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Navegando por Orientadores "SOARES, Joelson Lima"

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    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.
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    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.
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    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.
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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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    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.
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    Estratigrafia e geoquímica orgânica da formação Longá, neodevoniano/eocarbonífero da Bacia do Parnaíba, região de Pedro Afonso-To
    (Universidade Federal do Pará, 2017-05-30) BRITO, Ailton da Silva; LIMA, Sidney Gonçalo de; http://lattes.cnpq.br/1655930426274093; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
    The Late Devonian is marked by considerable paleoclimatic and paleogeographic changes related to a widespread colonization of the continent by vascular plants, exponential increase of organic production and development of background anoxia in the epeiric seas, typical of that period. In addition, during Famennian age the Gondwana continent was in high latitudes and glacial pulses occurred in South America. A postglacial phase in Late Famennian was responsible for the occurrence of a marine transgression and beginning of the Long Formation sedimentation until the Tournaisian. Devonian-Carboniferous boundary is marked by deposition of black shales in various parts of the world. The goal of this work is a paleoenvironmental reconstruction and a geochemical characterization of the postglacial organic matter deposits of Long Formation from southwest Parnaíba Basin. A lithofaciological analysis was accomplished of Longá deposits plus petrographic and X-ray diffraction. The quantification of Total Organic Carbon (TOC) plus Rock-Eval pyrolysis and biomarkers was the geochemical analysis of organic matter within Longá Shales. From the sedimentological analysis of the deposits five lithofacies was identified: conglomerate lag (Gmm), laminated shales (Fl), coarse sandstone with megaripple bedding (Sm), fine to medium hummocky cross-stratified sandstones (Sh) and wavy-linsen shale interbedding with fine sandstone (Fwl). The lithofacies were interpreted as belonging to a single facies association, representing offshore to shoreface deposits. The lower Longá Formation boundary is well delimited by a transgressive lag produced by waves that separate it from the non-marine deposits of the Cabeças Formation. The formation is characterized by the predominance of thick layers of the Fl and Fwl facies with episodic events of storms and occurrence of debris rain as result of remaining icebergs melting. In Fwl facies occur typical elements of the Cruziana Ichnofacies characterized by predominance of horizontal trace fossils. These characteristics suggest a stressful environment caused by changes in salinity during the input of ice melting water within the platform. The organic geochemistry analyzes showed that Longá shales had a low TOC content, less than 1%, values of free hydrocarbons (S1) below the detection limit of the Rock-Eval 6 equipment, and very low (0.06 to 0.23) hydrocarbons generation potential (S2). The maximum pyrolysis temperature (Tmax) as well as the thermal maturation parameters calculated on the biomarkers show that the Longá shales are immature. The values of pristane/n-C17, phytane/n-C18, Hydrogen Index (IH) and Oxygen Index (IO) suggest kerogen type III and IV, formed from conical land leaves, needles and plant waxes as are support by total sulfur (TS) <0.2 wt%, terrigenous/aquatic ratio (TAR), C29-sterol, hopane/sterane and Methylphenanthrene (MPs). This organic matter was deposited in an epeiric sea where prevailed shallow water, oxidizing conditions, normal salinity, and low temperatures.
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    Estratigrafia e paleoambiente da Formação Poti e relações de contato com as Formações Longá e Piauí, borda Leste da Bacia do Parnaíba
    (Universidade Federal do Pará, 2020-07-27) MIRANDA, Isabella de Fátima Santos de; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131; 1345968080357131
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    Gênese e distribuição estratigráfica das concreções carbonáticas da ilha de Baunilha Grande, região do Quatipuru - Pará
    (Universidade Federal do Pará, 2025-06-27) GARCIA, Danilo Sena; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
    In the Baunilha Grande Ecofacies, defined by Petri (1957) and located on Baunilha Grande Island, in the Quatipuru region, Pará, carbonate concretions known as carcinolites are found. However, near these carcinolites, there are other concretions whose origin and stratigraphic position had not yet been described. These concretions are part of the Pirabas Formation, from the Lower Miocene, composed of fossiliferous limestones and sedimentary deposits that record a shallow coastal marine environment influenced by tides. This study aims to characterize the formation of carbonate concretions on Baunilha Grande Island and their relationship with the diagenetic and stratigraphic processes of the Pirabas Formation. The methodology included: (I) Petrographic, mineralogical, and geochemical analysis of the concretions, using techniques such as optical microscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS); (II) Stratigraphic correlation of the concretions with similar deposits in Salinópolis and Maracanã, relating them to sedimentation events, bioturbation, and diagenesis. The results indicate that the concretions exhibit different shapes and compositions, classified into four main types: spherical, tubular, rough, and bulbous. Mineralogical analysis revealed the predominant presence of quartz and calcite, along with kaolinite and kutnohorite in some samples. Pyrite is present in all concretions, particularly associated with organic fossils and the diagenesis of diatoms. The presence of these concretions suggests early cementation processes in sandstone lenses and bioturbation in shales, influenced by sea-level variations and storm events. The high pyrite content in the concretions indicates a reducing depositional environment favorable for organic matter preservation and sulfide formation. The relationship between concretions and sedimentary structures suggests that these features are restricted to the top of the Pirabas Formation, near its contact with the Barreiras Formation. Thus, the occurrence of these concretions can serve as a stratigraphic marker for the top of the Pirabas Formation.
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    Icnologia, estratigrafia e paleoambiente da Formação Pastos Bons, Jurássico Superior -Cretáceo Inferior da Bacia do Parnaíba
    (Universidade Federal do Pará, 2021-11-05) SODRÉ, Argel de Assis Nunes; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
    After the voluminous lava eruption related to the Central Atlantic Magmatic Province (CAMP), in the Triassic–Jurassic (~200 Ma), a large subsiding area formed in West Gondwana, allowing the Upper Jurassic–Lower Cretaceous lacustrine system of the Pastos Bons Formation, in the Parnaíba Basin. Despite recent studies on this lacustrine system, these deposits still need to be investigated in detail with palaeoenvironmental mapping based on the ichnological content, facies analysis and lacustrine sequence stratigraphy. Outcrop-based facies analysis allowed the identification of four palaeoenvironments: central lake, lakeshore, braided fluvial, and delta front. The ichnological content is concentrated in the lakeshore deposits and includes of eight ichnofossils, organized in three ichnofacies: Mermia (Cochlichnus anguineus and Lockeia siliquaria), Scoyenia (Agrichnium isp., Gyrochorte comosa, Palaeophycus tubularis, Planolites berveleyensis, and Rusophycus isp.), and Skolithos (Skolithos linearis). This lacustrine succession is organized in five millimeter- to meter-scale depositional cycles bounded by erosive surfaces or flooding surfaces. Four cycles define a retrogradational and aggradational stratal stacking pattern composing the transgressive systems tract, and one cycle indicates the progradational stratal stacking pattern constituting the highstand systems tract. The sequence stratigraphy suggests that post-CAMP thermal subsidence and responsible for creating the accommodation space, controlling the sedimentary supply and water inflow/outflow, and the proportional relationship between them. At the base of this system, an underfilled lacustrine basin characterized by fossil and ichnofossil-bearing layers and thick mudstones predominated, and after the maximum subsidence, an overfilled lacustrine basin characterized by cross-laminated sandstone of the fluvio-deltaic system was established.
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    Paleoambiente e icnofósseis do arenito guamá (Siluriano), regiões de São Miguel do Guamá e Irituia, estado do Pará.
    (Universidade Federal do Pará, 2019-07-08) MARTINS, Taynara Cristina Matos; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
    The Guamá Sandstone is a restricted sedimentary unit that occurs in the Bragantina Platform, mainly in the São Miguel do Guamá and Irituia regions northeast of the state of Pará still needs a better geological detail. It is characterized by thick layers of well-rounded and selected, mature medium-grained quartz-sandstone with medium granulometry, well rounded, well selected and with high degree of textural and compositional maturity. Based on the petrographic, faciological and ichnological characteristics similar to the quartz sandstones of the Nhamundá Formation (Amazon Basin), a Silurian age for the Guamá Sandstone has been suggested. Commonly, the quartz-sandstone layers have a massive appearance and few preserved primary sedimentary structures (e.g., cross-stratified ribbed stratification, plane-parallel stratification and wavy and planar lamination). The facies association indicates that the studied deposits were formed in a sandy coastal region that covered the foreshore and shoreface zones. In the Guamá Sandstone the icnoespecies Skolithos linearis, Psammichnites isp., cf. Schaubcylindrichnus coronus, single vertical tube undetermined and Lingulichnus verticalis were identified, they commonly compose a mixture of the Cruziana and Skolithos ichnofacies. Periodic energy changes and sedimentation rate in the depositional environment are suggested by the regular distribution between Skolithos and Psammichnites in the sandstone layers. Skolithos occurs, generally, in massive layers and can reach up to 1 meter in length indicating high energy conditions and/or high sedimentation rates. While Psammichnites occur at the top of these layers and suggest lower energy and/or low sedimentation rate. Skolithos exhibit a bioturbation index (ii) ranging from 2 to 3 (5-40%). The Psammichnites exhibit ii between 4 and 5, which indicate a 40 to100% reworking of the substrate by excavating organisms. The low ichnodiversity and high abundance of ichnofossils suggest stressful conditions during the depositional period. The mixture of Skolithos-Cruziana ichnofacies is commonly associated with coastal marine environments of brackish waters. The reason for environmental stress conditions related to the presence of brackish water could be the influx of melting/defrosting waters in periglacial environments. The correlation of the Guamá Sandstone with the Silurian deposits of the Nhamundá Formation supports this idea, as this unit exhibits glacial, post-glacial, and coastal deposits that record the Silurian glaciation of Gondwana. Therefore, the Guamá Sandstone can be considered as the record of sandy coastal deposits influenced by the glaciations that affected the Amazon region during the Lower Silurian.
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    Proveniência sedimentar dos depósitos cretáceos da Formação Alter do Chão, Bacia do Amazonas, região de Ponta do Curuá, Prainha-PA
    (Universidade Federal do Pará, 2020-08-03) SANTOS, Raiza Renne Leitão dos; SOARES, Joelson Lima; http://lattes.cnpq.br/1345968080357131
    Deposits of the Alter do Chão Formation are found along the right bank of the Amazon River and are well registered in the locality of Ponta do Curuá, municipality of Prainha, the western region of the State of Pará. The outcrops are characterized by thick layers of fine to coarse sandstones interbedded with siltstones and claystones, and subordinate subordinate conglomerates. The facies analysis carried out in these outcrops allowed the individualization of 8 sedimentary facies, grouped in three facies associations (AF), configuring a high sinuosity and mixed load fluvial meandering depositional system. AF1 comprises facies with a thicker granulometry of the studied succession and was interpreted as the filling of the fluvial channel, characterized by massive to stratified conglomerates, massive sandstones, sandstones with trough and tabular cross-bedding, sandstones with convoluted laminations and climbing crosslaminations. AF2 was interpreted as abandoned channel filling deposits and corresponds to thick layers of massive to laminated mudstones that are sporadically associated with thin layers and very thin sandstone lenses forming wavy-linsen bedding. Well-preserved leaves and trunks are present in this association. AF3 corresponds to the flood deposits, composed of massive to laminate mudstones, massive sandstones, and sandstones with trough, tabular and sigmoidal cross-stratifications. The study of heavy minerals in the sandstones of this formation showed an assembly with a predominance of ultra-stable minerals such as zircon, tourmaline, rutile and anatase, and less frequent minerals such as kyanite, staurolite, sillimanite, andalusite, and garnet. Metasedimentary sources are suggested due to the presence of aluminum-rich metamorphic minerals. Whereas, rutile and tourmaline are present in both igneous and metamorphic rocks, being more common in the latter. Well-rounded minerals suggest an origin from sedimentary deposits, in the same way that subhedral and euhedral minerals suggest first cycle sediments. The high stability of this assembly is attested by the high compositional maturity exhibited by these sandstones, with values of the ZTR index ranging from 69% to 99%. These high values indicate that chemically unstable minerals have been eliminated over geological time, probably due to the action of interstitial fluids that circulate in the porous during weathering and diagenetic processes. However, the analyzed mineral assembly is more compatible with conditions of exposure to intense chemical weathering. The effects of intrastate dissolution in the area is directly proportional to the increase in the ZTR index, being attested by the presence of corrosion textures on the surface of the minerals that were analyzed from SEM images. Thus, the mineralogical assembly would reflect the effects of the intense chemical weathering, under a humid tropical climate, imposed on the deposits of the Alter do Chão Formation that would be associated with the lateritization event responsible for the genesis of bauxite deposits during the Paleogene. Recently, the luminescence (LC) characteristics of quartz grains have been used as provenance indicators, mainly in rocks affected by weathering or rich in quartz. In this work, luminescence signals were acquired by polychromatic cathodoluminescence to establish the relationship between luminescent signals and the genesis of this mineral. The studied grains present red, blue, violet and brown colors, with different intensities: the reddish-brown tones, are generally attributed to metamorphic rocks; dark blue luminescence is a characteristic observed in quartz of plutonic origin; grains with intense LC such as blue, red and violet of high bright, are volcanic quartz. Geochronological analyzes carried out on detrital zircons using the U-Pb method allowed to determine that the main sources for the Alter do Chão Formation are Paleoproterozoic ages, subdivided into two groups: (1) 1771 to 1906 Ma; and (2) 1957 to 2037 Ma, in addition to a small Archean contribution (Neoand Meso-Archean) aged between 2529 and 2977 Ma. The data from the first group, 1771 and 1906 Ma, were correlated with the age of provenance of metasedimentary rocks from the Araguaia Belt, which occurs on the eastern edge of the Amazon Craton. Ages around 1957 and 2037 Ma are consistent with rocks from the Maroni-Itacaiúnas Province, located on the eastern edge of the basin. It is possible to mention rocks associated with late to post-collisional orogenic magmatism such as the Igarapé Careta Intrusive Suites (2065 ± 33 Ma), Parintins (2030 ± 3 Ma) and paleoproterozoic indistinguishable granitoids occurring in the Amapá Block and Carecuru Domain, in addition to rocks related to post-orogenic magmatism such as the Granodiorito Sant'Ana (1986 ± 5 Ma) of the Bacajá Domain. Archean contributions can be associated with rocks from the Central Amazon Province or even to Archean nuclei distributed in the region.
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