M.Sc. (Geology) / The study was undertaken to investigate the stratigraphic and sedimentological character of the transition between the Ecca and Beaufort Groups in the northeastern region of the main Karoo basin. Detailed stratigraphic profiles demonstrate that the transition comprises a regressional sequence of dark basinal shale overlain by sandy delta-lobe deposits. This is overlain by lenticular sandstones and shale representing meandering stream deposits. The deltaic sedimentary rocks vary markedly along strike and record deposition in four different deltaic sUbenvironments, namely: (A) "Normal" central delta lobe areas characterized by distal mouth bar sandstone-shale rhythmites gradationally overlain by proximal distributary mouth bar sandstones. (B) Interdistributary bay areas characterized by stacked thin upward-coarsening shale-sandstone cycles. (C) Areas of strong distributary channel erosion where prodelta shale deposits are erosively overlain by distributary or fluvial channel sandstones. No distributary mouth bar deposits are present. (D) Storm-dominated areas comprising prodelta sedimentary rocks which are in turn overlain by storm and possible barrier sand deposits. Palaeocurrent directions indicate that sediment transport was from the north-west, north and north-east. The concentrations of the trace elements B, V, Zn and Ni in prodelta shales indicate the possible prevalence of both marine and freshwater conditions in the near-coastal waters of the Ecca basin. Lateral variation of depositional environments on the same stratigraphic level makes the placing of the Ecca-Beaufort contact based on genetic criteria unsuitable. It is therefore suggested that purely lithostratigraphic criteria be used. On this basis the Ecca-Beaufort contact is taken at the base of the first prominent sandstone which overlies the Volksrust Shale Formation.

M.Sc. (Geology) / Please refer to full text to view abstract

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 Llandovery succession across the Jupiter-Chicotte formational contact on Anticosti Island, Québec, allows us to study the sediment dynamics and stratigraphic architecture of a storm-dominated, carbonate ramp. The Anticosti paleotropical ramp was slowly subsiding and recording significant changes in sea level in a far field glacial setting during the early Telychian. Three facies associations, grouping nine facies, are recognized along the E-W outcrop belt, and from top to bottom as the: (FA-1) encrinitic carbonate facies, (FA-2) mixed siliciclastic and carbonate facies, and (FA-3) non-encrinitic carbonate facies. These mid to outer ramp sediments represent deposition mostly from episodic, high-energy storm events as evidenced by hummocky cross-stratification, large wave ripples, gutter casts, and wave-enhanced sediment-gravity flow deposits. Spatial and temporal changes in siliciclastic content imply basin margin depositional environments in the eastern sections and change in climate regime from arid to humid conditions. The Chicotte deposition marks a major faunal change with the domination of crinoids triggered by increasing siliciclastic supply, rapid sea level fluctuations and change in substrates. The recognition of one major transgressive-regressive (TR) sequence subdivided in distinct meter-scale cycles allows a high resolution E-W correlation. The development of the TR sequence and meter-scale cycles is driven by glacio-eustacy where the main sequence is 4th order (~400 Ky) with superimposed meter-scale cycles that are 5th and/or 6th order (~100 Ky). Nevertheless, erosional capping surfaces within the more proximal tempestites represent ancient rocky shorelines that developed during forced sea level falls. In order to explain this stratigraphic architecture, a carbonate open-ramp model is proposed with a concave-up profile and a narrow and steep inner ramp in equilibrium with a high-energy coastline.

Matrix-rich strata (20-70% mud matrix) have been increasingly recognized in deep-marine systems. These beds are thought to be deposited from mud-rich flows in a distal basin-floor setting; however they remain poorly understood, partly because details of lateral lithological changes are poorly known. In this study, matrix-rich strata are common in proximal basin-floor strata of the Neoproterozoic Windermere Supergroup. The objective of this thesis is to provide detailed description and interpretation of the lithological and mineralogical make-up and lateral facies trends of matrix-rich strata in in a unit 40 m thick and 800 m wide. Here, stratigraphic and petrographic analyses identified five facies: classic turbidites; sandstones; clayey sandstones; sandy claystones and fine-grained banded couplets, which laterally are arranged systematically from matrix-poor sandstones to thin-bedded turbidites. This lateral change is interpreted to represent a depositional continuum along the margins of an efflux jet that formed immediately downflow of an avulsion node.

A preocupação com a qualidade das águas vem promovendo o desenvolvimento de técnicas cada dia melhores de monitoramento e controle. Como os sedimentos transportam a maior parte dos contaminantes da água, seu estudo é fundamental. Diante do elevado número de variáveis existentes para a determinação da concentração de sedimentos e elevados custos de campanhas de monitoramento, torna-se necessário o desenvolvimento de métodos mais acessíveis e que tragam resultados práticos satisfatórios. Para tanto, este trabalho trata da aplicação da teoria da entropia, um método probabilístico, para determinar a concentração de sedimentos em calhas com diversas concentrações e granulometrias. Para isso, foi proposta uma relação entre os parâmetros da teoria da entropia com a finalidade de reduzir o esforço computacional. Os resultados mostraram-se satisfatórios para concentrações acima de 10 g/L com R² superiores a 0,88. Os erros quadráticos calculados neste trabalho foram inferiores aos encontrados quando utilizada a teoria da entropia por Tsallis e pela Equação de Rouse, modelos clássicos de determinação do perfil de concentração de sedimentos. A técnica também foi aplicada a jusante e no interior do Reservatório de Mogi. Pode-se observar que é possível utilizar a teoria da entropia para simular o perfil de concentração de sedimentos em reservatórios, uma vez que a utilização da relação entre os parâmetros facilita os cálculos, reduz o número de parâmetros modelados e consequentemente o esforço computacional além de representar melhor as variações da concentração de sedimentos ao longo do perfil. A aplicabilidade do modelo proposto e a facilidade da utilização do método probabilístico, já que não necessita fornecer os dados de condições hidráulicas do leito, nem mesmo de granulometria, torna-o viável. / The concern about quality of water has been promoting the development of each day better monitoring and control techniques. As sediments transport most water contaminants, their study is fundamental. Given the large number of variables for determining sediment concentration and high costs of monitoring campaigns, it becomes necessary to develop more accessible methods which bring satisfactory practical results. Therefore, this work deals with application of the theory of entropy, a probabilistic method to determine concentration of sediments in river channels with various concentrations and particle sizes. For this purpose, it was proposed a relationship between the theory of entropy parameters in order to reduce the computational effort. The results were satisfactory at concentrations above 10 g/L with R² greater than 0.88. The calculated squared errors in this study were lower than those found when using the theory of entropy by Tsallis and the equation of Rouse, classic models for determining the sediment concentration profile. The technique was also applied to downstream and inside the Mogi reservoir. It can be observed that it is possible to apply the theory of entropy to simulate sediment concentration profile of reservoirs, since the use of the relationship between parameters facilitates calculations, reduces the number of modeled parameters and consequently the computational effort as well as better represents the variation of sediment concentration along the profile. The applicability of the proposed model and the ease of using the probabilistic method, since it does not need provide data of hydraulic bed conditions not even grain size, make it feasible.

Visando garantir a disponibilidade hídrica em seus diferentes usos são construídos reservatórios, estes sempre associados a problemas de perda de volume de armazenamento devido ao processo de assoreamento. A atualização destes dados, bem como a quantificação do assoreamento geralmente é feita através de Levantamento Batimétrico. Apesar da grande importância do tema não é observado na literatura um método padronizado para a realização de estudos batimétricos, autores e organizações apresentam métodos dispares quanto à quantidade e disposição dos dados. Deste modo, a presente pesquisa buscou elencar os métodos apresentados na literatura e analisá-los quanto a precisão obtida no cálculo de volume do reservatório, utilizando como estudo de caso o reservatório da UHE Três Irmãos (SP). Observou-se que os MDTs gerados pelos métodos não representavam com fidelidade trechos estreitos do reservatório (braços) bem como o talvegue. Foi então proposto um método para a determinação do espaçamento entre seções bem como uma rotina para geração de MDT considerando características do talvegue. O método proposto para determinação do espaçamento entre seções se mostrou capaz de representar com relativa boa precisão trechos dos braços (diferença máxima encontrada de 5,01%) e apresentou tempo de coleta de dados de 60% do método mais preciso apresentado na literatura. A rotina de geração de MDT proporcionou em média melhora de aproximadamente 30% na qualidade dos dados de volume calculados. Por meio da aplicação dos métodos desenvolvidos na UHE Chavantes foi calculado um assoreamento de 3,91%, de acordo com os resultados, sem a utilização das rotina de geração de MDT desenvolvida cálculo do volume do reservatório seria subestimado em 1,61%, superestimando o cálculo do assoreamento. / Water reservoirs are built with the main purpose of guaranteeing water supply, however, their volume always decreases due the sedimentation processes. Bathymetric surveys can be deployed to assess the current volumetric capacity of a given reservoir and to estimate and quantify the sedimentation process. Although Bathymetric surveys are considered to be a key factor when analyzing and assessing properties of a given reservoir, a standard method for its deployment is yet to be defined. Authors and research groups presents different methods about the sampling rate as well as the choice of adequate spots for data collection. The overall goal of this research was to identify and analyze the different methods deployed in previous published literature analyzing the accuracy of the volume data provided by these different methods. Três Irmãos reservoir (São Paulo) was used as a case study where methods were compared. It was pointed out that the DEMs obtained were unable to accurately represent narrower reservoirs areas (tributaries) and the thalweg. Therefore was proposed a new method for determining the distance among survey sections as well as a routine for DEM generation takes into account the thalweg characteristics. Results revealed that the data pulled out was able to represent with accuracy the tributary areas (maximum difference was 5.01%). In addition, a reduced data collection time was observed (60%) when compared against the most accurate method found in published literature. The proposed technique for DEM generation indicated approximately 30% of quality improvement in the data calculated for the reservoir volume. The developed method was applied on a bathymetric survey conducted on the Chavantes reservoir (São Paulo). The loss of reservoir capacity assessed was 3.19%. According to results, a bathymetric survey which does not deploy the new method proposed would underestimate the reservoir\'s volume by 1.61% and overestimate the sedimentation process.

Holocene carbonate sediments from Mexican reefs in the Caribbean and Gulf of Mexico display variations in constituent composition, texture and mineralogy which are related to their locations on the reefs. Samples were collected at barrier reef environments at Akumal and Chemuyil, on the northeast coast of the Yucatan Peninsula; at the oceanic atoll of Chinchorro, off the southeast coast of the peninsula; and at the shelf atoll of Alacranes, in the Gulf of Mexico. Samples were collected through a depth range of 0-40 m, which encompasses back reef, shallow fore reef, and deeper fore reef environments. Constituent-particle analysis of reef sediments indicates that lagoon facies are dominated by Halimeda with lesser amounts of coral and coralline algae. In contrast, fore reef facies are dominated by coral, with lesser amounts of Halimeda and coralline algae. Greater than 90% of the sediments (dry weight) occur in the interval 0.125-2.00 mm, with mean grain sizes (Mz) approaching 0.5 mm at most sites. Mz generally decreases with increasing depth at three of the four sites. Reef sediments are moderately to poorly sorted and typically become more poorly sorted with increasing depth. Sediments collected from reef channels (grooves) are consistently better sorted than those from the reef interstices (spurs). Mineralogically, the sediment is predominantly aragonite (63-93%) and high-Mg calcite (3-33%), with minor amounts of low-Mg calcite (3-9%). The sediment is chiefly composed of these three polymorphs of CaC03 (96.32- 99.83%) with only a small percentage of insoluble (non-carbonate) material. The non-carbonate fraction of the sediment is dominated by organics (0.14-3.16%) with lesser amounts of clay minerals and amorphous silica (0.00-0.66%). Quantitative analysis of Mexican reef sediments in the Caribbean and Gulf of Mexico allows the delineation of reef zonations based on constituent-particle composition. Q-mode cluster analysis of constituent-particle data from epireefal sediments enables the separation of lagoon, shallow fore reef (10-15 m) lithofacies. These groupings were maintained even when constituent-particle data from the barrier reefs were combined, and also when data from the atoll reefs were combined. Similar cluster groupings were obtained when constituent-particle data from a Jamaican fringing reef were combined with data from the Mexican barrier reefs. This indicates that coastal reef sediments from Jamaica and Mexico are surprisingly similar in constituent-particle composition and facies zonations. However, cluster analysis failed to produce clear associations when constituent-particle data from barrier reefs and atoll reefs were combined. The sedimentological zonations observed in the study reflect the community composition of the living reefs, and indicate that community composition, at least for calcifying organisms, is potentially preservable.

The Red Pine Shale (RPS; ~1120m), uppermost formation of the Neoproterozoic Uinta Mountain Group, Utah, is an organic-rich sedimentary succession that represents marine deltaic systems delivering mature sediment from the east and immature sediment from the north. Multiple data sets suggest regional climate and sea-level changes associated with changing organic carbon burial rates. Six facies identified represent wave-, tidal-, and river-influenced parts of the distal prodelta to delta front. The shale facies is interpreted as distal prodeltaic deposition in a marine environment. The concretion facies is interpreted as prodeltaic deposition to distal prodelta. The shale-sandstone facies represents suspension settling with dilute density currents in a proximal prodelta to delta front environment. The slump fold facies was deposited on the proximal prodelta or delta front. The sandstone facies represents deposition on the delta front and shows marine- and river- influences. The pebbly sandstone facies is representative of a delta front environment. C-isotope values from this shale range from -29.46 / to -16.91 / PDB and TOC from 0.04% to 5.91%. Combined H/C, TOC, and local-regional isotopic correlations suggest that these values are representative of C-isotope composition of Neoproterozoic seawater. The composite C-isotope curve for the RPS is less negative values near the base, followed by a long decline to a thick interval of homogeneous lower values. Petrographic analyses reveal immature arkosic sandstone and mature quartz arenite populations. Detrital zircon data show an Archean population from the Wyoming Craton to the north and a mixed Proterozoic/Archean population from the east-southeast. Measured sections show north to south delta progradation with a proximal source to the north and a mature sediment source to the east. The composite section shows one low-order regressive cycle and ~11 high-order cycles. There is a relationship between C-isotope values, shale geochemistry, and lithostratigraphy. Less negative C-isotope values correspond with increased kaolinite and facies indicating higher sea-level. These relationships are seen in the correlative Chuar Group, Arizona, and a similar model is suggested for their origin: humid climate, high organic carbon burial rates, and high sea-level. This paper meets the requirements to revise the RPS as a formalized unit in accordance with the Stratigraphic Code guidelines.

Holocene sediments from intertidal and shallow subtidal zones in Bahia la Choya, Mexico exhibit significant differences based on their mineralogical content, constituent composition, textural parameters, and foraminiferal assemblages. The intertidal sediments are characterized by low calcium carbonate content, being dominated by quartz, and are moderately well sorted and coarse skewed with a fine mean grain size {Mz = 2.73 phi}. Total numbers {living and dead} of benthonic Foraminifera per ml of sediment are relatively low (12/ml) in the intertidal zones. In contrast, the subtidal sediments are characterized by high calcium carbonate content, being dominated by molluscan shell fragments, and are poorly sorted and nearly symmetrically skewed with a medium mean grain size {Mz = 1.41 phi}. Total numbers of benthonic Foraminifera per ml of sediment are relatively high (52/ml) in the subtidal zone. The analysis of bioerosion intensity indicates that differences in susceptibility to bioerosion exist not only at the subordinal level but also at the generic level of Foraminifera. Overall rates of test destruction are rapid, apparently due to the combination of biological, chemical, and physical processes. The experimental determination of test characteristics which correlate with settling or entrainment enables the delineation of foraminiferal morphotypes which are most likely to be transported. Test settling velocity is mostly affected by test size and weight. Movement threshold velocity is, also, mostly affected by test size, weight, and shape, in addition to the nature of the substrates and initial test orientation. Foraminifera from siliciclastic environments exhibit relatively low settling and movement threshold velocities. Thus, taxa from siliciclastic settings are more likely to be transported by currents than are those from carbonate environments, which show a wide range of settling and movement threshold velocities. Such information may be utilized to distinguish between autochthonous and allochthonous microfossil assemblages in the stratigraphic record.