Fundamentos da exploração de petróleo e gás natural e análise geoeconômica da matriz energética brasileira atual e projeções futuras

A análise da matriz energética mundial, assim como a brasileira, nos mostra que o gás natural representará em breve um importante insumo energético favorecendo a balança de pagamentos nacional, visto que o gás poderá ser usado tanto para consumo interno, quanto para exportação. O aumento das reservas nacionais de hidrocarbonetos se deve ao desenvolvimento de tecnologias, que favoreceram o conhecimento das bacias brasileiras quanto ao seu potencial produtor de combustíveis fósseis, permitindo a descoberta de novas jazidas. O amadurecimento do mercado nacional quanto ao consumo de gás natural passa pela construção de uma infraestrutura robusta, eficiente e que possibilite a captação, o armazenamento e distribuição do mesmo. O Brasil tem todos os requisitos necessários para adentrar ao seleto grupo de países exportadores de hidrocarbonetos, a descoberta do Pré-sal tende a incrementar a importância do gás natural para o país. Ao final do trabalho são descritos cenários futuros (quanto o consumo de energéticos), onde se vê que o consumo de energia para os próximos anos crescerá a taxas superiores as das duas últimas décadas. Análise destes cenários permite antecipar o interesse de futuros investimentos no desenvolvimento do conhecimento geológico para áreas promissoras.

Arquitetura crustal da bacia de Almada no contexto das bacias da margem lesste da América do Sul

A Bacia de Almada, localizada no estado da Bahia, compartilha características similares com as outras bacias da margem leste do Brasil, quando é analisada segundo aspectos como os processos sedimentares e o regime de esforço dominante durante a sua formação. Observa-se uma diferença marcante em relação as outras bacias quando é analisada sob a ótica da composição da crosta transicional, uma vez que não se registra atividade vulcânica durante a fase rifte. A aquisição de um extenso levantamento sísmico 3D, com cabos de 6 km de comprimento e 9.2 segundos de tempo de registro (tempo sísmico duplo), resultaram em imagens sísmicas de boa qualidade das estruturas profundas do rifte. Adicionalmente, estudos de modelagem gravimétrica foram integrados com a análise sísmica para corroborar o modelo geológico. A Bacia de Almada é parte dos sistemas de rifte continentais, desenvolvidos durante o Berriasiano até o Aptiano, que antecederam a quebra do continente do Gondwana, evoluindo posteriormente para uma margem passiva divergente. O processo do rifteamento desenvolveu cinco sub-bacias de orientação NNE-SSO, desde posições terrestres até marinhas profundas, produzindo um arcabouço estrutural complexo. Os perfis da sísmica profunda mostram o afinamento progressivo da crosta continental até espessuras da ordem de 5 km, abaixo da sub-bacia mais oriental, com fatores de estiramento crustal próximo a 7 antes do desenvolvimento de crosta oceânica propriamente dita. As imagens sísmicas de boa qualidade permitem também o reconhecimento de sistemas de falhas lístricas que se iniciam na crosta superior, evoluem atravessando a crosta e conectando as sub-bacias para finalizar em um descolamento horizontal na crosta inferior estratificada. Adicionalmente, a bacia apresenta um perfil assimétrico, compatível com mecanismos de cisalhamento simples. As margens vulcânicas (VM) e não vulcânicas (NVM), são os extremos da análise composicional das margens divergentes continentais. Na Bacia de Almada não se reconhecem os elementos arquiteturais típicos das VM, tais como são as grandes províncias ígneas, caracterizadas por cunhas de refletores que mergulham em direção ao mar e por intenso vulcanismo pré- e sin-rifte nas bacias. Embora a margem divergente do Atlântico Sul seja interpretada tradicionalmente como vulcânica, o segmento do rifte ao sul do Estado da Bahia apresenta características não-vulcânicas, devido à ausência destes elementos arquiteturais e aos resultados obtidos nas perfurações geológicas que eventualmente alcançam a seqüência rifte e embasamento. Regionalmente a margem divergente sul-americana é majoritariamente vulcânica, embora a abundância e a influência do magmatísmo contemporâneo ao rifte seja muito variável. Ao longo da margem continental, desde a Bacia Austral no sul da Argentina, até a Bacia de Pernambuco no nordeste do Brasil, podem ser reconhecidos segmentos de caráter vulcânico forte, médio e não vulcânico. Nos exemplos clássicos de margens não vulcânicas, como a margem da Ibéria, a crosta transicional é altamente afinada podendo apresentar evidências de exumação de manto. Na Bacia de Almada, a crosta transicional apresenta importante estiramento embora não haja evidências concretas de exumação de manto. Os mecanismos responsáveis pela geração e intrusão dos grandes volumes de magma registrados nas margens divergentes são ainda sujeitos a intenso debate. Ao longo da margem divergente sul-americana há evidências da presença dos mecanismos genéticos de estiramento litosférico e impacto de plumas. Alternativamente estes dois mecanismos parecem ter tido um papel importante na evolução tectônica da margem sudeste e sul, diferenciando-as da margem continental onde foi implantada a Bacia de Almada.

The lakes of Michoacan (Mexico): A brief history and alternative point of view

This article is intended to open a discussion about the historical development of lakes Zirahuen, Patzcuaro and Cuitzeo in the state of Michoacan, and the postulated relationships between lake ecology and evolution. Dr Fernando De Buen was the first man dedicated to limnology in Mexico who came to the country in the 1930s. He was adviser at the Estacion Limnologica de Patzcuaro and wrote outstanding papers dealing with Mexican lakes. The lakes of Michoacan probably formed in the late Pliocene or Holocene, and were part of a tributary to the Lerma River, which became isolated by successive volanic barriers to form lake basins. Lake Zirahuen is a warm monomictic waterbody with unique water dynamics amongst the Michoacan lakes. Because it is relatively deep (max depth 40m), seasonal patterns of alternating circulation and thermal stratification develop in the lake, a feature not shared by the other two polymictic shallow lakes, Patzcuaro and Cuitzeo.

New challenges in lake and river monitoring

Freshwater ecosystems are highly dynamic and change on time-scales that range from a few hours to several months. The development of models that simulate these processes is often hampered by the lack of sufficient data to parameterize the processes and validate the models. In this article, I review some of the challenges posed by this lack of information and suggest ways in which they can be met by using automatic monitoring systems. One of these studies is the project tempQsim (EVK1-CT2002-00112) funded by the European Commission. In this project, detailed field and model analyses have been performed at eight catchment study sites in south and south-east Europe. A number of perceptual models for the study sites have been established, and results are being used to improve selected catchment models and provide a more adequate description of pollution dynamics. Results from the extensive field studies and model tests are now being used to derive recommendations for more tailored monitoring concepts in highly dynamic, but ‘data scarce’ environments, such as are frequently found in Mediterranean river basins. The author includes implications of the EU Water Framework Directive on monitoring methods.

Site-Specific Isotopes in Small Organic Molecules

Stable isotope geochemistry is a valuable toolkit for addressing a broad range of problems in the geosciences. Recent technical advances provide information that was previously unattainable or provide unprecedented precision and accuracy. Two such techniques are site-specific stable isotope mass spectrometry and clumped isotope thermometry. In this thesis, I use site-specific isotope and clumped isotope data to explore natural gas development and carbonate reaction kinetics. In the first chapter, I develop an equilibrium thermodynamics model to calculate equilibrium constants for isotope exchange reactions in small organic molecules. This equilibrium data provides a framework for interpreting the more complex data in the later chapters. In the second chapter, I demonstrate a method for measuring site-specific carbon isotopes in propane using high-resolution gas source mass spectrometry. This method relies on the characteristic fragments created during electron ionization, in which I measure the relative isotopic enrichment of separate parts of the molecule. My technique will be applied to a range of organic compounds in the future. For the third chapter, I use this technique to explore diffusion, mixing, and other natural processes in natural gas basins. As time progresses and the mixture matures, different components like kerogen and oil contribute to the propane in a natural gas sample. Each component imparts a distinct fingerprint on the site-specific isotope distribution within propane that I can observe to understand the source composition and maturation of the basin. Finally, in Chapter Four, I study the reaction kinetics of clumped isotopes in aragonite. Despite its frequent use as a clumped isotope thermometer, the aragonite blocking temperature is not known. Using laboratory heating experiments, I determine that the aragonite clumped isotope thermometer has a blocking temperature of 50-100°C. I compare this result to natural samples from the San Juan Islands that exhibit a maximum clumped isotope temperature that matches this blocking temperature. This thesis presents a framework for measuring site-specific carbon isotopes in organic molecules and new constraints on aragonite reaction kinetics. This study represents the foundation of a future generation of geochemical tools for the study of complex geologic systems.

Quantifying Earthquake Collapse Risk of Tall Steel Moment Frame Buildings Using Rupture-to-Rafters Simulations

There is a sparse number of credible source models available from large-magnitude past earthquakes. A stochastic source model generation algorithm thus becomes necessary for robust risk quantification using scenario earthquakes. We present an algorithm that combines the physics of fault ruptures as imaged in laboratory earthquakes with stress estimates on the fault constrained by field observations to generate stochastic source models for large-magnitude (Mw 6.0-8.0) strike-slip earthquakes. The algorithm is validated through a statistical comparison of synthetic ground motion histories from a stochastically generated source model for a magnitude 7.90 earthquake and a kinematic finite-source inversion of an equivalent magnitude past earthquake on a geometrically similar fault. The synthetic dataset comprises of three-component ground motion waveforms, computed at 636 sites in southern California, for ten hypothetical rupture scenarios (five hypocenters, each with two rupture directions) on the southern San Andreas fault. A similar validation exercise is conducted for a magnitude 6.0 earthquake, the lower magnitude limit for the algorithm. Additionally, ground motions from the Mw7.9 earthquake simulations are compared against predictions by the Campbell-Bozorgnia NGA relation as well as the ShakeOut scenario earthquake. The algorithm is then applied to generate fifty source models for a hypothetical magnitude 7.9 earthquake originating at Parkfield, with rupture propagating from north to south (towards Wrightwood), similar to the 1857 Fort Tejon earthquake. Using the spectral element method, three-component ground motion waveforms are computed in the Los Angeles basin for each scenario earthquake and the sensitivity of ground shaking intensity to seismic source parameters (such as the percentage of asperity area relative to the fault area, rupture speed, and risetime) is studied.

Under plausible San Andreas fault earthquakes in the next 30 years, modeled using the stochastic source algorithm, the performance of two 18-story steel moment frame buildings (UBC 1982 and 1997 designs) in southern California is quantified. The approach integrates rupture-to-rafters simulations into the PEER performance based earthquake engineering (PBEE) framework. Using stochastic sources and computational seismic wave propagation, three-component ground motion histories at 636 sites in southern California are generated for sixty scenario earthquakes on the San Andreas fault. The ruptures, with moment magnitudes in the range of 6.0-8.0, are assumed to occur at five locations on the southern section of the fault. Two unilateral rupture propagation directions are considered. The 30-year probabilities of all plausible ruptures in this magnitude range and in that section of the fault, as forecast by the United States Geological Survey, are distributed among these 60 earthquakes based on proximity and moment release. The response of the two 18-story buildings hypothetically located at each of the 636 sites under 3-component shaking from all 60 events is computed using 3-D nonlinear time-history analysis. Using these results, the probability of the structural response exceeding Immediate Occupancy (IO), Life-Safety (LS), and Collapse Prevention (CP) performance levels under San Andreas fault earthquakes over the next thirty years is evaluated.

Furthermore, the conditional and marginal probability distributions of peak ground velocity (PGV) and displacement (PGD) in Los Angeles and surrounding basins due to earthquakes occurring primarily on the mid-section of southern San Andreas fault are determined using Bayesian model class identification. Simulated ground motions at sites within 55-75km from the source from a suite of 60 earthquakes (Mw 6.0 − 8.0) primarily rupturing mid-section of San Andreas fault are considered for PGV and PGD data.

Mechanism of red colouration in Tovel-See (”Conclusions” only) [Translation from: Archiv fur Hydrobiologie 38 299-302, 1941]

Cases of red colouration in small lake basins, due to the abundant appearance of microorganisms have long been known. Usually it is caused by a fast, sudden, intensive propagation (so called ”bloom”) of Cyanophycae and bacteria. (e.g. Oscillatoracae, thiobacteria etc.). An exception to this is the red colouration of Tovel-See, an alpine lake basin in the Dolomites of the Brenta group (Trentino), lying at a height of 1178 m and hidden in the woodland of a valley. Here the red bloom has a double rhythm: a daily and a yearly rhythm. The colouration of one part of the lake takes place in the warmest months of the year (i.e. July, August, September) and in the middle hours of the day. The immediate origin of the bloom has been known for a long time: it is caused by the Peridinacae Glenodinium sanguineum. This paper describes the phenomenon of red colouration of the lake and discusses its conditions.

Improved fisheries productivity and management in tropical reservoirs

The main objective of this 3.5 year project was to increase the productivity of reservoir fisheries and provide sustainable livelihoods to the rural poor through a series of interventions in tropical reservoirs. The main project activities focused on two reservoirs in the Indo-Gangetic basin (Dahob in Madhya Pradesh, and Pahuj in Uttar Pradesh, both in India), the Lake Nasser in Egypt as part as the Nile basin, and the Volta Lake in Ghana as part as the Volta basin. The project also encompassed an initial data inventory from a wide variety of tropical reservoirs within the three basins, and the detailed assessment of the selected reservoirs, including market evaluation and post-capture improvements. (PDF contains 117 pages)

Mechanics of sediment transport and bedrock erosion in steep landscapes

Erosion is concentrated in steep landscapes such that, despite accounting for only a small fraction of Earth’s total surface area, these areas regulate the flux of sediment to downstream basins, and their rugged morphology records transient changes (or lack thereof) in geologic and climatic forcing. Steep landscapes are geomorphically active; large sediment fluxes and rapid landscape evolution rates can create or destroy habitat for humans and wildlife alike, and landslides, debris flows, and floods common in mountainous areas represent a persistent natural and structural hazard. Despite the central role that steep landscapes play in the geosciences and in landscape management, the processes controlling their evolution have been poorly studied compared to lower-gradient areas. This thesis focuses on the basic mechanics of sediment transport and bedrock incision in steep landscapes, as these are the fundamental processes which set the pace and style of landscape evolution. Chapter 1 examines the spatial distribution of slow-moving landslides; these landslides can dominate sediment fluxes to river networks, but the controls on their occurrence are poorly understood. Using a case-study along the San Andreas Fault, California, I show that slow-moving landslides preferentially occur near the fault, suggesting a rock-strength control on landslide distribution. Chapter 2 provides the first field-measurements of incipient sediment motion in streams steeper than 14% and shows a large influence of slope-dependent flow hydraulics and grain-scale roughness on particle motion. Chapter 3 presents experimental evidence for bedrock erosion by suspended sediment, suggesting that, in contrast to prevailing theoretical predictions, suspension-regime transport in steep streams can be the dominant erosion agent. Steep streams are often characterized by the presence of waterfalls and bedrock steps which can have locally high rates of erosion; Chapters 4 and 5 present newly developed, experimentally validated theory on sediment transport through and bedrock erosion in waterfall plunge pools. Finally, Chapter 6 explores the formation of a bedrock slot canyon where interactions between sediment transport and bedrock incision lead to the formation of upstream-propagating bedrock step-pools and waterfalls.

Revisão anatômica e posicionamento filogenético das espécies de Ionoscopiformes (Actinopterygii: Holostei) do Cretáceo do nordeste do Brasil e de Puebla, México

Os gêneros de peixes fósseis Oshunia e Placidichthys são holósteos pertencentes à Ordem Ionoscopiformes e provenientes do Cretáceo Inferior do Brasil, das bacias do Araripe e de Tucano. No clado Ionoscopiformes sensu Grande & Bemis (1998) estão incluídas as famílias Ionoscopidae e Ophiopsidae, todavia as relações internas deste grupo ainda são duvidosas. Oshunia e Placidichthys fazem parte das famílias Ionoscopidae e Ophiopsidae, respectivamente, sendo o gênero Oshunia considerado como mono-específico (cf., O. brevis), enquanto que Placidichthys apresenta duas espécies nominais (cf., P. bidorsalis e P. tucanensis). Em função destas espécies terem sido descritas a partir de poucos espécimes, ainda existiam várias lacunas no conhecimento em relação as mesmas, como, por exemplo, a possibilidade da existência de outras espécies no gênero Oshunia e a falta de informações anatômicas, especialmente do crânio, da região occipital, dos ossos da face e da nadadeira caudal das espécies de Placidichthys. Outro ponto em aberto na literatura era a posição filogenética dos dois gêneros. Frente a estas questões, o objetivo da presente dissertação foi realizar uma revisão anatômica dos gêneros Oshunia e Placidichthys, a fim de ampliar o conhecimento anatômico e taxonômico acerca dos mesmos, além realizar uma análise filogenética da Ordem Ionoscopiformes, baseada em matrizes de caracteres existentes na literatura, para se obter um melhor posicionamento dessas espécies brasileiras. Em função da facilidade de acesso a material mexicano, também foram incluídos nesta revisão os gêneros Teoichthys e Tuetzalichthys provenientes do Cretáceo da Formação Tlayúa, estes também peixes fósseis holósteos pertencentes à Ordem Ionoscopiformes. Do ponto de vista taxonômico, não foi possível confirmar a existência de novas espécies para o gênero Oshunia, entretanto ficou clara a presença de uma nova espécie pertencente ao gênero mexicano Teoichthys. A presente revisão proporcionou uma série de novas informações sobre a anatomia destas espécies de Ionoscopiformes, tais como a descrição dos ossos circumorbitais e do teto craniano e uma reinterpretação acerca da nadadeira dorsal de Placidichthys bidorsalis, ou ainda sobre a forma do rostral de Teoichthys kallistos. Da mesma maneira, esta revisão também ofereceu novos dados para a construção de uma nova hipótese filogenética para Ionoscopiformes, a qual se mostrou consideravelmente distinta das hipóteses filogenéticas anteriores (cf., relações internas de Ionoscopidae e o posicionamento do gênero Teoichthys). O baixo suporte para grande parte dos clados torna evidente a fragilidade das hipóteses de relacionamento interno do clado Ionoscopiformes, bem como a necessidade de uma revisão mais aprofundada das outras espécies deste grupo e dos caracteres a serem utilizados em futuras análises filogenéticas.

A paleoictiofauna da Formação Missão Velha, Cretáceo Inferior da Bacia do Araripe, Nordeste do Brasil

A Bacia sedimentar do Araripe é uma das mais ricas localidades fossilíferas do mundo e representa algumas das principais fases da evolução tectônica ligadas ao processo de abertura do Atlântico Sul. Essa bacia se subdivide em dois pacotes estratigráficos distintos: o Grupo Cariri (constituído pelas formações Cariri, Missão Velha e Rio Batateiras) e o Grupo Araripe (constituído pelas formações Crato, Ipubi, Santana e Exu). No caso do Grupo Cariri, apenas a Formação Missão Velha (= Brejo Santo para alguns autores) apresenta restos de peixes fósseis. Essa fauna, típica da fase rift da separação da parte oeste do Gondwana, pode ser comparada à ictiofauna já descrita no Grupo Bahia e à fauna encontrada em diversas bacias interiores do Nordeste do Brasil. O presente trabalho constou da realização de coletas na Formação Missão Velha, identificação, preparação e descrição dos espécimes coletados; comparação da paleoictiofauna dessa formação com a de outras bacias de mesma idade; análise da distribuição paleobiogeográfica dos grupos ali presentes. Apesar de desarticulados, foram identificados seis táxons de peixes, assim como fragmentos de teleósteos não identificados. Os táxons identificados a partir do material coletado são: dentes, espinhos cefálicos e espinhos de nadadeira dorsal de Hybodontiformes; escamas, dentes e ossos desarticulados de Lepidotes sp.; escamas de Pleuropholidae; diversos ossos desarticulados de Mawsonia cf. gigas; placa dentária e outros ossos isolados de Ceratodus sp. Essa fauna é muito importante, pois representa uma biota lacustrina do Neocomiano do Brasil, depositada durante os estágios pré-rift/rift da separação do oeste do Gondwana. Durante a fase pré-rift e rift pode ser observada uma correlação estratigráfica entre a Formação Missão Velha e as bacias marginais da África ocidental. Portanto, a biota presente na Formação Missão Velha auxilia a compreensão da diversidade faunística presente nos estágios pré-rift e rift do Brasil e da África.

Wave induced oscillations in harbors of arbitrary shape

Theoretical and experimental studies were conducted to investigate the wave induced oscillations in an arbitrary shaped harbor with constant depth which is connected to the open-sea.

A theory termed the “arbitrary shaped harbor” theory is developed. The solution of the Helmholtz equation, ∇²f + k²f = 0, is formulated as an integral equation; an approximate method is employed to solve the integral equation by converting it to a matrix equation. The final solution is obtained by equating, at the harbor entrance, the wave amplitude and its normal derivative obtained from the solutions for the regions outside and inside the harbor.

Two special theories called the circular harbor theory and the rectangular harbor theory are also developed. The coordinates inside a circular and a rectangular harbor are separable; therefore, the solution for the region inside these harbors is obtained by the method of separation of variables. For the solution in the open-sea region, the same method is used as that employed for the arbitrary shaped harbor theory. The final solution is also obtained by a matching procedure similar to that used for the arbitrary shaped harbor theory. These two special theories provide a useful analytical check on the arbitrary shaped harbor theory.

Experiments were conducted to verify the theories in a wave basin 15 ft wide by 31 ft long with an effective system of wave energy dissipators mounted along the boundary to simulate the open-sea condition.

Four harbors were investigated theoretically and experimentally: circular harbors with a 10° opening and a 60° opening, a rectangular harbor, and a model of the East and West Basins of Long Beach Harbor located in Long Beach, California.

Theoretical solutions for these four harbors using the arbitrary shaped harbor theory were obtained. In addition, the theoretical solutions for the circular harbors and the rectangular harbor using the two special theories were also obtained. In each case, the theories have proven to agree well with the experimental data.

It is found that: (1) the resonant frequencies for a specific harbor are predicted correctly by the theory, although the amplification factors at resonance are somewhat larger than those found experimentally,(2) for the circular harbors, as the width of the harbor entrance increases, the amplification at resonance decreases, but the wave number bandwidth at resonance increases, (3) each peak in the curve of entrance velocity vs incident wave period corresponds to a distinct mode of resonant oscillation inside the harbor, thus the velocity at the harbor entrance appears to be a good indicator for resonance in harbors of complicated shape, (4) the results show that the present theory can be applied with confidence to prototype harbors with relatively uniform depth and reflective interior boundaries.

Imaging the earth with ambient noise and earthquakes

In this thesis, I develop the velocity and structure models for the Los Angeles Basin and Southern Peru. The ultimate goal is to better understand the geological processes involved in the basin and subduction zone dynamics. The results are obtained from seismic interferometry using ambient noise and receiver functions using earthquake- generated waves. Some unusual signals specific to the local structures are also studied. The main findings are summarized as follows:

(1) Los Angeles Basin

The shear wave velocities range from 0.5 to 3.0 km/s in the sediments, with lateral gradients at the Newport-Inglewood, Compton-Los Alamitos, and Whittier Faults. The basin is a maximum of 8 km deep along the profile, and the Moho rises to a depth of 17 km under the basin. The basin has a stretch factor of 2.6 in the center decreasing to 1.3 at the edges, and is in approximate isostatic equilibrium. This "high-density" (~1 km spacing) "short-duration" (~1.5 month) experiment may serve as a prototype experiment that will allow basins to be covered by this type of low-cost survey.

(2) Peruvian subduction zone

Two prominent mid-crust structures are revealed in the 70 km thick crust under the Central Andes: a low-velocity zone interpreted as partially molten rocks beneath the Western Cordillera – Altiplano Plateau, and the underthrusting Brazilian Shield beneath the Eastern Cordillera. The low-velocity zone is oblique to the present trench, and possibly indicates the location of the volcanic arcs formed during the steepening of the Oligocene flat slab beneath the Altiplano Plateau.

The Nazca slab changes from normal dipping (~25 degrees) subduction in the southeast to flat subduction in the northwest of the study area. In the flat subduction regime, the slab subducts to ~100 km depth and then remains flat for ~300 km distance before it resumes a normal dipping geometry. The flat part closely follows the topography of the continental Moho above, indicating a strong suction force between the slab and the overriding plate. A high-velocity mantle wedge exists above the western half of the flat slab, which indicates the lack of melting and thus explains the cessation of the volcanism above. The velocity turns to normal values before the slab steepens again, indicating possible resumption of dehydration and ecologitization.

(3) Some unusual signals

Strong higher-mode Rayleigh waves due to the basin structure are observed in the periods less than 5 s. The particle motions provide a good test for distinguishing between the fundamental and higher mode. The precursor and coda waves relative to the interstation Rayleigh waves are observed, and modeled with a strong scatterer located in the active volcanic area in Southern Peru. In contrast with the usual receiver function analysis, multiples are extensively involved in this thesis. In the LA Basin, a good image is only from PpPs multiples, while in Peru, PpPp multiples contribute significantly to the final results.

Estudo palinoestratigráfico e de petrografia orgânica do Cretáceo inferior da Bacia do Recôncavo

O presente estudo baseou-se na análise das variações verticais do conteúdo orgânico de 50 amostras derivadas do furo de sondagem 9-FBA-61-BA, que permitiu conhecer melhor os representantes palinofaciológicos e palinológicos do Cretáceo Inferior da Bacia do Recôncavo, na área estudada. Através da observação a luz da microscopia óptica em luz branca transmitida e luz ultravioleta, foi possível posicionar temporalmente a seção, e individualizar quatro tipos de palinofácies distintas, levando-se em conta os tipos e o grau de preservação da matéria orgânica. As análises quantitativas do conteúdo orgânico mostram um predomínio de material orgânico de origem alóctone, representado por grãos de pólen, esporos e fitoclastos na base e no topo da seção, sendo sua porção média dominada por material orgânico amorfo autóctone. As mais altas fluorescências são observadas nas porções média e basal da seção indicando um ambiente mais redutor à época de sedimentação, destes estratos. Os dados de ICE apresentam valores de maturação entre 4,5 e 5,0 caracterizando um material orgânico maturo para geração de hidrocarbonetos. A associação palinoflorística identificada, bem como os dados litológicos obtidos, indicam um paleoambiente exclusivamente continental, composto por um sistema fluvial e deltaico-lacustre, sob um clima quente árido para a época deposicional. Tal associação enquadra-se àquelas observadas nas bacias do nordeste brasileiro e insere-se nas características das associações pertencentes à Província Microflorística Dicheiropollis (ex-WASA). Foram identificadas 57 espécies de palinomorfos, incluindo grãos de pólen, esporos, algas e fungos. A detecção das espécies, Dicheiropollis etruscus e Aequitriradites spinulosus, nos permitiu posicionar o intervalo nas biozonas Vitreisporites pallidus e Dicheiropollis etruscus, consideradas como de idades Hauteriviano Barremiano.

Investigations on phytoplankton with special reference to water usage

Experiments and observations on the phytoplankton of certain lakes in the English Lake District were made from early 1973 to the end of March, 1974. They included laboratory and lake bioassays and observations on the quantity and quality of the phytoplankton in six lakes. The introductory sections of the report are about algae, the ecology of phytoplankton and the scope of the contracted work. Laboratory bioassays on water from one lake, Blelham Tarn, showed that phosphorus, silicon (for diatoms) and organic substances forming complexes with iron were the major substances limiting the growth of the algae tested. The growth of the test algae was limited to different degrees by those substances and, to some extent, to a greater or lesser degree at different times of year. It is suggested that a relatively simple form of bioassay could give valuable information to water undertakings. Lake bioassays and other experiments were carried out by using large in situ tubular plastic enclosures. Two such investigations are described. The effects of a change in sewerage in two drainage basins on the phytoplankton of three lakes is described and some data given about changes since 1945 in three other lakes in the same overall drainage basin. These latter lakes have been affected too by changes in sewerage and by increasing inputs of domestic and agricultural wastes. Throughout, the relevance of the work done to practical problems of water usage is kept in mind and discussed. In the last section special reference is made to the largely unpredictable results of water transfers. The report ends with a note on river phytoplankton.