Set against a background of vegetation change from grassland to shrubland, this project used the small agricultural stock ponds of the Jornada Experimental Range, in the semi-arid Chihuahuan Desert of New Mexico, to quantify sediment production from the expanding shrubland vegetation communities. In quantifying sediment production, conclusions can be drawn about the importance of land cover in rangeland management, but more significantly for this study, a valuable dataset is generated at a generally under-researched scale. Small pond studies are necessary to expand the existing knowledge on up-scaling of erosion datasets. Sediment yield data are primarily collected from erosion plots, or at a much larger scale using erosion models. These models rely on data from plots for calibration and validation. However, data collected at the plot scale do not accurately represent sediment production at larger scales, often resulting in the propagation of errors. New methods of considering sediment routing through a catchment are necessary if understanding at an intermediate (catchment) scale is to be gained. Three approaches were used to generate comparable datasets: repeated surveys, sediment dating, and reconstructing runoff coefficients from aerial photographs. The results from these projects show internally consistent results, as well as agreement with similar studies in the wider erosion-study literature. This demonstrates the potential of this technique to produce viable datasets. The principal findings of this research are that runoff coefficients calculated at the catchment scale do not show the expected reduction from those gained from plots. This is primarily thought to be a methodological problem. However, the principal aim of the research was met with two complimentary datasets showing variations in sediment fluxes from shrubland vegetation. The dataset was insufficient to conclude this was statistically different from the historic grasslands, but this does appear to be the case. The idea of travel distance of particles as a control on sediment production was only partially substantiated by this work: fining of sediment is evident only within the catchments of the ponds. No statistical difference was found between the particle-size distribution of pond and catchment samples.

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No description available.

Sediment of the Upper Albian Bow Island Formation in the subsurface of south-west Alberta were deposited in a foreland basin setting proximal to the western margin of the Cretaceous Western Interior Seaway. The formation can be divided into three lithostratigraphic units based on wireline log and core data. The 'Lower' Bow Island Formation, which directly overlies Mannville Group sediments, is composed of numerous stacked, upward-coarsening, shelf-shoreface successions and ranges in thickness from 130 to 420 feet. The 'Middle' Bow Island Formation comprises 20 to 300 feet of coastal-plain sediments which are laterally equivalent to, and also overlie, the 'Lower' Bow Island Formation. 'Upper' Bow Island sediments range up to 102 feet in thickness. They are composed of marginal-marine deposits with occasional thick sandstone/conglomerate development. Facies analysis allows the formation to be divided into three facies associations corresponding to the three stratigraphic divisions. The Shelf-Shoreface Facies Association comprises the 'Lower' Bow Island Formation. Upward-coarsening successions consist of mudstones, sandy mudstones, muddy sandstones and variably-bedded sandstones with occasional bentonite beds. Such deposits are typical of a progradational, wave-dominated, shelf-shoreface setting. The Coastal-Plain Facies Association comprises the 'Middle' Bow Island Formation. Vari-coloured mudstones were laid down in a coastal floodplain environment and commonly exhibit pedogenic alteration. The mudstones are cut by sharp-based sandstones deposited in meandering fluvial channels and crevasse-splay environments. The Transgressive Facies Association comprises the 'Upper' Bow Island Formation and is sub-divided into three Complexes: the Estuarine Channel Complex; the Embayment Complex and the Shelf-Shoreface Complex.

The sediment transport process for non-uniform mixtures involves a complex dynamic interaction between the material transported, the surface texture and the flow regime. However, the respective influence of each of these on the other, and on the transport rate is not well understood. The primary objective of this experimental study, was to consolidate and extend the understanding of these processes by investigating sediment transport, near bed flow structures and surface texture simultaneously, as various sediment mixtures were input upstream at differing feed rates, onto mobile mixed grain sediment beds. Three sets of laboratory experiments were completed. The first set of experiments were not fed with material, and acted as reference for later experiments. The second set, fed on two separate occasions, onto an already mobile gravel bed, two different sized uniform materials. Material was fed at a fixed rate that was similar in both runs. The third set of runs, fed material mixtures (again onto an already mobile gravel bed) at a rate that was fixed during each experiment, periodic measurements were made of bedload transport rates, bedload composition, bed surface texture and the near bed flow regime. Results showed that the stability of mixed grain bed was strongly influenced by the feed rate and composition of the upstream sediment supply. A relationship between the surface texture and the moving grain triggered a grain interaction process, which was thought to be as important as the fluid forces in governing the sediment transport rate. The interaction process either enhanced bed stability or promoted sediment movement. How the system responded was determined by the flow regime, the extent of surface texturing and the grain size distribution of the moving grains.

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The main topic of this thesis is the mechanical and non-mechanical compaction and fabric rearrangement of fine-grained siliciclastic sediments. Part A concentrates on the mechanical compaction of shallow «1000mbsf), fine-grained marine sediments, a majority of which was provided by DSDP/ODP. The used porosities and stresses were based on measurements by DSDP/ODP on fresh sample material. Results reveal, that the reduction of porosity with increasing effective stress is mainly controlled by lithology. Clay fraction (% material <2um) was used as parameter for the grain size of the sample material and found the single most important control on the relationship between porosity and effective stress. However, for a given clay fraction the porosities of samples containing significant amounts of microfossils exceeded those of the fossil-poor sediments. Larger amounts of grains between 2J.1m and 8J.1m in the fossil-rich material presumably led to these differences in pore space. Deviations between the porosities measured on fresh (wet) sample material by DSDP/ODP with those determined by mercury intrusion porosimetry on the partly dried out samples used in study highlighted the sensitivity of soft, clay-rich sediments to air drying. Experimental drying of two clay samples confirmed these observations and revealed the changes in total porosity and pore size distribution during air and oven drying. Furthermore, two case studies, one located in the Mid-Norway area and one offshore New Jersey, underlined the importance of a thorough assessment of lithology and confirmed the influence of microfossils on shallow mudstone compaction. In Part B of this thesis, a novel approach was applied to correlate the petrophysical changes of fine-grained sediments during compaction and early diagenesis to alterations of the sediment microfabric. High Resolution X-ray Texture Goniometry (HRXTG) was used to quantify the alignment of phyllosilicates and results reveal, that mechanical compaction does not necessarily lead to a Significant alignment of platy minerals. The analysis of the present mineralogies and grain size/shape distributions led to the conclusion, that only if both the clay and silt-fractions are dominated by platy minerals, mechanical compaction results in higher degrees of phyllosilicate alignment. On the other hand, if the silt-fraction is dominated by spherical grains (e.g. quartz, feldspar), increasing effective stress simply results in tight, poorly-aligned grain packing. Advanced stages of clay mineral diagenesis were only observed in two Gulf of Mexico wells. Here, the onset of the smectite-to-illite conversion was delayed until temperatures of at least 115°C, presumably due to the high sedimentation rates (>1000m/Ma). Although observed in other studies, an obvious influence of diagenesis on the clay mineral fabric of this sample set was not evident. It can therefore be assumed, that the mud- and siltstones from the Gulf of Mexico are still too immature to reflect diagenetic reactions in their phyllosilicate fabric.

No description available.

No description available.

No description available.