No description available.

No description available.

No description available.

This dissertation focuses on both a hydrodynamic and geomorphological study of the Mgeni Estuary. Within the hydrodynamic study, the channel discharge, suspended sediment fluxes and estuary bed sediment characteristics and dynamics were established. Within the geomorphological study, cross-shore topographical surveying of the lower estuary region, measurement of slope angles and surface sediment characteristics were established. The results of this study illustrate strong seasonal variability. Maximum channel discharges, suspended sediment concentrations and fluxes occur during the summer months, as a result of large amounts of rainfall. Furthermore, maximum suspended sediment concentrations and fluxes occur during spring tides, as a result of a greater tidal range, which enhances bed sediment re-suspension via concomitant increased turbulence. Generally, maximum fluxes occur along the flood tide and ebb tide, during spring tides and neap tides, respectively, which suggest that the estuary is a sink for marine sediment during spring tides and an exporter of sediment during neap tides. The estuary bed sediments are very well sorted and predominantly classified as near-symmetrical, as a result of strong tidal currents that constantly transport and re-work the sediments. On average, the bed sediments are medium sand and in all probability are largely derived from the marine environment. Estuary bed sediments contain negligible mud and organic contents, which as research suggests, is common in such highenergy estuary mouths. Apart from the seasonal variability, the survey profiles and surface sediments illustrate alongshore and cross-shore variations. The profiles become flatter and finer from the Beachwood Mangroves section of the barrier towards the estuary mouth in the south, as a result of sheltering due to the engineered groyne, conforming to Bascom (1959) and Komar’s (1998) sheltered and exposed coasts concept. The survey profiles conform to the summer and winter profiles put forward by Dardis and Grindley (1988). The winter profiles consist of higher, distinct berms and berm crests, as well as vertical erosional faces, whilst the summer profiles are lower, flatter, and consist of unclear berms and berm crests. Sediments are coarsest along the lagoonward slope and finest within the estuary. A strong, positive correlation was generated between slope angle and mean grain size. Despite the low organic contents, the estuary sediments consist of the highest values of organic matter, with the beach and barrier sediments displaying negligible amounts. Thus, the Mgeni can be classified as a very dynamic and active zone. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

No description available.

Submerged macrophyte beds provide a secondary realm of accumulation in lakes. Particles otherwise destined to reside in the deep-water profundal zone are intercepted by nearshore macrophyte communities that attenuate wave and current energy. The microenvironment found inside submerged macrophyte beds can be substantially more quiescent than that of the open-water, allowing for fine particles to be deposited out of the water column. Together with larger, eroded inorganic sediments and coarse organic particles, these materials comprise the sediments underlying macrophyte communities. / Thirty-four littoral sites were sampled in Lake Memphremagog (Quebec-Vermont) to quantify the role of morphometry (littoral slope and site exposure) and macrophyte beds (mean biomass and biomass density) on the accumulation of sediments. An established historical marker, stable Pb, was used to date the sediments (approx. 110 years) and calculate rates of accumulation (SARs). Identifiable stable Pb profiles were obtained at two-thirds of the sites confirming the utility and robustness of littoral sediment core analysis. Multiple regression analyses showed that macrophyte parameters were the best predictors of SARs. Macrophyte mean biomass and biomass density were clearly most important in predicting the volume (total SAR) and organic content (organic SAR) of the sediments ($R sp2=0.57 rm to 0.76$, $P<0.001$). The same macrophyte parameters, however, poorly predicted the bulk (mainly inorganic) accumulation of sediments. Biomass density was solely related to the long-term accumulation of stable Pb in the sediments supporting empirical models that credit growth form as an important factor explaining among species or among weedbed variability in sediment-plant tissue elemental concentrations. The quantification of SARs will benefit both lakewide modeling of nutrient and contaminant budgets, and the understanding of littoral succession and its contribution to lake ontogeny.

The reconstruction of past environmental conditions is a fascinating research area that attracts the interest of many individuals in various geological disciplines. Paleoenvironmental reconstruction studies can shed light on the understanding of past climates and are a key to the prediction of future climate changes and their consequences. These studies take on special significance when focused on areas sensitive to climate change. The Arctic region, which is experiencing dramatic changes today in its peatlands and in its ocean, is prime example. The entire region plays a major role in global climate changes and has recently received considerable interest because of the potential feedbacks to climate change and its importance in the global carbon cycle. For a better understanding of the role of Arctic peatlands and the Arctic Ocean to global climate changes, more records of past conditions and changes in the region are needed. This work applies different geochemical proxies, with special emphasis on lipid biomarkers, to the study of a permafrost peat deposit collected from the Eastern European Russian Arctic and a marine core retrieved from the Lomonosov Ridge in the central Arctic Ocean. The results reported of this study show that molecular stratigraphy obtained from the analysis of lipid biomarkers in both peat and marine profiles, combined with other environmental proxies, can contribute significantly to the study of Arctic ecosystems of the past. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p>

From measurements of thermal and electrical conductivities of 64 ocean sediment samples obtained from piston cores taken off the Oregon Coast, and from 37 water-saturated sandstone samples analyzed by Zierfuss and Van der Vliet (1956), as well as 51 thermal conductivities and water contents of ocean sediments analyzed by Ratcliffe (1960), this research shows that a useful relationship can be obtained giving thermal conductivity when electrical conductivity is known. Analysis of the data was made using theoretical concepts which have been known for many years to relate thermal and electrical conductivity to porosity. The results of this research may make possible a convenient determination of in situ thermal conductivity that would give the average conductivity in materials containing large variations in conductivity. / Graduation date: 1966

Sediments on the inner portion of the Oregon continental shelf consist of clean, well-sorted, detrital sand. This sand has an average median diameter of 2.53Φ (. 173 mm) and is both positively and negatively skewed. Deposits with median diameters in the coarse sand and gravel classes occur at depths of 20 to 40 fathoms and probably represent ancient beach or fluviatile deposits formed during lower stands of sea level. The outer shelf and upper slope are covered by poorly sorted sediments with median diameters in the fine sand to fine silt classes. Mean diameters of the sediments are almost always smaller than their median diameters and the sediments are positively skewed. The heavy mineral assemblages are dominated by the amphibole and pyroxene groups and the opaque-garnet association. Pyroxenes are most abundant in the coarser-grained sediments of the inner shelf and decrease in abundance offshore. Amphiboles are most abundant in the finer-grained sediments of the outer shelf and upper slope. Highest concentrations of the opaque-garnet association also are found in the inshore samples. Sediments of the continental shelf are derived from two principal sources, rivers and erosion of coastal terrace deposits. Rivers are probably contributing only fine-grained material to the shelf as much of the coarser fluviatile material is thought to be trapped in the estuaries. The terrace deposits are actively being eroded and are thought to contribute about 21,000,000 cubic feet (.00013 cubic miles) of sediment to the continental shelf annually. Evidence suggests that much of the inner-shelf sand is probably a relict transgressive sheet sand that was deposited during the last rise in sea level. Most of the deposition of the modern sand on the shelf has been confined to the inner portion of the inner shelf. Finer-grained sediments have been deposited on the outer shelf and upper slope. Characteristics of the sediments on the present continental shelves may be useful in identifying continental shelf deposits in the geologic column. / Graduation date: 1966

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1987. / Bibliography: leaves 150-164. / xiii, 164 leaves, bound ill. 29 cm