126 research outputs found
Characterisation of submarine depression trails driven by upslope migrating cyclic steps: Insights from the Ceará Basin (Brazil). Marine and Petroleum Geology
No full textThe Carboniferous MTD Complex at La Peña Canyon, Paganzo Basin (San Juan, Argentina)
No full textThe La Peña Canyon section (San Juan Province, western Argentina) provides outstanding examples of different varieties of mass‐transport deposits (MTDs) and related sediments, showing a wide range of lithologies (from mud to sand dominated), scales and styles of deformation (from imbricate thrusts comprising the entire thickness of the deposit down to meso‐ and microscale folding), and mechanical responses (ductile, brittle) according to the rheology of the sediment. Specific observations include (i) the amalgamation of MTDs and the recognition of amalgamation surfaces; (ii) the tendency for MTDs to make up a progressively smaller proportion of the succession as the basin fills; (iii) the progressive disaggregation and homogenization of the protolith, from clear boundaries between a muddy matrix and sandy blocks and slabs up to almost complete mixing generating a ?holomictite? (nom, nov.), via intermediate stages of peperite‐like lithologies; (iv) slow deformation contemporaneous with deposition of overlying sediments (progressive slumping), suggesting emplacement or post‐emplacement modification by creep; and (v) the tendency to find clean, structureless gravel at the sole of some larger MTDs, suggesting a mechanism for MTD sliding involving a layer of gravel with overpressured pore fluid, combining models of hydroplaning and linked cavity systems.Fil: Valdez Buso, Victoria. University of Aberdeen; Reino UnidoFil: Milana, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Sobiesiak, Matheus S.. University of the Sinos Valley; BrasilFil: Kneller, Benjamin. University of Aberdeen; Reino Unid
Memoirs of the celebrated persons composing the Kit-Cat Club : with a prefatory account of the origin of the association : illustrated with forty-eight portraits, from the original paintings by Sir Godfrey Kneller.
No full textErrata slip inserted.Anonymous. Author taken from NUC and BM Cat.Includes bibliographical references and index.Mode of access: Internet
Sedimentation of a high Alpine Hydropower Reservoir under Climate Change: What will disappear first, the Glacier or the Reservoir?
No full textGlacier retreat in the Alps has dramatically progressed since the 1980s due to climate change, and glacier shrinkage will be even more pronounced in the future. As a result, the flow regime and the sediment yield from watersheds will be subject to significant changes. Reservoirs are exposed to continuous sedimentation, reducing their storage volume and posing exploitation and security risks. The methodology is mainly based on literature review, combining various sources and datasets in order to answer the title question. This chapter discusses the case study of the Gries watershed (including the outlet, the reservoir, the glacier, and the Gries dam), which is currently mostly glacier covered at an altitude above some 2400 m asl. The change in length of the Gries glacier has been recorded since 1847, and data related to the annual mass balance is available starting in 1961. Future glacier evolution models, coupled with a hydrological model, that consider global warming show that the length of the glacier will continue to decline, and it is expected that around 2060 the entire catchment area will be virtually glacier free. Glacier runoff and erosion will be shifted to a pluvio-nival regime, and the water resources associated with this system will become less reliable. Past sediment yield and reservoir sedimentation surveys allow for the reservoir sedimentation patterns to be characterized, which are dominated by plunging turbidity currents. Sustainable sedimentation management measures preserve the reservoir storage volume, safety and economic operability beyond the disappearance of the glacier.PL-LC
Spontaneous Unsteadiness and Sorting in Pyroclastic Density Currents and Their Deposits
No full textPyroclastic density currents form from a range of volcanic eruption styles, as well as lava dome collapse and retrogressive failure of existing deposits. These source conditions, combined with erosion and particle evolution through transport, result in diverse grain sizes and componentry in currents. The deposits from pyroclastic density currents can show grading and stratification, highlighting these differences, but most commonly these deposits preserve unsorted or poorly sorted massive layers. This chapter explores the controls on these different behaviors in relation to the energy and structure of the currents that deposit them. We start by using powder flume experiments to explore the steadiness of currents supplied with a continuous mass flux and find that these currents are spontaneously unsteady, developing pulses that dominate the depositional behavior further downstream. By using a variety of grain sizes. we explore the formation of graded deposits and then discuss the implications of widespread massive lapilli tuffs in natural deposits. These heterogeneous, unsorted sediments imply relatively rapid deposition from currents in which large-scale mixing processes exceed the ability of granular segregation processes to generate grading
Architecture and controlling factors of canyon fills on the shelf margin in the Qiongdongnan Basin, northern South China Sea
No full textIntegrated U-Pb zircon and palynological/palaeofloristic age determinations of a Bashkirian palaeofjord fill, Quebrada Grande (Western Argentina)
No full textThis work presents a new age framework for the main Bashkirian glacio-eustatic transgression in Argentina, including the first absolute age for the Jejenes Formation, San Juan Province, based on radiometric dating of a crystal-rich tuff, supported by palynological and palaeofloristic studies, and presented within a revised palaeogeographic setting. The Jejenes Formation represents the glacial to postglacial fill of the Quebrada Grande palaeofjord carved in the Eastern Precordillera. The succession has been subdivided into five stages, the youngest of which suggests a previously unrecognised glacial event for this locality. Six productive levels for palynology were found within proglacial strata, and in the base and top of the succeeding interglacial stage. Palynoassemblages are characterized by poorly preserved trilete spores and monosaccate pollen grains along with a large amount of terrestrial phytoclasts. Main species indicating the Raistrickia densa-Convolutispora muriornata SubZone (DMa SZ) are Vallatisporites ciliaris, Cristatisporites rollerii, C. stellatus, C. chacoparanensis, C. inconstans and monosaccates such as Circumplicatipollis plicatus. This DMa SZ is estimated as Serpukhovian/Bashkirian and characterizes the glacial-related Guandacol Formation and equivalents units of the western Paganzo Basin. A tuffaceous level in the proglacial unit, bearing platyspermic seeds, plant remains and palynomorphs, yielded first-cycle volcanic zircons that were analysed by SHRIMP. An absolute age of 321.3 ± 5.3 Ma confirms a Bashkirian age for the main postglacial transgression in the Paganzo Basin, and offers a novel calibration for the palynoassemblages of DMa SZ that occurs elsewhere in Western Argentina.Fil: Valdez Buso, Victoria. Universidade do Vale do Rio Dos Sinos; BrasilFil: di Pasquo, Mercedes. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Milana, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Kneller, Benjamin. University of Aberdeen; Reino UnidoFil: Fallgatter, Claus. Universidade do Vale do Rio Dos Sinos; BrasilFil: Junior, Farid Chemale. Universidade do Vale do Rio Dos Sinos; BrasilFil: Gomes Paim, Paulo Sérgio. Universidade do Vale do Rio Dos Sinos; Brasi
Mega gravitational slides in Cerro Bola and Sierra de Maz Hills (Guandacol Formation), and their relationship with the Late Paleozoic Ice Age, La Rioja, Argentina
No full textLa Formación Guandacol en su localidad homónima es conocida por los extensos depósitos de la glaciación gondwánica. Sin embargo ésta área también es importante debido a la excelente exposición de Depósitos de Transporte en Masa (MTD) que debido a sus características y dimensiones, son ejemplos a escala sísmica en el mundo. La gran cantidad de sedimento acumulado rápidamente en una cuenca subsidente, favorecieron al desarrollo de estos depósitos, expuestos debido a la inversión tectónica a lo largo de la falla de Valle Fértil. Este trabajo documenta uno de los ejemplos más completo de una sucesión de MTD´s, desde la cicatriz de deslizamiento hasta el desarrollo de estos depósitos, con todos sus elementos sedimentarios y deformacionales característicos. Se describen tres intervalos de MTD´s: el MTD 1 aflora en los Cerros Bola y guandacol, donde en ésta última área algunos autores sugieren una discontinuidad separando la sección basal en una nueva formación. El MTD 2, de 200 m de espesor, presenta una exposición continua de 10 km en el Co Bola y 4 km en el Co Guandacol. El MTD 3 es más complejo ya que presenta fallas sinsedimentarias, que permiten el desarrollo de conglomerados de ?post-rilling? a lo largo de la superficie de la cicatriz de deslizamiento. Los tres MTDs son perfectamente correlacionables en ambos afloramientos, donde también se muestra cómo cambian facialmente desde un margen hacia el centro de cuenca. Estas sucesiones son ejemplares únicos, ya que una secuencia así, solo ha sido observada en registros sísmicos a la fecha.This paper reports and analyzes the presence of large, seismic-scale, mass transport deposits (MTDs) recorded within the Guandacol Formation. These major submarine landslides seem to be connected with the occurrence of glacial episodes. The Guandacol Formation is part of the Paganzo Basin fill of Norwest Argentina (Fig. 1), and it is well known for recording several glacial cycles of the Late Paleozoic Ice Age. In this contribution we report and describe three major glacial/deglacial cycles (Fig. 1b) of Mississippian/Pennsylvanian age (Valdez et al., 2013). Outcrops of Guandacol Formation in Cerro Bola and Sierra de Maz (Cerro Guandacol) areas preserve those glacial cycles and each consists in the succession from non-glacial deltaic deposits to proglacial and thick mass-transport deposits (resedimented diamictites), which are the aim of this study, and finally postglacial marine varied strata, including sandy turbidites, shales with and without dropstones and some deltaic deposits (Milana et al., 2010; Dykstra et al., 2011). This study focuses on Sierra de Maz and Cerro Bola localities because they show very well exposed seismic-scale MTDs that otherwise would be quite difficult to see (Fig. 2a, b). Thus, these outcrops give the opportunity to compare many characteristics that are usually seen in seismic records, directly on the ground. On this sense, this contribution is mainly oriented to describe the facial and geometrical interrelations between these large MTDs (as there are many minor MTDs) and not the detailed internal architecture or their comparison to specific seismic features. The occurrence of these large MTDs can be explained by the large amounts of sediment delivered to the basin triggered by glacial- deglacial episodes. Due to the scarcity of well-exposed mega-scale MTD successions, a detailed study is being carried out since a few years. The result of detailed mapping of this rough terrain allow an excellent correlation between single MTDs, for several kilometers from Guandacol to Bola Hill outcrops (Fig. 3), and also portraying how a single MTD changes laterally when passing from a basin-margin environment (Guandacol Hill) to a basin-center environment (Bola Hill). The local Guandacol Formation shows three large glacial cycles that are mainly represented by single large MTDs and/or MTD composite intervals. The oldest MTD1 crops out completely in the Guandacol Hill, but only the upper part is present at Bola Hill (Fig. 4). MTD1 particular diagenesis and broad folds caused some authors to separate it from the Guandacol Formation, but we did not find any significant unconformity other than the normal upper relief between it and the following inter-MTD deposits. MTD2 is the largest and occurs as basin widens and more accommodation space is available. Reaching up to 200 m thick, it crops out continuously for more than 10 km in Bola Hill and 4 km in Guandacol Hill (Figs. 5, 6). The MTD3 is more complex due to its encroaching with large syn-sedimentary faults that we interpret as a large-scale slide scar associated to the MTD3 interval (Figs. 9, 10). This potential slide scar is associated with other elements as incised valleys or rilling at the scar surface, which have been observed in subsurface examples. Therefore one of the largest example of MTD successions and probably the best exposed worldwide is documented for the first time as a large, seismic-scale slide-scar cropping out in association to an MTD interval, with all the suite of sedimentary and deformational elements that might be expected for this play. Due to the fact these features are rarely exposed altogether, we expect this outcrop could be a world-class example to observe features cropping out that otherwise could be only studied indirectly from deep-water seismic surveys. This succession also serves as an example of how some sedimentary features could be easily mistaken by tectonic features when the scale of the sedimentary processes involves the discrete movement of large volumes (several km3) of semiconsolidated sedimentary units, as in the case presented here.Fil: Buso, Victoria Valdez . Universidade do Vale do Rio Dos Sinos; BrasilFil: Milana, Juan Pablo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Juan. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Kneller, Benjamin. University Of Aberdeen; Reino Unid
Model-free Approach to Quasielastic Neutron Scattering from Anomalously Diffusing Quantum Particles
No full textInternational audienceThis paper resumes and extends recent work by the author on the dynamics of anomalously diffusing quantum particles that is probed by the quasielastic neutron scattering from complex molecular systems. A model-free description of the observed quasielastic neutron scattering spectra is developed which is valid for moderate momentum transfers
Caracterização arquitetural e distribuição de fáceis de lobos turbidíticos no Mioceno da Bacia de Adana, Turquia
No full textA crescente demanda por novas fronteiras exploratórias na geologia do petróleo e a melhoria do conhecimento dos reservatórios atuais, nos leva à necessidade de estudos detalhados sobre as rochas reservatórios e sua capacidade de acumulação de hidrocarbonetos. A análise de afloramentos ao longo de um perfil longitudinal contínuo, da borda da plataforma até a fundo da bacia onde os depósitos da Formação Cingöz (Mioceno Inferior ao Médio), Bacia de Adana, Turquia, teve como objetivo caracterizar mudanças na arquitetura de lobos turbidíticos ao longo do perfil deposicional, a partir da análise de associações de fácies, hierarquia e geometria dos lobos. Dois leques submarinos foram estudados, o Leque Oriental e o Ocidental. Dez associações de fácies foram identificadas com base na razão N:G, grau de amalgamação, distribuição de fácies, tamanho de grão modal, porcentagem de arenitos espessos, presença de laminações de ondulações de correntes e camadas gradadas, revelando padrões de distribuição espacial das associações de fácies. Quatro níveis hierárquicos dentro da arquitetura foram reconhecidos. O elemento básico, uma camada (bed) (espessura máxima de 1,9 m), representa sedimentos depositados em um único evento, o próximo nível hierárquico, elemento de espraiamento (splay element) (espessura máxima de 7,8 m) é empilhado para formar o lobo (lobe) (espessura entre 9,5 a 22 m); lobos empilhados formam o complexo de lobos (lobe complex) (espessura máxima de 40 m). Um total de 13 lobos (A a M) foi identificado. As dimensões estimadas do lobo (comprimento e largura), baseadas na taxa de afinamento obtida pela correlação entre os perfis colunares sedimentares, indicam uma espessura média de cerca de 15 m (máximo de 22 m), o comprimento varia de 5 a 12 km e a largura de 3 a 10 km. A razão comprimento/largura (L/W) (1,1 a 1,8) indica lobos sub-radiais à alongados. Os blocos construtores representados pelos níveis hierárquicos demonstram a importância da topografia do assoalho oceânico no controle do grau de confinamento e das trajetórias das correntes de turbidez. A análise das tendências verticais das camadas mostrou que a tendência geral é controlada por elemento de espraiamento empilhados. Em ambientes proximais (alto N: G) a sucessão é simétrica, tornando-se mais assimétrica à medida que a relação N: G diminui distalmente. Essa "assimetria distal" é interpretada como resultante do deslocamento lateral do elemento de espraiamento. Assim, o padrão de empilhamento dos lobos no Leque Oriental foi interpretado como agradacional, com algum empilhamento por compensação. Os lobos estratigraficamente inferiores são mais confinados e menores devido à ocorrência do talude ao norte e depósitos antigos ao sul. Os lobos superiores foram desenvolvidos em um sistema menos confinado, com direção preferencial da paleocorrent para NE, como todos os lobos da região. Em geral, os lobos foram construídos em um ambiente semi-confinado. A Formação Cingöz registra uma história evolutiva complexa. A interpretação da arquitetura dos lobos aponta para uma mudança sutil no grau de confinamento e nas direções de paleocorrente, que sugerem uma sobreposição de parte do Leque Oriental sob o Leque Ocidental contemporâneo.The increasing demand for new exploratory frontiers in Petroleum Geology and the improvement in knowledge of the current ones has prompted detailed studies on reservoir rocks and their potential for hydrocarbon accumulation. The analysis of outcrops along a continuous longitudinal profile, from the shelf edge to the bottom of the basin where deep-water deposits of the Cingöz Formation (Lower to Middle Miocene), Adana Basin, Turkey, purposed to characterize changes in the architecture of turbidite lobes along the depositional profile, based on the analysis of facies associations, lobe hierarchy and geometry. Two submarine fans were studied, the Eastern and the Western Fans, with the main lobes described in the eastern part of the Eastern Fan. Ten facies associations were identified on the basis of N-G ratio, degree of amalgamation, facies distribution, modal grain size, percentage of thick sandstones, presence of current ripple laminations and graded beds, revealing patterns of spatial distribution of the facies associations. Four hierarchical levels within lobe architecture were recognized. The basic element, a bed (maximum thickness of 1.9 m) represents sediments deposited in a single event; the next hierarchical level, splay element (maximum thickness of 7.8 m) are stacked to form a lobe (thickness between 9.5 and 22 m); stacked lobes form a lobe complex (maximum thickness of 40 m). A total of 13 lobes (A to M) was identified. Estimated of lobe dimensions (length and width), based on the thinning rate obtained from correlation of sedimentary logs, indicate average thickness of about 15 m (maximum 22 m), length varying from 5 to 12 km and width, 3 to 10 km. The L/W (1.1 to 1.8) indicates sub-radial to elongate lobes. Lobe building blocks represented by the hierarchical levels demonstrate the importance of basin-floor topography in controlling the degree of confinement and paths for turbidity currents. Analysis of vertical bed trends showed that the overall tendencies controlled by stacked splay elements. In proximal environments (high N:G), successions are symmetrical, becoming more asymmetrical as the N:G ratio decreases distally. This ―distal asymmetry‖ is interpreted as resulting from the shift of splay elements. Hence, the stacking pattern of lobes in the Eastern Fan was interpreted as aggradational, with some compensational stacking. Stratigraphically lower lobes are more confined and smaller due to the occurrence of the slope to the north and ancient deposits to the south. Upper lobes were developed in a less confined system, with preferential palaeocurrent direction towards NE, like all lobes in that region. Overall, the lobes were built in a semi-confined setting. The Cingöz Formation records a complex evolutionary history. Interpretation of lobe architecture points to a subtle change in the degree of confinement and palaeocurrent directions that suggest an overlapping of part of the Eastern Fan onto the coeval Western Fan
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