Hydrogeological, hydrochemical, and natural isotopes evaluation of groundwater and surface water interactions in the alluvial plain, tropical region of southeastern Brazil

Groundwater-Surface water interactions in alluvial plains facing morphological features are the subject of the study. Considered transitions zones, alluvial plains have different morphological features interfering with groundwater flow and hydrochemistry. The alluvial plain of Mogi Guaçu river (southeastern Brazil) presented topography-controlled groundwater flow, nevertheless, natural levees, wet fields, oxbow lakes, and abandoned meanders can control local flow and interfere in discharges points of the main river. Two sampling water campaigns were done in the dry and wet season for physicochemical and natural isotopes analysis, collecting in total 44 groundwaters samples from monitoring wells and eight water samples from the river, creek, and lake. The groundwaters in wet fields and terraces, and surface waters from creek and lake presented low mineralization (EC from 8 to 37 μS.cm), pH acidic (4.98 to 5.8), and essentially Ca and Na-HCO composition. River waters samples presented pH between 5.92 e 7.69 (acidic in the rainy season and basic in the dry season), and EC from 24.2 and 181.1 μS/cm (lower values in the wet season), Na-HCO and Na-HCO-SO (dry season) and Ca-HCO and Na-HCO (rainy season) compositions. In dry season groundwaters composition showed evolution from sodium mixed (SO – HCO) to bicarbonate waters and higher mineralization; in wet season waters varied from Ca to Na-HCO composition and low mineralization, denoting dilution due to rainwater infiltration. Closer to the river margins, in abandoned meanders and oxbows, the groundwaters have increased values of EC and major ions indicating GW-SW mixtures, and effluent-influent changes (descendent and ascendent flux) in wet and dry seasons, respectively. Natural isotopes in groundwaters imply meteoric origin, without evaporation during recharge and high d-excess can be influenced by continental air masses and Amazonia Basin low-level jet. Shallow water table, permeable silty-sand material of vadose zone, flat terrain, and pristine conditions can contribute to direct infiltration of rainwaters, recharging the shallow aquifer.

Multiscale Microbial Preservation and Biogeochemical Signals in a Modern Hot-Spring Siliceous Sinter Rich in CO2 Emissions, Krýsuvík Geothermal Field, Iceland

The microbial communities inferred in silica sinter rocks, based on multiscale morphological features (fabrics and textures) and the presence of lipid biomarkers and their carbon isotopic composition, are evaluated in the Krýsuvík geothermal area of Iceland. Close to vent environments (T > 75 °C and pH 1.7‒3), stream floors are capped with homogeneous vitreous crusts and breccia levels, with no distinct recognizable silicified microbes. About 4 m far from the vents (T 75‒60 °C and pH 3‒6) and beyond (T < 60 °C and pH 6‒7.6), microbial sinters, including wavy and palisade laminated and bubble fabrics, differ between abandoned meanders and desiccated ponds. Fabric and texture variances are related to changes in the ratio of filament/coccoid silicified microbes and associated porosity. Coatings of epicellular silica, less than 2 µm thick, favor identification of individual microbial filaments, whereas coalescence of opal spheres into agglomerates precludes recognition of original microbial textures and silicified microbes. Episodic fluctuations in the physico-chemical conditions of surface waters controlled the acidic hydrolysis of biomarkers. Wavy laminated fabrics from pond margins comprise fatty acids, mono- and dialkyl glycerol, mono- and diethers, monoalkyl glycerol esters and small traces of 10-methyl branched C16 and C18 fatty acids and archaeol, indicative of intergrowths of cyanobacteria, Aquificales, and sulfate reducing bacteria and methanogenic archaea. In contrast, wavy laminated fabrics from abandoned meanders and palisade laminated fabrics from ponds differ in their branched fatty acids and the presence vs. absence of bacteriohopanetetrol, reflecting different cyanobacterial contributions. δ13C values of biomarkers range from −22.7 to −32.9‰, but their values in the wavy (pond) and bubble fabrics have much wider ranges than those of the wavy (meander), palisade, and vitreous fabrics, reflecting dissolved inorganic carbon (DIC) sources and a decrease in 13C downstream outflow channels, with heavier values closer to vents and depleted values in ponds.

Transformações geomorfológicas, pedológicas e ambientais nos Baixos Terraços do rio Jacaré-Guaçu (sítio arqueológico Boa Esperança II, São Paulo) no Pleistoceno Tardio e Holoceno

R E S U M OCom o objetivo de discutir transformações geomorfológicas, ambientais e pedológicas quaternárias da paisagem, caracterizam-se os baixos terraços e a planície aluvial do rio Jacaré-Guaçu na área entre Boa Esperança do Sul (SP) e Araraquara (SP). O conjunto de dados geomorfológicos, pedológicos, granulométricos, petrográficos, micromorfológicos, mais datações absolutas (LOE e 14C), permitiram definir três fases de modificações ambientais. A primeira (14500-10900 anos atrás) caracteriza-se, ao menos parcialmente, por condições mais secas que as atuais e deposição de cascalheiras vinculadas a canais torrenciais efêmeros de granulometria média cinco vezes superior à do rio atual. A segunda (de 10900 até ao menos 8000 anos atrás) registra ascensão do nível de base local e do posicionamento altimétrico do canal do rio Jacaré-Guaçu de até 7 m, intercalada com pelo menos um intervalo de estabilização do nível de base e desenvolvimento de solo hidromórfico; é marcada por aumento de umidade, deposição de sedimentos areno-argilosos e estabelecimento de um sistema fluvial perene, com meandros abandonados cuja largura é quatro vezes maior que a do canal atual. A terceira caracteriza-se pela redução do nível de base e do rio Jacaré-Guaçu em 7 m, estabelecimento da planície de inundação atual, intensa migração rumo norte (ao menos 600 m) do canal principal, e transição para padrões geomorfológicos e ambientais próximos dos vigentes atualmente (formação de meandros abandonados de larguras similares às do atual canal). Artefatos de pedra lascada mostram-se correlatos às fases I e II da formação da paisagem local, indicando que antigos grupos humanos interagiram com as modificações ambientais descritas. A disposição das peças arqueológicas líticas contribui para a definição de paleossuperfícies, formadas no âmbito das modificações de nível de base e do rio Jacaré-Guaçu.Palavras chave: geomorfologia fluvial, mudanças climáticas, estrutura superficial da paisagem, pedologia, Quaternário Geomorphological, pedological and environmental transformations on the Low Terraces of the Jacaré-Guaçu River (Boa Esperança II archeological site, São Paulo) on Late Pleistocene and HoloceneA B S T R A C TWith the objective of discussing geomorphological, environmental and pedological Quaternary transformations of the landscape, the low terraces and alluvial plain of the Jacaré-Guaçu river are characterized in the area between Boa Esperança do Sul (SP) and Araraquara (SP). Geomorphological and pedological characterization, granulometric, petrographic and micromorphological analyzes, and absolute dating (LOE and 14C) were carried out to define three phases of environmental changes. The first phase (14500-10900 years ago) is characterized by, at least partially, drier conditions than the current ones and deposition of gravels linked to ephemeral torrential channels of average particle size five times coarser than those of the current river. The second (from 10900 to at least 8000 years ago) records a rise in the local base level and the Jacaré-Guaçu river altimetric position of until 7 m, interspersed by at least one stability interval with hydromorphic soil development; it is marked by increase in humidity, deposition of clayey sand sediments, and establishment of a perennial river system, whose abandoned meanders had width four times larger than the present channel. The third is characterized by the reduction of the base level and of the altimetry of Jacaré-Guaçu river by 7m, establishment of the current floodplain, intense migration towards the north (at least 600 m) of the main channel, and transition to geomorphological and environmental patterns close to the current ones (formation of abandoned meanders with similar width to the current channel). Flaked stone artifacts are correlated with phases I and II of the formation of the local landscape, indicating that ancient human groups had interactions with the mentioned environmental changes. The arrangement of lithics archeological pieces contributes to the definition of paleosurfaces developed within the changes of the base level and of the Jacaré-Guaçu river.Keywords: fluvial geomorphology, climate change, landscape surface structure, pedology, Quaternary

Uncertainty assessment in subsurface modeling: considering geobody shape and connectivity in complex systems.

&lt;p&gt;Modeling the subsurface is a complex task because the data scarcity leads to ambiguous interpretations. As a result, subsurface models are prone to many uncertainties, which can be accounted for by stochastically simulating a large set of possible models. These models are constrained by the data (of various resolution and types), but also by geological knowledge and concepts. Integrating the latter in simulation methods emerges as a key point to reduce uncertainties, although it adds another layer of complexity to the modeling process. In this presentation, I focus on two different geological contexts characterized by specific geobody shapes and connectivity: channelized systems and salt tectonics.&lt;/p&gt;&lt;p&gt;Channelized systems are, indeed, characterized by elongated and sinuous structures, the channels, which evolve through time by continuous lateral and vertical migrations, and abrupt events like avulsion or meander cut-offs. The combination of erosion and deposition processes is an additional source of complexity in the sedimentary records. When considering the 3D reconstruction of channelized systems, honoring data while reproducing the complex spatial architecture of these structures - so their specific connectivity - remains challenging. The various methods we have recently developed can now be combined to achieve such a goal: (i) single channels or channel parts (for avulsion) can be simulated consistently with well-data, probability cubes, or confinement thanks to a method based on Lindenmayer systems; (ii) from a channel path, consistent 3D architectures can be generated with a reverse-time channel migration approach (ChaRMigS) handling the observed abandoned meanders; (iii) to honor well data within this reverse-time reconstruction, the stochastic simulation of abandoned meanders and avulsions offers interesting solutions. The impact of such modelling methodology on connectivity reproduction has been demonstrated using static criteria, and a flow-based evaluation constitutes an obvious next step.&lt;/p&gt;&lt;p&gt;In the case of salt tectonics, one difficulty comes from the highly convoluted shapes taken by salt bodies, incompatible with the hypothesis of minimal surface classically used in geomodeling methods. To tackle this issue, we have developed a dedicated method to stochastically generate various salt envelopes in a pre-defined uncertainty zone. Simulations of welds, i.e. surfaces (or most often thin volumes) resulting from the removal of salt from a former layer or diapir stage, also allow us to reproduce topological singularities between salt and the surrounding sediments. Welds connect the different salt volumes, which let us recover a more geologically-consistent representation of such complex systems. The present method is still in its early days, and further improvements need to be undertaken to fully integrate the diversity of structures actually observed in the field.&lt;/p&gt;

ANÁLISE DA DINAMICA HIDROGEOMORFOLÓGICA NO RIO MIRANDA, ESTADO DE MATO GROSSO DO SUL POR MEIO DE IMAGENS LANDSAT SENSORES TM E OLI

Atualmente no Brasil, os estudos sobre as dinâmicas hidrogeomorfológicas por meio de dados de sensoriamento remoto ainda são escassos. Em rios com extensos percursos e áreas inóspitas faz jus o uso de técnicas de sensoriamento remoto para análise e monitoramento ambiental. Diante do exposto, o objetivo deste estudo foi analisar as mudanças na geomorfologia fluvial do rio Miranda no estado de Mato Grosso do Sul, MS por meio de séries de imagens multitemporais dos Sensores Tematic Mapper do satélite Landsat – 5 e OLI do Satélite Landsat- 8. A planície de inundação do rio Miranda apresenta aproximadamente 600 m de largura e padrão de canal meandrante com índice de sinuosidade de 2.13. Identificou-se áreas em processo erosivo nas margens côncavas, deposição de sedimentos nas margens convexas e presença de meandros abandonados. O paleocinturão de meandros, abandonos de canais e meandros abandonados foram os fenômenos naturais que ocorreram com maior frequência e mais distinguíveis nas imagens Landsat para o período analisado. Palavras-chave: Geomorfologia fluvial. Geoprocessamento. Recursos hídricos. Imagens de satélite. ANALYSIS OF HYDROGEOMORPHOLOGICAL DYNAMICS IN RIVER MIRANDA, MATO GROSSO DO SUL STATE BY IMAGE LANDSAT SENSORS TM AND OLI ABSTRACT Currently in Brazil, studies on the hydrogeomorphological dynamics through remote sensing data are still scarce. In rivers with extensive pathways and inhospitable areas the use of remote sensing techniques for analysis and monitoring environmental is justified. The objective of this study was to analyze the changes in the river geomorphology of the Miranda River in the state of Mato Grosso of Sul, MS, using multitemporal images series of the Landsat - 5 satellite and Landsat - 5 satellite OLS sensors The floodplain of the Miranda river is approximately 600 m wide and has a meandering channel pattern with a sinuosity index of 2.13. It was identified areas in erosive process in the concave margins, deposition of sediments in the convex margins and presence of abandoned meanders. The paleoculture of meanders, abandonments of channels and abandoned meanders were the natural phenomena that occurred more frequently and more distinguishable in Landsat images for the analyzed period. Keywords: Fluvial geomorphology. Geoprocessing. Water resources. Satellite images. ANÁLISIS DE DINÁMICA HIDROGEOMORFOLÓGICA EN EL RÍO MIRANDA, ESTADO DE MATO GROSSO DEL SUR POR MEDIO DE IMÁGENES LANDSAT SENSORES TM Y OLI RESUMEN Actualmente en Brasil, los estudios sobre las dinámicas hidrogeomorfológicas por medio de datos de sensoriamiento remoto todavía son escasos. En ríos con extensos recorridos y áreas inhóspitas, el uso de técnicas de detección remota para análisis y monitoreo ambiental. El objetivo de este estudio fue analizar los cambios en la geomorfología fluvial del río Miranda en el estado del Mato Grosso do Sul, MS por medio de series de imágenes multitemporales de los Sensores Tematic Maper del satélite Landsat - 5 y OLI del Satélite Landsat- 8 La planicie de inundación del río Miranda presenta aproximadamente 600 m de ancho y patrón de canal meandrante con índice de sinuosidad de 2.13. Se identificaron áreas en proceso erosivo en los márgenes cóncavos, deposición de sedimentos en las márgenes convexas y presencia de meandros abandonados. La paleocrelación de meandros, abandonos de canales y meandros abandonados fueron los fenómenos naturales que ocurrieron con mayor frecuencia y más distinguibles en las imágenes Landsat para el período analizado. Palabras-clave: Geomorfología fluvial. Geoprocessamento. Recursos hídricos. Imágenes de satélite.