 meters, and a minimum of 0.4 meters at low tide. In the dry season (July-December) the maximum height, 1.99 m, also occurred at high tide, while the minimum height, 0.40 m, occurred at low tide. the net discharge from the stream was measured only in the dry period and presented minimum and maximum values of 0.03 and 0.201 m3/s, respectively, with the minimum value occurring in the transition from the ebb to flood regime. Double cylinder infiltration tests, carried out in the occupied area and at the source, revealed a rapid stabilization of infiltration in the first area, in relation to the most preserved area. The water from the stream showed pH values close to or greater than 7, the highest being obtained in the dry period. The electrical conductivity was also higher in this period, with an average of 260 µS/cm. The DO contents, quite low, varied between 1.0 and 3.5 mg/L, with the highest values obtained in the rainy season, possibly resulting from a greater oxygenation of the water in this period. The presence of domestic waste and sewage in the stream is mainly portrayed by the high amount of fecal coliforms that, in station 1, during the rainy season, reach a maximum of 92,000 CF/100 mL, at high tide. In the spring area, although relatively preserved, the CF values were also high, reaching a maximum of 65,000 CF/100 mL in the dry period. Among the nitrogen components analyzed, the NH4+ contents stand out, reaching values above 3 mg/L, reaching 12 mg/L in station 2, during the dry period, reflecting a small "invasion" that was beginning to settle in that area. area. The load carried by the stream evaluated at station 1, only for the dry period, presented higher values in the ebb tide, due to higher discharges in this tidal regime. Nitrate discharge was the highest, reaching a maximum of 0.44 µg/sec in the ebb tide regime. The ionic balance (t+km-2+year-1) showed positive values for all analyzed parameters, indicating a greater outflow of substances to the Guajará Bay, in relation to the solutes brought from this bay, during the flood tide. According to CONAMA Resolution No. 20/86, the water in the creek is unsuitable for bathing (primary contact recreation). The free aquifer studied, the main source of supply for the residents of the area, has a static level with an average depth ranging from 2.26 m to 1.21 m, between the dry and rainy seasons, respectively. Hydraulic potential maps, prepared from static level measurements carried out in 30 excavated wells, in these two periods, indicate that the underground flow converges to the stream. The regulatory reserve, calculated from the natural flow rate (VEN), presented a value of 1,050,000 m3, with a restitution for the stream of 175,000 m3/Km2. Among the water quality indicators evaluated, the ammonium levels are worth mentioning, reaching 3.54 mg/L, well above the potability limit (0.06 mg/L) established by USEPA. The nitrate content reached 30 mg/L, still below the potability limit (45 mg/L), but already deserving attention, due to its conservative character. The presence of fecal coliforms in the water of some analyzed wells also indicates that their water is unfit for human consumption.
Acesso aberto (Open Access)
Avaliação experimental da mobilidade do dimetoato na zona não saturada, em áreas de agricultura intensiva na bacia hidrográfica do igarapé Cumaru, município de Igarapé-Açu (PA)
(Universidade Federal do Pará, 2003-10-21) LIMA, Lilianne Maia; SOUZA, Eliene Lopes de; http://lattes.cnpq.br/2060516413833723
Family farming in the eastern Amazon, and particularly in northeastern Pará, is characterized by the implementation of semi-perennial industrial crops with heavy application of pesticides. This study was carried out with the main objective of evaluating the mobility of pesticides, in particular dimeatoate, in the unsaturated zone of the Cumari creek watershed, in the municipality of Igarapé-Açu (PA). In the area, the aquifer is constituted by inconsolable sand-clay and sand-silt sediments belonging to the Post-Barreiras period. Specifically, the objective was to analyze the potential for contamination of groundwater by pesticides. The objective was also to quantify the geochemical process of sorption, relating it to the physical and chemical characteristics of the unsaturated zone. A mapping of the areas where passion fruit is cultivated was carried out, since a high volume of pesticides is used in this culture, together with a survey of the agricultural pesticides used in the area. Subsequently, the risk of groundwater contamination was assessed using the GUS index (Groundwater Ubiquity Score). This index has as parameters the half-life values of the compound in the soil (DT50) and the coefficient of adsorption to organic matter (Koc). In addition, manual auger drilling was carried out in order to collect sediment samples from the unsaturated zone for laboratory analysis. In the laboratory stage, the granulometry, mineralogy, natural pH and organic matter content of the different levels of the unsaturated zone were determined, aiming at its characterization. This step also included the sorption experiment and the determination of dimethoate. Based on the risk analysis, it was found that dimethoate has the greatest potential to contaminate groundwater, with a GUS index ranging from 2.36 to 3.36. The sorption experiment showed that, in percentage terms, the sorption of dimethoate by sediments in the unsaturated zone ranged from 2.5% to 3.2%. These data confirmed the high potential for groundwater contamination by this substance, which is mainly due to its mobility and low retention. It was also verified that the amount of organic matter and the pH exert a greater influence on the sorption of dimethoate.
Acesso aberto (Open Access)
Bioestratigrafia e paleoecologia dos depósitos marinhos Pensilvanianos da Formação Piauí a partir de novas ocorrências de conodontes
(Universidade Federal do Pará, 2021-08-08) DIAS, Sanmya Karolyne Rodrigues; SCOMAZZON, Ana Karina; http://lattes.cnpq.br/5002093091311202; https://orcid.org/0000-0002-2189-2664; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
Conodonts are primitive vertebrates useful along the Paleozoic and Triassic all over the world to establish age and marine environment facies and to correlate these sedimentary sequences. Among intracratonic Brazilian basins, the Parnaíba Basin presents evidence of the record of this marine invasion in the Pennsylvanian carbonate sequences in the Upper Member of the Piauí Formation, particularly the fossiliferous Mocambo Carbonate sequence. The study of the paleontological content of these carbonate rocks is significant for the understanding of the paleoecological and paleoenvironmental perspective of the succession, and for its biostratigraphic refinement, in the case of fossil guides such as conodont. The description of the conodont species allowed the taxonomic classification, biochronostratigraphical refinement and inferences of paleoecologic conditions of the study area from comparisons of this occurrence with biozones established for Pennsylvanian of Amazonas Basin and from classic areas such as North America, Russia and China. The conodonts fauna includes three distinct species - Diplognathodus orphanus, Idiognathodus incurvus and Adetognathus lautus -registered in Mocambo Carbonate outcrops, marine portion of the Piauí Formation, in José de Freitas (PI) region and suggesting a late Bashkirian age for the sequence. Of these three species, the inedited occurrence of Diplognathodus orphanus, an excellent biostratigraphic marker of Atokan, are registered here. The occurrence of these taxa together with megaspore, ostracods, benthic foraminifers and teeth fish, suggest a paleoenvironment of very shallow marine platform. These data make possible to correlate Mocambo Carbonate with the marine section of the Amazonas Basin, allowing the correlation of the Piauí marine portion of Parnaíba Basin with the transgressive-regressive epicontinental Itaituba-Piauí Sea in Northwest South America, Western Gondwana, during the late Paleozoic.
Acesso aberto (Open Access)
Bioestratigrafia e paleoecologia dos depósitos marinhos Pensilvanianos da Formação Piauí a partir de novas ocorrências de conodontes
(Universidade Federal do Pará, 2021-08-08) DIAS, Sammya Karolyne Rodrigues; SCOMAZZON, Ana Karina; http://lattes.cnpq.br/5002093091311202; https://orcid.org/0000-0002-2189-2664; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
Conodonts are primitive vertebrates useful along the Paleozoic and Triassic all over the world to establish age and marine environment facies and to correlate these sedimentary sequences. Among intracratonic Brazilian basins, the Parnaíba Basin presents evidence of the record of this marine invasion in the Pennsylvanian carbonate sequences in the Upper Member of the Piauí Formation, particularly the fossiliferous Mocambo Carbonate sequence. The study of the paleontological content of these carbonate rocks is significant for the understanding of the paleoecological and paleoenvironmental perspective of the succession, and for its biostratigraphic refinement, in the case of fossil guides such as conodont. The description of the conodont species allowed the taxonomic classification, biochronostratigraphical refinement and inferences of paleoecologic conditions of the study area from comparisons of this occurrence with biozones established for Pennsylvanian of Amazonas Basin and from classic areas such as North America, Russia and China. The conodonts fauna includes three distinct species – Diplognathodus orphanus, Idiognathodus incurvus and Adetognathus lautus -registered in Mocambo Carbonate outcrops, marine portion of the Piauí Formation, in José de Freitas (PI) region and suggesting a late Bashkirian age for the sequence. Of these three species, the inedited occurrence of Diplognathodus orphanus, an excellent biostratigraphic marker of Atokan, are registered here. The occurrence of these taxa together with megaspore, ostracods, benthic foraminifers and teeth fish, suggest a paleoenvironment of very shallow marine platform. These data make possible to correlate Mocambo Carbonate with the marine section of the Amazonas Basin, allowing the correlation of the Piauí marine portion of Parnaíba Basin with the transgressive-regressive epicontinental Itaituba-Piauí Sea in Northwest South America, Western Gondwana, during the late Paleozoic.
Acesso aberto (Open Access)
O Cinturão Araguaia na região de Xambioá (TO) - São Geraldo do Araguaia: geometria, cinemática e aspectos litológicos
(Universidade Federal do Pará, 1993-09-22) SANTOS, Raimundo Oliver Brasil dos; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286
The northern segment of the Araguaia belt, near the cities of Xambioá and São Geraldo do Araguaia, consists mainly of supracrustal rocks from the Estrondo Group, in addition to gneisses from the Colméia Complex, exposed in the cores of the Lontra and Xambioá structures, exposed in the cores of the structures from Lontra and Xambioá, and from rocks from the Pequizeiro Group, which make up a narrow strip at the western end of the area. Considering the geometry and nature of the larger structures as well as the complexity of the structural framework, the area was divided into 5 (five) sectors. According to this picture, it was deduced that the macro geometric arrangement corresponds to an imbricated system of ductile thrusts, with rare "nappe"-type features standing out. thrusts; holomorphic folds related to late thrusts, or the transpression between transcurrent systems; and transcurrent shear zones, interpreted as lateral ramps. At the mesoscopic level, the structures are represented by the mylonitic foliation, the stretch lineation, folds of different styles and the On the other hand, thin lamina analysis revealed microstructures such as: porphyroclasts and asymmetric porphyroblasts with pressure shadows; quartz ribbons; S-C arrangements, tectonic twins in feldspar crystals; pisciform features; quartz-feldspathic aggregates in the form of lenses, microbanding, and recovery features. chthonic, four main movements were characterized in the progression of shear deformation: the first is related to the intense imbrication of rocky bodies resulting from the propagation of ductile thrusts, which must have been accompanied by the individualization of the lateral slopes; the second is associated with the uplift of splinters from the basement, imposing kilometric folds in the initial arrangements, due to a second generation of thrusts that did not affect the uppermost packages. At this point, it is assumed that there was significant movement along the side ramps; the third refers to the rotation of the megafolds, preferably in the central part of the area, due to the intensification of movements on the side ramps; and the fourth corresponds to the imbrication that was superimposed on the geometric arrangement created by these lateral ramps. Tectonic evolution, as understood here, developed according to the oblique collision process of continental masses, with preferential transport of rock units from SE to NW. Finally, a brittle regime is recorded through fault and fracture systems that are associated with Paleozoic and Mesozoic extensional events and, in part, with the neotectonic framework.
Acesso aberto (Open Access)
Composição isotópica de carbono e oxigênio em ostracodes de depósitos Neógenos da Formação Solimões, estado do Amazonas
(Universidade Federal do Pará, 2011-08-10) SILVA, Melissa do Socorro Fonsêca da; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936; https://orcid.org/0000-0003-0276-0575
The Neogene period was marked by important global events such as subsidence, climate seasonality and changes in sea level. In South America, the uplift of the Andean Cordillera was the main event affecting the river system and, consequently, climate and biota of the Amazon during the Miocene. The knowledge of the depositional history contributes to the understanding of many environmental changes occurring in the Miocene. The question exists about possible marine incursions in the Miocene deposits of Western Amazonia, is a favorable scenario for the use of isotope analyze in the shells of ostracods from Solimões Formation. This work is a contribution for paleoenvironmental interpretations of data using the isotopic ratio of C and O in the ostracod shells from the Neogene Solimões Formation aiming to correlation with adjacent areas. The samples are from two cores (1-AS-31-AM e 1-AS-34-AM) and three outcrops (Morada Nova, Aquidabã e Torre da Lua) located in the southwestern state of Amazonas. Among the registered ostracofauna, it was observed that the most representative species for this study belong to the genus Cyprideis (Cyprideis pebasae and Cyprideis machadoi), given its occurrence both in outcrops and cores, as well as the preservation condition they were found. In general, the isotope analysis showed a distribution with only low values for 13C/12C and 18O/16O ratios. The lower depletion of δ18O the sample TL03 of Torre da Lua outcrop and the depth 138,20m of 1AS-31-AM core, reflecting increased evaporation. In these intervals cores increased evaporation occurred over the top where we found the less negative values. However the remaining samples from outcrops and cores presented greater depletion where the decrease of δ13C values possibly indicates humid environment and a reduction in the productivity of these species or organic matter preservation decay and the δ18O values registered lower evaporation.
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Correlação bioestratigráfica e paleoecológica de foraminíferos cenozóicos das Formações Marajó e Pirabas, Nordeste do Estado do Pará, Brasil
(Universidade Federal do Pará, 2022-07-18) GARZÓN ROJAS, Laura Estefanía; SOARES, Joelson Lima; EVANGELISTA, Anna Andressa
Previous studies have re-evaluated stratigraphic and geophysical aspects of the sedimentary sequences of the east coast in the northeast of Pará state, reinterpreting the geological limits of the Marajó Basin and the Bragantina Platform, structures separated by the Vigia- Castanhal fault. These geotectonic compartments demonstrate the influence of the major transgressive event that occurred globally at the beginning of the Neogene and the intervention of the increased inflow from the Andean transcontinental cratonic drainage of the Amazon River on the development of the Bragantina Platform marine carbonate sequences from the Pirabas Formation (Oligo-middle Miocene) and the expressive siliciclastic-carbonate sedimentation of the Marajó Formation developed in the post-rift phase at the Marajó Basin. The two study sites Inhangapi (Marajó Formation) and Vigia (Pirabas Formation) are located near the Vigia-Castanhal trough and correspond to the boundary between the Marajó Basin and the Bragantina Platform respectively. This study aims at correlating biostratigraphically the paleoenvironmental conditions and paleoecologies based on qualitative and quantitative multivariate analysis, foraminifera association analysis by cluster grouping and paleodepth measurement with P/B ratio; carried out according to taxonomic classification of benthic foraminifera following specific contributions. The fossiliferous contents of these formations present a great similarity and diversity in the benthic hyaline microforaminifera that occur in both siliciclastic and calcareous depositional environments. These habitats have been colonized by a diverse and abundant benthic life that indicate shallow, warm, good circulation, and oxygenation in the transitional marine zone. Thus confirming that these two Cenozoic sedimentary units present different lithologies and depositional environments, the Marajó Formation being generated in a dynamic, suboxic, variable salinity, restricted marginal marine environment and marine incursions confirmed by the abundance of species such as Cribroelphidium williamsoni, Ammonia tepida and A. beccarii; and the Pirabas Formation was interpreted as a brackish marine marginal environment and oxic of middle neritic platform with abundance of the species Cibicides subhaidingerii and Cassidulina laevigata. These two localities maintain micropaleontological silimarities, confirmed by the presence of species such as Hanzawaia mantaensis, C. pachyderma, Uvigerina peregrina and Lobulata lobulata which converts them into chrono-correlative units.
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Depósitos carbonáticos-siliciclásticos da porção superior da Formação Piauí, carbonífero da bacia do Parnaíba, região de José de Freitas-PI
(Universidade Federal do Pará, 2015-07-22) MEDEIROS, Renato Sol Paiva de; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
The northwestern margin of the Gondwana, in the Neocarboniferous period, was influenced by a large transgressive-regressive event, depositing thin carbonate sequences from Andean basins to center-southern portions of the paleocontinent, such as the stratigraphic boundaries of the Parnaíba Basin. The Higher Member of the Piauí Formation in the Parnaíba Basin, studied in the region of José de Freitas, displays richly fossiliferous carbonate deposits overlapped by prograding clinoforms, defining the transition from a transgressive system tract to an highstand system tract. The facies and stratigraphic analysis of this succession allowed the individualization of 17 sedimentary facies and microfacies grouped in four facies associations (FA): the FA1 – Campo de Dunas – is below to the further FA and is composed by thin and average sandstone, with well selected and rounded grains, displaying plane parallel stratification with high level of bioturbation, cross-tubular stratification and translatant subcritically climbing ripple cross-lamination. The FA2 - Shallow sea deposits – is composed by a carbonate plain with tubular and continuous layers of solid carbonate and fossiliferous peloids interspersed with thin lenses of bituminous shale. The FA3 – Frente Deltaica and FA4 – Prodelta consist of pelitic layers and thin and average sandstones, arcosians and quartz sandstones, marked by surfaces of subaerial exposure with shrinkage cracks, cemented by carbonate, arranged in continuous tabular layers or in the form of sigmoidal lobes, as well as liquefaction structures of the types load cast and flame, and fluidization of the type disruption of layers, which distort the strata. The facies data corroborate the idea that the sea in the Pennsylvanian retrograded up to the border of the Parnaíba Basin, and later with the Appalachian orogeny (300 Ma) the top of the Parnaíba River arched and stepped back the marine incursion, followed by a progradational event on marine deposits.
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Depósitos costeiros e microbialitos da Formação Itaituba, o Pensilvaniano da borda sul da Bacia do Amazonas, região de Placas, Pará.
(Universidade Federal do Pará, 2019-12-29) OLIVEIRA, Fernando Andrade de; ROMERO, Guilherme Rafaelli; SILVA JUNIOR, José Bandeira Cavalcante da; http://lattes.cnpq.br/8615194741719443
The Itaituba Formation in the Amazon Basin represents a Bhaskiriana-Moscowian carbonate succession, composed of fossiliferous limestone, fine dolomite, fine to coarsegrained sandstone, gray shales and evaporites. Outcrop-based facies and stratigraphic analysis combined with microfacies study allowed the paleoenvironmental reconstitution of the Itaituba Formation, on the southern border of the Amazon Basin, Southwestern of Pará State. The 14mthick carbonate succession with occurrence of microbialites, consists of 9 facies and microfacies, such as: a) laminated shale (F1); b) laminated sandstone (Al); c) laminated siltstone (Sl); d) massive sandstone (Mm); e) mudstone with desiccation cracks (Mg); f) wackestone bioclastic (Wb); g) packstone bioclastic (Pb), h) oncolitic floatstone (Fo) and i) boundstone. These facies are grouped into two facies association (AF): AF1, lagoon / tidal flat deposits, consisting of facies Fl, Al, Sl, Mm, Mg, Wb, related to the flat and laterally continuous buildings with predominance of facies F1, interlayed by centimeter layers of facies Wb and Pb, organized in a fining upward cycle and; and AF2, shoal / barrier island, constituted by Pb facies and Fo and Bd facies, with Pb displayed in continuous flat and lateral bodies and Fo and Bd in lensshaped bioherms. Fo facies are the oncolytic microbilites and associated with microstromatolites, described as M1 and M2a morphotypes, and Bd facies, include columnar stromatolitic forms, described as M2b and M2c morphotypes. The depositional model of the Itaituba Formation in the Placas-PA region consists of a coastal system with lagoon, shoals / barrier island and tidal flat. Microbialites developed in the coastal region in the Amazon Basin during the Bashkirian-Moscovian transition, representing a transition to more restrictive environmental conditions in relation to fauna and flora, and more conducive to the proliferation of cyanobacteria, with probably increased alkalinity in water. These cyanobacteria evidences are record, for the first time, in Carboniferous rocks of the Amazon Basin improved the knowledge related to the carbonate fabric dispersion during the implantation of the Itaituba epicontinental sea in the Western Gondwana.
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Depósitos de rampa carbonática ediacarana do Grupo Corumbá, região de Corumbá, Mato Grosso do Sul
(Universidade Federal do Pará, 2019-02-12) OLIVEIRA, Rick Souza de; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
Depositional events which occurred after Late Cryogenian global glaciations (850 - 635 Ma) were marked by the implantation of extensive carbonate platforms and ramps developed in several cratons worldwide. In this period, one of the bioevolutive innovations was the appearance of calcified skeleton animals, like the genus Cloudina (~548 Ma). In South America, one of the best records of Ediacaran carbonate deposits with these macrofossil is the Corumbá Group, exposed in the southern Amazon craton. These deposits were deformed by Brazilian/Pan-African tectonics which led to the establishment of the Paraguay belt in the Neoproterozoic-Cambrian transition. Outcrop-based facies and stratigraphic analysis, assisted with C, O and N isotope data of the Bocaina and Tamengo formations, belonging to the upper Corumbá Group, were carried out in the Corumbá and Porto Morrinhos regions, State of Mato Grosso do Sul, Brazil, and allowed the reconstitution of the Ediacaran carbonate ramp and the habitat of Cloudina. The Bocaina Formation consists of small-scale shallowing upward cycles grouped into two facies associations: 1) intertidal plain, consisting of well sorted and rounded fine-grained quartz-sandstones cemented by dolomite and fine dolomite with stratiform and columnar stromatolites, fenestral/bird´s eyes porosity and mud cracks; and 2) subtidal shoals, formed mainly by intraclastic dolomites (intraclasts of dolomicrite and peloidal dolomite) and subordinated fine-grained sandstones and shales. Deformation structures occur in both associations and are related to liquefaction and fluidization processes, possibly triggered by seismicity. The Tamengo Formation consists of the associations: 1) shoreface with oolithic bars, composed of intraclastic and oolithic packstones, lime mudstone/ bituminous shale rythmithes with Cloudina; and 2) storm-influenced offshore, consisting of crystalline limestone with rare terrigenous grains, massive bedding, hummocky/swaley cross stratification, low-angle cross lamination and Cloudina shell fragments. Mudrocks and shales separate discrete tempestite beds. Cloudina lived in protected environments in the shoreface zone, periodically reworked by storms that accumulated coquinas in the offshore zone. The high carbon concentration (TOC up to 0.41%), the enriched values of δ13C (1.5 ‰ to 5.4‰) and δ15N (between 3.5 and 4.5‰) found in the carbonate rocks with Cloudina, indicate high organic productivity and oxygen concentration for the Terminal Neoproterozoic, similar to those of the current atmosphere/ocean interface.
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Depósitos lacustres rasos da Formação Pedra de Fogo, Permiano da bacia do Parnaíba, Brasil
(Universidade Federal do Pará, 2015-04-15) ARAÚJO, Raphael Neto; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
The Permian Pedra de Fogo Formation, exposed in the east and west borders of Parnaíba Basin, northern Brazil, represent one of the most important terminal Paleozoic sedimentary record of the Western Gondwana. The main lithotypes of this unit are sandstones, shales, carbonate rocks, evaporites. The unit is famous for its large amounts of chert and presence of well-preserved Permian flora. In the last decades of the 20 th century, previous works interpreted the paleoenvironment of the Pedra de Fogo Formation as transitional fluvial-deltaic deposits, storm influenced-shallow neritic (marine) to coastal sabkha plain, lacustrine and fluvial deposits with contribution of marine-aeolian sediments and shallow to restrict sea or epicontinental type. Facies analysis focused principally on outcrops of the base and upper part of this unit, involving approximately 100 m thick of the siliciclastic succession. Eleven sedimentary facies were recognized and grouped into three facies associations (FA), representative of a shallow lacustrine depositional system associated with mudflat and ephemeral rivers. FA1 is interpreted as mudflat deposits, consisting of laminated claystone/siltstone, sandstones/pelites with mud cracks and sandstones with cross-lamination, massive and megaripple beddings. Silicified nodules and molds like popcorn indicate evaporites deposits. Other common features are silica concretions, silicified teppes and silcretes. FA2 represents deposits of nearshore and consists of fine-grained sandstones with even parallel lamination, climbing ripple cross-lamination, massive and megaripple beddings, as well as, laminated mudstone/siltstone. FA3 refers to wadi/inundite deposits, generally organized in fining upward meter-scale cycles, consisting of conglomerates and medium-grained pebbly sandstones with massive bedding and cross-stratification, and claystone/siltstone with even parallel to wavy lamination. Tabular beds are frequent in FA3 while scour-and-fill geometry is rare. The alternation of pelites and fine to medium-grained sandstones with even parallel to wavy lamination are the main framework of the Pedra de Fogo Formation. Bioturbations, shrinkage cracks and different types of siliceous concretions, as well as, teeth of fish, ostracods, bryozoans and scolecodontes are common in the studied succession. Silicified plant remains, preliminarily classified to the genus Psaronius, are found in situ, concentrated near the upper contact with Motuca Formation, considered here as excellent biostratigraphic markers for the upper Pedra de Fogo Formation. Mudflats deposits occur in the basal Pedra de Fogo succession suggesting arid and hot climates for the early Permian. The midlle Permian was predominated semiarid allowing the proliferation of fauna and flora in humid regions adjacent and into the lake margin. The ephemeral fluvial inflow or wadis carried plant remains and terrigenous to the lake generating inundites. Retreat and expansion phases characterized the Pedra de Fogo lake, induced by extreme climatic changes influencing not only the sedimentation pattern as also the fossilization of the best well-preserved Permian fauna and flora. In the late Permian, the climate again became hot and arid due to the complete aggregation of Pangea supercontinent, favoring the deposition of Motuca red beds and establishment of Sambaíba erg, near in the Permian-Triassic boundary.
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Diagênese da formação guia, Ediacarano da Bacia Araras -Alto Paraguai, sul do Cráton amazônico
(Universidade Federal do Pará, 2022-10-31) SANTOS, Caio Silva dos; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
The Guia Formation is a limestone unit of the Araras Group, exposed in central region of South America. They correspond to Ediacaran (622-614Ma) carbonate platform deposits, developed in an epicontinental sea. This deposits unconformably overlies diamictite of Puga Formation related to 635Ma Marinoan glaciation, also distributed over the metamorphic basement. The Guia Formation, aim of study, is composed of limestones interbedded with thin layers of black shales. The data were obtained from an analysis of a 350m stratigraphic profile in one of the best exposition of Guia Formation in a COPACEL mine open pit in Nobres town, State of Mato Grosso. The unit consist in six lithofacies, grouped in one facies association that records a deep carbonate platform: bituminous lime-mudstone, massive lime-mudstone and lime-mudstone rich in terrigenous grains, carbonate shale, carbonate breccias and deformed breccias. These rocks were intensive affected by diagenetic process such as aggrading neomorphism, organic matter maturation, physical compaction, spar calcite cement, dolomitization, chemical compaction and hydrocarbon migration. Aggrading neomorphism affect the matrix, turn it to microspar and pseudospar with hipidiotopic mosaic. The micrite rich in organic matter is partially dissolved by fluids capable of dissolving the matrix, generating the vug pores. That pores are cemented by spar calcite. This cement has coarse granulation, subhedral crystals, when it fills fractures it presents crystals with rhombohedral cleavage, with two directions. In cathodoluminescence, the cement has orange to red bright when it fills vug fracture, and it has zoned pink bright luminescence filling pore vug. The stylolites form serrated surfaces of low amplitude, insoluble material, composed by clays, quartz, and organic matter compound its. Dolomitization affects the rocks in three moments: the first one is the replacement of spar calcite filling fractures with subeuhedral dolomites in hipidiotopic mosaic and opaques minerals inclusions, the second on is the filling by the matrix replacement with anehedral dolomites; the third one is the formation of saddle dolomite associated with hydrocarbon. Spot analysis with SEM/EDS, shows a large amount of Ca, ang low range of Mg, Si, S, Ca, Mn, Fe, Ni, Zn, Sr, Cd, Ba and Pb. Reasserting that carbonate are scant changed by diagenetic/dolomitizing fluids. These rocks are part of the Araras Petroleum System, the Total Organic Content Analysis (TOC) indicated values between 0.04 and 0.50%, classified as a low to medium potential. The association among the petrographic and geochemistry data suggest that the bitumen migration occurred at 610 Ma, during thermal uplift of the Araras Intracratonic Basin, before the deposition of the Alto Paraguai Group, which led to exposure of the Araras Group and oxidation of the hydrocarbon, allowing the identification of type IV kerogen. Rock Eval pyrolysis, Hydrogen Index and Oxygen Index data of these rocks, do not have the potential to generate oil or gas, and are constituted by oxidized organic matter, with immature thermal evolution.
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Distribuição, comportamento e definição de valores de background do mercúrio em sedimentos da bacia hidrográfica do rio Tapajós, Pará, Brasil
(Universidade Federal do Pará, 2023-10-24) RENTE, Augusto de Farias Silva; MARQUES, Eduardo Duarte; http://lattes.cnpq.br/8256609331887637; https://orcid.org/0000-0003-1133-9408; KÜTTER, Vinicius Tavares; http://lattes.cnpq.br/6652786694334612; https://orcid.org/0000-0001-7295-6800
Geochemical mapping and background determination help identify anomalies in the environment and distinguish natural or anthropogenic sources. Mercury (Hg) is a worrying element because it is conservative and can bioaccumulate and biomagnify. In the watershed Tapajós River, miners apply Hg to recover gold, this Hg can be released into the environment together with Hg from the soil, resulting in contaminated areas, associated with forest suppression, exposing the soil to erosion. In the study carried out, 343 samples of river sediments were collected and analyzed by SGB/CPRM in 2005/2006, with a sampling density of 1/135 km². The Hg content in the samples was analyzed by ICP-OES with a hydride generator. Hg values ranged from 0.01 to 4.46 mg.kg-1, and the geochemical background established for the area was 0.48 mg.kg-1, close to the probable effect level, 0.486 mg.kg-1. When classifying the samples by lithology, namely, alkaline granitoids, calcium alkaline granitoids, sedimentary rocks and gneisses and volcanic rocks, the mMAD showed the respective results, 0.69; 10.19; 0.03 and 0.77 mg.kg-1 for the upper thresholds and 0.01, 0.00, 0.02 and 0.00 mg.kg-1 for the lower threshold. The use and occupation classification, namely, Pasture and Forest presented mMAD values of 6.10 and 0.10 mg.kg-1 respectively for the upper thresholds and 0.00 and 0.01 for the lower thresholds. It should be noted that such a calculation for the mining area cannot be carried out due to the significantly low percentage of samples above the lower detection limit of the analytical method, suggesting high concentrations of Hg only in specific samples. The Enrichment Factor (EF) revealed a significant increase in mercury (Hg) in areas with greater human influence in the interpolation maps, identifying iron manganese oxyhydroxides and clay minerals as the main components responsible for Hg adsorption. The Contamination Factor Maps (CF) identified the same areas as contaminated that the FE identified as enriched. The studied region is naturally enriched in Hg in relation to other biomes, due to the following factors: 1° geogenic, associated with rock erosion and the process of tropical weathering, which leads to the formation of duricrust and lateritic soil, causing Hg to accumulate efficiently in the soil; 2° the local anthropic factor, acting on soil degradation, promoting the conversion of forests into pastures and mining areas, remobilizing and dispersing Hg. Considering the scale of approach of this work, a greater impact related to land use change was observed. A more detailed approach is suggested, such as a greater number of samples on a larger cartographic scale to define local impacts.
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Efeitos hidrotermais em rochas carbonáticas-siliciclásticas da Formação Itaituba, Pensilvaniano da Bacia do Amazonas, região de Uruará (PA)
(Universidade Federal do Pará, 2020-10-26) SOUZA, Isabele Barros; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
Carbonate and siliciclastic rocks from the Neocarboniferous period are widely recorded in the western and central-western portions in the Uruará region, State of Pará, on the southern edge of the Amazon Basin. These deposits are represented by the Itaituba Formation, from which a 35 m drill was described and five carbonate microfacies (calcimudstone, dolomudstone, bioclastic wackestone, bioclastic packstone and bioclastic grainstone rich in terrigenous) and eigth siliciclastic facies (massive claystone, black shale, siltstone with truncated crosslamination, siltstone with low-angle cross-lamination, siltstone with parallel laminate, sandstone with truncated cross-laminate, sandstone with parallel laminate and massive sandstone) were describe. From petrographic analysis, cathodoluminescence, X-ray diffraction, scanning electron microscopy and dispersive energy spectroscopy, it was possible to identify the main hydrothermal and diagenetic processes that affected these rocks. In the carbonate rocks, micritization, dissolution, calcitization, mechanical and chemical compaction and cementation were observed. In sandstones, quartz overgrowth, carbonate cementation and chemical compaction occur. During the Triassic-Jurassic period, great volcanism event occurred in the central portion of the West Gondwana supercontinent, known as the Central Atlantic Magmatic Province (CAMP), with the placement of dikes and basalt sills represented in the Amazon Basin by the Penatecaua Magmatism. The percolation of hydrothermal fluids in the late phase of this magmatism, promoted several changes in the mineralogy and textures of these rocks, among them hydraulic fracturing, formation of vugular porosity, precipitation of mineral assemblages typical of hydrothermalism such as - saddle dolomite, calcite, apatite, pyrite, chalcopyrite, galena, sphalerite, iron and titanium oxides, chlorites, talc, garnet, fluorcarbonate enriched in REE, saponite and corrensite - in the venules, and silicification of the matrix and carbonate grains. Organic geochemistry analysis in the samples of carbonate and shale, exhibit extremely low total organic carbon values, with low maturity, generating type IV kerogen, probably originated from oxidized organic matter. Thus, the present work intends to expand the study of rocks that occur in subsurface in the Uruará region, enabling the understanding of depositional and diagenetic processes active in their formation and its alteration due to the hydrothermal effect.
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Estratigrafia e análise paleoambiental de rochas Neoproterozóicas do Cinturão Araguaia, região de Redenção–PA, Brasil
(Universidade Federal do Pará, 2020-12-26) MEDINA HIGUERA, Adriana Nataly; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
The Neoproterozoic age was marked by intense climatic changes that were accompanied by the reorganization of the continental masses at a global level. These climatic events are represented by the Sturtian and Marinoan Snowball Earth glaciations registered in the rocks of the Cryogenic age. The rearrangement of the continental masses was marked by the rupture of the Rodinia (870 - 750 Ma) and subsequent intracratonic collisions (600 Ma) that generated the amalgamation of Gondwana, which in turn originated several orogens such as the Araguaia Belt. This Neoproterozoic geotectonic unit located in the northern portion of the Tocantins Province, is composed of the sedimentary rocks of the Baixo Araguaia Supergroup, which subdivided into the Estrondo and Tocantins Groups. In the region of Redenção, the company WMC Resources Ltda drilled several cores, called SMD, to unveil the genesis of the São Martim prospect. Initially, the carbonate and siliciclastic rocks without evidence of metamorphism, in these cores (SMD 08 and SMD 15), were positioned in the Couto Magalhães Formation. However, the original definition of this unit involves rocks with low-grade metamorphism. This fact led to a lithostratigraphic review of the Couto Magalhães Formation that occurs on a subsurface in the Redenção region, in addition to the paleoenvironmental reconstitution proposed in the original work. Thus, this unit was redefined, in the study region, exclusively based on its lithological characteristics and named São Martim Formation (carbonate rocks) and Rio Arraias Formation (siliciclastic rocks). Due to the few testimonies that exist, it is not possible to define its lateral extension in subsurface. To achieve the proposed objectives, faciological, sedimentological and geochemical analyzes were performed, as well as interpretations of sedimentary microfacies and glacial microstructures. The most basal portion of the cores is characterized by the occurrence of banded iron formations (BIF) that are interpreted as the basin floor, these formations have age and compositional similarity correlated with the BIF’s of the Carajás Formation. In the overlying sequence, nineteen sedimentary facies were defined, which were grouped into four facies associations corresponding. In the São Martim Formation, carbonate rocks are interpreted as the record of a carbonate platform environment in an epicontinental sea (AF1) that is in discordant contact with the BIF’s. The Rio Arraias Formation is characterized by deposits of mud-sand-rich slope plain turbidites (AF2), glacial (AF3) and sand-rich slope turbidites (AF4). The ages of these rocks were inferred from the bibliographic survey. Meso-Archean ages (2,952.3 ± 7.3 Ma and 2,994.0 ± 5.8 Ma) of the BIF´s were determined based on U-Pb (SHRIMP) data of detritical zircons. There are no ages available for carbonates from the São Martim Formation. The ages obtained for the siliciclastic rocks of the Rio Arraias Formation are based on the Pb / Pb methodology in clastic pyrite (716 to 670 Ma), diagenetic pyrites (668–616 Ma) and vein pyrite (438 Ma - 394 Ma). As well as Sm / Nd ages of sedimentary provenance between 1660 Ma, 1710 Ma and 1720 Ma in diamictite clasts of the Rio Arraias Formation. Additionally, rhyolitic pyroclastic rocks (ages U-Pb) dated 634 ± 21 and 624 ± 11 Ma superimposed directly on the glacial deposits of the Rio Arraias Formation. According to these geochronological ages, a Cryogenian age for the carbonate-siliciclastic sedimentary sequence is inferred in this work. The first sedimentation event after the formation of BIF was the deposition of carbonate sediments that make up AF1, the contact between these two associations is abrupt and characterized by the presence of a thin layer of black shale. The AF1 is constituted in the basal portion by pseudonodular to pseudolaminar mudstone, which present structures generated by chemical compaction such as dissolution seams and stylolites, in addition to fine levels of volcanic tuff, in the upper portion are the carbonate and siltstone breccia facies with wavy lamination. The second deposition event was possibly marked by the subsidence of the basin generated by the post-collisional closure of the Amazon with São Francisco / Congo cratons, where the AF2 was deposited, which is composed of massive sandstones and with plane-parallel lamination, truncated by wave and deformed, rhythms with plane-parallel lamination and truncated by wave, massive mudstones and with plane-parallel lamination. The third sedimentation event occurred at the maximum glacial advance and subsequent lowering of sea level, with the deposition of materials corresponding to AF3. This association is made up of foliated and massive diamictites associated with the deposition of sediments from glaciers that advance in water bodies. The transition between AF2 and AF3, presents layers with deformations possibly produced by glaciotectonic. The fourth sedimentation event is marked by a rapid thaw accompanied by an increase in sea level which increased the potential for preservation of subglacial deposits and possibly controlled the deposition of AF4 materials. This association is composed of massive sandstones with planar-parallel, wavy, wave-truncated and deformed lamination, to a lesser extent rhythms with planar and wave-truncated lamination and thin layers of massive mudstones, in addition to two levels of siliciclastic breccias. In summary, a new Neoproterozoic lithostratigraphic definition for the Araguaia Belt is proposed that suggests for the first time that the platform, in certain periods, was subjected to glacial processes possibly within the context of Snowball Earth, precisely to the Marinoan glaciation.