The Parnaíba intracratonic basin exhibits sedimentation that reflects the different evolutionary stages of climate and paleogeography in the West Gondwana supercontinent. In this regard, we conducted ...a study comprising the Poti Formation in the southeast of Itaueira and Floriano regions in Piauí State, within the Parnaíba Basin. The facies analysis enabled the establishment of the depositional model for the study area, comprising ten sedimentary facies separated into two facies associations (FA) deposited in a shallow platform environment dominated by storm waves: Upper Shoreface (FA-1) and Lower Shoreface/Offshore transition (FA-2). It was possible to determine that the wave base line constantly varied, and a high-energy event provided the deposition of sediments with fine-to coarse-grained sandstone from FA-1 over those of FA-2, creating a first-order erosive surface (surf diastema) with a gradient varying from 40 to 45° that limits the two distinct facies association. This sedimentary event resulted in the excavation of the muddy offshore sediments by the lower shoreface, resulting in coarsening- and thickening-upward sandstones lying mostly under fine-grained sandstone with hummocky cross-stratifications. In the paleogeographic context, the cross-stratification paleocurrent indicates a direction towards the NW and, to a lesser extent, the SW. This direction suggests a connection between the epicontinental sea formed in the Parnaíba Basin and the paleosea of Tethys in the Late Carboniferous. Petrographic analysis classified the sandstones as subarkose and quartzarenite. This study employed petrography, X-ray diffractometry, architectural elements, and facies analysis to make inferences about the depositional system, climate, and geomorphology of the storm and wave-dominated deposits of the Poti Formation. The occurrence of kaolinite and illite in the studied deposits are typical clay minerals of humid and hot (dry) climatic conditions, respectively. Therefore, the overall data indicates a shift from retrogradational to progradational deposits that records changes in facies association and climate conditions in the Late Carboniferous.
•Facies analyses and facies association of the Visean Poti Formation.•Sedimentation in the Upper Carboniferous, West Gondwana.•Storm wave-dominated shallow platform depositional system of the Poti Formation.
The urban expansion of Teresina has caused environmental impacts on the Poti River due to the occurrence of eutrophication and proliferation of aquatic plants in the dry season of the year. ...Considering the characteristics related to water-quality monitoring in the Northeast region of Brazil, from remote sensing, this study aimed to evaluate the performance of semi-empirical algorithms in Sentinel-2 data in the detection and mapping of eutrophication and aquatic plants in the river Poti in Teresina, Piaui, Brazil. The eutrophication detection methodology involved the study of the reflectance of the water surface in the Sentinel-2 images and the respective correlation within situ data of chlorophyll-a, using the MCI, MPH and NDCI indexes. The NDCI index showed superior one-off performance than the MCI and MPH indexes. In this sense, with the NDCI, the spatio-temporal variation of eutrophication in the Poti River was identified broadly and no longer specific. In relation to aquatic plants, the NDVI index proved to be appropriate for the detection and mapping of water hyacinths, demonstrating the location of the areas covered by aquatic plants. At the beginning of proliferation, the maximum expansion rate of 854.7% was evaluated. At the end of the dry period, there was a peak of covered area of 570,145.6 m² and a production of 6,408.4 tons of fresh biomass from water hyacinths. Therefore, in both cases, it was found that the MSI sensor was suitable for the detection, mapping and monitoring of eutrophication and aquatic plants in the Poti River.Keywords: chlorophyll-a, Poti river, remote sensing, water hyacinth. Detecção e Mapeamento da Eutrofização e Plantas Aquáticas em um Rio na Região Nordeste do Brasil Usando Dados Sentinel-2 R E S U M OA expansão urbana de Teresina tem causado impactos ambientais no rio Poti devido à ocorrência de eutrofização e proliferação de plantas aquáticas na estação seca do ano. Considerando as características relacionadas ao monitoramento da qualidade da água na região Nordeste do Brasil, a partir do sensoriamento remoto, este estudo destinou-se avaliar o desempenho de algoritmos semiempíricos em dados Sentinel-2 na detecção e mapeamento da eutrofização e de plantas aquáticas no rio Poti em Teresina, Piauí, Brasil. A metodologia de detecção da eutrofização envolveu o estudo da reflectância da superfície da água nas imagens Sentinel-2 e a respectiva correlação com dados in situ de clorofila-a, por meio dos índices MCI, MPH e NDCI. O índice NDCI apresentou melhor desempenho pontual que os índices MCI e MPH. Neste sentido, com o NDCI, foi identificada a variação espaço-temporal da eutrofização no rio Poti de maneira ampla e não mais pontual. Em relação às plantas aquáticas, o índice NDVI se mostrou apropriado para a detecção e mapeamento dos aguapés, demonstrando a localização das áreas cobertas pelas plantas aquáticas. No início da proliferação foi avaliada a taxa de expansão máxima de 854,7%. No final do período seco ocorreu um ápice de área coberta de 570.145,6 m² e uma produção de 6.408,4 toneladas de biomassa fresca de aguapés. Portanto, nos dois casos, constatou-se que o sensor MSI foi adequado para a detecção, mapeamento e monitoramento da eutrofização e de plantas aquáticas no rio Poti.Palavras-chave: aguapé, clorofila-a, rio Poti, sensoriamento remoto
Poti, Osmanlı idaresinde Kafkas kıyıları ve iç kesimlerin güvenliğinin sağlamasında bir set görevi görmüştür. Bu fonksiyonu, XIX. yüzyılda Rusya’nın genişleme ile uluslararası ticareti Kafkasya’ya ...çekme yönündeki politikası neticesinde ticari açıdan daha fazla ön plana çıkmaya başlamıştır. Özellikle Poti, Trabzon-Tebriz ticaretinin Rus topraklarına çekilmesi ve sağlanan ticari kolaylıklarla hızlı bir gelişim seyri yakalamış, Kafkasya’nın idari merkezi Tiflis’in ana limanı haline gelmiştir. Bu bağlamda çalışmanın amacı Rusya’nın kuzeyden güneye doğru genişlemesine paralel olarak yeni limanların ortaya çıkışı, gelişimi ve gerileyişi şeklinde yaşanan değişim ile Redut Kale, Sohum, Batum ve Trabzon limanlarıyla rekabet çerçevesinde Poti’nin liman ve kentsel gelişim seyrini Rus ve Osmanlı kaynakları ışığında ele almaktır.
Recently, the Poti river mouth region has experienced environmental impacts that resulted in a change of landscape in its dry season, highlighting the eutrophication and proliferation of ...phytoplankton, algae, cyanobacteria and aquatic plants. Considering the aspects related to water-quality monitoring in the semiarid region of Brazil from remote sensing, this study aimed to evaluate the performance of Sentinel-2A satellite data in the retrieval of chlorophyll-a concentration in Poti River in Teresina, Piaui, Brazil. The chlorophyll-a concentration retrieval and mapping methodology involved the study of the water surface reflectance in Sentinel-2A images and their correlation with the chlorophyll-a data collected in situ during the years 2016 and 2017. The results generated by the Chl-1, Ha et al. (2017), Chl-2, Page et al. (2018), and Chl-3, Kuhn et al. (2019) equations show the need for calibrating the algorithms used for the Poti River water components. However, the empirical algorithm Chl-2 shows a correlation has been established to identify the spatiotemporal variation of chlorophyll-a concentration along the Poti River broadly and not punctually. The spatial distribution of this pigment in maps derived from Sentinel-2A is consistent with the pattern of occurrence determined by the in situ data. Therefore, the MSI sensor proved to be a tool suitable for the retrieval and monitoring of chlorophyll-a concentration along the Poti River.
This is the first work focusing on the provenance of Middle Devonian-Early Carboniferous sandstones in the eastern margin of the Parnaíba basin. This sedimentary succession represents the main ...petroleum system in this basin and is composed, from base to top, of the Itaim, Pimenteiras, Cabeças, Longá and Poti Formations of the Canindé Group. The internal textures and UPb analyses of detrital zircons allowed defining potential source areas for the sediments of this group. A global tendency of sea level rise in the Middle Devonian, in the evolutionary context of West Gondwana, resulted in the establishment of epicontinental seas and deposition of transgressive sedimentary sequences. Shales and sandstones of the Pimenteiras Formation represent extensive records of these Devonian seas on this paleocontinent. This succession provides zircon ages from 3443 to 438 Ma. Detrital zircons with ages of 538–486 Ma are the most abundant, suggesting derivation mainly from nearby younger sources in the Southern subprovince of the Borborema or Tocantins provinces. The transition between the Middle Devonian and Mississippian Periods is marked by progressive retreat of epicontinental seas with minor marine incursions (represented by the Longá Formation) and resulted in the continental deposits of the Cabeças and Poti Formations. Paleocurrent patterns in both formations suggest direct derivation from the Borborema province. The Cabeças, Longá and Poti Formations contain numerous zircons with ages ranging from 999 to 722 Ma. This detrital population indicates derivation from rocks formed during the Cariris Velhos event in the central portion of the Borborema province. The Cabeças Formation also provided an extensive number of zircons with ages ranging from 2034 to 1830 Ma. Further, the studied geologic units, except for the Pimenteiras formation, show detrital contingents with ages of 1.0–1.2 Ga, also suggesting provenance from distal areas. However, as the spectrum of zircon ages of the Canindé Group is similar to that of the Brasiliano belts surrounding the Parnaíba basin, these belts may also be considered candidates to provide sediments for the Middle Devonian-Early Carboniferous deposits.
•The Brasiliano belts of southern Borborema subprovince, may be considered the mainly candidate to provide sediments for the Middle Devonian-Early Carboniferous deposits.•Pimenteiras Formation display a essentially unimodal pattern, suggesting derivation also from Brasilia belt or reworking of the cratonic basins of the São Francisco craton.•Did the Cariris-Velhos event exclusively contribute to the Stenian-Tonian zircon age spectra found in the Parnaíba basin?
The article deals with mathematical literacy in relation to mathematical knowledge and mathematical problems, and presents the Slovenian project NA-MA POTI, which aims to develop mathematical ...literacy at the national level, from kindergarten to secondary education. All of the topics treated represent starting points for our research, in which we were interested in how sixth-grade primary school students solve non-contextual and contextual problems involving the same mathematical content (in the contextual problems this content still needs to be recognised, whereas in the non-contextual problems it is obvious). The main guideline in the research was to discover the relationship between mathematical knowledge, which is the starting point for solving problems from mathematical literacy (contextual problems), and mathematical literacy. The empirical study was based on the descriptive, causal and non-experimental methods of pedagogical research. We used both quantitative and qualitative research based on the grounded theory method to process the data gathered from how the participants solved the problems. The results were quantitatively analysed in order to compare the success at solving problems from different perspectives. Analysis of the students’ success in solving the contextual and non-contextual tasks, as well as the strategies used, showed that the relationship between mathematical knowledge and mathematical literacy is complex: in most cases, students solve non-contextual tasks more successfully; in solving contextual tasks, students can use completely different strategies from those used in solving non-contextual tasks; and students who recognise the mathematical content in contextual tasks and apply mathematical knowledge and procedures are more successful in solving such tasks. Our research opens up new issues that need to be considered when developing mathematical literacy competencies: which contexts to choose, how to empower students to identify mathematical content in contextual problems, and how to systematically ensure – including through projects such as NA-MA POTI – that changes to the mathematics curriculum are introduced thoughtfully, with regard to which appropriate teacher training is crucial.
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