Controls on the erosion of the continental margin of southeast Brazil from cosmogenic 10Be in river sediments

The Atlantic Ocean coast region of southeast Brazil contains two coast-parallel mountain ranges (the Serra do Mar and Serra da Mantiqueira) generated by tectonic activity pulses tens of millions years after the main continental rift event occurred around 120 Ma. Although the short-term erosion rates for the region are established, the relative importance of the factors controlling erosion is poorly constrained. We combine new and published catchment-averaged erosion rates (n = 48) using in situ-produced 10Be concentrations in quartz from river sediments to establish the regional erosion pattern. The river catchments are (i) escarpment topography, (ii) high-altitude low-relief and (iii) mixed topography, which record how escarpment fronts are migrating inland. Ocean-facing coastal escarpment catchments of the Serra do Mar (ε = 18–53 m/Ma) can be eroded approximately twice as fast as continent-facing escarpment catchments in the Serra do Mar and Serra da Mantiqueira (ε = 7–24 m/Ma). The correlation between the normalized channel steepness index (ksn) and slope angle indicates that river incision and hillslope erosion processes combine to maintain the high relief. The Serra do Mar catchments define a mean slope angle threshold indicating that landslides are the dominant erosional process when slope angles in excess of ~30°. Tectonic activity is low and plays no significant role in driving erosion. A first-order relationship between erosion rate and precipitation-temperature across the region implies that climate plays a key role in soil production, river incision and in triggering erosional processes. Although the high topographic relief is a pre-condition for the occurrence of significant erosion, the climatic condition is the outlining factor of the regional variation in erosion rates

Conglomeratic deposits of the Paleo Tietê River: event of fluvial aggradation during the evolution of the São Paulo peripheral depression

Os depósitos conglomeráticos situados nos arredores do distrito de Laras, São Paulo, capeiam colinas amplas de topo aplainado com altitudes entre 500 e 570 m. Ocorrem em discordância sobre as formações Piramboia e Teresina da Bacia do Paraná. São constituídos de fácies de ortoconglomerados polimíticos com matriz arenosa, mal selecionada. A análise de proveniência realizada evidenciou o predomínio de clastos de silexito, quartzito e quartzo de veio, bem arredondados e oblatos, sugerindo longo transporte. A análise estatística revelou maior frequência de litotipos resistentes ao transporte na porção sudeste da área. Na porção noroeste predominam clastos menos resistentes, representados por oólito e coquina, sugerindo erosão da Formação Teresina e transporte curto a partir de terrenos paleozoicos existentes na Depressão Periférica Paulista. Dados de Luminescência Opticamente Estimulada (OSL) possibilitaram conferir idade mínima de 371.4 ± 27.5 ka para a unidade. Os depósitos conglomeráticos são interpretados como produto de deposição em canais fluviais tributários de grande porte, ou mesmo de um canal tronco principal, de um extenso sistema deposicional fluvial com paleomergulho deposicional para sudoeste do Estado de São Paulo. Esse sistema fluvial antecessor do atual Rio Tietê, com proveniência de nordeste, tinha área de drenagem em terrenos pré-cambrianos situados ao leste da área de ocorrências das unidades paleozoicas. Devido à localização e ao porte, os depósitos descritos registram importante fase de agradação fluvial na história geológica do Rio Tietê, evento de sedimentação ocorrido durante o longo processo de denudação que deu origem à Depressão Periférica Paulista durante o Cenozoico.The conglomerate deposits located near the district of Laras, São Paulo, cover wide flat-topped hills with altitudes between 500 and 570 m. They occur in discordance on older Piramboia and Teresina formations of the Parana Basin and are consisted of poorly selected sandy matrix polymeric orthoconglomerates. The provenance analysis performed showed the predominance of well-rounded and oblate silex clasts, quartzite and quartz vein clasts, suggesting long-distance transport. Statistical analysis revealed a higher frequency of transport-resistant lithotypes in the southeastern portion of the area. In the northwest portion, less resistant clasts predominate, represented by oolite and coquina, suggesting erosion of the Teresina Formation and short transport from Paleozoic terrains existing in the São Paulo Peripherical Depression. Optically stimulated luminescence (OSL) data allowed for a minimum age of 371.4 ± 27.5 ka for the unit. Conglomerate deposits are interpreted as the product of deposition in large tributary fluvial channels, or even of a main trunk channel, of an extensive fluvial depositional system with depositional paleomoving diving to the southwest of São Paulo State. This predecessor river system of the current Tietê River, coming from the northeast, had drainage area in precambrian lands located to the east of the occurrence area of the Paleozoic units. Due to their location and size, these deposits represent an important phase of fluvial alluviation in the geological history of the Tietê River, a sedimentation event that occurred during the long-term denudation process that gave rise to the São Paulo Peripherical Depression during the Cenozoic

CALCULATING BEDLOAD TRANSPORT IN RIVERS: CONCEPTS, CALCULUS ROUTINES AND APPLICATION

Rivers are immensely important to human activities such as water supply, navigation, energy generation, and agriculture. They are also an important morphodynamic agent of erosion, transport and deposition. Their capacity to transport sediment depends on their hydraulic characteristics and can be predicted by mathematical models. Several mathematical models can be used to compute bed-load transport. Each one is appropriately better for certain conditions. In this paper, we present an application built in Microsoft Excel to compute the bed-load transport in rivers based on the Van Rijn mathematical model. The Van Rijn model is appropriate for rivers transporting sandy sediments in conditions of subcritical flow. Hydraulic parameters such as channel slope, stream power, and Reynolds and Froude numbers can be calculated using the application proposed here. The application was tested in the Parana River and results from the calculations are consistent with data obtained from fieldwork surveys. The error of the application was only 20%, which shows good agreement of the model with survey values.CNPqMato Grosso do Sul Research FoundationSao Paulo Research FoundationNational Council of Technological and Scientific DevelopmentCAPESSao Paulo Research Foundation (FAPESP)Univ Estadual Paulista, Inst Geociencias & Ciencias Exatas, Ave 24A,1515, BR-13506900 Rio Claro, SP, BrazilUniv Fed Mato Grosso do Sul, Dept Geog, Ave Rio Branco 1270, BR-79304902 Corumba, MS, BrazilUniv Fed Sao Paulo, Dept Ciencias Ambientais, Rua Sao Nicolau 210, BR-09913030 Diadema, SP, BrazilUniv Kentucky, Dept Earth & Environm Sci, 101 Slone Res Bldg, Lexington, KY 40506 USAUniv Fed Sao Paulo, Dept Ciencias Ambientais, Rua Sao Nicolau 210, BR-09913030 Diadema, SP, BrazilCNPq: 140334/2015-7CNPq: 308563/2013-1CNPq: 312386/2014-1FUNDECT/CNPq: 083/2016]FAPESP: 2007/55987-3FAPESP: 2014/06889-2CNPq: 443437/2014-9CNPq: 447402/2014-5CAPES: 140334/2015-7CAPES: 308563/2013-1CAPES: 312386/2014-1FAPESP: 2014/23334-4Web of Scienc

METHODOLOGY FOR ANALYSIS OF DISTRIBUTION AND CLASSIFICATION OF THE INTENSITY OF DEQUADA FISH KILL EVENTS IN THE PANTANAL WETLAND

Extensive fish mortality occurs occasionally in the Pantanal wetland and the phenomenon is called dequada by local inhabitants. The phenomenon originates by deterioration water quality in rivers and lakes, and the depletion of dissolved oxygen (DO) is the major indicator. Researches have shown that dequada occurs when DO reaches values lower than 3 mg/L. In addition, the duration of these low DO values determines the intensity of fish mortality. This paper presents a proposed classification of dequada event, using water quality data for Pantanal rivers surveyed by National Agency of Water (ANA). The proposed method has qualitative and quantitative bases and utilizes mean DO value and duration of these values, based on historical series of DO measurements. The results are compared to other studies of the dequada phenomenon, showing that the method is efficient to determine locales with higher probability of dequada. The Paraguay River has displayed highest dequada intensity. The rivers with narrower floodplains, such as Piquiri River, do not have dequada or the intensity is lower. The phenomenon is shown to be linked to basin hydrological condition

ANÁLISE COMPARATIVA ENTRE A FUSÃO DE IMAGENS CCD/HRC E TM/HRC NA REGIÃO DOS RIOS MIRANDA E ABOBRAL, PANTANAL SUL-MATO-GROSSENSE

As técnicas de mapeamento através do sensoriamento remoto se mostram cada vez mais importantes devido à sua eficiência, principalmente em áreas de difícil acesso e com alvos complexos por causa da heterogeneidade fisionômica. Neste contexto, o Pantanal se enquadra como uma região que necessita destas técnicas para melhorar o conhecimento sobre a área de estudo, além de ser um ótimo local para aplicação destas técnicas, devido a sua fisionomia heterogênica e por experimentar inundações anuais. O objetivo deste trabalho é a aplicação da técnica da fusão de imagens, utilizando o sensor de alta resolução CBERS-2B/HRC com os sensores CBERS-2B/CCD e Landsat5/TM, avaliando a técnica utilizada de forma a verificar qual dos instrumentos melhor ressalta as características fisionômicas na região dos rios Miranda e Abobral no Pantanal Sul-mato-grossense. Os resultados mostraram que a fusão é eficaz em ambos sensores, pois uniu a ótima resolução espacial da HRC com a boa resolução espectral da CCD e TM. Concluiu-se que a técnica da fusão contribuiu para a melhor definição dos elementos fisiográficos na área estudada, validando sua aplicação para outras áreas do Pantanal. Palavras-chave: Geotecnologia. Sensoriamento Remoto. CBERS. Landsat. Comparative analysis between the images fusion of Ccd/Hrc and Tm/Hrc in the region Miranda and Abobral rivers, Mato Grosso do Sul state pantanal The mapping techniques through the remote sensing are becoming more and more important due to its effectiveness mainly in sites of difficult access and with complex targets due to physiognomic heterogeneity. In this context, the Pantanal wetland fits like a region that needs the improvement of these techniques in order to improve the knowledge of the area, beyond being an excellent place for the application of these techniques, because of the its physiognomic heterogeneity and suffering annual flooding. Therefore, the aim of the paper was the application of the technique of image fusion, using the sensor of the high resolution CBERS-2B/HRC with the sensors CBERS-2B/CCD and Landsat5/TM, to evaluate the technique and which of the sensors better stand out the physiognomic characteristics of the region of the Miranda and Abobral rivers in the Pantanal of Mato Grosso do Sul. The result obtained was that the fusion showed efficiency in both sensors, because the excellent spatial resolution of the HRC and the good spectral resolution of the CCD and TM were joined. The conclusion is that the technique of the fusion contributed for the better definition of the physiographic elements in the region studied, this way, possibly applicable for all the Pantanal wetland. Key words: Geotechnology. Remote Sensing. CBERS. Landsat

The Fate of Carbon in Sediments of the Xingu and Tapajós Clearwater Rivers, Eastern Amazon

The Xingu and Tapajós rivers in the eastern Amazon are the largest clearwater systems of the Amazon basin. Both rivers have “fluvial rias” (i.e., lake-like channels) in their downstream reaches as they are naturally impounded by the Amazon mainstem. Fluvial rias are widespread in the Amazon landscape and most of the sedimentary load from the major clearwater and blackwater rivers is deposited in these channels. So far, little is known about the role of Amazon rias as a trap and reactor for organic sediments. In this study, we used organic and inorganic geochemistry, magnetic susceptibility, diatom, and pollen analyses in sediments (suspended, riverbed, and downcore) of the Xingu and Tapajós rias to investigate the effects of hydrologic variations on the carbon budget in these clearwater rivers over the Holocene. Ages of sediment deposition (~100 to 5,500 years) were constrained by optically stimulated luminescence and radiocarbon. Major elements geochemistry and concentration of total organic carbon (TOC) indicate that seasonal hydrologic variations exert a strong influence on riverine productivity and on the input and preservation of organic matter in sediments. Stable carbon isotope data (δ13C from −31.04 to −27.49‰) and pollen analysis indicate that most of the carbon buried in rias is derived from forests. In the Xingu River, diatom analysis in bottom sediments revealed 65 infrageneric taxa that are mostly well-adapted to slack oligotrophic and acidic waters. TOC values in sediment cores are similar to values measured in riverbed sediments and indicate suitable conditions for organic matter preservation in sediments of the Xingu and Tapajós rias at least since the mid-Holocene, with carbon burial rates varying from about 84 g m−2 yr−1 to 169 g m−2 yr−1. However, redox-sensitive elements in sediment core indicate alternation between anoxic/dysoxic and oxic conditions in the water-sediment interface that may be linked to abrupt changes in precipitation. The variation between anoxic/dysoxic and oxic conditions in the water-sediment interface controls organic matter mineralization and methanogenesis. Thus, such changes promoted by hydrological variations significantly affect the capacity of Amazon rias to act either as sources or sinks of carbon

Evidence confirms an anthropic origin of Amazonian Dark Earths.

Arising from: Silva et al. Nature Communications https://doi.org/10.1038/s41467-020-20184-2 (2021

Geomorfologia e paleo-hidrologia dos megaleques dos rios Cuiabá e São Lourenço, quaternário da Bacia do Pantanal

The Upper Paraguay River Basin (BAP) comprises three areas with remarkable different conditions regarding to physical and biological aspects: the plateaus, lowlands and plains of the Pantanal. The Pantanal dynamics depends directly on the interactions with the surroundings depressions and plateaus. Considering the peculiarities and environmental importance of the area, the goals of this study were to investigate aspects of the Quaternary evolution of fluvial megafans formed by the Cuiabá and São Lourenço rivers in the northern portion of the Pantanal, as well the degradational systems of the Cuiabana Depression in the source area. Remote sensing, sedimentological and geochronological data were used to achieve these goals. Satellite images and digital elevation models were used in geomorphological zoning and channel patterns analysis. Facies analysis and optically stimulated luminescence dating (OSL) allowed the characterization of depositional environments and establishment of the depositional events chronology. Cosmogenic nuclide analysis (10Be) enabled the determination of erosion rates and exposure ages in the Cuiabana Depression terrains. The results obtained showed that: 1) the depositional systems formed by Cuiabá and São Lourenço rivers were built during the Late Quaternary and may be classified as fluvial megafans; 2) the megafans consist in Pleistocene lobes with paleochannels with braided patterns and Holocene lobes created by meandering and distributaries channels; 3) the confined floodplains in the upper portions of the megafans truncate ancient lobes' surface, configuring incised valleys; 4) based on OSL ages, the shift from braided to meandering pattern occurred in a time interval between the Last Glacial Maximum and the Early Holocene, being an example of tropical river systems response to global climate changes; 5) 10Be cosmogenic erosion rates show us that the relief evolution of the Cuiabana Depression have strong...A Bacia Hidrográfica do Alto Paraguai (BAP) compreende três áreas que apresentam condições consideravelmente distintas no que se refere aos aspectos físicos e biológicos: os planaltos, as depressões e as planícies do Pantanal. A dinâmica do Pantanal depende diretamente das interações com as depressões e os planaltos do seu entorno. Considerando as peculiaridades e importância ambiental da região, o escopo da pesquisa foi investigar aspectos da evolução quaternária dos megaleques formados pelos rios Cuiabá e São Lourenço na porção norte da planície do Pantanal e dos sistemas degradacionais existentes em terrenos da Depressão Cuiabana situada no seu entorno. Para o desenvolvimento da pesquisa foram utilizados dados de sensoriamento remoto, sedimentológicos e geocronológicos. Imagens de satélite e modelos digitais do terreno foram utilizados na compartimentação geomorfológica e na análise dos padrões de canais. Descrição de fácies sedimentares e datações por luminescência opticamente estimulada (LOE) possibilitaram a caracterização dos subambientes deposicionais e o estabelecimento da idade dos eventos geradores. Análise por nuclídeos cosmogênicos (10Be) permitiu a determinação de taxas de erosão e idades de exposição de terrenos da Depressão Cuiabana. Os resultados alcançados permitiram concluir que: 1) os sistemas deposicionais formados pelos rios Cuiabá e São Lourenço foram construídos durante o Quaternário tardio e podem ser classificados como megaleques fluviais; 2) os megaleques são constituídos por lobos pleistocênicos caracterizados por paleocanais de padrão entrelaçado e lobos holocênicos formados por canais sinuosos e distributários; 3) as planícies fluviais confinadas nas porções superiores dos dois megaleques truncam a superfície de lobos antigos, configurando vales incisos; 4) com base em idades LOE, a mudança do padrão de canal entrelaçado para meandrante ocorreu em...Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Aspectos fisiográficos do município de Rio Claro - SP

Devido ao aumento da pressão antrópica sobre os ambientes naturais faz-se necessária a realização de levantamentos que contemplem diversos fatores ambientais (bióticos e abióticos) e corroborem com zoneamentos geoambientais e o planejamento territorial. O estudo da fisiografia permite a caracterização e classificação das paisagens terrestres levando em consideração os fatores formadores destas paisagens (clima atual e passado, hidrologia, geologia, geomorfologia e indiretamente aspectos bióticos) e as relações (processos) que os afetam. Desta forma, o objetivo da pesquisa foi investigar as características fisiográficas do município de Rio Claro-SP e, assim, contribuir para o melhor conhecimento dos aspectos do meio físico e suas relações. Para atingir o objetivo foram utilizados procedimentos e técnicas próprias das geociências, como interpretação de fotografias aéreas, geoprocessamento e levantamentos de campo. A sistemática de trabalho adotada se resume à quatro etapas: I) revisão bibliográfica; II) análise geomorfométrica; III) análise morfoestrutura e; IV) análise fisiográfica. Os resultados obtidos foram os mapas geomorfométricos (hipsometria, classes de declividade e curvatura do terreno), mapas morfoestruturais (lineamentos estruturais, traços de juntas, anomalias de drenagem e linhas de contorno estrutural não cotadas) e o mapa fisiográfico. A análise fisiográfica permitiu identificar e compreender os processos endógenos e exógenos que atuam e atuaram na evolução da paisagem. O município de Rio Claro-SP é caracterizado por paisagens policíclicas de origem fluvial, denudacional/paleoaluvial, denudacional e estrutural. A subdivisão das paisagens em unidades menores evidenciou a presença de subpaisagens do tipo planície de inundação e terraço para as paisagens fluviais; topos e encostas para as paisagens denudacionais/paleoaluviais,...Due to the increase of anthropogenic pressure on natural environments it is necessary to make surveys involving several environmental factors (biotic and abiotic) and the corroborating with geoenvironmental zoning and land use planning. The study of the physiography enables the characterization and classification of landscapes, considering the factors of landscape formation (current and past climate, hydrology, geology, geomorphology and indirectly biotic aspects) and relations (processes) that affect them. Therefore, the aim of this research is to investigate the physiographic characteristics of Rio Claro-SP district and thus to contribute to a better knowledge of physical environment aspects and their relationships. To achieve the main objective specific techniques and procedures from geosciences were taken, such as aerial photo interpretation, geoprocessing and field surveys. The systematic adopted for this work followed four steps: i) reiew; II) geomorphometric analysis; III) morphostructural analysis; IV) physiographic analysis. The results gathered were the geomorphometric maps (hypsometry, slope and terrain curvature), morphostructural maps (structural lineaments, traces of joints, abnormal drainage and structural contour lines unlisted) and a physiographic map. Physiographic analysis allowed us to identify and understand the endogenous and exogenous processes that acted in landscape evolution. Rio Claro-SP is characterized by polycyclic landscapes with fluvial, denudational / paleoalluvial, denudational and structural origins. The subdivision of landscapes into smaller units showed the presence of sub-landscapes, from the type floodplain and river terrace landscapes; summit and slope to the landscapes denudational / paleoalluvial, denudational and structural; abandoned ponds in landscapes denudational / paleoalluvialCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

ESTILOS FLUVIAIS E EVIDÊNCIAS DE MUDANÇAS AMBIENTAIS NA PLANÍCIE DO RIO MIRANDA, PANTANAL

<p>O rio Miranda é um importante afluente do rio Paraguai e tem grande parte de seu curso na planície do Pantanal. O rio tem sinuosidade média a alta, sendo do tipo meandrante na maior parte do seu percurso em domínio aluvial. Com base nos padrões do canal e da planície, três segmentos fluviais com diferentes estilos foram caracterizados e descritos. Ainda nos domínios do planalto, o rio forma um cinturão de meandros numa planície agradacional, que está confinada em vale no embasamento cristalino. O rio deixa de correr num cinturão de meandros ao adentrar no Pantanal, para formar um cordão composto por canal e diques marginais que se destaca pela elevação mais alta em relação à planície agradacional, que se torna mais larga ao deixar o vale confinado. Paleocinturões de meandros e grandes meandros abandonados com dimensões superiores às dos canais atuais, existentes nas planícies agradacionais, permitem interpretar importantes mudanças ambientais e paleohidrológicas ocorridas a partir do Pleistoceno tardio. No seu baixo curso o rio volta a correr num cinturão de meandros, porem inciso em depósitos aluviais mais antigos, o que denuncia a natureza degradacional da planície distal do rio. Esta planície é palco da ação erosiva de fluxos de águas em lençol durante as inundações e de incisão por rede de pequenos canais tributários que drenam a planície depois das cheias. A avulsão ocorrida na altura do Morro do Azeite desempenhou importante papel na configuração do traçado do canal atual do rio Miranda, deslocando em 20 km para norte sua foz no rio Paraguai.</p><p> </p> <p><strong> </strong></p> <p><strong>Palavras Chave – </strong>Rio Miranda, Pantanal, rio meandrante</p