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The Stability of Sand Waves in a Tidally-Influenced Shipping Channel, Tampa Bay, FloridaGray, John Willis 23 March 2018 (has links)
Tidally-influenced sandwaves are common coastal features present in various settings, including shipping channels. The main shipping channel in Tampa Bay under the Bob Graham Sunshine Skyway Bridge (a.k.a. the Skyway Bridge) contains such sandwave bedforms. Between the years 2000 and 2017, these bedforms have been surveyed with multibeam echosounders (MBES) on 21 occasions with ranging coverage and quality of returns. Surveys between 2000 and 2009 used a 300 kHz Kongsberg EM3000; surveys between 2015 and 2017 used a 400 kHz Reson Seabat 7125. For comparable surveys, bathymetry, backscatter, slope, curvature, planform curvature, and profile curvature maps were created and analyzed. Spectral analyses were completed on the same cross-section for usable surveys, providing a period and amplitude for the bedforms. Sediment samples were taken in September 2015 using a Shipek grab. The sediment samples were analyzed for grain size and carbonate content. A bottom-mounted ADCP recorded velocity data semi-continuously over the same time period. These data were analyzed in an effort to investigate the forcing mechanisms that influence the bedform morphology.
Mean grain sizes in the shipping channel under the Skyway Bridge range from 0.01 φ (0.99 mm, coarse sand) to 1.55 φ (0.34 mm, medium sand). Calcium carbonate content ranges from 25% to 87%. The sediment sample site most representative of the sandwave bedforms has a mean grain size of 0.01 φ and a calcium carbonate content of 87%. The calculated mean current velocity required to initiate transport of the D50 and D84 grain size percentile of the representative sediment sample site is 0.70 m/s and 1.05 m/s, respectively. Analysis of the ADCP-recorded velocity data shows that the calculated D50 critical velocity is frequently reached by peak flood and peak ebb currents except during neap tides, while the D84 critical velocity is reached only intermittently, mostly during spring tides. Analysis of MBES backscatter shows similar spatial patterns in two larger MBES surveys in 2004 and 2015. Bathymetric analysis of the sandwaves shows consistent characteristics through time. Wave crest analysis reveals that bedforms migrate in both the ebb and flood directions. Spectral analysis shows primary wave spatial frequencies range from 0.13 m-1 to 0.22 m-1, and primary wave periods range from 4.5 m to 6.0 m. The predominant wavelength of sandwaves within the study area is about 5 m, with an average wave height of 0.47 m. The maximum wave height along the axial cross-section analyzed is 0.8 m, observed in April 2017.
The sediments comprising the sandwave bedforms are likely winnowed by tidal currents resulting in larger grain size and carbonate content than other areas of the shipping channel and surrounding bay. Consistent patterns in MBES backscatter over time indicate that the sediment distribution pattern in the study area have not significantly changed. The size and shape of the bedforms in the shipping channel beneath the Skyway Bridge are have been in a quasi-dynamic equilibrium over the past 13 years. The bedforms are shown to migrate in both the ebb and flood directions despite an average faster ebb current velocity than a flood current velocity. More frequent and consistent MBES surveys as well as more continuous ADCP data availability would allow for better understanding of sediment transport via bedform migration in tidally-influenced environments.
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Sedimentary, geochemical and geophysical study of the Ecca group, Karoo supergroup and its hydrocarbon potential in the Eastern Cape Province, South AfricaBaiyegunhi, Christopher January 2017 (has links)
The Ecca Group of Karoo Supergroup is a sedimentary rock sequence that deposited between the Late Carboniferous (Dwyka Group) and the Late Permian-Middle Triassic (Beaufort Group). The Ecca Group investigated in this study is situated in the Eastern Cape Province of South Africa and it comprises mainly of shales, mudstones, siltstones and sandstones. The Ecca Group sequence contains considerable carbon content and suitable thickness to make it an ideal target for shale gas exploration. Previous studies put more emphasis on the geology and stratigraphy of the Ecca Group, this study revised the stratigraphy, and put new insight on the petrography, depositional processes, sedimentary facies, provenance, paleoweathering, tectonic setting, subsidence rates and history, electrical resistivity, source rock characteristics and diagenesis of the potentially feasible sandstone and mudrock reservoir rocks of the Ecca Group. Based on the lithological features, sedimentary structures and facies characteristics, the stratigraphy of the Prince Albert, Whitehill, Collingham and Fort Brown Formations of the Ecca Group is now subdivided into two informal members each, i.e. Lower Member and Upper Member. Furthermore, the Ripon Formation is now subdivided into three informal members. Each member has been asigned a lithological name. The grain size parameters show that most of the Ecca Group sandstones are very fine to fine grained, poorly to moderately well sorted, mostly near-symmetrical and mesokurtic in grain-size distribution. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under deep marine environment for Prince Albert, Whitehill and Collingham Formations, shallow marine environment for Ripon Formation, while the Fort Brown Formation is lacustrine-deltaic deposits. Modal composition analysis and petrography studies revealed that the detrital components of the sandstones are dominated by monocrystalline quartz, feldspar and lithic fragments. The sandstones are compositionally and texturally immature and can be classified as feldspathic wacke and lithic wacke. The provenance analysis revealed plutonic and metamorphic terrains as the main source rocks with minor debris derived from recycled sedimentary rocks. The detrital modal compositions of these sandstones are related to back arc to island and continental margin of tectonic setting. Based on the detailed sedimentological analyses of outcrop and borehole data, fourteen lithofacies were identified and seven facies associations (FAs) were recognised. The facies associations are: FA 1: Shale and mudstones intercalated with siltstones, FA 2: Carbonaceous shale, mudstone with subordinate chert and sandstone, FA 3: Mudstones rhythmite with thin bedded mudstone and lenticular siltstone, FA 4: Greyish medium bedded sandstone intercalated with laminated mudstone, FA 5: Dark-grey medium to thick bedded mudstone and siltstone, FA 6: Thin to medium bedded sandstone alternated with thin bedded carbonaceous mudstone, and FA 7: Varved mudstone rhythmite intercalated with siltstone and minor sandstone. Sedimentological characteristics of the identified facies associations indicate four deposition environments, namely, deep marine basin, turbidite, shallow marine and lacustrine environments, which constitute a gradually regression sequence as a result of sea-level dropping and shallowing of the basin during the developmental processes. Geochemical analysis of the Ecca mudrocks and sandstones revealed that the rocks are of quartzose sedimentary provenance, suggesting that they were derived from a cratonic interior or recycled orogen. The petrography and geochemistry of the sandstones indicated that the source areas are composed of plutonic and metamorphic rocks with a minor component from sedimentary rocks. The geochemical diagrams and indices of weathering suggested that the granitic source rocks underwent moderate to high degree of chemical weathering. The tectonic setting discrimination diagrams support passive continental margin setting of the provenance.
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Sedimentologia e estratigrafia dos turbiditos lacustres da Formação Candeias no nordeste da Bacia do Recôncavo, BahiaBrandão, Aglaia Trindade January 2015 (has links)
A Formação Candeias (PACK & ALMEIDA, 1945) pertencente ao Grupo Santo Amaro, consiste em arenitos e folhelhos do período Cretáceo e corresponde aos primeiros depósitos da abertura plena do rifte da Bacia do Recôncavo. A idade destes sedimentos varia do Berriasiano médio ao Valanginiano inferior (~143M. a.), com uma amplitude temporal de 4,5 M.a. e uma espessura média de 1000 m. Localiza-se no andar Rio da Serra, e os sedimentos são interpretados como lacustres e depósitos de corrente de turbidez, da fase de clímax do Rifte (PROSSER, 1993), possuindo um papel muito importante na historia do desenvolvimento da extração de petróleo e gás na Bacia do Recôncavo, pois os folhelhos desta formação são as rochas geradoras desta bacia, e os arenitos são importantes reservatórios de hidrocarbonetos. Entender os processos sedimentológicos desta formação, bem como sua evolução estratigráfica, ainda é um desafio, pois a maioria das informações provém de dados indiretos (sísmica, perfis elétricos e dados de produção de petróleo), já que os afloramentos são escassos. Assim, os estudos das rochas de testemunhos seriam os dados diretos principais e aqui explorados. A área de estudo está localizada no compartimento estrutural denominado Borda Nordeste da Bacia do Recôncavo, e abrange os campos de Rio Itariri, Fazenda Bálsamo e Riacho da Barra, que estão alinhados ao longo da Falha de Salvador (borda falhada do rifte) no Patamar de Patioba. O sistema deposicional é interpretado como lacustre com depósitos arenosos provenientes de corrente de turbidez, é composto principalmente por pelitos, heterolitos, arenitos arcoseanos (FOLK, 1968) e arenitos híbridos (ZUFFA, 1980). Os fluxos turbiditicos são interpretados como resultado da desestabilização do talude lacustre em período de atividade tectônica intensa. Durante o período de quiescência tectônica, a maior parte da sedimentação é atribuída a rochas pelíticas. Estes depósitos podem ser correlacionados em toda a borda nordeste e os pelitos possuem uma boa resposta em perfis elétricos e sísmica. A estratigrafia de sequências (ES) em bacias tipo rifte pode utilizar os mesmos critérios dos utilizados em bacias intracratônicas ou de margem passiva, porém deve-se levar em conta a intensa atividade tectônica atuante, como propõem Prosser, (1993) e Martins - Neto & Catuneanu (2010). A metodologia utilizada baseia-se identificar tendências Transgressiva – Regressiva (T-R) segundo Embry & Johannenessen (1992), de 3ª e 4ª ordens e, a partir destas, identificar as principais superfícies estratigráficas. Foram assim, identificadas cinco superfícies estratigráficas (duas superfícies de inundação máxima (SIM) e três limites de sequência (LS)) para as três sequências deposicionais, denominadas como Sequencia I, Sequencia II e Sequencia III. Estas superfícies permitiram correlacionar os depósitos arenosos, utilizando os perfis elétricos (Raios Gama, Resistividade e densidade-neutrão). Para isso, foram descritos 1430m de testemunhos, 54 lâminas petrográficas, feita a interpretação sísmica dos horizontes estratigráficos de duas sísmicas 3D, análises geoquímica de minerais pesados, análise de palinofácies e geoquímica orgânica, de seis poços dos três campos em estudo. A análise estratigráfica e sedimentológica baseou-se na correlação rocha x perfil destes poços, descrição granulométrica e interpretação das fácies, suas associações e petrofácies. As fácies arenosas são descritas como arenitos finos a grossos, com estratificação plana paralela a cruzada de baixo ângulo, muitas vezes com fluidização e carga e maciços. Estas fácies estão relacionadas à fácies de canais turbidíticos ou a lobos turbidíticos proximais. Heterolitos e arenitos muito finos com ripples de corrente e intensa fluidização e pelitos cinza laminados e maciços estão relacionados a lobos turbidíticos distais ou a depósitos de fundo de bacia. A análise petrográfica dos arenitos revelou que estes são essencialmente arcoseanos, e com presença abundante de bioclastos de ostracodes, oncolitos, além de pelóides e alguns aloquímicos indiferenciados, para sequencia I, e fragmentos de rocha metamórfica, ígnea e sedimentar, além de cristais de carbonato, fosfatos e intraclasto lamoso, para a sequência II. Calcita, calcita ferrosa, dolomita, dolomita ferrosa e são os principais cimentos encontrados provavelmente devido à dissolução dos aloquímicos carbonáticos. Porém os processos diagenéticos mais frequentes são a autigênese de sílica gerando crescimento de quartzo e albita. Muitos destes processos diagenéticos podem contribuir para redução substancial da porosidade primária e permeabilidade, porém quando a principal porosidade (primária intergranular) está combinada com a secundária (dissolução de feldspatos ou bioclastos gerando porosidade móldica ou intragranular), pode melhorar consideravelmente a porosidade destes arenitos. As características permoporosas melhores estão localizadas na sequência II, porém os reservatórios mais extensos, e de boa correlação lateral estão na sequência I, isso de dá pelo fato da sequencia I ter sido depositada em um ambiente desconfinado, e a sequencia II estar numa região mais confinada. Além da sequencia I ter sofrido maior processo de diagênese que a sequencia II, resultado provavelmente da cimentação de carbonato abundante neste intervalo estratigráfico e autigênese de sílica nos grãos de quartzo. Porém a porosidade secundária gerada pela dissolução dos constituintes carbonáticos e feldspato, proporcionou um aumento desta porosidade. A análise de palinofácies e geoquímica orgânica revelaram um aumento de fitoclastos para o topo da formação, o que indica que estes ficam cada vez mais continentais e com influencia fluvial mais acentuada. A intensa concentração de matéria orgânica resultando em um COT alto corresponde as SIM, reconhecidas em perfil e sísmica, sendo estes os intervalos Geradores da Bacia. Os dados de geoquímica dos minerais pesados permitiu reconhecer a existência de duas proveniências diferentes para os arenitos da sequencia I e sequência II, com base na assembleia de minerais pesados e principalmente pelos índices de Ar e Titanio+Zr. Revela ainda que a sequência I corresponde a sedimentos de segundo ciclo, ou seja, a retrabalhamento de rochas sedimentares preexistentes, e a grande quantidade de granada em todo o poço revela que estas rochas sofreram pouco processo de intemperismo, com rápida erosão e deposição. A importância dos estudos sedimentológicos e estratigráficos em escala de campo é principalmente para a previsão das fácies e sistema deposicional e consequentemente do reservatório encontrado. Sob o ponto de vista da ocorrência de reservatórios, estas correlações são muito importantes, pois permitem realizar previsões destes depósitos, e das suas fácies. / Candeias Formation (PACK & ALMEIDA, 1945) is belonging to the Santo Amaro Group, and consisting in sandstones and shales of the Cretaceous period and corresponds to the first deposit of the Rift phase from Recôncavo Basin. The age of these sediments varies from Medium Berriasian to lower Valanginian (~ 143M.a.). With a time range from of 4.5 M.a. and an average thickness of 1000 m. Located in Rio da Serra stage and this sediments are interpreted as lacustrine shales and deposits of turbidity current. The Rift climax (PROSSER, 1993), or Candeias Formation had a very important role in the history of development of oil and gas extraction in the Recôncavo Basin, because the shales are the source rocks from this basin, and the sandstones are important hydrocarbon reservoirs. Understanding the sedimentological processes of this formation and their stratigraphic evolution, is still a challenge, because most of the information comes from indirect data (seismic, logs and oil production data), because the outcrops are scarce. Thus, studies of the cores are the main and direct data explored here. The study area is located in the structural compartment from Recôncavo Basin, called Borda Nordeste, and covers the Rio Itariri field, Fazenda Bálsamo field and Riacho da Barra field, which are aligned along the Salvador Fault in Patioba plateau. The depositional system is interpreted as lake with sandy deposits from turbidity current, and is mainly composed of shales, intercalation of shale and very fine sandstones, arkosean sandstones (FOLK, 1968) and sandstones hybrids (ZUFFA, 1980). The turbidite flows are interpreted as a result of destabilization of the lake platform in intense tectonic activity period. During the tectonic quiescence, most of shale sedimentation is assigned. These deposits can be correlated throughout the study area and the shale has a good response in electrical and seismic profiles. The sequence stratigraphy (SE) in rift basins could be used with the same criteria from those used in intracratonic basins or passive margin basins, but always thinking that this kind of basin are constantly affected by tectonics, as proposed by Prosser (1993) and Martins - Neto & Catuneanu (2010). The methodology is based on identify tendencies Transgressive - Regressive (TR) as proposed for Embry & Johannenessen (1992), from 3rd and 4th orders of sequence and, identify key stratigraphic surfaces then. Have been interpreted five stratigraphic surfaces (two of maximum flood surfaces (MFS) and three sequence limit (SL)) for the three depositional sequences, referred to as Sequence I Sequence II and Sequence III. These surfaces allowed correlating the sandy deposits, using the electric logs (Gamma, Resistivity and neutron-density). Have been described 1430m core, 54 thin sections, seismic interpretation of the stratigraphic surfaces of two 3D seismic, geochemical analysis of heavy minerals, palynofacies analysis and organic geochemistry, of six wells from the three fields in study. The stratigraphic and sedimentological analysis was based on the rock x core correlation, size description and interpretation from facies, and their associations. The sandstones facies are described as fine and coarse sandstones, parallel stratification and cross low angle stratification, often fluidization and massive sandstones happens. These facies are related to facies of turbidite channels or proximal turbidite lobes. Very fine sandstones with intercalation of shales and sandstones with current ripples and intense fluidization and gray shales laminated and massive are related to distal turbidite lobes or the basin bottom deposits. The petrographic analysis of sandstones showed that they are essentially arkosean, and had presence abundant of ostracod bioclasts, oncolites, and peloids to sequence I, and metamorphic rock fragments, and plutonic, and carbonate crystals, phosphates to the sequence II. Calcite, ferrous calcite, dolomite, ferrous dolomite are the main cements probably found due to the dissolution of carbonate components. But the most common diagenetical processes are silica authentic growth of quartz and albite. Many of these diagenetic processes can contribute to substantial reduction of primary porosity and permeability, but when the main porosity (primary intergranular) is combined with secondary porosity (dissolution of feldspars or bioclasts) can greatly improve the porosity of these sandstones. Best permoporosity features are located in the sequence II, but the most extensive reservoirs and good lateral correlation are in sequence I. It happens because the sequence I was placed in a large environment and the sequence II is a region more confined. Sequence I have suffered larger process of diagenesis that the sequence II, probably as result of the carbonate cementation in this stratigraphic interval and authigenic silica in quartz grains. But the secondary porosity generated by dissolution of carbonate constituents and feldspar, provided an increase of this porosity. The palynofacies and geochemical organic analysis showed an increase of phytoclasts to the top of the Candeias Formation, showing increasingly more severe continental and river influences. The intense concentration of organic matter is resulting in a high organic total carbon matches the MFS recognized in profile and seismic, which are the generators of the Recôncavo Basin. The geochemical data of heavy minerals allowed to recognize the existence of two different sources for the sandstones of sequence I and II, based on the assembly of heavy minerals and especially the rates of ARi and Titanium + Zr. It also reveals that the sequence I is formed by the second cycle sediments, like an erosion of pre-existing sedimentary rocks, and the large amount of garnet around the well shows that the rocks have no significant intemperism process, with quickly erosion and deposition. The importance of sedimentological and stratigraphic studies in field scale is mainly for the prediction of facies and depositional system of the reservoir. From the point of view of the occurrence of reservoirs, these correlations are very important, since these allow to forecast deposits and their facies.
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Digital outcrop characterisation of syn-rift structure and stratigraphy : Nukhul half-graben, Suez Rift, EgyptRarity, Gil January 2012 (has links)
Syn-rift exposures are a prime source of knowledge on the structure and stratigraphy of rift basins and are vital for the petroleum industry as analogues for subsurface reservoirs. Focusing on superb exposures of the Oligo-Miocene rift initiation Nukhul half-graben in the Suez Rift, Egypt, this study investigates applications of 3D digital survey techniques, particularly terrestrial light detection and ranging (lidar), for (i) the analysis of syn-rift fault and facies architecture, and (ii) the building and testing of outcrop-based reservoir analogue models for early syn-rift settings. Lidar-based digital outcrop mapping of the Nukhul half-graben, combined with conventional fieldwork, facilitated quantification of thickness and facies relationships within syn-rift strata, and variations of throw along normal faults. The results provide new insights into the tectono-sedimentary evolution of the intra-block half-graben. At rift initiation, regional/eustatic sea-level and antecedent drainage are interpreted as the dominant controls on accommodation development and deposition, respectively. However, after just c. 2.5 myr of rifting, the structural template imposed by the propagation and linkage of four initially isolated pre-cursor segments of the Nukhul Fault became the dominant control on accommodation development and basin physiography. Progressive SE-NW back-stepping of facies strike-parallel to the Nukhul Fault suggests hangingwall subsidence was locally sufficient to outpace falls in regional sea-level, resulting in a dynamic transgressive system that progressed from a restricted tidal embayment to shallow marine seaway along fault strike. After c. 4.3 myr of rifting, regional drowning of the tidal system provides evidence for progressive localisation of displacement onto the present-day block-bounding structures and declining activity on the intra-block Nukhul Fault during the transition from rift initiation to rift climax. Development of digital outcrop techniques such as point cloud facies classification, 3D deterministic channel modelling and net-to-gross analysis provided reliable geostatistics on the geometry, distribution and heterogeneity of tide-influenced facies of the syn-rift Nukhul Formation. The high volume, reliability and spatial coverage of data reduced uncertainties related to stochastic facies modelling (in this case sequential indicator simulation and object-based techniques), facilitating building and testing of high-resolution analogue models for the complex facies and sequence architecture of early syn-rift tidal reservoirs. Visual analysis of static reservoir connectivity suggests some of the smallest-scale depositional elements, i.e. thin intercalations of mudstone and sandstone lamina in heterolithic facies, have the biggest impact on both reservoir volume and vertical connectivity in this syn-rift tidal system. Heterogeneities at the sequence stratigraphic scale also have significant impact on vertical reservoir compartmentalisation, whereas tidal channel lag deposits and tidal mud drapes have more localised effects. Use of lidar, when combined with conventional fieldwork, offers a powerful tool for quantitative spatial analysis of fault and facies architecture, tightly constraining 3D structural and stratigraphic interpretations and effectively increasing the statistical significance of outcrop analogues for reservoir characterisation. Future developments in survey technologies alongside geoscience-specific software for the integration and analysis of outcrop datasets will provide more diverse and quantitative information on geological heterogeneity, and promote wider-ranging applications in Earth sciences.
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Sedimentology and Stratigraphy of the Miocene-Pliocene Bouse Formation near Cibola, Arizona and Milpitas Wash, California: Implications for the Early Evolution of the Colorado RiverHoman, Mindy 14 January 2015 (has links)
The ~5.6-4.8 Ma Bouse Formation, exposed along the lower Colorado River, contains a well exposed but debated record of river integration. Sedimentologic and stratigraphic analysis aid interpretation of depositional processes, relative water depth, depositional environments, stratal architecture, and basin-filling history. Data collected include detailed measured sections, facies descriptions, and fault measurements. Seven lithologically distinct units have been identified along with numerous marine sedimentary structures and fossils. The Bouse Formation preserves a systematic sequence-stratigraphic architecture that records two cycles of base level rise and fall. Lacustrine versus estuarine interpretation remains elusive, though new isotope and micropaleontology data suggest a shift from marine to lacustrine. Constructed stratigraphic facies panels reveal a wedging geometry indicative of syn- to post-depostional tilting, leading us to propose a "sag basin" model during deposition of the Bouse. Finally, the newly described Bouse upper limestone unit resolves a long-standing debate over the age of the first through-going river.
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Áreas potenciais à exploração de granulados marinhos siliciclásticos para a recuperação artificial de praias na plataforma continental interna adjacente ao Porto do Recife-PEAndrade, Carla Danielle Pereira de January 2013 (has links)
O mapeamento da Plataforma Continental Interna visando localização, qualificação e quantificação das reservas de material litoclásticos marinho possui poucos trabalhos relacionados. O Estado de Pernambuco sofre com erosões ao longo de todo seu litoral, e principalmente junto às cidades de Recife e Olinda. Assim, este estudo contribui tanto para o conhecimento da sedimentologia da plataforma continental interna adjacente ao Porto do Recife e à Praia dos Milagres em Olinda, quanto para a execução de futuras intervenções na recuperação das praias da região. Portanto, com objetivo de identificar áreas com concentrações de granulados litoclásticos marinhos compatíveis com especificações necessárias à regeneração de praias, foram analisadas 36 amostras, que foram coletadas ao longo de seis perfis equidistantes em 1 km, perpendiculares à linha de costa na plataforma interna do Porto do Recife. Em laboratório foram realizadas análises granulométricas e o estudo composicional de todas as amostras. Os resultados granulométricos mostram a predominância de sedimentos mal selecionados, ocorrendo classes variadas de tamanho entre seixo pequeno (8 mm) e lama (< que 0,062 mm), com predominância da fração areia grossa. A análise composicional revelou uma hegemonia de carbonatos marinhos. Os dados obtidos apresentam uma redução do suprimento sedimentar terrígeno local. Também de acordo com os resultados obtidos no presente estudo, a plataforma continental interna adjacente ao Porto do Recife e à praia dos Milagres em Olinda-PE, é essencialmente recoberta por areias biogênicas mal selecionadas, oriundas da morte e fragmentação dos organismos componentes dos recifes coralíneos e algálicos que ocorrem na plataforma continental interna. Dessa forma, esta área não possui material siliciclástico suficiente para ser utilizado na exploração mineral para recuperação artificial de praias no Estado de Pernambuco. / There are few studies that map the Internal Continental Platform referring to localization, qualification and quantification of reserves of litoclastic marine material. The Brazilian state Pernambuco suffers from erosions along the whole coast and particularly in areas close to the cities of Recife and Olinda. This study offers new knowledge about the sedimentology of the internal continental platform adjacent to the harbor of Recife and the Beach Milagres in Olinda. Furthermore, it points out measures that can be used to recover regional beaches. Along 6 profiles with a distance of 1km and perpendicular to the coast line at the internal platform of the harbor of Recife, 36 samples were collected and analyzed. Thus, areas with concentrations of litoclastic marine aggregates with the necessary characteristics for the recovery of the beaches were identified. A laboratory was used for granulometry and a compositional study of all samples. The granulometric results show mainly badly selected sediments. There are different sizes from small pebbles (8 mm) to mud (< than 0,062 mm), predominantly coarse sand fraction. The compositional analysis reveals hegemony of marine carbonates. Thus the obtained data indicates a reduction of local terrigenous sedimentary supply. This is probably due to the fact that the selected area is undergoing an initial transgressive process. Also in accordance with the obtained results of this study, the internal continental platform adjacent to the harbor of Recife and the Beach Milagres in Olinda, Pernambuco, is mainly covered by badly selected biogenic sand which has its origin in the death and fragmentation of components of the coral reef of the internal continental platform. As a result the area is not indicated to mineral exploration for the artificial recovery of the beaches in the state of Pernambuco.
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Geomorfologia e sedimentologia dos depósitos sedimentares recentes da porção superior do Estuário do Rio Pará (Baía de Marajó, Amazônia)Martins, Silvio Eduardo Matos January 2010 (has links)
A dissertação visa caracterizar os depósitos sedimentares superficiais da planície arenosa de maré e de fundo/canal da porção superior da baía de Marajó, na área de influencia do Porto de Vila do Conde quanto sua geomorfologia, distribuição sedimentar e assembléia mineralógica de fundo, com ênfase nos minerais pesados. Os sedimentos foram classificados em nove classes texturais. A granulometria variou de argila à matacão. Os principais minerais pesados que ocorrem nos depósitos superficiais são: zircão, estaurolita, turmalina, cianita, granada e rutilo. Secundariamente ocorrem sillimanita, andaluzita, epidoto, apatita, topázio, muscovita, tremolita-actinolita, hornblenda, diopsídio, monazita, augita e biotita. Os grãos de estaurolita, zircão, turmalina e cianita apresentam ampla distribuição em todas as amostras dos sedimentos de fundo e planície. A assembléia mineralógica de pesados indica mais de uma área fonte de sedimentos. As feições geomorfológicas do curso fluvial estudado puderam ser descritas quanto suas formas, profundidades e composições sedimentares. A distribuição sedimentológica apresenta estreita relação com a morfologia e, sobretudo, evidencia as características de alta hidrodinâmica para esta área. Os sedimentos nas planícies de maré arenosas, localmente denominadas de “praias” de uma forma geral, ocorrem pela deposição de material arenoso fino, mal selecionado. Tais áreas, continuamente, recebem sedimento, de origem terciária, devido à proximidade com os afloramentos do grupo Barreiras. A suíte de minerais indica uma proveniência potencial de rochas metassedimentares, metamórficas de alto, médio e baixo grau e ígneas que afloram nas adjacências da área, tais quais de forma primaria a formação Barreiras e pós-Barreiras e secundariamente o complexo cristalino Xingu e o grupo Tocantins. / The dissertation aims to characterize the bottom sediments deposits of the tidal sandy plain and bottom/channel of the upper portion Marajó Bay, in area of the port of Vila do Conde about your geomorphology, sediment distribution and mineralogical assembly background, with emphasis on heavy minerals. The sediments were classified into nine textural classes. The particle size ranged from clay to boulder. The main heavy minerals that occur in the superficial deposits are zircon, staurolite, tourmaline, kyanite, garnet and rutile. Secondly occur sillimanite, andalusite, epidote, apatite, topaz, muscovite, tremolite-actinolite, hornblende, diopside, monazite, augite and biotite. The grains of staurolite, zircon, tourmaline and kyanite are widely distributed in all samples of bottom and tidal plain sediments. The heavy mineral assemblage indicates more than one source area of sediments. The geomorphological features of the studied river course could be described as their shapes, depths and sedimentary compositions. Features of sedimentological distribution are closely related to the morphology and, especially, highlights high hydrodynamics for this area. The sediments in sandy tidal flats, locally called "beaches" in general, occur by the deposition of fine sandy material, poorly selected. Such areas continuously receive sediment of Tertiary origin, due to the proximity of the outcrops of the Barriers group. The mineral suite indicates a potential provenance, metasedimentary rocks, metamorphic high, medium and low grade and igneous rocks that outcrop in the vicinity of the area, in a primary form the Barriers formation and post-Barriers and, then the Xingu crystalline complex and Tocantins group.
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Modelagem do aporte de sedimentos aplicada à bacia hidrográfica contribuinte da PCH Costa Rica (MS) e proposta de mitigação do assoreamento / Modeling of sediment delivery applied to the watershed of SHP Costa Rica (MS) and a siltation mitigation proposalZanella, Bruno Pavanelli [UNESP] 28 January 2016 (has links)
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Previous issue date: 2016-01-28 / Fundação para o Desenvolvimento da UNESP (FUNDUNESP) / A avaliação do potencial de produção de sedimentos de uma bacia hidrográfica contribuinte de uma hidrelétrica é de extrema importância para a análise da viabilidade de implantação de uma planta geradora, sobretudo quando se trata de uma Pequena Central Hidrelétrica (PCH), pois o assoreamento pode comprometer a longevidade do empreendimento. Este estudo teve como objetivo aplicar e avaliar modelos de predição de aporte de sedimentos na bacia hidrográfica contribuinte da PCH Costa Rica, no Estado de Mato Grosso do Sul, gerados pelos softwares SWAT e InVEST. A bacia contribuinte desta PCH, com aproximadamente 1.200km², é integrante da bacia do Alto Rio Sucuriú, e apresenta escassez de dados de séries históricas de hidrologia e sedimentologia. A modelagem pelo software SWAT e InVEST permitiu verificar que a produção de sedimentos ocorre em altas taxas na bacia contribuinte desta PCH. A perda total de solo nesta bacia obtida pelo InVEST foi de 19,23 Mg ha-1 ano-1 (2.392.353,10 Mg ano-1), superior em 2,2 vezes o valor gerado pelo software SWAT, de 8,54 Mg ha-1 ano-1 (1.062.402,15 Mg ano-1). O total de sedimentos que efetivamente chega ao canal de adução da PCH Costa Rica estimada pelo InVEST foi de 100.674,20 Mg ano-1 de sedimentos, enquanto o SWAT apresentou um total 10,43 vezes superior (1.049.521,72 Mg ano-1). A diferença obtida entre os dois modelos pode ser atribuída às peculiaridades de cada software, sendo utilizada no InVEST, a relação máxima do aporte de sedimento definida em 80% que não é aplicada no SWAT representa a capacidade máxima de retenção possível em cada célula. A modelagem da perda de solo em bacias hidrográficas realizada pelos softwares SWAT e InVEST mostrou-se promissora, com elevada correlação entre si e com o Método de Einsten Modificado. Estes sedimentos são carreados e se acumulam nos cursos d’água, gerando problemas operacionais para esta PCH, que necessita de dragagem constante para permitir o funcionamento do empreendimento, gerando custos que não foram previstos na concepção do projeto. Diante deste cenário foi proposta a recomposição vegetal das áreas degradadas por processos erosivos intensos, com a utilização de biotecnologia, em sistema de plantio direto de espécies nativas do Cerrado em consórcio com leguminosas inoculadas com rizóbio. A simulação do InVEST para o cenário futuro com recomposição vegetal de 13,78 km2 das APPs hídricas desta bacia gerou uma redução na produção de sedimentos de 6.464,99 Mg ano-1, demonstrando que a adoção de práticas conservacionistas pelos produtores da bacia contribuinte da PCH Costa Rica pode amenizar os processos erosivos, aumentar a capacidade produtiva dos solos e diminuir os custos desta hidrelétrica com o desassoreamento do canal de adução. / The evaluation of sediment production potential in a hydroelectric watershed is extremely important for the deployment of assessing the feasibility of a generating plant, especially in the case of a Small Hydroelectric Plant (SHP) because the sediment deposition may compromise the longevity of the project. This study aimed to implement and evaluate sediment delivery prediction models in the watershed of SHP Costa Rica in the state of Mato Grosso do Sul, generated by SWAT and InVEST software. The basin of this SHP, with approximately 1.200km², is an upper portion of the Sucuriú river basin and presenting scarcity of data time series of hydrology and sedimentology. Modeling by SWAT and InVEST software has shown that the production of sediments occurs at high rates in the basin of this SHP. The total soil losses in watersheds of this SHP obtained by InVEST was 19,23 Mg ha-1 ano-1 (2392353,10 Mg ano-1), higher than the value obtained by SWAT software with 8,54 Mg ha-1 ano-1 (1062402,15 Mg ano-1). The sediment that reaches the adduction channel of SHP Costa Rica estimated by InVEST is 100,674.20 Mg year-1 of sediments, while the SWAT has a total 10.43 times higher (1.049.521,72 Mg ano-1). The difference obtained between the two models can be attributed to the peculiarities of each software being used in InVEST, the maximum ratio of sediment contribution set at 80% which is not applied in SWAT is the maximum capacity possible retention in each cell. The modeling of soil loss in river basins performed by SWAT and InVEST software proved promising, with high correlation with each other and the method of Modified Einstein. These sediments are carried and accumulate in streams, creating operational problems for SHP Costa Rica, which requires dredging to allow operation, and generates costs that were not anticipated in the initial project. In this scenario was proposed a plant recovery of degraded areas with the use of biotechnology in no-tillage system of native Cerrado species intercropped with legumes inoculated with Rhizobium. The simulation of InVEST for future scenario with plant recovery of 13.78 km2 of hydric permanent preservation areas in the SHP Costa Rica basin generated a reduction of 6464.99 Mg year-1 in the total loss of sediment in small watersheds. The adoption of conservation practices by farmers of the SHP Costa Rica basin can mitigate the erosive processes, increase the productive capacity of soils and reduce the costs of this hydropower plant with dredging in the adduction channel. / FUNDUNESP: 1886/2011
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A floresta de Araucária em Monte Verde (MG): história sedimentológica, palinológica e isotópica desde o último máximo glacialEliane de Siqueira 12 November 2012 (has links)
A regiäo de Monte Verde (Camanducaia, MG) está sìtuada a 1500 m de altitude, na porção sul da serra da Mantiqueira. Alvéolos do relevo serrano, como o entroncamento dos córregos do cadete e da Minhoca com o rio Jaguari, junto à sua área urbana, propìciaram o acúmulo de sucessões métricas de sedimentos argilo-arenosos em condiçöes favoráveis à formação de material turfoso e à preservação de palinomorfos. Nesta área, o presente estudo reconstitui, a partir da integração dos registros palinológico, sedimentológico (granulometria e minerais pesados) e geoquímico/isotópico (C e N) de três testemunhos rasos (até 230 cm), a evoluçäo e os possíveis controles sedimentares e paleoclimáticos do cenário paleoflorístico no Quaternário tardio, com especial atençäo para a Floresta de Araucária. O contexto geral registrado nos testemunhos é de planície de inundação fluvial, com cobertura arbórea próxima, e influência varìável de fluxos de encosta. Na parte montante do vale do cadete, obtiveram-se idades compreendidas entre 38695 - 40522 anos cal A.P., em 220 cm de profundidade, e 2060 - 1880 anos cal 4.P., em 5 cm. Na parte inferior da coluna, até cerca de 16000 anos A.P., há indícios de aumento de distalidade para cima. Entre cerca de 16000 e 3500 anos A.P., evidencia-se redução da influência da matéria orgânica de plantas terrestres, em detrimento de algas, possivelmente em momento de abeÍura relativa da cobertura florestal. Os últimos 3500 anos seriam de restabelecimento da cobeÍura florestal, possivelmente já nos moldes da existente hoje, com redução gradual do aporte de areia. Mais a jusante do mesmo vale, as idades ficaram compreendidas entre 26764-26023 anos cal 4.P., em 210 cm de profundidade, e 2350 - 2150 anos cal A.P., em 10 cm, A parte inferior do intervalo, mais antiga que 20830-20370 anos cal A.P., é dominada por influência de áreas fontes locais, graníticas. Em 20000 anos A.P., fontes distais, metamórficas, passam a atuar, com aumento da influência de algas. Nos últimos 5000 a 6000 anos A.P., tem-se o readensamento da Floresta de Araucária, com manutenção de brejos, sob condiçöes climáticas frias e úmidas. Os resultados sugerem que as mudanças climáticas nos últimos 40 mil anos em Monte Verde não foram acentuadas a ponto de exercer grande impacto florístico e que houve predomínio de Araucaria e elementos associados a essa floresta durante todo intervalo estudado, sob condições climáticas frias e úmidas. / he Monte Verde region (Camanducaia, MG) is located in the southern portion of the Mantiqueira Range, with 1500 m of elevation. Relief alveoli, as the junction of cadete and Minhoca creeks with Jaguari River, sited close to the urban area, propitiated the accumulation of metric sucessions of sandy-mud sediments, under cond itions favorable to the formation of peat material and preservation of paìynomorphs. ln this area, the present study integrates palynological, sedimentological (grain size and heavy minerals) and geochemical/isotopic (C and N) records of three shallow cores (up to 230 cm deep) to reconstruct the evolution and possible sedtmentary and paleoclimatic controls of the Laie Quaternary paleofloristic scenario, with special emphasìs in the Araucaria Forest. The general sedimentary context recorded in the cores is a river floodplain close to tree cover areas, and with variable influence of slope flows. On the upstream Cadete valley, were obtained ages of 38695-40522 cal years BP, at the deep of 220 cm, and 2060-1880 cal years BP, at 5 cm. From the bottom of the column until about 16000 BP, there is evidence of increased distality upwards The time interval between about 16000 and 3500 yr BP shows a reduction in the influence of organic matter derived from terrestrial plants, to the detriment of algae, possibly in a moment of relative opening of the forest cover. The last 3500 years would be characterized by the restoration of forest cover, possibly similar to the existing today, with gradual reduction of the sand supply ln the downstream of the same valley, the ages vary from 26,764 fo 26,023 cal years BP, at 210 cm deep, to 2350 to 2150 cal years BP, at 10 cm. The lower part of the sedimentary column, older than 20830-20370 AP\' is dominated by the influence of local granitìc sources areas. ln 20000 years BP, distal metamorphic sources begin to act paralel with a increased influence of algae. over the last 5000-6000 years, a increase of Araucaria Forest is recorded, with maintenance of weflands under cold and wet climatic conditions. This results suggest that climate changes during the last 40 k years in Monte Verde region were not sufficient to exert great floristic impact. Araucaria and associated forest elements predominated during the whole studied interval, under cold and wet weather conditions.
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Caracteriza??o morfodin?mica do estu?rio do Rio A?u, Macau/RNRocha, Ana Karolina Rodrigues da 25 February 2010 (has links)
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Previous issue date: 2010-02-25 / Estuaries are coastal environments ephemeral life in geological time, derived from
the drowning of the shoreline as a function of elevation relative sea level. Such parallel
systems is characterized by having two sources of sediment, the river and the sea. The
study area comprises the Acu River estuary, located on the northern coast of Rio Grande do
Norte State, in a region of intense economic activity, mainly focused on the exploration of
oil onshore and offshore, likely to accidental spills. In the oil sector are developed for salt
production, shrimp farming, agriculture, fisheries and tourism, which by interacting with
sensitive ecosystems, such as estuaries, may alter the natural conditions, thus making it an
area susceptible to contamination is essential in understanding the morphodynamic
variables that occur in this environment to obtain an environmental license. Information
about the submarine relief the estuaries are of great importance for the planning of the
activity of environmental monitoring, development and coastal systems, among others,
allowing an easy management of risk areas, and assist in the creation of thematic maps of
the main aspects of landscape. Morphodynamic studies were performed in this estuary in
different seasonal periods in 2009 to observe and quantify morphological changes that have
occurred and relate these to the hydrodynamic forcing from the river and its interaction
with the tides. Thus, efforts in this area is possible to know the bottom morphology through
records of good quality equipment acquired by high resolution geophysical (side-scan sonar
and profiler current by doppler effect). The combination of these data enabled the
identification of different forms of bed for the winter and summer that were framed in a
lower flow regime and later may have been destroyed or modified forms of generating fund
scheme than the number according Froude, with different characteristics due mainly to the
variation of the depth and type of sedimentary material they are made, and other
hydrodynamic parameters. Thus, these features background regions are printed in the
channel, sandy banks and muddy plains that border the entire area / Estu?rios s?o ambientes costeiros de vida ef?mera no tempo geol?gico, derivados
do afogamento da linha de costa em fun??o da eleva??o relativa do n?vel do mar. Tal
sistema par?lico se caracteriza por ter duas fontes de sedimentos, a fluvial e a marinha. A
?rea em estudo compreende o Estu?rio do rio A?u, localizado no litoral setentrional do
estado do Rio Grande do Norte, que se encontra em uma regi?o de intensa atividade
econ?mica, principalmente voltada ?s atividades de explora??o de petr?leo onshore e
offshore, pass?veis de derrames acidentais. Al?m da atividade petrol?fera s?o desenvolvidas
produ??o de sal marinho, carcinicultura, agricultura, pesca e turismo, que ao interagir com
ecossistemas sens?veis, como no caso dos estu?rios, podem modificar as condi??es naturais,
tornando assim uma ?rea suscept?vel a contamina??es sendo essencial o entendimento das
vari?veis morfodin?micas que ocorrem nesse ambiente para obten??o de licenciamento
ambiental. Informa??es a respeito do relevo submarino dos estu?rios s?o de grande
import?ncia para o planejamento da atividade de monitoramento ambiental, evolu??o e
din?mica costeira, entre outros, possibilitando num f?cil gerenciamento de ?reas de risco,
al?m de ajudar na cria??o de mapas tem?ticos dos principais aspectos da paisagem. Estudos
morfodin?micos foram realizados neste estu?rio em diferentes per?odos sazonais no ano de
2009 a fim de observar e quantificar as mudan?as morfol?gicas ocorridas e correlacion?-las
com as for?antes hidrodin?micas proveniente da a??o fluvial, bem como sua intera??o com
as mar?s. Desta forma, os trabalhos realizados nesta ?rea possibilitaram o conhecimento da
morfologia de fundo atrav?s de registros de boa qualidade adquiridos por equipamentos
geof?sicos de alta resolu??o (sonar de varredura lateral e perfilador de corrente por efeito
doppler). A jun??o destes dados possibilitou a identifica??o de diferentes tipos de formas
de leito para o per?odo de inverno e ver?o que antes eram enquadradas em um regime de
fluxo inferior e que posteriormente podem ter sido destru?das ou modificadas gerando
formas de fundo de regime superior segundo o n?mero de Froude, com caracter?sticas
diferenciadas devido principalmente ? varia??o da profundidade e ao tipo de material
sedimentar que s?o constitu?dos, al?m de outros par?metros hidrodin?micos. Desta forma,
estas fei??es de fundo est?o impressas em regi?es de canal, bancos arenosos e plan?cies
lamosas que margeiam toda ?rea
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