Orientador: Giorgio Basilici / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-19T02:29:09Z (GMT). No. of bitstreams: 1 Fioriti_LenitadeSouza_M.pdf: 9172636 bytes, checksum: 3ae99280216e3efccb7e0ac6bd5c83c0 (MD5) Previous issue date: 2011 / Resumo: Simulações físicas de correntes de densidade em escala reduzida têm sido desenvolvidas para o entendimento dos processos físicos que ocorrem nos eventos naturais. O presente trabalho apresenta modelagens físicas de fluxos gravitacionais realizadas em tanque com forma de canal (4,5x0,15x0,5m). O objetivo foi o entendimento dos processos hidrodinâmicos e deposicionais de tais fluxos, mediante variações de vazão e concentração. Os dados obtidos experimentalmente foram correlacionados com informações extraídas de afloramentos e do monitoramento dos eventos naturais, obtidas na literatura. Os sedimentos eram constituídos por 30% carvão, 30% ballotini e 40% caulim do volume total de massa da mistura, com frações granulométricas entre argila e areia fina. Foram simuladas correntes: i) com vazão constante e alta concentração (20%); ii) com vazão constante e baixa concentração (10%); iii) com vazão variada e alta concentração (20%); iv) com vazão variada e baixa concentração (10%). As variações da vazão foram diretamente proporcionais às variações da altura e velocidade da corrente. A maior intensidade das vazões e das velocidades ocasionou uma maior força de resistência do fluído ambiente. O desenvolvimento da altura da corrente foi favorecido devido a essa ação de reação da água ambiente. A variação da concentração foi diretamente proporcional à variação da velocidade e inversamente proporcional à variação da altura da corrente. Esse comportamento foi explicado pelo número de Reynolds. O aumento da concentração do fluxo ocasionou a diminuição da intensidade da turbulência e das alturas desenvolvidas pelo corpo da corrente. Quanto menor a viscosidade de um fluxo, maior é o número de Reynolds, e seu escoamento tende a caracterizar um fluxo turbulento. As correntes apresentaram estratificação vertical de densidade (fluxo bipartido). A porção inferior foi caracterizada pelo fluxo cisalhante basal, onde a deposição ocorreu por progressiva gradação, e pelo fluxo laminar ou região de plug, onde a deposição ocorreu por congelamento em massa. A porção superior foi caracterizada pelo fluxo de turbidez cujo mecanismo de deposição foi a decantação e tração. O aumento da concentração favoreceu o desenvolvimento do debris flow. A porção superior turbulenta foi substituída por uma nuvem diluída de grãos finos. Os sedimentos apresentaram tendência de acumulação na porção proximal do tanque, com diminuição da espessura e frações granulométricas dos depósitos em direção à porção distal. Concluiu-se que o aumento da concentração implicou no aumento da massa do depósito, porém a sua espessura tendeu a permanecer constante. Os grãos foram transportados para mais longe, o que fez com que o comprimento do depósito aumentasse. Isso foi decorrente da interação entre os grãos, a qual favoreceu a capacidade de transporte e inibiu a decantação dos sedimentos (hindered settling). As correntes simuladas corresponderam aos fluxos gravitacionais subcríticos monitorados na natureza, cujos sedimentos foram representados por grãos de tamanho entre areia muito fina e seixos. Os resultados experimentais apresentaram analogia com a Unidade Apiúna, localizada na Bacia do Itajaí (Santa Catarina/Brasil), a qual representa uma seqüência clássica de depósitos de água profundo / Abstract: Physical simulations of density currents in small scale have been developed to study the physical processes that occur in natural events. The present study deals with laboratory models in flume of gravitational flows (4,5x0,15x0,5m). It was devoted to understanding hydrodynamic and depositional processes, depending on variations in discharle and concentrations of density currents. The experimental data were correlated with information derived from outcrops and monitoring of natural events, which were obtained from literature. Sediments used in the model consisted of 30% coal, 30% silica and 40% kaolin, with grain size range between clay and fine sand. The currents ran down with i) constant discharle and high concentration; ii) constant discharle and low concentration; iii) varied discharle and high concentration; iv) varied discharle and low concentration. Discharle variations were directly proportional to height and velocity variations of the flow. The highest intensity of flows and velocities resulted in greater resistance force from the fluid environment. The development of high current was favored because of this response action of the fluid environment. Concentrations variations were directly proportional to the velocity and inversely proportional to the height variations of the flow. This behavior was explained by Reynolds number. Flow concentration increases caused the decrease of turbulence intensity and the decrease of heights carried by the current. The currents showed density stratified profile (bipartite flow). The sediments were deposited by progressive aggradations from a basal shear flow, by "freezing" en masse from laminar flow and by settling and traction from turbulent/dilute flow. The increase in concentration favored the development of debris flow. The upper turbulent flow was replaced by a dilute cloud of fine grains. The sediments showed a tendency to accumulate in the proximal portion of the flume with deposit thickness and grain size range decreasing towards the distal portion of the flume. The increase in discharle and concentration resulted in increase of the depositional mass, but its thickness tended to remain constant. The grains were transported over longer distances, which meant that the length of the deposit increase. This was due to the interaction among the grains, which increased the carrying capacity and inhibited the settling of sediments (hindered settling). The simulated currents corresponded to subcritical gravity flows monitored in nature, whose sediments were represented by grain size between fine sand and pebbles. The experimental results showed analogy with Apiúna Unit, located in the Itajaí Basin (Santa Catarina/Brazil), which represents a classic sequence of deep water deposits / Mestrado / Geologia e Recursos Naturais / Mestre em Geociências

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An Fourier Series solution is presented that describes the simultaneous, one-dimensional, vertical flow of heat and ground water in homogeneous, porous media beneath streams. Use of this analytical solution provides an indirect method of determining vertical flow rates and the effective vertical hydraulic connection between sediments and overlying streams. The method consists of varying the Darcy velocity in the solution until the temperature profiles predicted by the solution match those measured in the field. The method was applied at three field sites in Central Massachusetts. At the first site, which is underlain by lacustrine clay, the vertical flow rate through the clay was determined to be less than 5x10⁻⁷ cm/s and the vertical hydraulic conductivity was less than 0.08 cm/s. The vertical flow rate through mixed sand and gravel underlying the second site equaled 7.5x10⁻⁶ cm/s and vertical hydraulic conductivities of sediments underlying the site ranged from 3.8x10⁻⁴ to 3.1x10⁻³ cm/s. The vertical flow rate through mixed sand and gravel underlying the third site ranged from 3x10⁻⁵ to 7x10⁻⁵ cm/s and vertical hydraulic conductivities of sediments underlying the site ranged from 1x10⁻³ to 4x10⁻³ cm/s. The simultaneous flow of heat and ground water in sediments beneath streams may be more complex than that assumed for the Fourier Series solution. The additional complexity may be partially attributable to two factors: the presence of horizontal ground-water flow, and the presence of thermal conditions near the stream that differ from conditions in the stream itself. The effects of that these two factors have on thermal regimes in sediments beneath streams were investigated using numerical simulations. Results indicate, for example, that under conditions of no horizontal ground-water flow, thermal conditions near the stream can affect temperatures in sediments beneath the stream as far as 900 cm from the stream bank. For horizontal flow rates greater than about 1x10⁻⁴ cm/s, thermal conditions near the stream can affect temperatures in sediments beneath the stream as far as 1500 cm from the stream bank. The method of determining flow rates and hydraulic connection has been applied to stream-aquifer systems. However, the method also may have application in other hydrologic settings. Two such applications might be to determine flow rates to and from lakes and rates of recharge to aquifers.

Magister Scientiae - MSc / This study described porosity and permeability distribution in the deep marine play of the central Bredasdorp Basin, Block 9, offshore South Africa using methods that include thin section petrography, X-ray diffraction, and scanning electron microscopy, in order to characterize their porosity and permeability distributions, cementation and clay types that affect the porosity and permeability distribution. The study included core samples from nine wells taken from selected depths within the Basin. / South Africa

The Cape Supergroup (Sequence) comprises three groups, embracing a total of twenty-three formations, with a maximum combined thickness of approximately 8 km. The Table Mountain Group consists of medium-grained (occasionally fine- or coarse-grained), "clean", ultra-quartzose sandstone plus subordinate fine-grained, "dirty", subfeldspathic to feldspathic sandstone, mudrock, and rhythmitite. Average total thickness is about 3000 m. The Bokkeveld Group is composed of mudrock, rhythmitite and subordinate subfeldspathic to feldspathic sandstone (generally fine-grained and "dirty"), with a maximum total thickness of over 3000 m. The Witteberg Group comprises fine- to medium-grained ultra-quartzose sandstone, icaceous streaky rhythmitite, mudrock, and one thin diamictite unit; total thickness is about 1700 m. The strata belonging to the Cape Supergroup appear to have been largely deposited under marine conditions in environments ranging from outer shelf to beach. Deltaic deposits are,however, common in the upper part of the Bokkeveld Group and the Witteberg Group, while the main sandstone units in the upper third of the Table Mountain Group may have accumulated on a coastal alluvial plain. Deposition took place in a basin elongated in an east-west direction, with the palaeoslope inclined towards the south. Palaeocurrents were generally directed down the palaeoslope, but westerly 1 transport directions parallel to the palaeostrike and presumed shoreline are present in both the Table Mountain and Witteberg Groups. I The sedimentary rocks o~ the Karoo Sequence are subdivided into two groups (containing a total of eleven formations) and four ungrouped formations. Using the maximum thicknesses of the individual formations, a combined total thickness of about 12 km can be calculated. The sequence commences with the Dwyka Tillite, a 700-m-thick diamictite unit. The overlying Ecca Group consists of "varved" rhythmitite, dark, massive, fine- to very fine-grained ultra-lithofeldspathic sandstone and subordinate mudrock with a total thickness of 2000 - 3000 m. The Beaufort Group is composed of thick mudstone layers alternating with thinner fine-grained ultra-lithofeldspathic, lithofeldspathic and lithic sandstones, with the exception of the Katberg Formation which consists largely of sandstone. Fining-upward cycles are ubiquitous, while red mudstone is com~on, especially in the upper half of the group. A maximum thickness of about 6000 m was obtained in the East London area. The Molteno Formation Consists of up to 600 m of alternating fine- to coarse-grained sublithic sandstones (frequently pebbly) and grey mudstones, generally forming finingupward cycles. The Elliot Formation (up to 500 m thick) consists of red and grey mUdstones and subordinate fine-grained lithofeldspathic sandstones arranged in fining-upward cycles. The bulk of the Clarens Sandstone consists of very fine-grained massive (occasionally cross-bedded) sandstone, with a maximum thickness of 300 m. The Drakensberg Group, consisting of up to 1200 m of basalt with some pyroclastic intercalations near the base, caps the Karoo sedimentary succession. The deposition of the Dwyka Tillite by glacier action coincided with a major change from the generally shallow marine conditions which characterised the sedimentation of the Cape Supergroup (with the source area located on the craton to the north of the basin) to a deep linear trough receiving clastic sediments from a source area situated south and south-east of the basin. The Ecca Group,the lower half of which is characterised by the presence of "proximal" turbidite sandstones, records the gradual infilling of this basin, with deltaic conditions developing in the upper part of the group in the western half of the study area (i.e. in the Waterford Formation). The overlying strata were virtually all deposited under fluviatile conditions, the chief exceptions being a stratigraphic interval within the lower half of the Beaufort Group which appears to have formed in a large body of water, a~d the aeolian Clarens Sandstone. The fluviatile sediments were all deposite1 by rivers flowin~ towards the north and nort~-west, while the Clarens Sandstone was laid down by winds blowing from the west. The Ecca and Beaufort Group sandstones are characterised by a high rock fragment content with "felsit ic" gra ins being a prc;>minent constituent. This, together with the relative abundance of quartzfeldspar porphyry pebbles in the Katberg Sandstone unit (Beaufort Group) near East London, indicates that volcanic material probably formed a prominent part of the post-Dwyka Karoo provenance.

The Upper Cretaceous (Campanian) Cedar District Formation of the Gulf Islands and adjacent areas is composed of shale and sandstone, which are present as thick sequences of shale, which may or may not be fossiliferous, and as alternating rhythmic sandstone-shale sequences of the flysch-type. Presence of graded bedding, ripple and convolute laminations, and sole marks in the latter suggest a turbidity current origin. The internal structures of the individual turbidite units correspond largely to the C-E divisions of Bouma (1962) and other authors, and indicate that their deposition took place largely within the lower flow regime. Convolute lamination in the sandstones was formed by oversteepening and deformation of pre-existing ripple lamination and by the deformation of pre-existing plane-parallel lamination by the drag of the overpassing currents. Flute and groove casts and frondescent marks were only found in beds thicker than a foot and a half. Calcareous concretions, most abundant in the shales and occasionally phosphatic, are crossed by organic borings and burrows which are filled with sediments of the surrounding beds. Host rocks of the calcareous concretions tend to thicken around them. The concretions show deformation when present in beds involved in soft-sediment deformation. All these observations suggest their formation in the early stage of diagenesis, probably shortly after, burial. Sandstones of the Cedar District Formation show a gradation from arenites that lack matrix and have a cal-cite cement, to wackes rich in fine-grained matrix. The majority of the wackes and the arenites are feldspathic and arkosic, using the classification of Gilbert (1954). Their composition indicates that the major source was acidic to intermediate igneous and/or low to medium grade metamorphic rock , sedimentary and volcanic rocks were a secondary source. The major source area was possibly a region of high relief that had undergone rapid uplift and erosion, and experienced mainly mechanical weathering. Paleocurrents and lithologic lateral variation indicate that the major source area for the coarse elastics was situated to the east and southeast of the study area. The pre-Jurassic low grade metamorphic rocks of the Cascade Mountains to the east, and the pre-Carboniferous- crystalline rocks of the San Juan Islands to the southeast served as possible source areas for the coarse elastics. Deposition of shaley, fossilif erous parts, of the formation in the southeastern part, of the study area, took place in littoral to upper neritic depths. Turbidite (flysch-type) sequences were deposited in deeper water, below the wave base. The unfossiliferous shale of the central and northern parts of the study area was deposited either at about the same depths as the turbidites, or in deeper water, since thin, delicate, horizontal and-cross laminations are preserved in these rocks. Paleontologic evidence suggests that deposition took place in a somewhat restricted basin having a narrow connection with the open ocean to the west. Paleontologic and mineralogic data suggest that the bottom conditions of the central and northern parts of the basin of deposition were stagnant and reducing. Facies relationships suggest that the basin of deposition had its longest dimension trending SE-NW. Its eastern, southeastern, and southern boundaries were situated between the mainland of British Columbia-Washington and the Gulf-San Juan Islands. Its northern and northwestern boundaries were possibly near the city of Nanaimo and Gabriola Island. To the west, it was connected at least partially to the open ocean. In the southeastern part of the study area, alternation of thick, fossiliferous shale sequences, and sequences which are predominantly turbidites suggests fluctuations in the depth of the basin floor, either due to changes in sea level or to tectonic movements. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Sediments from the northern end of Juan de Fuca Ridge are Late Quaternary in age and contain widely correlatable cycles of turbidity current and hemipelagic sedimentation. Sediments from the Ridge were examined for their mineralogy, structure, components of the sand fraction, rates of sedimentation and grain size distribution to establish processes of sedimentation, stratigraphy, correlation and local hydrothermal relationships. Ten gravity and Phleger core sites along two profiles of the Ridge were examined in detail, one section was perpendicular to West Valley, the main spreading centre, and one section was within and parallel to West Valley. Sediment from Cascadia Basin was compared to the results of the Ridge study. Changes in sedimentation defined by core X-radiograph structure, components of the sand fraction and grain size distribution, indicated cycles of relatively coarse sediment overlain by finer bioturbated sediment with a repeated stratigraphic relationship in all but one Juan de Fuca Ridge core. Changes in sediment composition are attributed to brief, episodic, continent derived turbidity current deposition followed by lengthy periods of hemipelagic sedimentation for each cycle. Differences in composition exist between sediment of ridges and valleys, with a greater winnowed foraminiferal-hemipelagic and a lesser turbidity current influence in the former area. Radiocarbon dated foraminiferal-rich intervals from ridge sediments were exclusively Late Pleistocene with Middle Ridge sediment having an inferred 9000-9500 B.P. Late Pleistocene-Holocene boundary. Similar sedimentation cycles between Middle Ridge and valley localities enabled correlation of ridge and valley stratigraphy and the Late Pleistocene-Holocene boundary. A stratigraphic relationship based on the episodic deposition of continent derived turbidites exists between the northern end of Juan de Fuca Ridge and the continental Pacific Northwest. Pulses of turbidity current sedimentation coincide with initial interglacial warming trends during the Late Pleistocene. Holocene sedimentation for Juan de Fuca Ridge is of hemipelagic origin with rare local turbidity current deposition. Hydrothermal minerals were not detected. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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