O Subgrupo Itararé apresenta o registro sedimentar mais expressivo da glaciação que assolou a Bacia do Paraná durante o Neopaleozóico. Próximo à borda leste da bacia, em especial na área do estudo, entre os municípios de Sorocaba e Itapetininga, este registro é caracterizado basicamente por depósitos glaciomarinhos, representativos de períodos de mar relativamente mais baixo intercalados com registros de mar relativamente alto. Através da definição e análise de fácies foi possível identificar, na área do estudo, 15 (quinze) unidades faciológicas: Diamictito maciço compactado, Diamictito maciço não compactado, Diamictito maciço compactado deformado, Diamictito tabular, Diamictito lenticular, Arenito maciço tabular, Arenito maciço lenticular, Arenito com estratificação gradacional, Arenito com estratificação cruzada e granodecrescência ascendente, Arenito com estratificação cruzada de baixo ângulo e truncamentos, Siltito maciço, Siltito maciço com clastos dispersos, Folhelho ou argilito maciço, Folhelho ou argilito maciço, com clastos dispersos e Interlaminado. A análise dessas fácies, bem como seu agrupamento em associações diagnósticas (AF1, AF2, AF3 e AF4), permitiu o reconhecimento de tratos de sistemas deposicionais, TSMB, TST, TSMA e TSRGi, os quais, por sua vez, levaram à identificação de 9 (nove) seqüências de 3ª ordem, que permitiram o estabelecimento um arcabouço cronoestratigráfico para os sedimentos do Subgrupo Itararé, ao longo do perfil selecionado na área do estudo. Para se realizar a correlação pretendida entre os sedimentos do Subgrupo Itararé na área do estudo e os aflorantes na região localizada ao sul do Arco de Ponta Grossa no Paraná e Santa Catarina, foram identificados planos ou horizontes que podem ser utilizados, segundo suas características, como datum litoestratigráfico e datum bioestratigráfico. Os resultados das análises palinológicas, bem como os próprios dados físicos de superfície, demonstraram confiabilidade e viabilidade de correlação. A análise petrográfica efetuada em quatro amostras de arenitos revelou porosidades da ordem de 8 a 13%, o que permitiu caracterizar esses sedimentos como potencialmente bons para reservatórios relativamente a hidrocarbonetos ou aqüíferos. / The Itararé Subgroup (Carboniferous-Permian) of the Paraná Basin of southeastern Brazil contains the thickest, most extensive and one of the longest records of late Paleozoic glaciation in all of the Gondwana supercontinent. In the studied area, situated between the cities of Sorocaba and Itapetininga, São Paulo State, this record is characterized by glaciomarine sediments depicting intercalation of periods of high and low relative sea-level. Facies analysis of the glacigenic sediments allowed the identification of 15 lithofacie units: compact massive diamictite, massive non compact diamictite, massive non compact deformed diamictite, tabular diamictite, lenticular diamictite, massive tabular sandstone, massive lenticular sandstone, sandstone with gradational bedding, sandstone with cross bedding and normal grading, sandstone with low angle cross bedding and truncations, massive siltstone, massive siltstone with clasts, massive shale or mudstone, massive shale or mudstone with dispersed clasts and laminites. The analysis of facies and their clustering into the associations AF1, AF2, AF3 and AF4 enabled the identification of the systems tracts TSMB, TST, TSMA and TSRGi and 9 sequences of 3rd order. These provided the base to set up a local chronostratigraphic framework for the Itararé Subgroup in the studied area. In view of the possibility of correlation between the sediments of the studied area and those outcropping in the south of the Ponta Grossa arch, in the States of Paraná and Santa Catarina, some datum planes were determined. The results of the palinological analysis as well as the surface data surveyed pointed out that this correlation is feasible. Petrographic analysis of 4 samples of sandstones indicated porosities between 8 and 13 % which characterize them as potentially reservoirs for water and hydrocarbon.

No description available.

Here we examine seasonal grain-size trends on 18 beaches in the Northeastern US and dispersed along the post-glacial coast of Massachusetts (USA) in order to explore the mechanisms influencing median grain size and slope. Over 800 grain size samples were collected along 200 summer and winter cross-shore beach elevation surveys. Obtained grain size and beach slope data are compared to coastal morphology, sediment source, wave height, and tidal magnitude in order to ascertain controls on beach characteristics. In general, median grain size increases with intertidal beach slope in the study region. However, grain sizes along post-glaciated beaches in the study are as much as an order of magnitude coarser for the same beach slopes when compared to beaches for other regions of the US. Grain size and slope for beaches in the northeastern US also exhibit less correlation with oceanographic processes (i.e. wave climate and tidal magnitude). Instead, grain size trends are primarily driven by the composition of nearby glacial deposits that serve as the primary source of sediment to beaches in the study region. Results provide quantitative support for the distribution and composition of legacy glacial deposits rather than oceanographic conditions serving as the predominant governor of beach grain size along post-glaciated coastlines of the Atlantic continental margin.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2017-08-16T16:46:32Z No. of bitstreams: 1 Mega, A. M..pdf: 4299230 bytes, checksum: 4ff04b898e1e7eebe891e2a5a4dfcd98 (MD5) / Made available in DSpace on 2017-08-16T16:46:32Z (GMT). No. of bitstreams: 1 Mega, A. M..pdf: 4299230 bytes, checksum: 4ff04b898e1e7eebe891e2a5a4dfcd98 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ / Os oceanos funcionam como um reservatório natural de carbono, no qual sua solubilidade na superfície dos oceanos varia de acordo com a temperatura. Antes do período industrial, as variações na concentração de CO2 atmosférico estavam fortemente associadas às transições glacial-interglacial (G-IG), onde os menores valores de CO2 na atmosfera foram registrados nos períodos glaciais, decorrente do aumento da solubilidade do CO2 nos oceanos. Nesses períodos, o aumento da solubilidade do CO2 na coluna d’água estimulou a produção de íons carbonato, beneficiando organismos que calcificam carbonato de cálcio (CaCO3) em suas conchas e esqueletos. O processo inverso, ou seja, menor solubilidade do CO2 e, consequentemente, menor disponibilidade de íons carbonatos nos oceanos marcou os períodos interglaciais. O presente estudo teve como objetivo avaliar os efeitos das variações no peso-normalizado pelo tamanho (do inglês, size-normalized weight, SNW) de foraminíferos planctônicos durante os últimos 70.000 anos no Sudoeste do Atlântico visando compreender os efeitos da calcificação e/ou dissolução do carbonato e da microestrutura das testas de foraminíferos planctônicos que viviam na porção superior da coluna d'água (G. ruber-white e G. sacculifer-sem saco). Para tanto, foi utilizado um testemunho coletado na Bacia de Santos a 2225 m de profundidade, que compreende os últimos 185 mil anos, dos quais os primeiros 70 mil anos foram estudados. Os resultados mostraram que ambas as espécies apresentaram um aumento do SNW na transição entre os períodos G-IG, associado com indícios de dissolução nas testas do período glacial, quando observada a microestrutura. Esses resultados demonstram a ação corrosiva das águas de fundo durante os glaciais e diferem dos obtidos em outros estudos realizados no Atlântico Norte que registram características menos corrosivas durante o último glacial em profundidades de até 3500 metros. A redução no peso das testas durante o período glacial foi atribuída à ação da dissolução dos carbonatos. A dissolução pode ocorrer abaixo da camada denominada lisoclina, porém apesar da grande mudança na profundidade da lisoclina durante os glaciais no Atlântico Sul, o testemunho, ainda assim, estaria 800 m acima da influência da lisoclina. Acima da lisoclina, a dissolução dos carbonatos pode ocorrer por diversos outros fatores, tais como pelo aumento da geração de CO2 pela atividade bentônica durante eventos de aumento de produtividade. Essa atividade bentônica tornaria a camada da interface água-sedimento corrosiva às estruturas carbonáticas. Nesse sentido, foram registrados no testemunho estudado um aumento nos teores de sílica e ferro, nutrientes que poderiam estimular um aumento da produtividade primaria, o que se refletiria nos altos níveis de carbono orgânico também registrados no testemunho durante o período glacial, estimulando, assim, a atividade bentônica. Outra possibilidade que explicaria a dissolução observada é decorrente de mudança na geometria das massas d’água durante os glaciais, o qual promoveria o contato do sedimento com massas d’água Antárticas (Águas de Fundo Antárticas-AFA), que são mais corrosivas. Entretanto, estudos anteriores realizados com o mesmo testemunho e baseados em isótopos de neodímio não corroboram a ocorrência de mudanças na geometria das massas d’água na região, pelo menos para os últimos 25 mil anos. / Oceans work as a natural reservoir of carbon, where the solubility in the surface varies with temperature. Before the industrial period, variations in the atmospheric CO2 concentration were strongly associated with the glacial-interglacial (G-IG) transitions, where the lowest atmosphere CO2 values were recorded in the glacial periods, due to the increase in the CO2 solubility. In these periods, the increase of the CO2 solubility in the water column stimulated the production of carbonate ions, benefiting organisms that calcify calcium carbonate (CaCO3) in their shells. The inverse process, that is, the lower CO2 solubility and, consequently, lower carbonate ions availability in the oceans marked the interglacial periods. The objective of this study was to evaluate the effects of size-normalized weight during the last 70.000 years in the Southwest Atlantic to understand the effects of calcification and/or dissolution of carbonate and microstructure analysis of the Planktonic foraminifera that lived in the upper portion of the water column (G. ruber-white) and G. sacculifer). For that, a core collected in the Santos Basin at 2225 m depth was used, which includes the last 185 thousand years, of which the first 70 thousand years were studied. The results showed that both species showed an increase in SNW at the transition between the G-IG periods, associated with evidence of dissolution in the glacial period, when the microstructure was observed. These results demonstrate the corrosive action of the bottom waters during the glaciers and differ from those obtained in other studies conducted in the North Atlantic that record less corrosive characteristics during the last glacial in depths of up to 3500 meters. The reduction in the weight of the shells during the glacial period was attributed to the action of the carbonate dissolution. The dissolution may occur below the lysoclin layer, but despite the large change in lysoclin depth during the glaciers in the South Atlantic, the corer would still be 800 m above the influence of lysoclin. Above lysoclin, the carbonate dissolution can occur due to several other factors, such as the increase of CO2 generation by benthic activity during productivity increase events. This benthic activity would make the water-sediment interface layer corrosive to carbonate structures. In this sense, an increase in silica and iron contents was recorded in the studied corer, nutrients which could stimulate an increase in primary productivity, which would be reflected in the high levels of organic carbon also recorded in the corer during the glacial period, stimulating benthic activity. Another possibility that would explain the observed dissolution is due to a change in the geometry of the water masses during the glaciers, which would promote the contact of the sediment with Antarctic water masses (Antarctic Bottom Water-ABW), which are more corrosive. However, previous studies carried out with the same evidence and based on neodymium isotopes do not corroborate the occurrence of changes in the geometry of water masses in the region, at least 25 ka years

Modern Pine Island and Thwaites Glaciers, which both drain into Pine Island Bay, are some of the fastest moving portions of the cryosphere and may be the most unstable ice streams in Antarctica. I examined over 133 cores to conduct a detailed sedimentological facies analysis. These data, augmented by new radiocarbon and 210Pb dates, and bathymetric data, are used to reconstruct the post-LGM deglacial history of PIB and gain a better understanding of the causes of ice sheet retreat. My results record a clear retreat stratigraphy in PIB composed of, from top to base; terrigenous sandy silt (plumite), pebbly sandy mud (ice-proximal glacimarine), and till. Initial retreat from the outer-continental shelf began shortly after the LGM and before 16.4 k cal yr BP, in response to rising sea level. Bedforms in outer PIB document episodic retreat in the form of back-stepping grounding zone wedges and are associated with proximal glacimarine sediments. A sub-ice shelf facies is observed in central PIB that spans ∼12.3–10.6 k cal yr BP. Widespread impingement of warm water onto the continental shelf caused an abrupt change from sub-ice shelf sedimentation to distal glacimarine sedimentation dominated by dispersal of terrigenous silt between 7.8 and 7.0 k cal yr BP. The uppermost sediments in Pine Island Bay were hydrodynamically sorted by meltwater plumes. Inner Pine Island Bay contains several large basins that are linked by channels. The most recent release of sediment coincides with rapid retreat of the grounding line, and has an order of magnitude greater flux relative to the entire unit, indicating episodic sedimentation. This is the first identification of a meltwater-derived deposit in Antarctica and demonstrates that punctuated meltwater-intensive glacial retreat occurred at least three times throughout the Holocene in this region. Quartz sand grains were used to conduct an analysis of mode of transport for sediments in the Antarctic Peninsula region from the Eocene to present to record the onset of glaciation. Glacial transport imparts a unique suite of microtextures on quartz grains from high shear-stresses. Eocene samples are free of glacial influence. Late Eocene samples show the inception of glacially derived high-stress microtextures, marking the onset of alpine glaciation. Oligocene grains are similar to the late Eocene samples. Middle Miocene microtextures are characteristic of transport from far-field large ice sheets, originating from ice rafting from the West Antarctic Ice Sheet. The Pliocene and Pleistocene samples indicate the existence of the northern Antarctic Peninsula Ice Sheet at this time, consistent with other proxies.

The bedrock under Griesgletscher is formed in a bowled-shaped cavity, an overdeepening. This is known to affect the flow of ice and subglacial water by causing inefficient drainage through the overdeepening. This report aims to, from field data, investigate what further consequences overdeepenings might have for subglacial drainage mechanisms and seasonal evolution. A field campaign was performed at Griesgletscher, Switzerland, during the summer 2017. Turbidity, discharge and electrical conductivity were monitored in a proglacial stream throughout the ablation season. 115 water samples were collected for calibration of the turbidity measurements and the relationship between the concentration of suspended sediments in the meltwater and the magnitude of discharge was investigated through simple and multiple linear regression. In addition, ten tracer experiments were conducted by injecting dye in moulins on the glacier tongue, and measuring the fluorescence of the water in the proglacial streams. The results obtained during the field campaign suggest that the main part of the overdeepened area at Griesgletscher is drained via a lateral channel passing around the overdeepening and that subglacial water from the overdeepening is drained at times of high discharge. The driving force for drainage of subglacial water from the overdeepening is suggested to be the gradient created from rising water pressure in the ice above the overdeepening. Results further suggest that subglacial drainage at a part of the adverse slope is inefficient and remains inefficient throughout the ablation season. This differs from the seasonal evolution normally seen at nonoverdeepened glaciers, in which an efficient, channelized system evolves during the course of the season. / Formen på berggrunden under en glaciär är avgörande för flödet av smältvatten och is. Det är vanligt att berggrunden under en glaciär utgör en skålformad fördjupning kallad överfördjupning. Det är sedan tidigare känt att flödet genom överfördjupningar är begränsat och forskning tyder på att smältvatten tenderar att välja kanaler över eller runt överfördjupningen i de fall då sådana finns tillgängliga. Många frågor kvarstår dock gällande vilken betydelse överfördjupningar har för det subglaciala dräneringssystemet och dess säsongsutveckling och antalet fältstudier som berör ämnet är få. Den här rapporten syftar till att, från fältdata, tillföra kunskap om överfördjupningars inverkan på subglacial dränering. Under sommaren 2017 utfördes en fältstudie på Griesgletscher, en överfördjupad glaciär belägen i de Schweiziska alperna. Turbiditet, elektrisk konduktivitet och flöde mättes i en av de proglaciära smältbäckarna. 115 vattenprover samlades in för bestämning av koncentrationen suspenderade sediment och användes för att omvandla mätningar av turbiditet till koncentration av suspenderade sediment. Relationen mellan transport av suspenderade sediment och flöde kunde sedan undersökas genom enkel och multipel linjär regression. I tillägg utfördes tio försök då ett fluorescerande spårämne injicerades i en moulin på glaciärtungan och fluorescensen mättes i smältbäckarna som avrinner från Griesgletscher. Utifrån resultaten kunde Griesgletschers dräneringssystem och dess utveckling kartläggas. De resultat som uppnåtts under fältstudien tyder på att det överfördjupade området av Griesgletscher i huvudsak dräneras via en sidokanal som passerar runt överfördjupningen samt att subglacialt vatten från överfördjupningen främst dräneras vid högt flöde. Drivkraften för dränering av subglacialt vattnet från överfördjupningen föreslås vara den gradient som skapas vid hög avrinning, då vattentrycket i isen ovanför överfördjupningen stiger. Resultatet från de regressionsanalyser som utförts visade sig vara representativt enbart för en del av det överfördjupade området. Tolkningar av resultaten tyder på att det subglaciala dräneringssystemet i detta område var ineffektivt att evakuera smältvatten och förblev ineffektivt under hela smältsäsongen. Detta skiljer sig från den säsongsmässiga utvecklingen som normalt kan ses på glaciärer utan överfördjupning, där ett effektivt kanaliserat dräneringssystem utvecklas under sommaren. Slutligen kunde graden av flöde fastställas som den viktigaste drivvariabeln för koncentrationen av suspenderade sediment i smältvattnet tillsammans med förändringen av flöde, tidigare koncentration av suspenderade sediment och nederbörd.

The shape of the thermocline and the depth of the lysoline in the western tropical Pacific are both influenced by the overlying atmosphere, and both the shape of thermocline and the depth of the lysocline can be reconstructed from foraminifera-based paleo-proxies. Paleoclimate proxy evidence suggests a southward shift of the Intertropical Convergence Zone (ITCZ) during times of Northern Hemisphere cooling, including the Last Glacial Maximum (LGM), 19-23 ka before present. However, evidence for movement over the Pacific has mainly been limited to precipitation reconstructions near the continents, and the position of the Pacific marine ITCZ is less well constrained. In this study, I address this problem by taking advantage of the fact that the upper ocean density structure reflects the overlying wind field. I reconstruct changes in the upper ocean density structure during the LGM using oxygen isotope measurements on the planktonic foraminifera G. ruber and G. tumida in a transect of sediment cores from the Western Tropical Pacific. The data suggest a ridge in the thermocline just north of the present-day ITCZ persists for at least part of the LGM, and a structure in the Southern Hemisphere that differs from today. The reconstructed structure is consistent with that produced in a General Circulation Model with both a Northern and Southern Hemisphere ITCZ. I also attempt to reconstruct the upper ocean density structure for Marine Isotope Stages 5e and 6, the interglacial and glacial periods, respectively, previous to the LGM. The data show a Northern Hemisphere thermocline ridge for both of these periods. There is insufficient data to draw any conclusions about the Southern Hemisphere thermocline. Using the same set of sediment cores, I also attempt to reconstruct lysocline depth over the last 23,000 years using benthic foraminiferal carbon isotope ratios, planktonic foraminiferal masses, and sediment coarse fraction percentage. Paleoclimate proxy evidence and modeling studies suggest that the deglaciation following the LGM is associated with a deepening of the lysocline and an increase in sedimentary calcite preservation. Although my data lack the resolution to constrain the depth of the lysocline, they do show an increase in calcite preservation during the last deglaciation, consistent with lysocline deepening as carbon moves from the deep ocean to the atmosphere.

No description available.

Une partie de la region de Paspebiac a ete recouverte par deux glaces contemporaines, lors du dernier stade glaciaire du Wisconsinien. Une premiere s'est ecoulee du nord-nord-ouest, a recouvert la partie ouest de la region a l'etude et a erige une grande moraine laterale nord-sud a sa marge orientale; il n'a pu etre determine si cette glace etait l'inlandsis laurentidien ou une calotte gaspesienne. Une seconde glace progressant vers le nord-ouest a englace le sud-est du territoire et a construit une moraine terminale ouest-est, perpendiculaire et jointive a la premiere moraine. Un lac proglaciaire s'est forme a l'encoignure des deux glaces et a recouvert une partie d'un plateau demeure deglace au nord-est. Lors du dernier rechauffement climatique, le front de la glace du sud a regresse le premier, avant que la mer de Goldthwait noit les basses terres jusqu'a 46 metres vers 12 200 BP. Alors seulement, l'autre glace decouvre a son tour le territoire a l'etude. L'emersion est rapide, et certains elements laissent croire que les terres sont de nouveau transgressees depuis quelques millenaires.

No description available.