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Detailed understanding of sediment architecture is crucial for planning well placements and minimizing bypassed oil in low net-to-gross fluvial successions (those with a high proportion of mudstones and siltstones). Field development planning relies greatly on architectural models. These, in turn, are dependent on obtaining an adequate description of the subsurface and accurate interpretation of the fluvial style. But this is difficult due to the limited quantity of data available. Inevitably, therefore, the models are biased by preconceptions and assumptions. For low net-to-gross fluvial succession, the common presumption is that they are the products of high-sinuosity rivers, because of the high proportion of mudstone present. This choice drives the selection of parameters of reservoir modelling. Comprehensive architectural analysis of the well-exposed Wasatch Formation (Late Paleocene to Early Eocene) in the SE part of the Piceance Basin, in western Colorado, USA, shows this presumption to be an unsafe choice. The upper part of this formation (the Shire Member) is almost entirely the product of straight rivers. Evidence of high-sinuosity rivers is distinctly lacking, with just a single example found of point-bar deposits, and even that is laterally restricted and weakly developed. The bulk of the member, which is over 200m in thickness, is composed of mudstones showing pedogenic alteration of a wide range of intensities, and with evidence of both poorly and well drained soils. Isolated within these mudstones are narrow ribbon sandstones, up to 30m wide and 3m thick, interpreted to be the product of low-sinuosity single-thread (anastsomosed) rivers. At intervals through the succession are a small number of sheet sandstones up to 1km wide and 12m thick. These sheets are an amalgamation of downstream-accreting bars, some of them gravely, and channel-fill deposits, and are interpreted to be the product of a low-sinuosity but multi-threaded (braided) river. The predominance in the succession of mudstone, of relatively high cohesive strength, suggests at first sight conditions favourable for the development of high-sinuosity rivers.

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<p> A detailed section of the Duck Cove Member (Nadon, 1981) of the Triassic Lepreau Formation of Southern New Brunswick is measured.</p> <p> The section consists of a complex sequence of conglomerates and sandstones with a minor occurrence of mudstones and breccia. A description of the facies is provided and an interpretation is based on observations of ancient and marine braided stream deposits of Miall (1978) and Allen (1983). The Markov chain analysis is used to describe the vertical succession of facies.</p> <p> Paleoflow indicators suggest a flow towards the south or southeast. However this conclusion is based on limited availability of data.</p> / Thesis / Bachelor of Science (BSc)

Fine grained sediments were common in epicontinental seas, with shallow slopes, such as the Cretaceous Western Interior Seaway. However, proposed mechanisms for offshore mud transport, such as turbidity currents, tempestites, and hyperpycnal flows, require significant slopes. A core from the Upper Mancos Shale, Mancos C, located in the San Juan Basin of New Mexico was analysed to determine the dominant transport processes bringing sediment offshore. A detailed facies analysis was conducted, over 54 m of slabbed core, using sedimentological data, such as grain size, type of sedimentary structures, bed thickness, lithology, clay content, fossils, ichnofacies, and degree of bioturbation. The facies observed in the core show that multiple processes, including ignitive turbidity currents, hypopycnal and hyperpycnal flows, and tempestites, were responsible for the deposition of the Mancos C core. The resuspension of mud on the inner shelf by storm waves also played a key role in moving mud further offshore. Tidal influence within the Mancos C was relatively small. / Thesis / Master of Science (MSc)

The problem of how sand and mud was distributed downslope, within linked alluvial-brackish water-marine shoreline systems of an extensive clastic wedge is addressed here. The Iles Clastic wedge accumulated over a time period of a few million years (my), and its component high-frequency regressive-transgressive sequences have a duration of a few 100 thousand years (ky). The sediment partitioning study provides insight into where the thickest sandstones and mudstones were located, and generates a model that can be applied to improving the management of hydrocarbons or water resources. A 300 km 2-D study transect across the Iles Clastic Wedge in SW Wyoming and N Colorado included subsurface well log information and outcrop stratigraphic columns. This information was used to correlate high-frequency sequences across several hundred kilometers, characterize depositional processes from proximal to distal reaches, develop a sediment partitioning model, and understand the role of the likely drivers in the development of the wedge and its internal sequences. The main results of this study are: (1) The Iles Clastic Wedge spans 3 my (500 m thick) and is composed internally of 11 sequences of 200-400 ky, each of which have significant regressive-transgressive transits of up to 90 km. Sediment partitioning analysis shows that within the regressive limb of the large wedge, the component regressive compartments tend to thicken basinwards, whereas transgressive compartments thicken landwards. This geometry is driven by preferential erosion in proximal areas during regression, bypassing much sediment to the marine shorelines, and transgressive backfilling into proximal areas previously eroded more deeply. (2) The greatest concentration of sands tends to be located in the proximal fluvial and estuarine facies of the transgressive compartments and within the medial shoreline/deltaic facies of the regressive compartments. (3) As the high-frequency sequences developed, the effectiveness of basinward sand partitioning reaches a maximum value near the peak regression level of the wedge, reflecting stronger erosion and sediment bypass during this times. (4) The development of the Iles Clastic Wedge was influenced by both tectonic and eustatic drivers, with important tectonic control in the upstream reaches. On a 4th-order timescale, the Iles Wedge internal sequences were likely influenced mainly by eustasy. / text