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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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)
Aspectos litoestruturais e mineralizações Salobo 3A (Serra dos Carajás-PA)
(Universidade Federal do Pará, 1996-10-29) SIQUEIRA, José Batista; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286
The Salobo district is located at the Carajás Province in the Cinzento strike-slip system, and is formed of supracrustal rocks of the Salobo Group and gneisses of Xingu Complex, which were assembled by several generations of shear zones. The Salobo Group includes magnetite-fayalite schist, biotite-almandine-magnetite-fayalite-grϋnerite schist, biotite schist, anfibol schist, chlorite schist, banded iron formation and quartzite. The Xingu Complex includes banded tonalitic gneisses, trondhjemitc and granodiritic gneisses, partialy migmatized. The older shear zones correspond to ductile thrusts to which the generalized imbrication of the lithological units and the tectonic layering, defined by strips and lenses of supracrustais rocks alternated with gneisse is due. Their movements is synchronous to that of the Itacaiúnas belt; minerals transformations under thermal conditions of amphibolite facies, as well as important modifications in the stratigraphic relationships of several lithological units, are related to therm. The second generation of shear zones formed the transtensive Salobo-Mirim duplex. They are sinistral strike-slip shear zones, linked by normal shear zones along which minerals transformations of greenschist facies occurred. The development of the duplex was controled by the former tectonic layering, and its assymetric shape was influenced mainly by the presence of a basement gneiss megalense. The third generation of shear zones is of transcurrent type, with NW-SE and NNW-SSE trends, which modified the Salobo-Mirim duplex geometry, and are interpreted as X features linked to the sinistral moviments. The shear zones of the west corner of the area represent the propagation of a horse tail structure at the west end of the Carajás fault; in these case, they could be oblique thrust. The Salobo 3A deposit is situated in the central part of a normal oblique shear zone, which belongs to a release bend along the main strike-slip shear zone of the Salobo-Mirim duplex. The copper and gold mineralizations are hosted in extension structures, as single and composite pull-apart structures, transtensive sigmoide stringers, tension gashes, pressure shadows and star strucutures in the cross-cutting zones of descontinuities. The Salobo 3 A deposit is an example of concentracion/reconcentracion of cooper and gold mineralizations in s transtensive shear zone due to deformational, hydrothermal and metamorphic processes.
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)
Braquiópodes devonianos da Bacia do Amazonas: novos dados taxonômicos, paleobiográficos e relações com as mudanças ambientais
(Universidade Federal do Pará, 2024-10-01) CORRÊA, Luiz Felipe Aquino; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936; https://orcid.org/0000-0003-0276-0575
The Devonian marked a significant phase in the evolutionary history of the Brachiopoda. During this period, the Phylum achieved its peak diversity (Emsian) and suffered one of its most significant declines (Frasnian–Famennian), ranking second only to the mass extinction event Permo-Triassic. Among the Brazilian sedimentary basins, the Amazonas Basin has the greater diversity of Devonian brachiopod genera, distributed among the following formations: Manacapuru (Lochkovian), Maecuru (early Eifelian), Ererê (Late Eifelian), and Barreirinha (early Frasnian). Studies of Devonian brachiopods from the Amazonas Basin began in the late 19th century with identifications of material collected during the Morgan Expeditions (1870–1871) and the Imperial Geological Commission of Brazil (1876). These expeditions focused primarily on the Maecuru and Ererê formations. The brachiopod fauna of the Manacapuru Formation (Lochkovian) was unknown until 2015, when during paleontological salvage at the Belo Monte hydroelectric plant in Vitória do Xingu, Pará, Brazil, a significant number of Rhynchonelliformes and Linguliformes samples were recovered. This work aims to carry out the taxonomic identification of brachiopods from the Manacapuru Formation, in addition to analyzing and discussing the possible factors that influenced the diversity of brachiopod genera among the sedimentary units of the Amazonas Basin (Mancapuru, Maecuru, Ererê, and Barreirinha formations). The taxonomic study of brachiopods from the upper part of the Manacapuru Formation (Lochkovian) has allowed, to date, the identification of two genera, Orbiculoidea d'Órbigny, 1847 and Schellwienella Thomas, 1910. Among the materials, Orbiculoidea has the greater diversity, totaling five species: Orbiculoidea baini Sharpe, 1856, Orbiculoidea bodenbenderi Clarke, 1913 and Orbiculoidea excentrica Lange, 1943 in addition to two new species: Orbiculoidea xinguensis Corrêa & Ramos, 2021 and Orbiculoidea katzeri Corrêa & Ramos, 2021. The species O. baini, O. bodenbenderi, and O. excentrica were recorded for the first time in the Manacapuru Formation and Northern Brazil, and they are also the oldest records (Lochkovian) from South America. The presence of Orbiculoidea in the region can be explained by two reasons: the proximity of the Amazonas Basin, located in the northwest of Gondwana during the Lower Devonian, with the paleocontinent Laurussia (where most occurrences of Orbiculoidea are recorded during the Silurian), favored the specific exchange between these two geographic regions; and the global rise in sea level during this period, which flooded much of northwest Gondwana, resulting in the presence of shallow seas in the Amazonas Basin, represented by marine sediments in the upper part of the Manacapuru Formation. These conditions favored the colonization of inarticulate brachiopods during the Early Devonian in northern Brazil. Furthermore, the new species Schellwienella amazonensis Corrêa et al. 2024, of the Pulsiidae Family Cooper and Grant, 1974, is proposed, this being the first record of the genus in the Amazonas Basin. Schellwienella amazonensis n. sp. and Schellwienella marcidula Amsden, 1958 from the Bois d’Arc Formation (Lochkovian), USA, are the oldest records of the genus. In the Devonian, Schellwienella occurred in all stages (Lochkovian, Pragian, Emsian, Eifelian, Givetian, Frasnian, and Famennian), mainly in the marine siliciclastic environments of Gondwana, transiting between temperate and polar latitudes. In the Carboniferous, its stratigraphic distribution was restricted to the Tournaisian-Visean interval, with a preference for warm water environments and carbonate platforms typical of low latitudes. We identified three distinct stages when analyzing the variation in Devonian brachiopod diversity in the Amazonas Basin. In stage 1, the peak of brachiopod diversity occurred in the early Eifelian (Maecuru Formation), when the Amazonas Basin was between subtropical latitudes 30°S and 60°S, under shallow and cold marine conditions, justified by the absence of carbonates, evaporites, and reefs in the region. In stage 2, the first decline in diversity occurred, recorded in the Ererê Formation (late Eifelian), attributed to a warmer climate and deeper waters than in the Maecuru Formation. Stage 3 occurred during the Frasnian when there was a second decline in brachiopod diversity in the Amazonas Basin (Barreirinha Formation). A major global transgression happened at the end of the Devonian. During this period, the Amazonas Basin experienced the deepest marine conditions in its history. Brachiopods of the Barreirinha Formation occur in black shale layers (offshore), attributed to a dysoxic to the anoxic environment of high stress, which explains the low diversity of brachiopods in this unit.
Acesso aberto (Open Access)
O Cambriano no Sudeste do Cráton Amazônico: paleoambiente, proveniência e implicações evolutivas para o Gondwana Oeste
(Universidade Federal do Pará, 2018-06-15) SANTOS, Hudson Pereira; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
Transgressive events recorded in many cratonic regions marked the Cambrian period, hypothetically related to the glacioeustasy and/or the progressive opening of the Iapetus ocean (~600 Ma). Such events influenced the paleoceanography of this period, including the progressive biota evolution – the ‘Cambrian Revolution’. Although the Gondwana Supercontinent margins, entirely amalgamated in the Lower Cambrian (540 Ma), were flooded, the inner part of this supercontinent was emergent, probably triggered by postcollisional epirogenic uplifts. Epeiric seas covered subsiding areas with projections towards the interior of the Western Gondwana, developing shallow platforms that covered ancient colisional suture zones. In the southeastern Amazon Craton, the recurrence of platform environments dates from Upper Cryogenian (~635 Ma) until the Cambrian with the installation of glacial deposits, overlaid by carbonatic and siliciclastic successions. Despite the previous insertion in the context of a foreland type basin related to the evolution of North Paraguai Belt (650-640 Ma), these deposits have been included in an inverted intracratonic basin in the Ordovician. The bottommost deposits of the Cambrian sequences, here presented, are comprised dominantly by siliciclastic rocks. These consist in the Upper and Lower members of the Raizama Formation and the base of Lower Member of the Sepotuba Formation, Alto Paraguai Group, exposed in the central and northeast portions of the inverted intracratonic basin, Mato Grosso state. Two depositional sequences (DS1 and DS2) characterize the Cambrian successions of the base of Alto Paraguai Group. The DS1 presents as a sequence boundary (SB1) an erosional hiatus previously interpreted in the southwestern basin. This stratigraphic surface becomes a correlative conformity towards the central and northern portions, where this covers the Araras carbonates and Cryogenian glacial deposits from Puga diamictites. The SB1 represents an erosional or non-depositional period of approximately 80 Ma developed over the carbonates of the Lower Ediacaran Araras Group, related to the epeirogenic uplifts of the basin. A second thermal subsidence phase would have led to the installation of a siliciclastic platform during the Cambrian, characterized by DS1 composed by two facies associations denominated FA1 and FA2. FA1 consists of subarkoses, quartz-wackes and pelites dominated by wave and storm processes, inserted in the offshoretransition, lower-middle shoreface and upper shoreface zones. The presence of infaunal vertical trace fossils belonging to the Skolithos Ichnofacies (Skolithos linearis; Diplocraterion parallelum; and Arenicolites isp.) at the base of the lower-middle shoreface deposits indicated a Lower Cambrian age, or younger, to the Raizama Formation, previously considered as Ediacaran. The FA2 comprehends subarkoses, quartzarenites, sublitarenites, quartz-wackes and sandstone/pelite rhythmites interpreted as complex tidal plain deposits, unconformably overlaid (SB2) by braided fluvial channel deposits of (FA3), which belong to the DS2. The DS1 would have been deposited during lowstand to transgressive system tract, organized in progradational parasequences. This stacking pattern is not compatible with the traditional stratigraphy sequence for TST, which is attributed to a slow subsidence rate concomitantly to a high sediment supply indicated by the Skolithos Ichnofacies. Subsequently, a less expressive drop in the sea level promoted a progradation of distal braided deposits (FA3) over the DS1, related to the lowstand system tract (LST) characterized by an abrupt change of the tidal heterolitic deposits to medium and coarse-grained quartzarenites from fluvial deposits. Paleoflow data oriented preferentially to NE and SE obtained in coastal beds from FA2 and FA3 allied to the Paleo- to Mesoproterozoic U-Pb detrital zircon ages have indicated provenance exclusively from SW and NW sources from Amazon Craton. Besides that, the detrital quartz grains analysis of sandstones of the bottommost Cambrian deposits indicate mainly igneous and metamorphic sources. Previous works indicated that the fluvial deposits of DS2 were succeeded by a transgressive system tract, marking this as the last transgressive event that influenced the Cambrian deposits of the intracratonic basin. Slowly, the ocean connection was interrupted as a consequence of the closing of Iapetus Ocean (~500 Ma) as a result of basin uplift. In this way, Cambrian epeiric seas were confined and consequently started the lacustrine phase of the basin in the Ordoviacian, represented by the Diamatino Formation deposits. Posteriorly, the intracratonic basin of the southeast Amazon Craton would have been inverted by the transtensional tectonics which propitiated the implantation of post-Cambrian intracontinental basins of the Western Gondwana.
Acesso aberto (Open Access)
O Camp nas bacias dos Solimões, Amazonas, Parnaíba e Parecis, Norte do Brasil: implicações geotectônicas e deposicionais para o jurássico do Gondwana Ocidental.
(Universidade Federal do Pará, 2024-08-23) REZENDE, Gabriel Leal; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
Geological studies in conjunction with applications of geophysical techniques are being widely used to highlight and characterize CAMP gravimetric anomalies throughout Northern Brazil, including the Solimões, Parecis, Amazonas and Parnaíba basins. Interpretations of a residual gravimetric anomaly from these basins were used to expand the understanding of the distribution of CAMP throughout the subsurface. This study was carried out through qualitative and quantitative interpretations of gravimetric data, supported by surface geological information, mainly stratigraphic data based on outcrops. From direct gravimetric modeling, based on available crustal gravitational structure models to separate a residual gravity signal from observed gravity data, realistically detailed geological and tectonic features were interpreted, providing useful information for a geophysical interpretation of geological sources. With the residual gravity anomaly, a map of the elastic thickness (Te) of the basins was obtained, using a new procedure, presumably allowing some gaps presented in the current literature on the CAMP to be filled. For each Te value, the residual gravimetric signal was calculated, considering the surfaces described by topography and Moho for a regional model with standard density and discretized into prisms. The cross-correlation between the observed gravity signal and calculated gravity signal made it possible to obtain a map of the elastic thickness of the studied areas. The highest correlation value is directly related to the best value of elastic thickness and Moho depth associated with crustal deformation. Our study used a combination of these techniques to presumably define the possible extent of Jurassic magmatism, the basin rheology of igneous body intrusion and history of thermal subsidence that largely controlled depositional control during and after the CAMP. The presence of low gravity values is closely related to the less dense lithological units of the upper crust, while the high gravity values are related to high-density rocks correlated to the continental tholeiitic flood basalts of the CAMP. The use of residual gravity anomaly based on crustal modeling combined with previous geological data was effective in identifying the CAMP record in these Amazonian sedimentary basins. Furthermore, some gravimetric signatures correlate well with the main structural discontinuities, particularly with the Monte Alegre Dome and Xambioá, Serra Formosa and Vilhena arches, respectively, in the Amazon, Parnaíba and Parecis basins. This interpretation provides a reasonable explanation for understanding structural lineaments without exclusively tectonic connotations, assuming a new interpretation for the gravitational field related to intracrustal density contrast or residual gravity field for these basins. Eastern Gondwana was gradually uplifted by subvolcanic bodies of the Penatecaua magmatism in the Amazon and Solimões basins. In contrast, extrusive volcanism characterizes Mosquito magmatism in the Parnaíba basin interspersed with intertrap sediments. Information obtained from the elastic thickness map, Moho depth and residual gravity signal indicate a thinner crust in the Parnaíba basin favoring the magmatic eruption induced by a hot spot installed on the western edge of the basin. On the other hand, in basins with denser and thicker crust, magma accumulates mainly as sills, providing greater resistance to rupture due to the swelling of the CAMP. The Parnaíba Basin experienced three magmatic pulses at intervals of approximately 1 Myr, alternating with the development of aeolian-fluvial-lacustrine systems (intertrap sediments) during non-magmatic periods, indicating short intervals of magmatic resump-tion and cooling in the CAMP, contrasting with the longer and continuous magmatism in the Amazon and Solimões basins, which lack intertrap deposits. These results are important for a new disposition of the tectonomagmatic, structural and stratigraphic history for these basins, since from a new context or geological evolution for the area it will allow a better understanding of the studied basins in lava-sediment interaction, preserved from the Jurassic and related to the CAMP events, which preceded the main continental rupture in northwestern Pangea.
Acesso aberto (Open Access)
A capa carbonática marinoana do Sul do Cráton Amazônico: multiproxies aplicados na reconstituição paleoceanográfica e geobiológica do início do Ediacarano.
(Universidade Federal do Pará, 2024-08-30) SANTOS, Renan Fernandes dos; SANSJOFRE, Pierre; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
The post-Marinoan glaciation (~650-635 Ma) was the most severe event from the late Cryogenian period of the planet. The snowball Earth conditions induced a climate anomaly, triggering major changes in the paleoenvironmental and ocean chemistry recorded in the carbonate cap sequences. The dramatic effects on the global sea level were caused by glacial-isostatic adjustment (GIA) and ice gravity on the coastal zones associated with the ocean thermal expansion under greenhouse conditions. The fast input of meltwaters contributed to a stable density ocean stratification formed by hypersaline deep waters and meltwater surface layers. The ocean destratification occurred in a timescale ranging from tens of thousands to thousands of years. The Puga cap carbonate (~635 Ma), the basal deposits of the Araras-Alto Paraguai basin from the southern Amazon Craton, is revisited in the classical sections from the Tangará da Serra and Mirassol d'Oeste, Mato Grosso State. This succession is one of the best records for evaluating the supersaturation events under GIA and transgression conditions that controlled the accommodation space in the southern Amazon Craton. Sedimentological and stratigraphic data were integrated with new paleoceanographic, and paleo-redox data combined with diagenetic, crystallographic, geochemical (primarily rare earth elements and trace metals), and isotopic (whole rock 87Sr/86Sr, εNd(t), δ 13C, δ 18 O, Sm/Nd) results providing further insights to understand the post-Marinoan conditions. The Puga cap carbonate sequence spans approximately 90 meters, with the first 10 meters composed of glaciomarine deposits, diamictites, and dropstones from the Puga Formation. The basal contact with diamictites is plastically deformed, indicating rapid carbonate precipitation. The cap dolostone consists of stratiform doloboundstones with gypsum pseudomorphs and domal doloboundstones with tubestone, which were deposited in a shallow platform with intense microbial activity. Peloidal dolomudstone/dolopackstone with laminations parallel to bedding planes and peloidal dolograinstones/dolomudstone with quasi-planar laminations and low-angle truncation were formed in a wave-influenced shallow platform. The cap limestone conformably overlies the cap dolostone deposits, marked by dolomitic marlstone with calcite crystal fans (aragonite pseudomorphs) interbedded with mega-rippled limestone. The facies association of the cap limestone indicates moderately deep-water conditions dominated by waves and storms transitioning to a deep platform supersaturated with CaCO3. The main diagenetic process is dolomitization during syn-depositional and shallow burial stages. Rare earth element + yttrium patterns have been analyzed in these deposits. Low Y/Ho ratios (<36) in the cap dolostone suggest a mixture of meltwater and seawater, while the base records superchondritic Y/Ho values up to 70 and high Eu/Eu* values up to 3, indicating upwelling of hypersaline seawater with hydrothermal fluid interaction, suggesting dolomite precipitation during ocean destratification. The radiogenic isotopic compositions of Nd, combined with other proxies such as δ 13C and 87Sr/86Sr, indicate the influence of continental and marine contributions. The Nd isotopic system, less susceptible to diagenetic exchanges, revealed distinct signatures of water masses and enhanced weathering of the Amazon Craton during deglaciation. This process is indicated by geochemical trends (e.g., Y/Ho) and 87Sr/86Sr, εNd(t), δ 13C values. 87Sr/86Sr data in the cap dolostone range from 0.7264 to 0.7084, higher than pre- and postglacial seawater values. More radiogenic 87Sr/86Sr values associated with less radiogenic εNd(t) values, similar to those found in diamictites, reinforce coastal weathering contribution to meltwaters. This multiproxies approach is a reconciliation with the previous rapid cap carbonate precipitation model following the short-term timescale for ocean destratification. Redox-sensitive trace metal data, U, Mo, V, Ni, Cu, P, and δ13C isotopes, indicated paleo-redox states and paleoproductivity during the post-glacial transgression. The cap dolostone precipitated under oxygenated conditions with extensive microbial community contributions, transitioning to predominantly dysoxic conditions with wave action in the last deposition phase. The abrupt sea-level rise altered the biogeochemical cycle, indicating a direct relationship between oxygen production and rapid microbial community colonization. The rapid sea-level rise and continental weathering reduced seawater Mg/Ca ratios with substantial Ca2+ input, also demonstrated by εNd(t) values, causing the change of dolomitic platform to CaCO3 -supersaturated seas in the Amazon Craton margin. Additionally, low siliciclastic content in the cap dolostone is consistent with the siliciclastic starvation model, and the abrupt increase caused the decline of microbial communities coincident with the predominance of dysoxic conditions and longterm transgression. During specific Cryogenian-Ediacaran deglaciation scenarios, anomalous sedimentary and geochemical processes generated one of the most complex paleoenvironmental disturbances in the biogeochemical cycle. They strongly influenced the rapid primary productivity, directly impacting microbial life. The analysis of Precambrian scenarios in the Amazon Craton unraveling the extreme climates sheds critical light on extremophile life proliferation and has strong implications for understanding other planetary surfaces.
Acesso aberto (Open Access)
Caracterização geomorfológica estratigráfica e geoquímica da Planície Costeira do município de Itarema-CE.
(Universidade Federal do Pará, 2011-09-01) PEREIRA, Lamarka Lopes; FREIRE, Geoerge Satander Sá; http://lattes.cnpq.br/6803944360256138; 6803944360256138; EL-ROBRINI, Maâmar; http://lattes.cnpq.br/5707365981163429; 5707365981163429
The Itarema coastal plain, situated at the western coast of Ceará, in the area dominated by the Cenozoic sedimentary cover. This thesis shows the geomorphological, sedimentological and geochemical features of this coastal plain. The Itarema coastal plain is subdivided in two major morpho-structural units: pre-coastal ¨plateaus¨ and coastal plain, that is subdivided into lithostratigraphic units, lagoon plain, tidal plain with and without mangroves, marine and fluvial plain, mobile and fixed dunes, beach ridges, tidal channels, sand bars and beaches. The supply and sediment transport in the area are closely linked to the climatic, meteorological and oceanographic conditions. The sedimentary, stratigraphy, geomorphological and geochemical data have been defined: (1) five lithological units: Lagoon Deposits, dune deposits, eolianits deposits, beach deposits and alluvial deposits and (2) seven lithofacies: mud sandy, mud, Sand mud, fine sand, medium sand, thick sand, conglomeratic sand-clay with different characteristics which have been drawn through the lateral and vertical correlations, thus allowing the interpretation of depositional paleoenvironments related to the evolution of the Itarema Coastal Plain. The analysis of the lithological units allowed the reconstruction of the processes indicative of a transgressive sucession prograded during which the lagoon-barrier system was installed on the system of alluvial fans, the bus of small streams, forming the lagoon plain, it was also noted that the lagoon has undergone changes in their size both by progradation of the barrier and subsequently by the deposition of sediments within the same wind. The Itarema coastal plain presents physiographic features of an coastal promontory or embaiments of central nuclei as a spiral, that would have provided the evolution to the current environment and the current model of coastline with beaches of the barrier beach-type and suggests that is occurring repetition in the construction of comparative morphology morphogenetic active in the region's past.
Acesso aberto (Open Access)
O cenozoico superior do centro-oeste da Bacia do Amazonas: paleobotânica do embasamento cretáceo e evolução do Rio Amazonas
(Universidade Federal do Pará, 2018-11-08) BEZERRA, Isaac Salém Alves Azevedo; NOGUEIRA, Afonso César Rodrigues; http://lattes.cnpq.br/8867836268820998
At the end of the Neogene and during the Quaternary, the development of the Amazon River caused significant paleoenvironmental and geomorphological changes that generated current ladscape at Amazonia. Previous models elaborated on a continental scale were based on data obtained from a drill core carried out on the Atlantic continental shelf, distant 200 km of the Amazon River mouth, suggesting the establishment of this drainage with Andean provenance from the Middle to Upper Miocene. In contrast, studies based on outcrops in the western and central portions of the Amazon have indicated younger ages for this ecosystem, from Pliocene to Quaternary. The sedimentological-stratigraphic study of the fluvial terraces of the Amazon River, exposed in the center-west portion of the Amazon Basin, assisted by luminescence geochronology, allowed to sequence the sedimentation events and discuss the paleoenvironmental and paleogeographic since Late Neogene. The studied Neogene- Quaternary deposits overlies Cretaceous rocks whose sedimentological and paleobotanical study revealed the preservation of impressions and counter-impressions of leaves and other macro-plant remains in pelites interpreted as flood plain and abandoned channel deposits of meandering rivers. The first record of angiosperms in this unit with possible affinities to the families Moraceae, Fagaceae, Malvaceae, Sapindaceae and Anarcadiaceae with appearance from Late Cretaceous, and the family Euphorbiaceae with record starting in the Mid- Cretaceous confirm the Cretaceous age for these rocks. The terraces of the Amazon River informally subdivided into lower and upper units are composed of sand, gravel and clay, organized in finning upward cycles representative of channel filling and overbank deposits. The lower unit was interpreted as a record of the proto-Amazonas, with migration to the east and deposition around 2 Ma. During this stage, the alluvial plain was restricted, preferentially following weakness zones coincident with fractures in the Paleozoic and Cretaceous basement. The climatic oscillations during the Quaternary and the increase of the volume of orographic rains in the headwaters region of the fluvial systems, in the eastern flank of the Andean ridge modified the hydrological regime, amplifying the escarpment erosion. The gradual expansion of the alluvial plain formed a large area of 120 km around 1 Ma to 140 ka, recorded by the upper unit deposits. At this stage, the eastern portion of the Amazon Basin topographically higher restricted the Pleistocene sedimentation in minimum accommodation space. The lower unit deposits are correlate in part to the Miocene-Pliocene deposits of the Amazon Basin, while the upper units are correlate with the Pleistocene deposits of the Solimões and Amazon basins. The dynamics of the construction of the Amazon River valley during the end of the Neogene and Quaternary was influenced by neotectonics (106 yr) and climatic oscillations (104-105 yr). The landscape of the central-eastern portion of the Amazon dominated no Pleistoceno by terra firme in elevated areas was governed by the dynamics of expansion and contraction of the alluvial plain. At the end of the Quaternary, the várzea formed by floodplains within the alluvial plain, which used to occupy a wide area, became increasingly restricted by the continuous processes of fluvial incision during the glacial maximum (18 to 22 ka). The continuous lateral migration of the meandering channel to the north led to the confinement of the channel by the fluvial scarps developed in the Cretaceous basement, which culminated in the current landscape in the Center-East of the Amazon. Testing the reliability and accuracy of some Pleistocene and older OSL ages for Amazon River deposits revealed that are much more minimum ages than buried ages for pre- Quaternary deposits.
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.
Acesso aberto (Open Access)
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.
Acesso aberto (Open Access)
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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